Mold for ball grid array semiconductor package

A mold for BGA semiconductor packages which includes a height adjusting member adapted to adjust the height of the top cavity insert of the top mold or the bottom cavity insert of the bottom mold, an elastic member disposed between the height adjusting member and associated insert, clamping regions of different heights formed at its top or bottom cavity insert, or air vents having a width and depth of an optimum ratio to the area and depth of cavities, thereby being capable of maintaining an optimum and uniform clamping pressure between the top and bottom molds for a variety of PCB strips having a thickness deviation among different portions thereof or having various average thicknesses, upon molding resin encapsulants on those PCB strips, thereby achieving an improvement in the quality of finally produced packages while preventing a sweeping phenomenon of bonding wires electrically connecting a semiconductor chip to conductive traces.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a mold for ball grid array (BGA) 
semiconductor packages, and more particularly to a mold for BGA 
semiconductor packages which is capable of applying uniform and optimum 
clamping pressure to engaging surfaces of top and bottom molds upon 
molding a resin encapsulant in the portion of a printed circuit board 
(PCB) where a semiconductor chip is mounted, thereby preventing the PCB 
from being damaged while achieving an improvement in the quality of 
packages. 
2. Description of the Prior Art 
BGA semiconductor packages have been developed to overcome a limitation in 
fine pitch surface mounting. BGA semiconductor packages achieve a high 
integration of circuits because they can accommodate a maximum number of 
input/output terminals per unit area. Such BGA semiconductor packages also 
have a light, thin, simple and compact structure while exhibiting a 
superior electrical characteristic and a superior heat discharge 
characteristic. In addition, the BGA semiconductor packages have 
advantages in that they achieve a high productivity, an easy extension to 
multi-chip modules, and a minimized cycle from the designing step to the 
manufacturing step. 
In this regard, BGA semiconductor packages have a high applicability 
obtained by their high-quality characteristic and high reliance, an easy 
applicability to a variety of electronic devices having a very compact 
size, and a high added value obtained by inexpensive manufacturing costs. 
Such BGA semiconductor packages include a PCB having a semiconductor chip 
mounting plate at the upper surface of its central portion. Circuit 
patterns are formed on the upper and lower surfaces of the peripheral 
portion of the PCB, respectively. The circuit patterns are electrically 
connected to each other through via holes. A semiconductor chip is 
attached to the semiconductor chip mounting plate of the PCB. The circuit 
patterns of the PCB are also electrically connected to the circuit of the 
semiconductor chip by means of bonding wires. The BGA semiconductor 
packages also include a resin encapsulant molded to protect the 
semiconductor chip and bonding wires from the environment such as 
moisture, dust or impact, and a plurality of solder balls used as 
input/output terminals for electrically connecting the lower circuit 
pattern of the PCB to an external device. 
The PCB has a multilayer structure essentially consisting of a flat, 
central resin layer made of a polymer resin such as polyimide or 
bismaleimidetriazine, signal layers comprised of metal thin films 
respectively formed over the upper and lower surfaces of the central resin 
layer while interposing coating layers therebetween, and insulating solder 
mask layers respectively formed over the signal layers while being 
externally exposed. The signal layers respectively formed over the upper 
and lower surfaces of the flat resin layer are electrically connected to 
each other through via holes. If necessary, the PCB may have at least two 
laminated flat resin layers on which signal layers are formed. 
Accordingly, the PCB has an optional thickness. 
Typically, the fabrication of BGA semiconductor packages using PCB's having 
the above-mentioned structure is carried out in the unit of a PCB strip on 
which a plurality of unit PCB's are continuously arranged in such a manner 
that they are aligned with one another, taking into consideration the 
processing at each processing step and the package feeding efficiency 
between successive processing steps. The fabrication procedure of BGA 
semiconductor packages involves a semiconductor chip mounting step, a wire 
bonding step, a molding step, a solder ball fusing step, and a singulation 
step. At the semiconductor chip mounting step, semiconductor chips are 
mounted on respective semiconductor chip mounting plates of the unit PCB's 
of a PCB strip by bonding each semiconductor chip to the associated 
semiconductor chip mounting plate using an epoxy resin. At the wire 
bonding step, bond pads of each mounted semiconductor chip are bonded to 
conductive traces of the associated unit PCB by means of bonding wires, 
respectively, so that the associated semiconductor chip and PCB are 
electrically connected. At the molding step, a resin encapsulant is formed 
using a mold in order to protect each semiconductor chip and associated 
bonding wires from the environment. At the solder ball fusing step, a 
plurality of solder balls are fused as input/output terminals on the lower 
surface of each unit PCB. At the singulation step, the PCB strip processed 
at the above-mentioned steps is cut into individual unit packages. 
Practically, it is very difficult for PCB strips used in the fabrication of 
BGA semiconductor packages to maintain a uniform thickness at all portions 
thereof during the package fabrication, in particular, at steps of 
laminating desired layers and steps of coating a solder mask layer. Each 
PCB strip has a relatively large thickness deviation because its portions 
disposed adjacent to cutting lines to be used at the cutting step have an 
increased thickness due to a generation of burrs, as compared to other 
portions. As a result, such PCB strips are problematic in that they have a 
relatively non-uniform flatness. 
Since such PCB strips having a non-uniform flatness due to a thickness 
deviation exhibited among different portions thereof are used in the 
fabrication of BGA semiconductor packages, various problems occur. For 
instance, where low clamping pressure is used to engage top and bottom 
molds in a molding process for forming a cavity where a resin encapsulant 
is molded as a melted molding resin is injected into the cavity and then 
cured, the melted molding resin may be flashed between the top and bottom 
molds at a thinner portion of the PCB. On the other hand, where the 
clamping pressure is excessively high, a thicker portion of the PCB is 
severely depressed as compared to other portions of the PCB, thereby 
causing the PCB to be deformed. In this case, a sweeping caused by a short 
circuit of wires and a generation of cracks in packages may occur. Air 
vents may be blocked due to the deformation of the PCB. In this case, it 
is difficult to easily vent air left in the cavity, thereby resulting in a 
degradation in the quality of molded packages such as a formation of voids 
or blisters. 
Now, a procedure for molding BGA packages in accordance with a conventional 
method will be described in conjunction with FIG. 33. 
FIG. 33 is a schematic view illustrating a general automatic transfer type 
molding apparatus TMA having a conventional configuration. As shown in 
FIG. 33, the TMA includes a mold M comprising a top mold 10 and a bottom 
mold 20. A feeding unit F is disposed at a position spaced from the mold M 
by a desired distance. The feeding unit F serves to store PCB strips 
(denoted by the reference numeral 100 in FIG. 31) and to feed the stored 
PCB strips. The TMA also includes a transferring unit T for transferring a 
PCB strip stored in the feeding unit F to the mold M, a guide unit G for 
guiding the PCB strip during the transfer, and a receiving unit C for 
receiving molded PCB strips. 
In the feeding unit F, PCB strips subjected to the semiconductor chip 
mounting and wire bonding steps are sequentially stacked. The transferring 
unit T transfers the PCB strips stacked in the feeding unit F one by one 
to the bottom mold 20 via the guide unit G. The PCB strip transferred to 
the bottom mold 20 is positioned in such a manner that its portions 
(namely, square regions indicated by dotted lines in FIG. 31), where resin 
encapsulants are to be formed, are received in cavities defined when the 
bottom mold 20 is engaged with the top mold 10, respectively. As a melted 
resin is injected into the cavities and then cured, resin encapsulants are 
formed on the PCB strip. PCB strips formed with resin encapsulants in the 
above-mentioned manner are sequentially stacked in the receiving unit C. 
Although not shown in the figures, the PCB strips stacked in the receiving 
unit C after the completion of the molding step are subsequently subjected 
to a solder ball fusing step so as to fuse solder balls as input/output 
terminals on the lower surface of each unit PCB. Subsequently, the PCB 
strips are subjected to a singulation step in order to cut each PCB strip 
into package units. Thus, BGA semiconductor packages are obtained. 
FIG. 34 is a sectional view illustrating a typical configuration of the 
conventional automatic transfer type mold M. As shown in FIG. 34, a PCB 
strip 100, in which mounting of semiconductor chips 103 and bonding of 
wires 104 have been carried out, is interposed between the top and bottom 
molds 10 and 20 of the mold M in such a manner that the semiconductor 
chips 103 are positioned within cavities CA defined between the top and 
bottom molds 10 and 20. As a melted resin is injected into the cavities CA 
and then cured, resin encapsulants are formed on the PCB strip 100. 
The top mold 10 includes a base 11 provided at the lower surface thereof 
with a longitudinally extending recess 12, a top center block 30 extending 
downwardly from the central portion of the lower surface of the base 11, 
and a top cavity insert 40 fitted in the recess 12 around the top center 
block 30. 
The top cavity insert 40 has a plurality of clamping holes 502 respectively 
corresponding to a plurality of through holes 501 formed in the base 11 so 
that it is firmly coupled to the base 11 by clamping members B1 extending 
through the clamping holes 502 and through holes 501. A top drive plate DP 
is mounted on the top portion of the base 11 by means of a plurality of 
clamping members B. 
Similarly to the top mold 10, the bottom mold 20 includes a base 21 
provided at the upper surface thereof with a longitudinally extending 
recess 22, a bottom center block 30A extending upwardly from the central 
portion of the upper surface of the base 21, and a bottom cavity insert 
40A fitted in the recess 22 around the bottom center block 30A. 
The bottom center block 30A of the bottom mold 20 has a pot (not shown) 
adapted to melt a molding resin, and a runner (not shown) adapted as an 
elongated conduit for feeding the melted resin. The bottom cavity insert 
40A fitted in the recess 22 around the bottom center block 30A has a 
plurality of concave portions 41 at the upper surface thereof. 
FIG. 35 is a plan view illustrating a conventional configuration of the 
bottom cavity insert 40A included in the bottom mold. As shown in FIG. 35, 
the bottom cavity insert 40A has a base 211, a plurality of aligned 
concave portions 212 formed at the upper surface of the base 211 and 
adapted as resin encapsulant molding regions, and a plurality of clamping 
portions 213 extending upwardly from the upper surface of the base 211 at 
the peripheral edges of the concave portions 212 to have a uniform height. 
A PCB strip (not shown) to be subjected to a molding process is laid on a 
portion of the base 211 where the concave portions 212 and clamping 
portions 213 are formed. 
When the bottom cavity insert 40A of the bottom mold is engaged with the 
top cavity insert (not shown) of the top mold, the concave portions 212 of 
the bottom cavity insert 40A form cavities which define resin encapsulant 
molding regions, respectively. A runner gate RG is formed at one corner of 
each concave portion 212 to provide a passage for injecting a melted 
molding resin into the associated cavity. Air vents are also formed at the 
remaining corners of each concave portion 212 in order to achieve a good 
filling of the molding resin. Each air vent AV has a predetermined width 
W2 and a predetermined depth D2 in order to achieve a good air ventilation 
while minimizing the leakage of the molding resin therethrough (FIG. 37). 
FIG. 36 is a cross-sectional view taken along the line F--F of FIG. 35. 
Referring to FIG. 36, it can be found that the concave portions CV of the 
bottom cavity insert 40A are deeper than the clamping portions by a depth 
D1 (corresponding to the height of resin encapsulants) while the air vents 
AV have a depth D2. 
The molding of resin encapsulants on PCB strips 100 using the TMA mentioned 
above in conjunction with FIG. 33 is carried out as follows. That is, when 
one of PCB strips 100 stacked in the feeding unit F is transferred to the 
bottom mold 20 in accordance with an operation of the transferring unit T, 
the bottom mold 20 is raised to clamp the chip-mounted and wire-bonded PCB 
strip 100 between the bottom and top molds 20 and 10. At this time, 
cavities CA are defined between the bottom and top molds 20 and 10 by the 
concave portions 41 of the bottom mold 20. Thereafter, a molding resin is 
injected into the cavities CA and then cured. Thus, the molding procedure 
is completed. 
As shown in the enlarged portion of FIG. 34, the top cavity insert 40 is 
fitted in the recess 22 of the base 11 included in the top mold 10 in such 
a manner that its lower surface is higher than the lower surface of the 
base 11 by a height t, thereby forming a step. Accordingly, it is possible 
to prevent the PCB strip 100 laid on the bottom cavity insert 40A of the 
bottom mold 20 from being over-depressed when the top cavity insert 40 
depresses the upper surface of the PCB strip 100. 
However, such a PCB strip has a relatively large thickness deviation among 
different portions thereof. This is best shown in FIG. 14 and Table 2. As 
a result, clamping pressures respectively applied to different portions of 
the PCB strip 100 by the cavity inserts 40 and 40A of the clamped top and 
bottom molds 10 and 20 may be different. That is, non-uniform clamping 
pressure is applied to the PCB strip 100. This results in a plurality of 
locally deformed portions on a solder mask layer which is the uppermost 
layer of the PCB strip. Consequently, a generation of cracks or a 
degradation in the reliance of finally obtained semiconductor packages may 
occur. 
Furthermore, portions of the PCB strip 100 disposed in the vicinity of the 
air vents AV of the bottom cavity insert 40A are not supported by the 
upper surface of the bottom cavity insert 40A during the application of 
clamping pressure to the PCB strip 100 by the top cavity insert 40. As a 
result, the PCB strip 100 may be severely deformed by the clamping 
pressure, thereby resulting in a sweeping phenomenon, namely, a short 
circuit of wires. In this case, the air vents AV may be partially or 
completely blocked, thereby resulting in a poor air ventilation of the 
cavities. As a result, a generation of blisters or voids may increase. 
When excessively high clamping pressure is applied to the PCB strip 100, 
the above-mentioned phenomenons are exhibited at all portions of the PCB 
strip 100. 
FIG. 37 is a partially-enlarged plan view illustrating, in a perspective 
manner, a wire sweeping phenomenon generated in a semiconductor package 
due to a non-uniform application of clamping pressure upon molding a resin 
encapsulant (corresponding to an inner region indicated by the dotted 
line) using the conventional mold. In FIG. 37, the reference numeral 103 
denotes a semiconductor chip, 102 conductive traces of a circuit pattern, 
and 104 bonding wires electrically connecting the conductive traces 102 to 
the semiconductor chip 103. 
FIG. 38 is a schematic view illustrating a poor resin filling profile 
exhibited after molding a resin encapsulant by use of the conventional 
mold of FIG. 34 including the bottom cavity insert having the conventional 
configuration of FIG. 37. As shown in FIG. 38, portions of the PCB strip 
(not shown) disposed near air vents AV are in a severely deformed state 
due to clamping pressure applied to the PCB strip. As a result, the air 
vents AV may be partially or completely blocked. In this case, air left in 
the cavity concentrates toward air vents AV not blocked, so that venting 
pressure in the air vent AV increases, thereby generating voids or 
blisters. As a result, a poor resin filling profile is exhibited as shown 
in FIG. 38. That is, the quality of the finally produced package is 
degraded. 
Where BGA semiconductor packages are fabricated using PCB strips having a 
structure including at least two laminated flat resin layers, on which 
signal layers are formed, it is difficult to adjust the height t of the 
step shown in the enlarged portion of FIG. 35 when the conventional mold 
is used. This is because the structure of the above PCB strips has a 
variable thickness. In this case, a PCB strip thickness less than the 
height t of the step results in an insufficient clamping pressure for 
coupling the top and bottom molds to each other. As a result, there is a 
serious problem in that the molding resin is flashed. On the contrary, 
where the PCB strip thickness is much greater than the height t of the 
step, the clamping pressure generated upon coupling the top and bottom 
molds is excessively high, thereby generating a deformation of the PCB 
strip or a sweeping phenomenon of bonding wires. Furthermore, the portions 
of the PCB strip disposed near the air vents AV of the bottom cavity 
insert 40A are severely deformed due to the clamping pressure from the top 
cavity insert 40 applied to the PCB strip because they are not supported 
by the upper surface of the bottom cavity insert 40A. As a result, the air 
vents AV may be partially or completely blocked, thereby generating voids 
or blisters. 
Table 1 shows results obtained after resin encapsulants are molded on PCB 
strips having different average thicknesses, respectively, using the 
conventional mold of FIG. 34 in which its step has a constant height t. 
TABLE 1 
______________________________________ 
Result of Molding Test Depending on Average Thickness of PCB Strip 
PCB Molded State of 
State of Strip 
Sam- Th. Resin Encapsulant Sweep- 
ple (mm) Void Flash 
Flister 
Deform 
Crack 
ing Results 
______________________________________ 
1 0.336 .largecircle. 
X .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Bad 
2 0.339 .largecircle. 
X .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Bad 
3 0.342 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
4 0.345 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
5 0.346 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
6 0.360 X .largecircle. 
X X .largecircle. 
X Bad 
7 0.360 X .largecircle. 
X X X X Bad 
8 0.363 X .largecircle. 
X X X X Bad 
______________________________________ 
Not Generated: 
Generated: X 
*Molding Condition for Resin Encapsulant 
Step t: 0.220 mm 
Molding Resin Injection Pressure: 80 kg/cm.sup.2 
Molding Time: 10 to 12 sec. 
PCB Clamping Pressure: 200 to 250 kg/cm.sup.2 
As apparent from the above results, where the step between the lower 
surface of the top mold 10 and the lower surface of the top cavity insert 
40 has a height t of 0.220 mm, the molded state of resin encapsulants is 
good only for PCB strips having an average thickness ranging from 0.342 mm 
to 0.346 mm. In this case, the PCB strips maintain a normal state. In the 
case of PCB strips having a thickness beyond the above-mentioned thickness 
range, undesirable results are obtained, as shown in Table 1. 
FIG. 39 is a bottom view illustrating the top cavity insert 40 fitted in 
the recess 12 of the conventional top mold 10. Since the entire bottom 
surface including a packaging region PA of the top cavity insert 40 is 
roughly surface-treated in accordance with a sanding method, a molding 
resin outwardly leaked through the runner (not shown) of the bottom mold 
serving as a resin feeding conduit and air vents (not shown) may be firmly 
attached to the rough surface of the top cavity insert 40 during the 
molding process. For this reason, it may be difficult to separate a molded 
PCB strip 100 from the mold. As a result, the quality of finally obtained 
packages and the process efficiency are degraded. 
Moreover, since the top cavity insert 40 has a configuration integral with 
the top center block 30, it is difficult to replace the top cavity insert 
40 when the top cavity insert 40 is damaged or abraded at its portion 
corresponding to the packaging region PA. In this case, there is also a 
problem in that the top mold should be completely replaced by a new one. 
This results in an increase in costs. 
FIG. 40 is an exploded perspective view of top and bottom molds 
constituting another conventional mold which has a manual transfer-type 
configuration. In this mold denoted by the reference character M, loading 
bars 330 are mounted on the bottom mold denoted by the reference numeral 
20. A cavity plate 350 provided with cavities for molding resin 
encapsulants is mounted on each loading bar 330. The top mold, which is 
denoted by the reference numeral 10, is coupled to the bottom mold 20. The 
top mold 10 is formed with packaging regions PA. 
FIG. 41 is an exploded perspective view of a PCB strip interposed between 
the loading bar and cavity plate in the conventional mold of FIG. 40 upon 
its molding. FIG. 42 is a lateral sectional view illustrating a loaded 
state of the PCB strip shown in FIG. 41. 
As shown in FIGS. 41 and 42, the cavity plate 350 defines 4 sides of resin 
encapsulant molding regions on the PCB strip 100. The loading bar 330 is 
mounted in a recess 12A of the bottom mold 20. A plurality of uniformly 
space pins 332 are arranged on the loading bar in such a manner that they 
are longitudinally aligned with one another. The PCB strip 100 and cavity 
plate 350 have holes 106 and 351 corresponding in position to the pins 
332, respectively. By such a configuration, the PCB strip 100 and cavity 
plate 350 can be sequentially mounted on the loading bar 330 in a manual 
manner. The basic configuration of this mold is identical to that of FIG. 
34. 
In the case of the conventional mold M having the configuration of FIG. 40, 
the loading bar 330, on which the PCB strip 100 and cavity plate 350 have 
been mounted, is manually mounted on the bottom mold 20. Thereafter, the 
bottom mold 20 is raised to be coupled to the top mold 10. In this state, 
a molding resin is supplied to the cavities defined in the cavity plate 
350 and then cured. Thus, molding of resin encapsulants having a desired 
shape is completed. 
In this case, however, it is difficult to manually mount the loading bar 
330 on the bottom mold 20 because the loading bar 330 is very heavy due to 
its thick plate type structure. Since the pins 332 are integral with the 
loading bar 330, they may be easily damaged upon manually mounting the 
loading bar 330 on the bottom mold 20. In this case, there is an 20 
inconvenience in that the loading bar 330 should be re-machined. 
Furthermore, a higher clamping pressure is required upon coupling the 
molds 10 and 20 because of the use of the cavity plate 350. This may 
result in a deformation of the loading bar 330. Accordingly, a degradation 
in the stability occurs in the molding of packages. 
Where the diameter of the holes 351 formed in the cavity plate 350 is 
unallowably larger than the diameter of the pins 332 inserted in the holes 
351, it is impossible to obtain an accurate setting position, thereby 
resulting in a degradation in the quality of finally produced packages. 
Where the pins 332 and holes 351 have substantially identical diameters in 
order to solve the above-mentioned problem, it may be necessary to 
forcibly insert the pins 332 in the holes 351. In this case, it is 
difficult to easily separate the cavity plate 350 from the loading bar 
330. Moreover, the pins 332 may be easily damaged. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above-mentioned problems 
involved in the prior art and has various objects, as follows. 
A first object of the invention is to provide a mold which includes a 
height adjusting member adapted to adjust the height of the top cavity 
insert of the top mold or the bottom cavity insert of the bottom mold in 
order to maintain an optimum clamping pressure between the top and bottom 
molds for a variety of PCB strips having a thickness deviation among 
different portions thereof or having various average thicknesses, upon 
molding resin encapsulants on those PCB strips, thereby achieving an 
improvement in the quality of finally produced packages while preventing a 
sweeping phenomenon. 
A second object of the invention is to provide a mold which includes a 
height adjusting member adapted to adjust the height of the top cavity 
insert of the top mold or the bottom cavity insert of the bottom mold, and 
an elastic member disposed between the height adjusting member and 
associated insert, in order to maintain an optimum and uniform clamping 
pressure between the top and bottom molds for a variety of PCB strips 
having a thickness deviation among different portions thereof or having 
various average thicknesses, upon molding resin encapsulants on those PCB 
strips, thereby achieving an improvement in the quality of finally 
produced packages while preventing a sweeping phenomenon of bonding wires 
electrically connecting a semiconductor chip to conductive traces. 
A third object of the invention is to provide a mold which has clamping 
regions having different heights at its top or bottom cavity insert for 
PCB strips having a thickness deviation among different portions thereof, 
in order to offset the thickness deviation of those PCB strips, so that an 
optimum and uniform clamping pressure is maintained between the top and 
bottom molds upon molding resin encapsulants on the PCB strips, thereby 
achieving an improvement in the quality of finally produced packages while 
preventing a sweeping phenomenon. 
A fourth object of the invention is to provide a mold which includes a top 
or bottom cavity insert configured in such a manner that the width and 
depth of air vents has an optimum ratio to the area and depth of cavities, 
thereby achieving an improvement in the quality of molded resin 
encapsulants on a PCB strip. 
A fifth object of the invention is to provide a mold which includes a 
cavity insert having a smooth surface at its portion except for the 
portions corresponding to packaging regions of the top or bottom cavities, 
namely, resin encapsulant molding regions, thereby achieving an 
improvement in the separability of a molded PCB strip from the mold after 
the molding and curing of resin encapsulants on the PCB strip and an 
improvement in the appearance of the molded resin encapsulants. 
A sixth object of the invention is to provide a manual transfer type mold 
which includes a detachable liner mounted to its bottom mold in order to 
maintain an optimum clamping pressure between the top and bottom molds for 
a variety of PCB strips having a thickness deviation among different 
portions thereof or having various average thicknesses, upon molding resin 
encapsulants on those PCB strips, thereby achieving an improvement in the 
quality of finally produced packages while preventing a sweeping 
phenomenon. 
A seventh object of the invention is to provide a manual transfer type mold 
which includes a loading bar having a longitudinally extending block at 
the upper surface thereof and a wide recess at the lower surface thereof, 
and a cavity plate provided with stopper holes at its opposite ends and 
adapted to ensure an accurate position setting, in order to reduce the 
weight of the loading bar, thereby achieving an improvement in the 
workability upon molding resin encapsulants on PCB strips while preventing 
a deformation of the loading bar. 
In accordance with one aspect, the present invention provides a mold for 
fabricating ball grid array semiconductor packages, the mold including a 
top mold and a bottom mold to mold resin encapsulants on portions of a 
printed circuit board (PCB) strip respectively including semiconductor 
chip mounting regions, the PCB strip being mounted with a plurality of 
semiconductor chips at the semiconductor chip mounting regions, 
respectively, and bonded with wires adapted to electrically connect 
respective circuit patterns of the semiconductor chips to conductive 
traces, wherein: the top mold comprises a top mold base provided at a 
lower surface thereof with a longitudinally extending recess, a top center 
block centrally disposed in the recess beneath the top mold base, a pair 
of detachable height adjusting members respectively disposed in the recess 
in opposite sides of the top center block, the height adjusting members 
having a flat plate shape, and a pair of top cavity inserts respectively 
disposed in the recess just beneath the height adjusting members; each of 
the top cavity inserts has a lower surface positioned at a higher level 
than flush lower surfaces of the top mold and the top center block, 
thereby forming a step having a desired height; the bottom mold comprises 
a bottom mold base provided at an upper surface thereof with a 
longitudinally extending recess, a bottom center block centrally disposed 
in the recess on the bottom mold base, and a pair of bottom cavity inserts 
respectively disposed in the recess in opposite sides of the bottom center 
block; the bottom center block has a pot adapted to melt a molding resin, 
and a runner adapted as an elongated conduit for feeding the melted resin, 
and each of the bottom cavity inserts is provided at an upper surface 
thereof with a plurality of concave portions and clamping regions 
respectively disposed around the concave portions to define the concave 
portions, each of the concave portions communicating with the runner at 
one of the corners thereof while having air vents at the remaining corners 
thereof; the clamping regions of the bottom cavity insert define, along 
with a lower surface of the top cavity insert, resin encapsulant molding 
cavities in which the semiconductor chips mounted on the PCB strip and 
electrically connected to the conductive traces are received, 
respectively, when the top and bottom molds are coupled to carry out a 
molding process; and each of the detachable height adjusting members has a 
thickness selected to provide the step defined between the lower surface 
of the top cavity insert and the lower surfaces of the top mold base and 
the top center block so that an optimum clamping pressure is applied to 
the PCB strip between the top and bottom molds in the molding process 
where the PCB strip has a thickness deviation among different portions 
thereof. 
In accordance with another aspect, the present invention provides a mold 
for fabricating ball grid array semiconductor packages, the mold including 
a top mold and a bottom mold to mold resin encapsulants on portions of a 
PCB strip respectively including semiconductor chip mounting regions, the 
PCB strip being mounted with a plurality of semiconductor chips at the 
semiconductor chip mounting regions, respectively, and bonded with wires 
adapted to electrically connect respective circuit patterns of the 
semiconductor chips to conductive traces, wherein: the top mold comprises 
a top mold base provided at a lower surface thereof with a longitudinally 
extending recess, a top center block centrally disposed in the recess 
beneath the top mold base, a pair of detachable height adjusting members 
respectively disposed in the recess in opposite sides of the top center 
block, the height adjusting members having a flat plate shape, and a pair 
of top cavity inserts respectively disposed in the recess just beneath the 
height adjusting members while being spaced from the height adjusting 
members, a pair of elastic members respectively disposed in spaces defined 
between the height adjusting members and the associated top cavity inserts 
by mounting members, and a plurality of clamping members adapted to mount 
the top cavity inserts to the top mold base in such a manner that the top 
cavity inserts are vertically slidable with respect to the top mold base; 
each of the top cavity inserts has a lower surface positioned at a higher 
level than lower surfaces of the top mold and the top center block, 
thereby forming a step having a desired height; the bottom mold comprises 
a bottom mold base provided at an upper surface thereof with a 
longitudinally extending recess, a bottom center block centrally disposed 
in the recess on the bottom mold base, and a pair of bottom cavity inserts 
respectively disposed in the recess in opposite sides of the bottom center 
block; the bottom center block has a pot adapted to melt a molding resin, 
and a runner adapted as an elongated conduit for feeding the melted resin, 
and each of the bottom cavity inserts is provided at an upper surface 
thereof with a plurality of concave portions and clamping regions 
respectively disposed around the concave portions to define the concave 
portions, each of the concave portions communicating with the runner at 
one of corners thereof while having air vents at the remaining corners 
thereof; the clamping regions of the bottom cavity insert define, along 
with a lower surface of the top cavity insert, resin encapsulant molding 
cavities in which the semiconductor chips mounted on the PCB strip and 
electrically connected to the conductive traces are received, 
respectively, when the top and bottom molds are coupled to carry out a 
molding process; and an optimum and uniform clamping pressure is applied 
to the PCB strip between the top and bottom molds in the molding process 
where the PCB strip has a thickness deviation among different portions 
thereof, by virtue of the step defined between the lower surface of each 
of the top cavity inserts and the lower surfaces of the top mold base and 
the top center block by the associated detachable height adjusting member, 
the clamping members adapted to mount the top cavity inserts to the top 
mold base in such a manner that the top cavity inserts are vertically 
slidable with respect to the top mold base, and the mounting and clamping 
members elastically supporting the top cavity inserts. 
In accordance with another aspect, the present invention provides a mold 
for fabricating ball grid array semiconductor packages, the mold including 
a top mold and a bottom mold to mold resin encapsulants on portions of a 
printed circuit board (PCB) strip respectively including semiconductor 
chip mounting regions, the PCB strip being mounted with a plurality of 
semiconductor chips at the semiconductor chip mounting regions, 
respectively, and bonded with wires adapted to electrically connect 
respective circuit patterns of the semiconductor chips to conductive 
traces, wherein: the mold comprises the top and bottom molds, loading bars 
for mounting PCB strips, and cavity plates for supporting the PCB strips 
in cooperation with the loading bars in such a manner that each of the PCB 
strips is interposed between the associated loading bar and cavity plate; 
the top mold comprises a top mold base provided at a lower surface thereof 
with a longitudinally extending recess, a top center block centrally 
disposed in the recess beneath the top mold base, and a pair of top cavity 
inserts respectively disposed in the recess in opposite sides of the top 
center block, each of the top cavity inserts having a plurality of 
packaging regions at a lower surface thereof; the bottom mold comprises a 
bottom mold base, a pot centrally disposed on the bottom mold base in such 
a manner that it extends longitudinally, the pot serving to melt a molding 
resin, and a runner adapted to feed the melted molding resin; each of the 
loading bars is mounted on the bottom mold base in opposite sides of the 
central portion of the bottom mold base extending in a longitudinal 
direction, and the loading bar is provided with at least one groove at one 
longitudinal edge portion of an upper surface thereof, on which a PCB 
strip is laid, a fixing pin upwardly protruded from a bottom surface of 
the groove and adapted to fix the PCB strip and the cavity plate laid on 
the PCB strip, and support blocks arranged along the longitudinal edge 
portion of the loading bar at portions of the loading bar except for the 
portion where the groove is disposed; each of the cavity plates has at 
least one hole adapted to receive the pin formed on the associated loading 
bar, and a plurality of cavity regions respectively having cavity openings 
for molding resin encapsulants, and each of the cavity regions has a 
runner for feeding the melted resin and air vents; and a plurality of 
cavities, in which resin encapsulants are molded, are defined by the upper 
surface of the PCB strip mounted on each of the loading bars, surfaces of 
the associated cavity plate defining the cavity openings, and the 
packaging regions of the associated top cavity insert, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is an exploded perspective view illustrating an automatic transfer 
type mold including top and bottom molds in accordance with a first 
embodiment of the present invention. In FIG. 1, the mold is denoted by the 
reference character M whereas the top and bottom molds are denoted by the 
reference numerals 10 and 20, respectively. As shown in FIG. 1, a pair of 
height adjusting members 50 are mounted on the top mold 10. Bottom cavity 
inserts 40A are mounted on the bottom mold 20. Each bottom cavity insert 
40A has concave portions 45 which serve as resin encapsulant molding 
regions. 
A top drive plate DP is mounted on the upper surface of the top mold 10. 
The top mold 10 also has a base 11 provided with a longitudinally 
extending recess 12 at the central portion of its lower surface. A top 
center block 30 is laid on the central portion of the recess 12. The 
height adjusting members 50 are laid on portions of the recess 12 
respectively disposed in opposite sides of the top center block 30. In the 
recess 12, a pair of top cavity inserts 40 are laid on the height 
adjusting members 50, respectively. In order to fix the top center block 
30 and top cavity inserts 40 to the top mold 10, end blocks EB are fixedly 
mounted to the lower surface of the base 11 at opposite ends of the top 
center block 30 and top cavity inserts 40 by means of clamping members B, 
respectively. 
FIG. 2 is a sectional view illustrating a coupled state of the top and 
bottom molds 10 and 20 in the automatic transfer type mold M whereas FIG. 
3 is a sectional view illustrating the top mold 10 shown in FIG. 2. 
As shown in FIGS. 2 and 3, a PCB strip 100, in which mounting of 
semiconductor chips 103 and bonding of wires 104 have been carried out, is 
interposed between the top and bottom molds 10 and 20 in such a manner 
that the semiconductor chips 103 are positioned within cavities CA defined 
between the top and bottom molds 10 and 20. As a melted resin is injected 
into the cavities CA and then cured, resin encapsulants are formed on the 
PCB strip 100. 
As apparent from the above description, the top mold 10 basically includes 
the base 11 provided at the lower surface thereof with the longitudinally 
extending recess 12, the top center block 30 disposed beneath the base 11 
at the central portion of the base 11, the height adjusting members 50 
respectively disposed in the recess 12 in opposite sides of the top center 
block 30, and the top cavity inserts 40 respectively disposed in the 
recess 12 just beneath the height adjusting members 50. 
Each top cavity insert 40 has a plurality of clamping holes 44 respectively 
corresponding to a plurality of through holes 11B formed in the base 11 
and a plurality of through holes 51A formed in the associated height 
adjusting member 50 so that it is firmly coupled to the base 11 along with 
the height adjusting member 50 by clamping members B1 extending through 
the clamping holes 44 and through holes 11B and 51A. The top drive plate 
DP is mounted on the top portion of the base 11 by means of a plurality of 
clamping members B. 
Similarly to the top mold 10, the bottom mold 20 includes a base 21 
provided at the upper surface thereof with a longitudinally extending 
recess 12A, and a bottom center block 30A extending upwardly from the 
central portion of the upper surface of the base 21. The bottom cavity 
inserts 40A, which are also included in the bottom mold 20, are disposed 
in the recess 12A in opposite sides of the bottom center block 30A, 
respectively. 
The bottom center block 30A of the bottom mold 20 has a pot (not shown) 
adapted to melt a resin, and a runner (not shown) adapted as an elongated 
conduit for feeding the melted resin. Each bottom cavity insert 40A 
disposed in the recess 12A in each side of the bottom center block 30A has 
a plurality of concave portions 45 at the upper surface thereof. 
FIG. 4 is an enlarged sectional view showing the portion D of FIG. 3. The 
top center block 30 centrally arranged in the recess 12 has a lower 
surface flush with the lower surface of the base 11 (best shown in FIG. 
3). As shown in FIG. 4, in opposite sides of the top center block 30, the 
top cavity inserts 40 and height adjusting members 50 having a thickness 
of t2 are arranged in an overlapped manner, respectively, so that the 
lower surface of each top cavity insert 40 is higher than the lower 
surface of the top center block 30 by a height t, thereby forming a step. 
The height t of the step is appropriately selected to apply an optimum 
clamping pressure to a PCB strip clamped between the top and bottom molds 
10 and 20. 
FIG. 5 is a perspective view of the height adjusting member 50 according to 
the first embodiment of the present invention. As shown in FIG. 5, the 
height adjusting member 50 is provided with a plurality of through holes 
51A. These through holes 51A are formed at positions respectively 
corresponding to those of the through holes 11B formed in the base 11 and 
clamping holes 44 formed in the associated top cavity insert 40. As 
mentioned above, the clamping members B1 extend through the associated 
through holes 51A, through holes 11B and clamping holes 44, respectively, 
to firmly couple each top cavity insert 40 to the base 11 along with the 
associated height adjusting member 50. 
In accordance with the illustrated embodiment of the present invention, a 
plurality of height adjusting members having a variety of thicknesses are 
prepared in order to select height adjusting members 50 having a thickness 
t2 capable of providing an optimum clamping pressure in a molding process, 
depending on the thickness t1 of a PCB strip 100 laid on the bottom mold 
20. 
Although the height adjusting members 50 have been described as being 
arranged in the top mold 10 in the illustrated case, they may be arranged 
in the bottom mold 20. 
Where the mold M including the height adjusting members 50 according to the 
first embodiment of the present invention is used, it is possible to 
maintain an optimum clamping pressure between the top and bottom molds 10 
and 20 for a variety of PCB strips having a thickness deviation among 
different portions thereof or having various average thicknesses, upon 
molding resin encapsulants on those PCB strips, thereby achieving an 
improvement in the quality of finally produced packages while preventing a 
sweeping phenomenon. This will be described in more detail. 
Since each top cavity insert 40 of the top mold 10 is mounted in such a 
manner that a step having an optimum height t is defined between the lower 
surface of the top cavity insert 40 and the lower surfaces of the base 11 
and top center block 30 by the associated height adjusting member 50, it 
is possible to select an optimum clamping pressure applied to a PCB strip 
100 between the coupled top and bottom molds 10 and 20. The height t of 
the step depends on the thickness of the PCB strip 100. By virtue of the 
application of such an optimum clamping pressure, it is possible to 
prevent the generation of cracks resulting from a deformation of the PCB 
strip 100 and the generation of a wire sweeping phenomenon such as a wire 
short circuit resulting from a deformation of bonding wires 104 
electrically connecting a semiconductor chip 103 to conductive traces 102 
of a circuit pattern. In addition, there is no phenomenon that air vents 
AV are partially or completely blocked. Accordingly, air existing in 
cavities CV can be easily vented through the air vents AV by a pressure 
generated upon filling the cavities CV with a molding resin to mold resin 
encapsulants 105. Therefore, it is possible to prevent a formation of 
voids or blisters in the resin encapsulants 105, thereby preventing a 
degradation in the quality of molded packages (FIGS. 17 and 21). 
FIG. 6 is a sectional view illustrating a mold having a configuration 
according to a second embodiment of the present invention. In FIG. 6, a 
coupled state of top and bottom molds 10 and 20 included in the mold M is 
shown. FIG. 7 is a sectional view illustrating the top mold 10 shown in 
FIG. 6. In this embodiment, constituting elements respectively 
corresponding to those in the first embodiment are denoted by the same 
reference numerals or characters. 
As shown in FIGS. 6 and 7, the top mold 10 basically includes a base 11 
provided at the lower surface thereof with the longitudinally extending 
recess 12, a top center block 30 disposed beneath the base 11 at the 
central portion of the base 11, height adjusting members 50 respectively 
disposed in the recess 12 in opposite sides of the top center block 30, 
and top cavity inserts 40 respectively disposed in the recess 12 just 
beneath the height adjusting members 50. Each height adjusting member 50 
has through holes 51 and 52. The top mold 10 also includes elastic members 
65 each disposed in a space S defined between the associated height 
adjusting member 50 and top cavity insert 40 and adapted to elastically 
support the top cavity insert 40, and a plurality of clamping members 81 
adapted to fix each top cavity insert 40 to the base 11. Each elastic 
member 65 is mounted to the associated top cavity insert 40 by means of 
mounting members 60. 
The head of each mounting member 60, which is provided with a bush 61 and 
washer 62, is received in an associated one of the through holes 51 formed 
in the associated height adjusting member 50 adjacent to the top center 
block 30. The mounting member 60 extends through an associated one of 
clamping holes 41 formed in the associated top cavity insert 40 and 
respectively corresponding to the through holes 51, so that it is 
threadedly coupled to the top cavity insert 40. 
Each clamping member 81 extends through a spacer 80 slidably fitted in an 
associated one of through holes 52 formed in the associated height 
adjusting member 50 adjacent to the base 11 and an associated one of holes 
13 formed in the base so that it is threadedly coupled to an associated 
one of the clamping holes 41 formed in the associated top cavity insert 
40. Thus, each clamping member 81 supports an associated one of the top 
cavity insert 40. A washer 82 is interposed between the head of each 
clamping member 81 and the upper surface of the base 11. 
Each elastic member 65, which is disposed in the space S defined between 
the associated height adjusting member 50 and top cavity insert 40, 
comprises an elastic means such as a disc spring. Each bush 61 is fitted 
in an associated one of the elastic members 65. Each mounting member 60 
extends through an associated one of the bushes 61 to mount an associated 
one of the elastic members 65 to the associated top cavity insert 40. Each 
washer 62 is interposed between the head of each mounting member 61 and 
the upper surface of the associated elastic member 65. 
Meanwhile, the bottom mold 20 includes a base 21 provided at the upper 
surface thereof with a longitudinally extending recess 21, and a bottom 
center block 30A disposed over the base 21 at the central portion of the 
base 21, and bottom cavity inserts 40A respectively disposed in the recess 
21 in opposite sides of the bottom center block 30A. Each bottom cavity 
insert 40A is provided at the upper surface thereof with a plurality of 
concave portions 45 serving as resin encapsulant molding regions. Each 
concave portion 45 has air vents AV. 
FIG. 8 is an enlarged sectional view showing the portion A of FIG. 7 
whereas FIG. 9 is an enlarged sectional view showing the portion B of FIG. 
7. As shown in FIGS. 7 and 8, each top cavity insert 40 is supported on 
the base 11 by the associated clamping members 81 in such a manner that it 
is upwardly slidable while being elastically supported by the associated 
mounting members 60 and elastic member 65. The lower surface of the top 
cavity insert 40 is higher than the lower surfaces of the top mold 10 and 
top center block 30 by a height t, thereby forming a step. By virtue of 
the step having a height t, an optimum clamping pressure is applied to a 
PCB strip clamped between the top and bottom molds 10 and 20. 
As in the first embodiment, the height t of the step can be appropriately 
selected to apply ant optimum clamping pressure to a PCB strip clamped 
between the top and bottom molds 10 and 20. However, the range of the step 
height selection in the second embodiment is wider than that in the first 
embodiment, because of the use of the elastic members 65. 
Now, the procedure of molding resin encapsulants on a PCB strip 100 using 
the mold M according to the second embodiment of the present invention 
will be described in conjunction with FIG. 6. 
When a PCB strip 100 is fed to the bottom mold 20, the bottom mold 20 is 
raised to be coupled to the upper mold 10. As the bottom mold 20 is 
coupled to the upper mold 10, the PCB strip 100 is depressed by an 
associated one of the top cavity inserts 40 of the upper mold 10. As the 
top cavity insert 40 clamps the PCB strip 100, it moves upwardly against 
the elastic force of the associated elastic member 65 by an appropriate 
distance. Thus, the clamping pressure applied to the PCB strip 100 is 
maintained in an optimum state. 
In accordance with the second embodiment of the present invention, 
accordingly, it is possible to maintain an optimum clamping pressure 
between the top and bottom molds 10 and 20 for a variety of PCB strips 
having various thicknesses in a relatively wide range, upon molding resin 
encapsulants on those PCB strips, by virtue of the elastic force of the 
elastic members 65. This will be described in more detail. 
When a PCB strip 100 laid on the bottom mold 20 is clamped between the top 
and bottom molds 10 and 20 as the top and bottom molds 10 and 20 are 
clamped to each other, the top cavity insert 40 moves upwardly against the 
elastic force of the associated elastic member 65 due to the thickness t1 
of the PCB strip 100. By virtue of the upward movement of the top cavity 
insert 40 along with the associated clamping it members 81 and spacers 80 
due to the thickness t1 of the PCB strip 100, the clamping pressure 
applied to the PCB strip 100 is maintained in an optimum state without 
being insufficient or excessive. 
Consequently, it is possible to prevent damage to the PCB strip 100 and a 
flash of the molding resin because the clamping pressure applied to the 
PCB strip 100 is maintained in an optimum state depending on the thickness 
of the PCB strip 100. 
In the mold configuration according to the second embodiment of the present 
invention, the portion of the top cavity insert 40 disposed beneath the 
elastic member 65 clamps portions of the PCB strip 100 disposed near 
runner gates. Since the portions of the PCB strip 100 have a thickness 
smaller than other portions of the PCB strip 100 (FIG. 15 and Table 2), 
such a thickness deviation of the PCB strip 100 can be effectively offset 
by the clamping effect. 
In addition, it is possible to easily carry out the molding for PCB strips 
100 having various thicknesses in a considerably wide range by selecting 
height adjusting members 50 having an appropriate thickness. As apparent 
from the above description, the height adjusting members 50 can be easily 
mounted and separated. 
FIG. 10 is a sectional view illustrating a modification of the second 
embodiment of the present invention. In this case, the height adjusting 
members 50 and elastic members 65 are installed in the bottom mold 20, as 
shown in FIG. 10. In this case, the clamping members 81 serve to fixedly 
mount the bottom cavity inserts 40A to the base 21 of the bottom mold 20. 
Since the remaining configurations are identical to those in the case of 
FIG. 6, no detailed description thereof will be made. 
Where the mold M including height adjusting members and elastic members in 
accordance with the second embodiment of the present invention is used, it 
is possible to maintain an optimum and uniform clamping pressure between 
the top and bottom molds for a variety of PCB strips having a thickness 
deviation among different portions thereof or having various average 
thicknesses, upon molding resin encapsulants on those PCB strips, thereby 
achieving an improvement in the quality of finally produced packages while 
preventing a sweeping phenomenon of bonding wires electrically connecting 
a semiconductor chip to conductive traces. 
FIG. 11 is an exploded perspective view illustrating a manual transfer type 
mold according to a third embodiment of the present invention. The mold M 
according to the third embodiment has the same basic configuration as that 
of FIG. 1 except that it includes clamping regions 213 having different 
heights to offset a thickness deviation among different portions of a PCB 
strip. Accordingly, no detailed description will be made for the basic 
configuration. In this embodiment, constituting elements respectively 
corresponding to those in the first embodiment are denoted by the same 
reference numerals or characters. 
Before describing the mold configuration according to the third embodiment 
in conjunction with FIGS. 12 and 13, a thickness deviation among different 
portions of a PCB strip 100 for BGA semiconductor packages will be 
described in conjunction with FIG. 14. As shown in FIG. 14, the PCB strip 
100, which has a multilayer structure, is provided with a plurality of 
molding regions (indicated by the dotted lines in FIG. 14). The regions a 
to h of the PCB strip 100 have different thicknesses because of, for 
example, a solder mask layer coated over the substrate of the PCB strip in 
such a manner that the thickness at both ends thereof is larger than that 
at the other portions. 
The following Table 2 shows the thicknesses of different portions of the 
PCB strip 100. 
TABLE 2 
__________________________________________________________________________ 
Thicknesses of Different Regions of PCB strip 
Unit: mm 
REGIONS 
NO. a b c d e f g h MIN 
MAX Avg 
__________________________________________________________________________ 
1 0.360 
0.350 
0.348 
0.348 
0.342 
0.341 
0.342 
0.342 
0.341 
0.360 
0.347 
2 0.351 
0.352 
0.344 
0.345 
0.342 
0.340 
0.341 
0.340 
0.340 
0.352 
0.344 
3 0.348 
0.347 
0.340 
0.345 
0.338 
0.339 
0.340 
0.340 
0.338 
0.348 
0.342 
4 0.340 
0.342 
0.330 
0.332 
0.330 
0.298 
0.331 
0.331 
0.298 
0.342 
0.329 
5 0.372 
0.358 
0.342 
0.345 
0.340 
0.340 
0.343 
0.341 
0.340 
0.358 
0.348 
6 0.352 
0.347 
0.343 
0.342 
0.340 
0.340 
0.340 
0.338 
0.338 
0.352 
0.343 
7 0.370 
0.362 
0.361 
0.355 
0.358 
0.350 
0.351 
0.352 
0.350 
0.370 
0.358 
8 0.360 
0.357 
0.352 
0.352 
0.349 
0.345 
0.346 
0.352 
0.345 
0.360 
0.351 
9 0.350 
0.353 
0.347 
0.345 
0.340 
0.341 
0.340 
0.340 
0.340 
0.353 
0.345 
10 0.360 
0.372 
0.360 
0.368 
0.358 
0.358 
0.358 
0.365 
0.358 
0.372 
0.363 
MIN 0.340 
0.342 
0.330 
0.332 
0.330 
0.298 
0.331 
0.331 
MAX 0.372 
0.372 
0.361 
0.368 
0.358 
0.358 
0.358 
0.365 
Avg 0.356 
0.354 
0.347 
0.348 
0.344 
0.339 
0.343 
0.344 
__________________________________________________________________________ 
As shown in Table 2, the PCB strip 100 has the greatest thickness at both 
end regions a and b thereof while having gradually reduced thicknesses at 
resin encapsulant molding regions (indicated by the dotted lines) at the 
end regions, namely, regions c and d facing respective degating regions D 
which are molding regions for surplus molding resin, at regions e and h 
disposed near the degating regions D respectively associated with the end 
resin encapsulant molding regions, at a region g facing a degating region 
D for the central resin encapsulant molding region, and at a runner region 
f. 
Accordingly, the PCB 100 has a great thickness at both end regions and 
regions facing degating regions D. 
FIG. 12 is a perspective view illustrating a bottom cavity insert 40A 
mounted in the bottom mold 20 according to the third embodiment of the 
present invention. As shown in FIG. 12, the bottom cavity insert 40A 
includes a base 211, a plurality of central and end concave portions 212 
and 212A longitudinally arranged on the upper surface of the base 211, and 
a plurality of peripheral clamping regions 213 defining the concave 
portions 212 and 212A. 
Each of the central and end concave portions 212 and 212A is provided at 
one corner thereof with a runner gate RG serving as a passage for a melted 
resin in a molding process. 25 Air vents AV are formed at the remaining 
three corners of each concave portion, respectively. 
Clamping regions 213 are formed along outer edges of each concave portion 
212 or 212A. Each clamping region 213 has a protrusion extending upwardly 
from the upper surface of the base 211 to a desired height. The clamping 
regions 213 associated with each concave portion 212 or 212A comprise a 
first clamping region 213A having the greatest height H1, a second 
clamping region 213B having a medium height H2, and a third clamping 
region 213C having the least height H3. The junction or boundary between 
adjacent clamping regions has a smooth gradient. That is, round portions 
RO are formed at the junction or boundaries of clamping regions, 
respectively. The bottom cavity insert 40A is also provided, at its upper 
surface portion adjacent to the opposite ends 211A, with a protrusion 213D 
having the same height as the first clamping regions 213A having the 
greatest height H1 and a protrusion 213E having the same height as the 
second clamping regions 213B having the medium height H2. 
FIG. 13 is a plan view illustrating the protruded state of the bottom 
cavity insert shown in FIG. 12. 
Now, the procedure of molding resin encapsulants on a PCB strip 100 having 
a thickness deviation among different portions thereof using the mold M 
including the bottom cavity insert 40A provided with the clamping regions 
213A to 213C having different heights in accordance with the third 
embodiment of the present invention will be described in conjunction with 
FIG. 13. 
When a PCB strip 100 is fed to the bottom mold 20, it is laid on the bottom 
cavity insert 40A in such a manner that the thinnest portions e, f and h 
thereof adjacent to the degating region D are positioned on the first 
clamping regions 213A (corresponding to the white portions disposed on the 
outside of the concave portions 212 and 212A) having the greatest height 
H1, that the regions c, g and d thereof facing the degating region D and 
having a thickness slightly larger than the thickness of the regions e, f, 
and h are positioned on the second clamping regions 213B (corresponding to 
the shaded portions) having the medium height H2, and that the thickest 
end regions a and b thereof are positioned on the third clamping regions 
213C (corresponding to the black portions) having the least height H3 and 
disposed on the outside of the end concave portions 212A. 
When the PCB strip 100 is laid on the bottom cavity insert 40A in the 
above-mentioned manner, the bottom mold 20 is raised to be coupled to the 
upper mold 10. As the bottom mold 20 is coupled to the upper mold 10, the 
PCB strip 100 is depressed by an associated one of the top cavity inserts 
40 of the upper mold 10. At this time, a uniform clamping pressure is 
applied over the whole portion of the PCB strip 100, which has a thickness 
deviation among different portions thereof, because the bottom cavity 
insert 40A has clamping regions 213A to 213C having different heights to 
offset the thickness deviation. 
In other words, the clamping regions 213A to 213C of the bottom cavity 
insert 40A have height deviations respectively corresponding to the 
thickness deviations of the PCB strip 100 so as to offset those thickness 
deviations. Accordingly, a uniform clamping pressure from the bottom 
cavity insert 40A is applied over the whole portion of the PCB strip 100. 
Since the bottom cavity insert 40A has the round portions RO at the 
boundaries of the clamping regions 213A to 213C, as mentioned above, it is 
possible to prevent the PCB strip 100 from being damaged during the 
application of the clamping pressure. 
Although the clamping regions having different heights to offset a 
thickness deviation among different portions of the PCB strip has been 
described as being provided at the bottom cavity insert of the bottom 
mold, the third embodiment of the present invention is not limited 
thereto. If necessary, such clamping regions may be provided at the top 
cavity insert of the top mold. 
Where the mold provided with clamping regions having different heights at 
its top or bottom cavity insert is used to mold PCB strips having a 
thickness deviation among different portions thereof, it is possible to 
offset the thickness deviation of those PCB strips, so that an optimum and 
uniform clamping pressure is maintained between the top and bottom molds 
upon molding resin encapsulants on the PCB strips, thereby achieving an 
improvement in the quality of finally produced packages while preventing a 
sweeping phenomenon. 
FIG. 15 is a perspective view illustrating a PCB strip 100 which has been 
mounted with semiconductor chips and molded with resin encapsulants 105 by 
use of the mold M according to 11 one of the first, second and third 
embodiments of the present invention. Individual regions of the PCB strip 
100 including molded resin encapsulants 105 are unit PCB's. As shown in 
the enlarged portion of FIG. 15, the PCB strip 100 has an increased 
thickness at its cut end due to burrs generated in a cutting process. 
FIG. 16 is a partially-enlarged plan view illustrating the portion C of 
FIG. 15 in a perspective manner. Referring to FIG. 16, it can be found 
that bonding wires 104, which electrically connect a semiconductor chip 
103 to conductive traces 102 of a circuit pattern, are maintained in a 
uniformly spaced state without any wire sweeping phenomenon because an 
optimum clamping pressure is applied to the PCB strip between the top and 
bottom molds upon molding resin encapsulants (regions indicated by the 
dotted line). 
Since a uniform and optimum clamping pressure is applied to the PCB strip 
100 between the bottom and top molds, it is possible to prevent the PCB 
strip 100 from being deformed. Accordingly, there is no blocking of air 
vents AV. As a result, air existing in cavities CV are smoothly and 
uniformly vented when a melted molding resin of high temperature and 
pressure is introduced into the cavities CV through runner gates RG. That 
is, a desirable resin filling profile is exhibited. Consequently, the 
quality of the finally produced package is superior (FIG. 22). 
FIG. 17 is a perspective view illustrating a bottom cavity insert 40A 
mounted in a bottom mold 20 included in a mold M according to a fourth 
embodiment of the present invention. In this embodiment, constituting 
elements respectively corresponding to those in the first embodiment are 
denoted by the same reference numerals or characters. As shown in FIG. 17, 
the bottom cavity insert 40A has a plurality of aligned concave portions 
45. Each of the concave portions 45 is provided at one corner thereof with 
a runner gate RG communicating with a bottom center block (not shown). Air 
vents AV are formed at the remaining three corners of each concave portion 
45, respectively. Since these configurations are the same as those in the 
above-mentioned embodiments of the present invention, no detailed 
description thereof will be made. 
FIGS. 18A and 18B are plan views respectively illustrating the bottom 
cavity insert 40A according to the fourth embodiment of the present 
invention whereas FIG. 19 is a cross-sectional view taken along the line 
E--E of FIG. 18A or 18B. 
The width W of the air vents AV respectively formed at the corners of each 
concave portion 45 except for the corner formed with the runner gate RG 
corresponds to about 3 to 20% of the width Wl of the concave portion 45. 
The depth D of each air vent AV corresponds to about 0.5 to 15% of the 
depth D1 of the concave portion 45. 
Air existing in cavities CV are smoothly and uniformly vented through the 
air vents AV when a melted molding resin is introduced into the cavities 
CV through the runner gate RG. Accordingly, a desirable resin filling 
profile is exhibited. That is, the quality of the finally produced resin 
encapsulants is superior, as shown in FIG. 22. 
Although the air vents AV have been described as being formed at the 
corners of each concave portion 45 included in the bottom mold 20, they 
may be formed at the top mold 10. 
Table 3 shows results obtained after resin encapsulants are molded using 
the mold which is provided with the air vents AV having the 
above-mentioned dimensions in accordance with the present invention. 
The mold M used to mold resin encapsulants has a step having a height of 
0.22 mm. 
TABLE 3 
______________________________________ 
Result of Molding Test Depending on Average Thickness of PCB Strip 
PCB Molded State of 
State of Strip 
Sam- Th. Resin Encapsulant Sweep- 
ple (mm) Void Flash 
Flister 
Deform 
Crack 
ing Results 
______________________________________ 
1 0.336 .largecircle. 
.DELTA. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
2 0.339 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
3 0.342 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
4 0.345 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
5 0.346 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
6 0.352 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
7 0.360 .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
Good 
8 0.363 X .largecircle. 
.DELTA. 
X .largecircle. 
.DELTA. 
Bad 
______________________________________ 
Not Generated: 
Unclear: 
Generated: X 
*Molding Condition for Resin Encapsulant 
Molding Resin Injection Pressure: 80 kg/cm.sup.2 
Molding Time: 10 to 15 sec. 
PCB Clamping Pressure: 200 to 250 kg/cm.sup.2 
As apparent from the above results, where the step between the lower 
surface of the top mold base and the lower surface of the top cavity 
insert 40 has a height t of 0.22 mm, molded states of resin encapsulants 
105 molded on integrated circuits respectively included in units of 
individual PCB strips 100 depend on the average thicknesses of those PCB 
strips 100. That is, a slight flash phenomenon occurs in the case of a PCB 
strip 100 of 0.336 mm having a great average thickness. In the case of a 
PCB strip of 0.363 mm, a generation of voids and a degradation in the 
quality due to a deformation of the PCB strip are experienced. Desirable 
molded states of resin encapsulants 105 are obtained for the remaining PCB 
strips 100 having thicknesses different from those of the above-mentioned 
samples. Accordingly, it is possible to improve the quality of finally 
produced BGA semiconductor packages while minimizing a production of 
degraded packages. 
As shown in FIG. 18B, a protrusion 40G may be inwardly protruded from one 
side surface of each runner gate RG formed in the bottom cavity insert 
40A. The protrusion 40G serves to prevent a molding resin from being 
leaked from a runner R when the molding resin fills a cavity under 
pressure. 
FIG. 20 is a schematic view illustrating a desirable resin filling profile 
exhibited after molding a resin encapsulant by use of the mold according 
to the fourth embodiment of the present invention. In the mold according 
to the fourth embodiment, air existing in cavities CV is smoothly and 
uniformly vented when a melted molding resin is introduced under pressure 
into the cavities CV through runner gates RG. That is, a desirable resin 
filling profile is exhibited, as shown in FIG. 20. 
Thus, in accordance with the fourth embodiment of the present invention, it 
is possible to achieve an improvement in the quality of resin encapsulants 
molded on PCB strips by using a mold including a top or bottom cavity 
insert having air vents configured to have a width and a depth 
appropriately determined with regard to the area and depth of the cavity. 
FIG. 21 is an exploded perspective view illustrating a manual transfer type 
mold according to a fifth embodiment of the present invention. In this 
embodiment, constituting elements respectively corresponding to those in 
the first embodiment are denoted by the same reference numerals or 
characters. The mold M according to the fifth embodiment includes a bottom 
mold 20 and a top mold 10 which are upwardly and downwardly movable with 
respect to each other. 
Runners RN are arranged on the upper surface of the bottom mold 20. A 
molding resin passes through each runner RN. Loading bars 330 are mounted 
on the upper surface of the bottom mold 20. 
As shown in the bottom view of FIG. 22 and the sectional view of FIG. 23, 
the top mold 10, which is disposed above the bottom mold 20, includes a 
base 11, and a top center block 30 arranged at the central portion of the 
base 11 and provided with a pot PT. A plurality of top cavity inserts 40 
are arranged in opposite sides of the top center block 30. Each top cavity 
insert 40 has concave portions 45 each having a rough surface formed by a 
discharge treatment process. Each top cavity insert 40 has a smooth 
surface formed by a polishing process at portions thereof other than the 
concave portion 45. A plurality of blocks BL are mounted to the base 11 on 
the outside of the top cavity inserts 40. 
In accordance with the fifth embodiment of the present invention, as shown 
in FIG. 21, a PCB strip 100 and a cavity plate 350 are sequentially laid 
on each loading bar 330. The resulting assembly is fixedly mounted to the 
upper surface of the bottom mold 20. 
When the bottom mold 20 is raised to the top mold 10 after the 
above-mentioned mounting procedure, the PCB strip 100 and cavity plate 350 
are clamped between the top and 20 bottom molds 10 and 20. At the same 
time, a molding resin from the pot PT is supplied to packaging regions PA 
of the cavity plate 350 via each runner RN, so that resin encapsulants are 
molded on the PCB strip 100. After the resin encapsulants are cured, the 
bottom mold 20 moves downwardly to 25 separate the molded PCB strip 100 
therefrom. Thus, the resin encapsulants of the PCB strip 100 are separated 
from the packaging regions PA of the associated top cavity insert 40 
included in the top mold 10. 
Since each top cavity insert 40 has a smooth surface formed by the 
polishing process at portions thereof other than the portions 
corresponding to the packaging regions PA, a surplus cured resin leaked 
from each runner RN and air vents AV can be easily separated from the top 
cavity insert 40. Accordingly, an improvement in the workability is 
achieved in the package molding process. 
Where the top cavity insert 40 has damaged or abraded packaging regions PA, 
it should be replaced by a new one. This replacement is easily achieved 
because the damaged or abraded top cavity insert 40 can be easily 
separated from the base 11 of the top mold 10 by virtue of the use of 
individually separable blocks BL. 
As apparent from the above description, where the mold of the fifth 
embodiment is used, which includes cavity inserts each having a smooth 
surface formed by the polishing process at portions thereof other than the 
portions corresponding to the packaging regions, it is possible to achieve 
an easy separation of the top and bottom molds after molding resin 
encapsulants on PCB strips, thereby achieving an improvement in the 
workability and an improvement in the appearance of molded products. 
FIG. 24 is an exploded perspective view illustrating a manual transfer type 
mold M including top and bottom molds 10 and 20 in accordance with a sixth 
embodiment of the present invention. FIG. 25 is a sectional view 
illustrating a coupled state of the top and bottom molds 10 and 20 shown 
in FIG. 24. The mold of the sixth embodiment has the same basic 
configuration as that of the fifth embodiment shown in FIG. 21, except 
that liners 320 having a desired thickness are used to control the height 
of molded resin encapsulants. Accordingly, only the configuration of the 
sixth embodiment different from that of the fifth embodiment will be 
described. In this embodiment, constituting elements respectively 
corresponding to those in the fifth embodiment are denoted by the same 
reference numerals or characters. 
The base of the bottom mold 20 is provided at its upper surface with 
longitudinally extending recesses 310, as shown in FIGS. 24 and 25. Liners 
320 are arranged on the bottom surface of each recess 310. A loading bar 
330 is laid on the liners 320 in each recess 310. PCB strips 100 and 
cavity plates 350 are sequentially laid on the loading bar 330. 
Where the above-mentioned liners 200 are used in the mold M, it is possible 
to control the height of resin encapsulants molded on a PCB strip, in 
which mounting of semiconductor chips and bonding of wires have been 
carried out. It is also possible to maintain an optimum clamping pressure 
between the top and bottom molds 10 and 20 for a variety of PCB strips 
having various average thicknesses. In order to offset a thickness 
deviation among different portions of a PCB strip, each liner 320 may have 
a thickness deviation corresponding to the thickness deviation of the PCB 
strip. In this case, a uniform clamping pressure can be applied over the 
whole portion of the PCB strip 100 between the top and bottom mold 10 and 
20. 
The above-mentioned control for the height of molded resin encapsulants is 
achieved by preparing a plurality of liners having a variety of 
thicknesses and appropriately selecting a desired one of the prepared 
liners capable of molding resin encapsulants having a desired thickness. 
That is, liners 320, which have a thickness meeting a desired is thickness 
of resin encapsulants to be molded, are first mounted in the bottom mold 
20. On the liners 320, the loading bar 330, PCB strips 100 and cavity 
plates 350 are sequentially loaded. In this state, the bottom mold 20 is 
raised to be coupled to the top mold 10. A molding resin is then supplied 
to cavities, thereby forming resin encapsulants. After curing the resin 
encapsulants, the packaging process is completed. 
Since it is possible not only to easily adjust the height of molded 
packages by the use of the liners 320, but also to easily select liners 
320 having a desired thickness depending on a desired thickness of resin 
encapsulants to be molded, an improvement in the workability in the 
molding process and an improvement in the quality of molded PCB strips are 
obtained. 
Where the manual transfer type mold, which includes detachable liners 
mounted to its bottom mold in accordance with the sixth embodiment of the 
present invention, is used, it is possible to maintain an optimum clamping 
pressure between the top and bottom molds for a variety of PCB strips 
having a thickness deviation among different portions thereof or having 
various average thicknesses, upon molding resin encapsulants on those PCB 
strips, thereby achieving an improvement in the workability and an 
improvement in the quality of finally produced packages while preventing a 
sweeping phenomenon. 
FIG. 26 is an exploded perspective view illustrating a manual transfer type 
mold M including top and bottom molds 10 and 20 in accordance with a 
seventh embodiment of the present invention. FIG. 32 is a sectional view 
illustrating a coupled state of the top and bottom molds 10 and 20 shown 
in FIG. 26. Since the basic configuration of the mold according to the 
seventh embodiment is identical to that according to the sixth embodiment, 
no detailed description thereof will be made. 
FIG. 27 is an exploded perspective view illustrating a loading bar 330 
mounted on the bottom mold 20, a chip-mounted and wire-bonded PCB strip 
100 to be molded, and a cavity plate 350 laid on the PCB strip 100. FIGS. 
28 and 29 are lateral and longitudinal sectional views respectively 
illustrating a loaded state of the PCB strip 100 shown in FIG. 27. 
As shown in FIG. 27, the loading bar 330 is provided with at least one 
groove 333 at its upper surface on which a PCB strip 100 is laid. In the 
illustrated case, a plurality of grooves 333 are longitudinally arranged 
along one longitudinal edge of the loading bar 330. A fixing pin 332 is 
upwardly protruded from each groove 333 in order to fix the PCB strip 100 
and cavity plate 350. A plurality of support blocks 335 are provided along 
the longitudinal edge of the loading bar 330 at portions of the loading 
bar 330 except for the portions where the grooves 333 is disposed. The 
support blocks 335 serve to guide and support the PCB strip 100. The 
loading bar 330 is also provided at its lower surface with a plurality of 
recesses 334. A pair of stoppers 331 are provided at opposite end portions 
of the upper surface of the loading bar 330. 
As shown in FIG. 31, the PCB strip 100 has a plurality of holes 106 adapted 
to receive the pins 332 of the loading bar 330. In the molding process, 
the PCB strip 100, in which mounting of semiconductor chips and bonding of 
wires have been carried out, is loaded on the loading bar 330 in such a 
manner that its holes 106 receive the associated pins 332 of the loading 
bar 330, respectively. In this state, the loading bar 330 is fixedly 
mounted in a manual manner on the bottom mold 20 in which a liner 320 has 
been mounted. 
After mounting the loading bar 330, the cavity plate 350 is laid on the PCB 
strip 100. In this state, the bottom mold 20 is raised to be coupled to 
the top mold 10. 
Since the loading bar 330 has a plurality of recesses 334, it has a reduced 
weight while having a function of distributing a clamping pressure applied 
thereto. Accordingly, it is possible to achieve an improvement in 
workability while preventing a deformation of the loading bar 330. 
Since the pins 332, which are adapted to support the PCB strip 100, are 
formed on the bottom surfaces of the grooves 333 of the loading bar 330 
between adjacent blocks 335, respectively, it is possible to effectively 
prevent the pins 332 from being damaged. Although the pins 332 are 
partially damaged, their replacement can be easily carried out. 
Accordingly, the workability of the loading bar 330 is improved in 
accordance with the seventh embodiment of the present invention. 
FIG. 30 is a plan view illustrating the mounted states of loading bars 330, 
PCB strips 100 and cavity plates 350 on the bottom mold 20 in accordance 
with the seventh embodiment of the present invention. As shown in FIG. 30, 
a pair of stoppers 331 are provided at the opposite ends of each loading 
bar 330. Each cavity plate 350 has stopper grooves 352 respectively 
corresponding to the stoppers 331 at the opposite ends thereof. The cavity 
plate 350 also has a plurality of cavity regions 353 respectively having 
cavity openings corresponding to the pins 332 formed at one longitudinal 
edge portion of the loading bar 330. The cavity plate 350 is also provided 
with holes 351 respectively adapted to receive the pins 332. The holes 351 
are arranged along one longitudinal edge of the cavity plate 350. A runner 
R is formed at one corner of each cavity region 353 of the cavity plate 
350. Air vents AV are formed at the remaining corners of each cavity 
region 353. 
In the above-mentioned configuration, a PCB strip 100 is laid on the 
loading bar 331 in such a manner that the pins 331 of the loading bar 330 
extend upwardly through the holes 106 of the PCB strip 100. The cavity 
plate 350 is then laid on the PCB strip 100 in such a manner that the pins 
331 of the loading bar 330 are received in the holes 351 of the cavity 
plate 350. In this state, the loading bar 330 is fixedly mounted to the 
bottom mold 20. Thereafter, the bottom mold 20 is raised to be coupled to 
the top mold 10. In this state, a molding resin is supplied to the cavity 
regions 353 through the runners R and then cured. Thus, molding of resin 
encapsulants having a desired shape is completed. 
The holes 351 of the cavity plate 350 have a diameter slightly larger than 
the diameter of the pins 332 of the loading bar 330. Since the stopper 
grooves 352 formed at the opposite ends of the cavity plate 350 are 
engaged with the stoppers 331 formed at the opposite ends of the loading 
bar 330, the cavity plate 350 is firmly supported without any movement 
during the molding of packages. 
Where the mold of the seventh embodiment, which includes a loading bar 
having longitudinally-extending blocks at the upper surface thereof and 
wide recesses at the lower surface thereof, and a cavity plate provided 
with stopper grooves at its opposite ends and adapted to ensure an 
accurate position setting, is used, it is possible to reduce the weight of 
the loading bar, thereby achieving an improvement in the workability upon 
molding resin encapsulants on PCB strips while preventing a deformation of 
the loading bar. 
As apparent from the above description, the present invention provides an 
automatic or manual transfer type mold which includes a height adjusting 
member adapted to adjust the height of the top cavity insert of the top 
mold or the bottom cavity insert of the bottom mold, an elastic member 
disposed between the height adjusting member and associated insert, 
clamping regions of different heights formed at its top or bottom cavity 
insert, or air vents having a width and depth of an optimum ratio to the 
area and depth of cavities. Accordingly, it is possible to maintain an 
optimum and uniform clamping pressure between the top and bottom molds for 
a variety of PCB strips having a thickness deviation among different 
portions thereof or having various average thicknesses, upon molding resin 
encapsulants on those PCB strips, thereby achieving an improvement in the 
quality of finally produced packages while preventing a sweeping 
phenomenon of bonding wires electrically connecting a semiconductor chip 
to conductive traces. 
Although the preferred embodiments of the invention have been disclosed for 
illustrative purposes, those skilled in the art will appreciate that 
various modifications, additions and substitutions are possible, without 
departing from the scope and spirit of the invention as disclosed in the 
accompanying claims.