Socket for inspection of semiconductor device

A socket for the inspection of semiconductor devices is disclosed which has laterally extended leads. The device is mounted in a mounting seat of the socket body and results in improvement of the inspection process because difficult steps such as soldering can be omitted. The socket is composed of a socket body which is mountable on a circuit board having a mounting seat therefor, a lead frame intervening between the socket body and the circuit board and an anisotropically electroconductive elastic connector sheet.

BACKGROUND OF THE INVENTION 
The present invention relates to a socket for inspection of a semiconductor 
device or, more particularly, to a socket for inspection of, in 
particular, a surface-mountable semiconductor package having a plurality 
of leads on the side surfaces such as QFPs (quad flat packages), SOPs 
(small outline packages), PLCCs (plastic leaded chip carriers) and LCCs 
(leadless chip carriers). 
In conducting a burn-in test of semiconductor packages, it is conventional 
to employ an IC socket for electrical connection between the electrode 
terminals of the semiconductor package and the electrode terminals of the 
testing circuit board. An IC socket for such a purpose of a known type 
comprises a socket body provided with a mounting seat to which a 
semiconductor package is mountable, a plurality of leads or pins fixed to 
the mounting seat of which the electrode terminals are connected to the 
side surfaces and bottom surfaces of the socket body with lead wires and a 
covering member pivotally rotatable up and down to open or close the upper 
opening of the mounting seat. 
While the above mentioned covering member serves, when the covering member 
is brought into a position to close the upper opening of the mounting 
seat, to press down the semiconductor package mounted in the mounting seat 
so as to bring the electrode terminals of the semiconductor package and 
the leads or pins of the socket appearing inside of the mounting seat into 
a press-contacting state, it is usual that the covering member is provided 
on the lower surface thereof with a resilient cushioning member utilizing 
a rubber pad or spring so as to ensure uniformity of the contacting 
pressure between the above mentioned contact points. The IC socket of this 
type is mounted on a circuit board by soldering the leads to the electrode 
terminals of the circuit board, when the leads are provided on the side 
surfaces of the socket body, or by inserting the pins through the 
through-holes in the circuit board, when pins are provided on the bottom 
surface of the socket body. 
The above described conventional IC socket has disadvantages that, since a 
plurality of electrode terminals must be provided on the mounting seat of 
the socket body and a plurality of leads or pins must be provided on the 
outer surface of the socket body, the number of necessary parts is so 
large and the assembling work is accordingly very troublesome. 
Conventional IC sockets of this type have problems that soldering is always 
involved in the assembling work on a circuit board so that the number of 
process steps is increased so many and, in particular, when pins are to be 
provided, through-holes must be formed in the circuit board so that the 
design of the circuit board is complicated correspondingly. 
SUMMARY OF THE INVENTION 
The present invention has an object, in view of the above described 
problems in the prior art sockets, to provide an improved socket for 
inspection of semiconductor devices having a simple structure to be 
assembled from a relatively small number of parts as well as excellent 
high-frequency characteristics and capable of giving a great freedom to 
the design of circuit boards. 
Thus, the present invention provides a socket for inspection of a 
semiconductor device or, in particular, for inspection of a semiconductor 
device having leads or electrode terminals on the outer surface of the 
body of the device by electrically connecting the leads or electrode 
terminals to the electrode terminals of a circuit board, which comprises: 
(a) a socket body mountable on the circuit board by positioning having a 
mounting seat for the body of the semiconductor device in a freely 
demountable fashion; 
(b) a lead frame intervening between the socket body and the circuit board 
having contacting shoes extended out of the surface facing the circuit 
board in the mounting seat of the socket body, the contacting shoes being 
brought into contact, when the semiconductor device is mounted on the 
mounting seat, with the leads or electrode terminals of the semiconductor 
device; and 
(c) an anisotropically electroconductive elastic connector sheet interposed 
between the lead frame and the circuit board to be in contact with the 
electrode terminals of the circuit board on one surface and with the 
contacting points of the contacting shoes of the lead frame on the other 
surface. 
In particular, the above mentioned anisotropically electroconductive 
elastic connector sheet is a sheet body consisting of a matrix of a 
rubbery elastomer sheet and a multiplicity of electroconductive 
filamentous bodies embedded in parallel each to the others in and 
penetrating the matrix sheet from one surface to the other. Preferably, 
the rubbery elastomer has a hardness of 20.degree. H to 60.degree. H 
according to JIS K 6301 for the type A rubber hardness and the metallic 
filament has a volume resistivity not exceeding 10.sup.-1 ohm.cm and has a 
diameter in the range from 20 to 90 .mu.m. These metallic filaments are 
embedded in the insulating matrix sheet keeping a distance of 10 to 125 
.mu.m each from the adjacent ones and each filament penetrates the matrix 
sheet in an inclined direction with an offset within the plane of the 
sheet not exceeding a half of the thickness of the matrix sheet. 
Further, the above mentioned lead frame is a flexible circuit board made 
from a base film of an insulating resin having patterning on one surface. 
The above mentioned contacting shoes of the lead frame are each formed from 
a metallic material having resilience such as phosphor bronze and 
beryllium copper and capable of being resiliently bent in an arched 
configuration inside of the mounting seat. 
Though optional, the contacting point of the contacting shoe of the lead 
frame has a roughened surface or sharpened points so as to be able to 
scratch off a surface film on the contacting surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As is described above, the socket for inspection of semiconductor devices 
provided by the invention comprises, as the essential parts, a socket body 
as the element (a), a lead frame as the element (b) and an elastic 
connector sheet as the element (c) intervening between the elements (a) 
and (b). The inventive socket is suitable for inspection of various types 
of semiconductor packages such as QFPs, SOPs, PLCCs and LCCs, in 
particular, having leads or electrode terminals on the side surfaces of 
the device body. 
In the following, each element of the inventive socket is described in 
detail by making reference to the accompanying drawing, where necessary. 
The socket body 30 serves to mount a semiconductor device with exact 
positioning and is employed by repeating mounting and demounting of 
semiconductor devices 10 so many times that the socket body 30 should have 
high durability both in the material and in the design. The socket body 30 
is formed from a synthetic resin having good surface lubricity and capable 
of withstanding hard working environmental conditions within a temperature 
range from -60 to +150.degree. C. such as epoxy resins, acrylic resins, 
polyester resins, polyphenylene sulfide resins, polyether sulfone resins 
and polyether imide resins. The socket body can be shaped by injection 
molding of these resins or by mechanical working of a resin block. Since 
the socket body 30 is mounted on a circuit board with exact positioning, 
it is preferable that the socket body 30 is provided with a positioning 
means such as positioning pins 33, by means of which the socket body 30 is 
freely mountable on and demountable from the circuit board 20. The 
mounting seat 31 of the socket body 30 is an openwork or cavity having a 
form and dimensions just to fit the molded part or mounting substrate of 
the body 11 of the semiconductor package 10, if necessary, with a 
positioning means for the semiconductor package. 
The socket body 30 is accompanied, if necessary, by a presser member 60 and 
a covering member 70. The presser member 60 has such a structure as to 
press and urge the semiconductor package 10 or the leads thereof in such a 
direction as to establish contacting of the leads 12 and the contacting 
shoes 42 of the lead frame 40 by means of its body weight per se or by 
means of separately provided spring or rubber members. The covering member 
70 has such a structure as to be pivotally rotatable around a hinge along 
a side line of the socket body 30 and to be fixedly engageable with the 
socket body 30 or, when the covering member 70 is separable from the 
socket body 30, as to be fixedly engageable with the socket body 30 with 
claws. The covering member 70 can be shaped from the same synthetic resin 
as that for the socket body 30. The covering body 70 is assembled to the 
socket body 30 by means of a resilient means such as a spring in such a 
fashion as to be able to directly press down the semiconductor package 10, 
to indirectly press down the semiconductor package 10 by means of a rubber 
pad bonded to the lower surface of the covering member 70 or to press down 
the semiconductor package from above the covering member 70 so that the 
leads 12 of the semiconductor package 10 and the contacting shoes 42 of 
the lead frame 40 are brought into a contacting condition under an 
appropriate contacting load. 
The lead frame 40 is formed from a base sheet or plate of a synthetic 
resin, on one surface of which a plurality of contacting shoes 42 are 
formed to be exposed. The contacting shoes 42 are extended into the 
mounting seat 31 of the socket body 30, preferably, in an archwise bent 
form. As a particular embodiment, the lead frame 40 can be a flexible 
board having contacting shoes 42 of a metal of good electric conductivity 
such as copper integrally patterned on one surface of a base sheet of a 
synthetic resin. The lead frame 40 can be shaped from the same synthetic 
resins as the socket body 30 since the requirements therefor are 
approximately identical with those for the socket body 30. The contacting 
shoes 42 of the lead frame 40 each have a dimensions of, for example, 0.15 
mm thickness and 0.2 mm width and shaped from a resilient metallic 
material suitable for springs such as phosphor bronze and beryllium 
copper. 
Though optional, an electroconductive layer 43 is formed on the surface of 
the base sheet of the lead frame 40 opposite to the contacting shoes 42 
and the electroconductive layer 43 is grounded so as to exhibit an effect 
of shielding against external electromagnetic waves. Further, the 
electroconductive layer 43 is connected to the power source line via a 
chip capacitor so as to reduce the influences by the fluctuation of the 
power source voltage and to facilitate setting of the impedance. As a 
particular embodiment, the impedance of the lead frame 40 is set at about 
50 ohm relative to the high frequency signals for inspection. The 
contacting shoes 42 are preferably provided with a plating layer of gold 
or silver. For example, an underplating layer of nickel having a thickness 
of 0.5 to 3 .mu.m is first formed on the contacting shoes 42 followed by 
overplating of gold in a thickness of 0.05 to 5 .mu.m. Further, the 
contacting surface of the contacting shoes 42 is roughened by sandblasting 
or provided with sharp-pointed protrusions so that the oxidized surface 
film on the leads 12 of the semiconductor package 10 can be broken by 
scratching with this surface film breaking means. 
The anisotropically electroconductive elastic connector sheet 50 is a 
composite body consisting of a matrix sheet 51 of a polymeric material 
having elasticity such as silicone rubbers, elastic thermosetting resins, 
e.g., epoxy resins, synthetic rubbers and thermoplastic resins, e.g., 
polyethylene resins, polyurethane resins, ABS resins and plasticized 
polyvinyl chloride resins, and fine metallic filaments 52 embedded in 
parallel each to the others in the matrix sheet 51 penetrating the matrix 
sheet 51t from one surface to the other. 
The matrix sheet 51 has a thickness in the range from 0.3 to 2.0 mm and a 
volume resistivity of at least 10.sup.12 ohm.multidot.cm. The elastic 
polymer forming the matrix sheet 51 of the connector 50 has a type A 
hardness in the range from 20 to 60.degree. H or, preferably, from 30 to 
60.degree. H specified in JIS K 6301. The fine metallic filament 52 has a 
diameter in the range from 20 to 90 .mu.m or, preferably, from 20 to 70 
.mu.m and the metallic material forming the filaments 52 should have a 
volume resistivity not increasing 10.sup.-1 ohm.multidot.cm. The 
distribution density of the metallic filaments 52 embedded in parallel in 
the matrix sheet 51 is in the range from 70 to 1000 filaments or, 
preferably, from 100 to 1000 filaments per mm.sup.2 of the surface area of 
the matrix sheet 51 keeping a distance of 10 to 125 .mu.m each from the 
adjacent filaments. The end portions of each of the metallic filaments 52 
should be protruded out of the surface of the matrix sheet 51 by 5 to 50 
.mu.m or, preferably, by 5 to 30 .mu.m. Further, each of the metallic 
filaments 52 has a running direction perpendicular to the surface of the 
matrix sheet 51 but can be inclined with an offset x (see FIG. 7) within 
the plane of the sheet surface not exceeding a half of the thickness of 
the matrix sheet 51. 
As is described above, the inventive socket for inspection of semiconductor 
devices comprises a socket body 30 and a lead frame 40 mounted on a 
circuit board 20 with exact positioning by means of positioning pins 33 
and the like with intervention of an anisotropically electroconductive 
elastic connector sheet 50 between the contacting shoes 42 of the lead 
frame 40 and the electrode terminals 21 on the circuit board. Accordingly, 
the socket has a simple structure consisting of a small number of parts 
and can be assembled without necessitating soldering or other troublesome 
means and further, through-holes or other openworks need not be formed in 
the circuit board 20 so as to afford a large freedom in the design of the 
circuit board 20. 
In conducting inspection of a semiconductor package 10 by using the socket 
of the invention, the semiconductor package 10 is mounted on the mounting 
seat 31 of the socket body 30 by exact positioning so that the electrode 
terminals or leads 12 of the semiconductor package 10 are brought into 
electric conduction by contacting with the contacting shoes 42 of the lead 
frame 40 while the contacting shoes 42 are electrically connected to the 
electrode terminals 21 on the circuit board 20 through the elastic 
connector sheet 50. Namely, each electrode terminal 12 of the 
semiconductor package 10 is in contact with the contacting shoe 42 of the 
lead frame 40 with resilience to cause arch-wise bending of the contacting 
shoe 42 to establish electric conduction between the electrode terminals 
12 of the semiconductor package 10 and the contacting shoes 42 of the lead 
frame 40 which in turn is in electric conduction with the metallic 
filaments 52 of the connector sheet 50 which are in contact with the 
electrode terminals 21 on the circuit board 20. It is noted that, when the 
running direction of the metallic filaments 52 in the matrix sheet 51 of 
the connector sheet 50 is not perpendicular to the surface of the sheet 
but is inclined by an offset x, the position of the electrode terminals 12 
of the semiconductor package 10 and the position of the electrode 
terminals 21 on the circuit board 20 are displaced each from the other by 
a distance corresponding to the offset x. 
In an embodiment in which the lead frame 40 is in the form of a flexible 
circuit board, the lead frame 40 can be designed by utilizing the 
versatile designing rules undertaken for flexible circuit boards so that 
excellent high frequency characteristics can be accomplished. 
Advantages are obtained by using contacting shoes 42 of the lead frame 40 
made from a resilient copper-based alloy that very reliable electric 
conduction can be obtained between the contacting shoes 42 and the leads 
12 of the semiconductor package 10 along with excellent durability. 
When each contacting shoe 42 of the lead frame 40 is provided on the 
contacting point thereof with a surface film-breaking means mentioned 
above, the electric conduction between the contacting shoes 42 and the 
leads of the semiconductor package 10 can be more reliable because, even 
when the contacting surface of the leads 12 is covered with an oxidized 
surface film, the surface film can be efficiently destroyed or removed. 
Further, the above described requirements for the anisotropically 
electroconductive elastic connector sheet 50 are important in order to 
ensure reliable electric conduction between the electrode terminals 12 of 
the semiconductor package 10 and the lead frame 40 in relation to an 
adequate elasticity of the sheet 50 and excellent durability. In addition, 
a possibility of an advantage can be obtained that, when two or more 
terminal electrodes 21 on the circuit board 20 could be connected to a 
single contacting shoe 42 of the lead frame by using a suitable connector 
sheet 50, inspection of the semiconductor package 10 could be performed by 
utilizing testing signals of different modes through different sets of the 
electrode terminals 21 on the circuit board 20 successively so that the 
efficiency of the inspection process can be greatly improved. 
In the following, the socket of the invention for inspection of a 
semiconductor device is described in more detail by making reference 
particularly to the accompanying drawing. 
FIG. 1 is a perspective view of the inventive socket consisting of a socket 
body 30, lead frame 40 and connector sheet (not shown in this figure) as 
disassembled into parts with addition of a circuit board 20, semiconductor 
package 10 of the QFP type having a square plan, a covering member 70 and 
a presser member 60 intervening between the semiconductor package 10 and 
the covering member 70. As is usual, the semiconductor package 10 has a 
molded body 11 in the form of a square plate and arrays of a plurality of 
leads 12 extended out of the four side surfaces of the molded body 11 as 
arranged at a regular pitch. Each of the leads 12 has a configuration bent 
something like an arch. 
The circuit board 20 is provided on the surface with groups of electrode 
terminals 21 at a regular pitch along the four side lines of the square or 
rectangular area corresponding to the openwork 31 of the socket body 30 to 
serve as the mounting seat 31 to receive the semiconductor package 10. The 
circuit board 20 is provided with mounting holes 22 in the vicinity to 
each of the corners within the square or rectangular area and also with 
two positioning holes 23 in the vicinities of about the center points of 
the opposite two side lines of the above mentioned square or rectangular 
area. As is described later, each of the mounting holes 22 corresponds to 
one of the mounting holes 32 in the socket body 30 so that the socket body 
30 and the circuit board 20 can be fastened together by means of bolts and 
nuts (not shown in the figure) for the sets of the mounting holes 22 and 
32. The positioning holes 23 correspond to the positioning pins 33 on the 
lower surface of the socket body 30, each of which is inserted into the 
corresponding positioning holes 23. 
The socket body 30, which is in a square or rectangular form, is shaped by 
injection molding or from a block of a resin such as an epoxy resin, 
acrylic resin, polyester resin, polyphenylene sulfide resin, polyether 
sulfone resin or polyether imide resin by machining. The socket body 30 
has an openwork or upwardly opening cavity to serve as a mounting seat 31 
for a semiconductor package 10 and, on the lower surface, provided with 
mounting cavities 39 (see FIG. 4) along the four side lines of the square 
or rectangular area opposite to the mounting seat 31. Each of these 
mounting cavities 39 serves for positioned mounting of the lead frame 40 
and the elastic connector sheet 50 by screwing. The mounting seat 31 is 
also in a square or rectangular form corresponding to the molded body 11 
of the semiconductor package 10 which can be inserted into and demounted 
from the mounting seat 31. A positioning bank 35 is provided at each 
corner of the mounting seat 31 to facilitate exact and rapid mounting of 
the semiconductor package 10 to the mounting seat 31 while a connecting 
cavity 36 is formed on the lower surface of the positioning bank 35 (see 
FIG. 2). 
Each of the positioning banks 35 has inclined facets 35A to face the 
positioning bank 35 at the next corner of the mounting seat 31 and 
vertical facets 35B in parallel to the vertical facet 35B of the 
positioning bank 35 at the next corner as well as a positioning notch 35C 
having a right-angled plan view. Each of the inclined facets 35A is so 
inclined as to guide the leads 12 of the semiconductor package 10 mounted 
in the mounting seat 31 onto the connecting cavity 36. The distance 
between two oppositely facing vertical facets 35B at the adjacent corners 
is approximately equal to the length of an array of leads 12 on one side 
surface of the semiconductor package 10 to define the position of the 
leads 12 above the connecting cavity 36. The distance between the 
diagonally facing positioning notches 35C is approximately equal to the 
diagonal length of the molded body 11 of the semiconductor package 10 to 
serve for positioning of the molded body 11. 
The socket body 30 is provided with positioning pins 33 each on the bottom 
surface facing the circuit board 20 implanted at a position in the 
vicinity of one of the opposite side peripheries of the body 30 while a 
notched recess 37 is formed on one of the other side surfaces to serve for 
engagement and a mounting through-hole 32 is formed in the vicinity of 
each of the four corners of the socket body 30. Each of the positioning 
pins 33 is, when the socket body 30 is mounted on the circuit board 20, 
inserted into and fixed to one of the positioning holes 23 in the circuit 
board 20 while the mounting hole 32 in the socket body 30 and the mounting 
hole 22 in the circuit board 20 are penetrated together with a bolt and 
fastened by means of a nut (not shown in the figures). After mounting the 
semiconductor package 10 in the mounting seat 31 of the socket body 30, a 
presser member 60 is mounted on the semiconductor package 10 and further a 
covering member 70 is put thereon which is fastened to the socket body 30 
by means of engagement of the engagement claws 71 with the engagement 
recess 37 in the socket body 30. 
As is illustrated in FIG. 4, the lead frame 40 has a structure in which a 
plurality of contacting shoes 42 are bonded at regular intervals of 
alignment onto the lower surface of a base film 41 of an insulating resin 
such as polyimide resins and polyester resins while the upper surface of 
the insulating resin film 41 is covered with an electroconductive layer 43 
of, for example, a copper foil which is electrically grounded. Each of the 
contacting shoes 42 is bonded to the base film 41 on the contacting point 
42A while the other end of the contacting shoe is extended in a cantilever 
fashion to form a combteeth-like arrangement and bent in an arch-wise 
configuration. The electroconductive layer 43 is connected to the electric 
power source line via a chip capacitor in order to reduce the influences 
caused by fluctuation of the source voltage. The lead frame 40 can be 
prepared by a known method conventional in the manufacture of printed 
circuit boards by utilizing, for example, the techniques of patterning. 
The contacting shoe 42 is a resilient spring member made of a fine ribbon 
of, for example, 0.2 mm width and 0.15 mm thickness made from a resilient 
metallic material such as phosphor bronze and beryllium copper. The end 
portion opposite to the contacting point 42A, at which the contacting shoe 
42 is bonded to the lower surface of the base film 41, is extended above 
the contacting hole 36 in an elastically bendable fashion. As is 
illustrated in FIG. 5 by a plan view, the end portion of the contacting 
point 42A of each contacting shoe 42 is formed to have a circular contour 
having a diameter larger than the width of the shoe body per se to ensure 
good bonding strength to the base film 41 and reliable electric connection 
while these circular end portions of the contacting shoes 42 are arranged 
in a zigzag or staggering arrangement with an object to enable a finer 
arrangement pitch. 
Since the cantilever-like extended end of the contacting shoe 42 is 
contacted with one of the leads 12 of the semiconductor package 10, as is 
illustrated in FIG. 6A, it is advantageous, though not essential, to form 
a sharp contacting point 42B at or near the extended end which serves as a 
surface film-breaking point to break the oxidized surface film on the 
surface of the lead 12 by scratching to ensure good electric conduction 
therebetween even when the surface of the lead 12 is covered with an 
insulating oxidized film. The contacting shoe 42 preferably has such a 
resilience that, when a load of 30 gf is applied to the end point thereof, 
the resilient displacement of the end point is in the range from 0.3 to 
0.5 mm. 
FIGS. 6B to 6E are each an illustration of an alternative embodiment 
relative to the contacting condition between the contacting shoe 42 and 
the lead 12 of the semiconductor package 10. In the embodiment illustrated 
in FIG. 6B, rivet head-like semispherical protrusions 42F are provided on 
the contacting surface of the contacting shoe 42 or the protrusions can be 
conical or pyramidal protrusions 42G with a sharp apex point illustrated 
in FIG. 6C. Further, as is illustrated in FIGS. 6D and 6E, the contacting 
shoe 42 can be contacted with the lead 12 at the sharply edged ends formed 
by cutting. It is of course effective that the contacting shoe 42 has a 
contacting surface roughened by sandblasting where the contacting shoe is 
contacted with the lead 12 of the semiconductor package 10. 
Though optional, furthermore, it is advantageous to have the contacting 
shoes 42 provided with a plating layer of a precious metal such as gold at 
least on the contacting surface with the leads 12 of the semiconductor 
package 10 with an object to ensure high corrosion resistance and low 
contact resistance for reliable electric conduction therebetween. The gold 
plating layer having a thickness of 0.03 to 1.0 .mu.m, e.g., 0.5 .mu.m, is 
formed usually on an underplating layer of nickel having a thickness of 2 
to 6 .mu.m, e.g., 3 .mu.m. 
Following is a description of the elastic connector sheet 50 to be 
interposed between the socket body 30 or lead frame 40 and the circuit 
board 20. As is illustrated in FIG. 7 by a partial cross sectional view, 
the elastic connector sheet 50 consists of an insulating matrix sheet 51 
made from a rubber and a multiplicity of fine filaments 52 of a metallic 
material embedded in parallel each to the others in the insulating matrix 
sheet 51 in such a fashion that both end points of each filament are 
exposed on or protruded out of the respective surfaces of the matrix sheet 
51 so that, when the connector sheet 50 is sandwiched between two 
electrode terminals under a moderate compressive load, the electrode 
terminals are electrically connected through the conductive filaments 52 
of the connector sheet 50 running in the direction approximately in 
parallel to the thickness of the connector sheet 50. In the inventive 
socket for inspection, the elastic connector sheet 50 is put into the 
mounting cavity or groove 39 of the socket body 30 and bonded by using an 
adhesive so that the connector sheet 50 is contacted, on one surface, with 
the array of the contacting points 42A of the lead frame 40 and, on the 
other surface, with the electrode terminals 21 on the circuit board 20. 
The insulating matrix sheet 51 of the connector sheet 50 has a thickness 
of, for example, 0.3 to 2.0 mm and the rubbery material forming the matrix 
sheet 51 should have a volume resistivity of at least 10.sup.12 
ohm.multidot.cm and a rubber hardness of 20.degree. H to 60.degree. H or, 
preferably, 30.degree. H to 60.degree. H according to JIS K 6301 for the 
type A hardness. The rubbery material forming the matrix sheet 51 is 
selected, though not particularly limitative, from heat-curable rubbery 
polymers such as silicone rubbers, epoxy rubbers and other synthetic 
rubbers and thermoplastic resins having elasticity such as polyethylene 
resins, polyurethane resins, ABS resins and plasticized polyvinyl chloride 
resins, of which silicone rubbers are preferred in respect of their high 
durability to withstand adverse environmental conditions and heat 
resistance as well as excellent electrical properties. 
The metallic fine filaments 52 should have a diameter in the range from 20 
to 90 .mu.m or, preferably, from 20 to 70 .mu.m and made from a metallic 
material having a volume resistivity not exceeding 0.1 ohm.multidot.cm 
such as pure gold, gold-based alloys, solder alloys, copper and 
copper-based alloys, if desired, having a plating layer of gold or a 
solder alloy. The embedding density of the metallic filaments 52 in the 
insulating matrix sheet 51 is usually in the range from 70 to 1000 
filaments per mm.sup.2 or, preferably, from 70 to 1000 filaments per 
mm.sup.2, each filament keeping a distance of 10 to 125 .mu.m or, 
preferably, 50 to 100 .mu.m from the adjacent ones. The running direction 
of each metallic filament 52 is basically perpendicular to the surface 
plane of the matrix sheet 51 but can be inclined, as is illustrated in 
FIG. 7, in such an angle that the offset value x between the two end 
points of the filament 52 within the plane of the surface of the matrix 
sheet 51 does not exceed a half of the thickness of the matrix sheet 51. 
FIGS. 8A, 8B and 8C are each an illustration of a different embodiment of 
the connector sheet 50 relative to the modification of the end points of 
the metallic filament 52 by a vertical cross sectional view. FIG. 8A 
illustrates an embodiment in which the end portion of the filament 52 is 
cut as bent to form a sharp cutoff end 52A which has an effect to break 
the oxidized surface film on the electrode terminals with which the end 
point 52A is brought into contact so as to ensure reliable electric 
connection therebetween. 
In the embodiment illustrated in FIG. 8B, the end portion of the filament 
52 is shaped in a configuration of a ball point 52B having a diameter 
larger than the diameter of the filament 52 per se while, in the 
embodiment illustrated in FIG. 8C, a semispherical bump 52C is built up on 
the end surface of the filament 52 by the techniques of gold plating. The 
connector sheets 50 illustrated in FIGS. 8A to 8C are advantageous in 
respect of the improved reliability of the electric connection to be 
established between the surface of the electrode terminals and the 
metallic filament 52. 
The presser member 60 (see FIG. 1) consists of a square or rectangular 
rigid board 61 which is provided on the lower surface to face the 
semiconductor package 10 with four pressing bars 62 each along one of the 
side lines of the board 61 at a position to correspond to one of the 
arrays of leads 12 of the semiconductor package 10. The board 61 and the 
pressing bars 62 can be shaped integrally by molding the same synthetic 
resin as the socket body 30. The presser member 60 is mounted on the 
semiconductor package 10 in the mounting seat 31 of the socket body 30 in 
such a fashion that each of the four pressing bars 62 is contacted with 
one of the arrays of the leads 12 so as to press down the leads 12 against 
the contacting shoes 42 of the lead frame 40. The presser board 61 is 
provided with guide holes 63 which, when the covering member 70 is mounted 
on the presser member 60, guide the guide pins 73 of the covering member 
70 inserted thereinto in a freely slidable fashion. 
The covering member 70 is also in the form of a square or rectangular board 
and provided with two engagement claws 71 on the opposite sides of the 
board. The engagement claw 71 is pivotally supported at about the middle 
height by means of supporting pins (not shown in the figure) within the 
notched recess on the side surface of the square or rectangular board in a 
freely rotatable fashion. The engagement claw 71 has an inwardly protruded 
claw edge 71A along the lower end line and, when the covering member 70 is 
mounted on the socket body 30 with the semiconductor package 10 and the 
presser member 60 interposed therebetween, the claw edge 71A comes into 
engagement with the notched recess 37 of the socket body 30 as being urged 
against the socket body 30 by means of a torsion spring (not shown in the 
figure) provided around one of the supporting pins so that the covering 
member 70 and the socket body 30 are fastened together holding the 
semiconductor package 10 and the presser member 60 under an appropriate 
pressing load. The engagement claw 71 is provided along the upper 
periphery with a protruded rib 71B which serves as an antiskid member to 
facilitate finger manipulation for disengagement. 
The covering member 70 is further provided with four spring pins 72 each 
penetrating the board by screwing into an opening in such a fashion that 
the length of protrusion out of the lower surface of the board is 
adjustable. Two guide pins 73 are implanted to be protruded out of the 
lower surface of the board each along one of the opposite side lines of 
the board at a position corresponding to the guide opening 63 in the 
presser member 60. 
The spring pin 73 has a structure consisting of a shell body with a 
hexagonal opening to be thrusted into the board of the covering member 70 
by screwing and a plunger encased in the shell body and urged downwardly 
by means of a spring. When the covering member 70 is mounted on the 
presser member 60, the plungers protruded out of the lower surface of the 
covering member 70 come into contact with the upper surface of the presser 
member 60 while the contacting pressure therebetween can be adequately 
controlled by turning the shell body by using a suitable tool such as a 
wrench. 
The guide pins 73 are made, preferably, from a metallic material. As 
protruded out of the lower surface of the covering member 70 at 
symmetrical positions corresponding to the guide holes 63 in the presser 
member 60, each of the guide pins 73 penetrates the guide hole 63 when the 
covering member 70 is mounted on the presser member 60 to secure exact up 
and down movement of the presser member 60. 
Incidentally, the covering member 70 is not an essential part of the 
inventive socket for inspection of semiconductor packages provided that an 
appropriate contacting load can be ensured between the leads 12 of the 
semiconductor package 10 and the contacting shoes 42 of the lead frame 40. 
Namely, a good contacting condition can be obtained with about 30 gf of 
the contacting load per a single pair of one of the leads 12 and one of 
the contacting shoes 42 so that a sufficient contacting load can be 
obtained, for example, by adequately selecting the body weight of the 
presser member 60 enabling omission of the covering member 70. 
In mounting the inventive socket onto the circuit board 20, firstly, the 
lead frame 40 is mounted to the socket body 30 with exact positioning 
along with mounting of the elastic connector sheet 50. Namely, the lead 
frame 40 is mounted so as to have the contacting shoes 42 extended above 
the contacting opening 36 of the socket body 30. The contacting points 42A 
of the contacting shoes 42 are brought into contact with a surface of the 
elastic connector sheet 50. In the next place, the positioning pins 33 of 
the socket body 30 are inserted to the respective positioning holes 22 of 
the circuit board 20 and the socket body 30 and the circuit board 20 are 
fastened together by means of bolts each penetrating the mounting hole 32 
of the socket body 30 and the mounting hole 22 of the circuit board 20. 
Thus, assemblage of the socket body 30 and the circuit board 20 can be 
conducted absolutely without soldering. Further, the lead frame 40 and 
elastic connector sheet 50, when degraded or damaged, can be easily 
demounted from the circuit board 20 without leaving any contamination by 
soldering so that the circuit board 20 can be repeatedly used. 
The burn-in test of a semiconductor package 10 can be performed with the 
inventive socket very conveniently by mounting the semiconductor package 
10 in the mounting seat 31 of the socket body 30 which can be secured at 
the position by means of the presser member 60 and the covering member 70 
mounted thereon and fastened together so as to ensure an appropriate 
contacting load of about 30 g between a pair of one of the leads 12 and 
one of the contacting shoes 42 consequently to establish reliable electric 
connection between the leads 12 of the semiconductor package 10 and the 
electrode terminals 21 on the circuit board 20. 
FIG. 9 is for illustration of a modified embodiment of the inventive socket 
as mounted on a circuit board 20 by a partial enlarged vertical cross 
sectional view. In this embodiment, the circuit board 20 is provided with 
two sets of electrode terminals 21A and 21B of which each set serves for a 
different testing mode from the other set and one of the first set 
terminals 21A and one of the second set terminals 21B are simultaneously 
contacted with a single contacting shoe 42 with intervention of an elastic 
connector sheet 50 so that the semiconductor package can be subjected to 
the inspection tests of two different testing modes by switching the 
working set of the terminals from 21A to 21B.