Apparatus for providing a two-sided, cavity, inverted-mounted component circuit board

An apparatus and method of providing a printed wiring board is disclosed. The printed circuit board comprises a printed wiring board that has at least one opening. The printed circuit board further comprises a circuit component that is located within the opening and is electrically connected to the printed wiring board. Various embodiments are disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates in general to printed circuit boards and a 
method of manufacturing a printed circuit board. In particular, the 
present invention relates to a thin, flat, two-sided printed circuit board 
having openings in which components are mounted. 
2. Description of the Related Art 
High density printed circuit boards create greater utility in a smaller 
electronic device. Increasing the density of circuit components on a 
printed circuit board, however, often results in overheating of the 
components, leading to eventual burnout and replacement of the components. 
The resulting overheating can also cause higher stress and strain in the 
interconnects, such as solder joints, leading to an early failure. 
Moreover, the trend towards an increasingly compact product has resulted 
in increasing use of thinner and smaller printed circuit boards. 
Consequently, chips have decreased in thickness and are attached closer 
and closer to the printed circuit board. 
Conventional methods of mounting circuit components on a printed circuit 
board include a "thorough-hole" technique which involves extending leads 
of a circuit component through the printed circuit board and then 
soldering the leads in place. The leads electrically connect circuit paths 
embedded on or within the board. 
Another mounting method, known as "Surface Mount Technology" (SMT), 
involves initially placing circuit components onto circuit paths embedded 
on the upper surface of the printed circuit board and then soldering the 
component in place using a process called "reflow soldering." Surface 
mount components utilize connector leads commonly referred to as "J-leads" 
which rest on the surface of the printed circuit board rather than 
penetrate through it as with the through-hole technique. 
The application of SMT increases the density of circuit components on a 
printed circuit board by enabling the use of smaller components which are 
arranged in a flat configuration on the surface of the board. In such 
surface mounted components, the leads to be mounted may be tightly spaced, 
as compared to components mounted by the thorough-hole technique, enabling 
increased access per unit area of the component. However, the resulting 
circuit board is still bulky, as the components extend from either surface 
of the board. In addition, in printed circuit boards manufactured using 
SMT, components occupy approximately 60% of the board, severely limiting 
routing connections. In contrast, in circuit boards designed for receiving 
dual-in-time packaging (DIP) components, typically only 19% of the board 
surface is covered by components, leaving ample room for routing 
connections. 
Other current techniques of mounting circuit components include embedding 
chips into recesses in the board to further reduce the overall thickness 
of the board. However, such a technique suffers from several drawbacks. 
First, the chips are not firmly held in place. Second, the use of recesses 
for embedding the chips prevent two-sided wiring. Thirdly, only selected 
components are placed in these recesses, while the remaining components 
are surface mounted. This results in providing a printed circuit board 
that is still bulky. 
Accordingly, there is a need in the technology for a method and apparatus 
of providing a printed wiring board that is cost-effective, thin, flat and 
strong. The printed wiring board must also provide two-sided wiring, high 
integrated component density and must also hold the components securely in 
place. 
BRIEF SUMMARY OF THE INVENTION 
An apparatus and method of providing a printed wiring board is disclosed. 
The printed circuit board comprises a printed wiring board that has at 
least one opening. The printed circuit board further comprises a circuit 
component that is located within the opening and is electrically connected 
to the printed wiring board. A method of manufacturing and assembly a 
plurality of printed wiring boards is also disclosed. Various embodiments 
are included.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a top view of one embodiment of the printed wiring board of the 
present invention. The printed wiring board 10 has a first side 12 and a 
second side 14. Each side 12 and 14 includes a substrate having printed 
interconnections 16 and 18, respectively. The printed wiring board 10 also 
defines openings 20a-20g each having a sufficient size to receive an 
electrical component such as a semiconductor chip or a resistor. For 
discussion purposes, the openings 20a-20g will be collectively referred to 
as an opening 20. 
FIG. 2 is an enlarged view of the opening 20f of the printed wiring board 
of the present invention, taken along lines 2--2. As shown in the Figure, 
each opening 20, such as the opening 20f, has rounded edges 30a-30d which 
are tooled to provide a secure fitting for the electrical component 32. In 
particular, each of the corners 32a-32d of the electrical component 32 fit 
securely into the edges 30a-30d. 
FIG. 3 is a side view of the printed wiring board 10 of FIG. 1, taken along 
lines 3--3. As shown in FIG. 3, the printed wiring board 10 also has a 
plurality of via connections or through holes 40a and 40b (collectively 
referred to as through-holes 40). Once the component 32 has been securely 
fitted in the opening 20, its leads 34a and 34b are soldered to the 
appropriate printed interconnections 16 and/or 18 (FIG. 1) at the 
appropriate through holes. To ensure a secure connection, and to 
facilitate interconnections on either side of the printed wiring board 10, 
solder is permitted to flow into each through hole 40. The component 32 is 
then epoxy coated. In one embodiment, the opening 20 which receives the 
component 32 is also filled with epoxy. Examples of the epoxy used include 
that manufactured by ITW DEVCON under the tradename FR4 or "5-minute epoxy 
resin" and that manufactured by Al Technology under the part designation 
E67655-5-SM21. 
FIG. 4 is a side view of a second embodiment of the printed wiring board 
100 of the present invention. As shown in FIG. 4, the printed wiring board 
100 has a first side 112 and a second side 114. Each side 112 and 114 is 
laminated with a metal 112a and 114a respectively, such as copper foil. 
The printed wiring board 100 also defines a plurality of openings (only 
one opening 120 is shown), each having a sufficient size to receive an 
electrical component 132 such as a semiconductor chip or a resistor. The 
opening 120 is out such that the metal laminate on the second side 114 is 
left in tact. The printed wiring board 100 also has a plurality of via 
connections or through holes 140a and 140b (collectively referred to as 
through holes 140). Once the component 132 has been securely fitted into 
the opening 120, its leads 134a and 134b are soldered to the appropriate 
printed interconnections 16 and/or 18 (FIG. 1) at the appropriate through 
holes. To ensure a secure connection, and to facilitate interconnections 
on either side of the printed wiring board 100, solder is permitted to 
flow into each through hole 140. The component 132 is then epoxy coated. 
Another aspect of the present invention involves the manufacture and 
assembly of printed wiring boards, as shown in FIGS. 5A-5D. In particular, 
FIG. 5A illustrates a printed wiring board 300, which is divided into a 
plurality of smaller board sections 300a, 300b and 300c, for example, 
along lines 322a and 322b. Alternatively, the smaller board sections 300a, 
300b and 300c may be predesigned and/or manufactured so as to fit 
together. In this case, cutting of the board 300 into smaller pieces is 
not required. The printed wiring board 300 may be manufactured in the same 
manner as printed wiring board 10 or 100 as discussed above. For example, 
openings 320a, 320b and 320c (collectively referred to as "openings 320") 
may be cut in each of the board sections 300a, 300b and 300c respectively. 
In addition, components (not shown) may be fitted into the openings 320 as 
discussed above. Next, the printed wiring board 300 is cut along lines 
322a and 322b, as shown in FIG. 5B. Solder bump interconnections 330 are 
provided to facilitate electrical connections between adjacent board 
sections 300a, 300b and 300b, 300c (FIG. 5D), before the printed wiring 
board sections 300a, 300b and 300c are stacked together, as shown in FIG. 
5C. It is apparent to one of ordinary skill in the art that a plurality of 
printed wiring boards 10 and/or 100 may be interconnected using the solder 
bump interconnection technique as shown in FIG. 5D. In a preferred 
embodiment, the board sections are coated with a non-conductive material 
so that each board section 300a, 300b or 300c is insulated from the other 
board sections except at the interconnections 330. In one embodiment, the 
interconnections 330 are coated with a substance that negates the 
non-conductive coating. An example of such a coating is that manufactured 
by Dupont under the tradename Teflon. In addition, solder-filled vias such 
as via 332 may be used to facilitate interconnection between non-adjacent 
boards. It should be noted that, although some components, such as large 
capacitors, will not fit within an opening in a single board, additional 
boards that are stacked above the first board may be conformed and/or cut 
to fit around the large components. For example, corresponding openings 
may be cut in the additional boards so that a large component that is 
mounted in an opening of a first board may also be accommodated in 
corresponding openings in the other stacked boards. As a result, a very 
high density solution may be provided. 
Such a manufacturing and assembly process is advantageous because 
2-dimensional layout tools may be used to make 3-dimensional boards. In 
addition, vertical interconnects may be easily provided. Most importantly, 
such a manufacturing and assembly process (which facilitates stacking of 
the resulting board section) is possible because of the flatness of the 
resulting component mounted boards. 
A further aspect of the present invention involves the use of a 
thermocooling layer to provide cooling for a plurality of stacked printed 
wiring boards 10, 100 and/or 300a, 300b, 300c. As shown in FIG. 6, a 
plurality of printed wiring boards 10, may include a thermocooling layer 
350. Examples of the thermocooling layer 350 include that manufactured by 
RMT Limited of Moscow, Russia, under the part designation 1MS 03-030-L and 
that manufactured by Alpha and Omega Computer Incorporated of Anaheim, 
Calif., under the tradename "Peltier Junction Active Cooler". The use of 
such a thermocooling layer 350 will facilitate the dissipation of heat 
from high power processors. In one embodiment, the thermocooling layer 350 
may be embedded into any one of the printed wiring boards 10. An example 
of such an arrangement is shown FIG. 7, where a thermocooling layer 422 is 
embedded in a printed wiring board 420. 
Yet another aspect of the present invention involves the use of flat 
batteries to provide the voltage and current requirements of a system 
which implements the use of printed wiring boards. Such a system 400 
comprises a plurality of layers 410, 420, 430 and 440. In one embodiment, 
layers 410 and 430 are printed wiring boards such as the printed wiring 
board 10, 100, 300a, 300b or 300c. Each board 410 and 430 has an opening 
in which a component 412 and 432 respectively, such as a chip, may be 
fitted and epoxied, as described above. The printed wiring board 410 may 
be electrically connected with the non-adjacent printed wiring board 430 
by means of the solder bumps 424a, 424b and a via 426. In one embodiment, 
layer 420 is printed wiring board 10, 100, 300a, 300b or 300c, in which a 
thermocooling layer 422 is embedded. The thermocooling layer 422 is 
identical to that shown in FIG. 6 and described above. In another 
embodiment, the thermocooling layer 422 is located adjacent to a heat sink 
424, which facilitates the transfer of heat from one end of the layer 420 
to the other end. In a further embodiment, layer 440 is a flat battery. 
Examples of such a flat battery includes the flat lithium-ion battery 
manufactured by Ultralife, Inc. under the tradename "Solid State System". 
One embodiment of the process S100 for manufacturing the printed wiring 
board 10 of the present invention, as illustrated in FIG. 8, will now be 
described. The board 10 is first laminated on a first side (step S102) 
with a metal. In one embodiment, the metal is copper foil. A circuit 
pattern is then etched onto the first side of the board 10 (step S104). 
The openings 20a-20g are then cut from the board 10 (step S106). The 
openings 20a-20g are cut so that each opening has rounded edges 30a-d 
which are tooled to provide a secure fitting for a corresponding 
electrical component. At the same time, holes 40 for via connections are 
also drilled. Next, the components 32 are fitted into their corresponding 
openings 20 and then soldered (step S108). In particular, solder is 
permitted to flow into the through holes 40 to ensure a secure connection. 
Once the components 32 are situated, they are coated with epoxy (step 
110). The openings in which the components 32 are located are also fitted 
with epoxy. The second side of the board 10 is then laminated with a 
metal. In one embodiment, the metal copper is foil. A circuit pattern is 
then etched onto the metal on the second side of the board 10 (step S114). 
FIG. 9 illustrates an alternate embodiment of the process S200 for 
manufacturing the printed wiring board 10 of the present invention. The 
board 10 is first laminated with a metal, patterned and etched on a first 
side (step S202). In one embodiment, the metal is copper foil. Next, the 
openings 20 are cut and the through holes are drilled (step S204). A 
second side of the board 10 is then laminated with a metal, patterned and 
etched (step S206) before the components 32 are fitted into the openings. 
In one embodiment, the metal is copper foil. Next, the components 32 are 
fitted into their corresponding openings 20 and then soldered into place 
(step S208). The components 32 are then epoxy-coated and the openings 20 
are filled with epoxy (step S210). 
FIG. 10 illustrates a third embodiment of the manufacturing process S300 of 
the printed wiring board 100 of the present invention. The board 100 (FIG. 
4) is first laminated with metal 112a and 114b on sides 112 and 114 of the 
board 100 (step S302). In one embodiment, the metal is copper foil. Next, 
holes 140 for via connections are drilled and plated with metal, such as 
copper foil (step S304). The circuit pattern for the first side 112 of the 
board 100 is then etched (step S306). Next, the openings 120 are cut from 
the board 100, such that the metal laminate 114b on the second side 114 of 
the board 100 is left intact (step S308). The components 132 are then 
fitted into the corresponding opening 120 and the component leader 134a, 
134b of each component 132 are soldered into place (step S310). The 
components 132 are then coated with epoxy and the openings 120 (with the 
components 132 in place) epoxy and the opening 120 (with the components 
132 in place) are also coated with epoxy (step S312). The second side 114 
of the board 100 are then patterned and etched (step S314). The process 
S300 then laminates. 
It is apparent to one of ordinary skill in the art that in each of the 
processes described above, additional layers of routing can be added on 
one or both sides of the finished board where each layer is provided by 
plating the board with metal (such as copper), etching the metal and then 
depositing of an insulating layer on the metal. Vias may be used to 
provide interconnection between the layers. 
The process of the present invention lends itself well to automation 
because component placement is accurately determined by the holes, which 
are easy to provide, with good alignment. The resulting board thickness is 
uniform and is determined by the largest electronic component used, which 
is typically 1 mm. As a result, the board is flush, and no components will 
be sticking out from the board. The board is further strengthened through 
the use of epoxy and can support a very high integrated density, with a 
component to wiring area ratio of 2:1. The board can also be maintained at 
a reasonable cost. This is because the board is totally flat, with no 
exposed leads or pins, so that dirt, grime and metal particles will not be 
trapped on the board. As a result, shorts (and thus unreliable operation) 
are eliminated or greatly reduced. 
In the process of the present invention also facilitates connections to 
non-adjacent boards, and for providing circuit boards that may be 
integrated into a compact package, while providing sufficient cooling, 
through the use of special thermoelectric cooling. 
The present invention may be embodied in other specific forms without 
departing from its spirit or essential characteristics. The described 
embodiments are to be considered in all respects only as illustrative and 
not restrictive. For example, the electrical component may be an 
integrated chip or a discrete component such as a resistor, a capacitor or 
a transistor. The scope of the invention is, therefore, indicated by the 
appended claims rather than the foregoing description. All changes which 
come within the meaning and range of equivalency of the claims are to be 
embraced within their scope.