Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With work feeding or handling means
Reexamination Certificate
2001-10-29
2004-06-29
Mayes, Melvin C. (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With work feeding or handling means
C269S287000, C269S288000
Reexamination Certificate
active
06755229
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to a method for preparing a high performance BGA (ball grid array) board and a jig applicable to the method, and in particular, to a method for preparing the high performance BGA board by use of an individual heatsink and a strip-type jig without a strip-type heatsink, in which the Ni-plated side of the heatsink can be prevented from being contaminated.
2. Description of the Prior Art
The great advance in the electronics industry is, at least in part, based on the development of the electronic parts industry. As electronic parts have been developed into slim ones of high performance, they can be more highly integrated in one board. To the development of electronic parts, multi-layer printed circuit boards make a contribution.
With the aim of mounting highly integrated electronic parts thereon, multi-layer printed circuit boards have a structure in which elemental boards having a plurality of circuits are laminated. Multi-layer printed circuit boards may have various forms, and be manufactured by various methods. However, conventional boards suffer from the disadvantage of not guaranteeing the full performance of high-speed IC chips because a large quantity of heat generated from I/O multifins of semiconductor chips cannot be effectively dissipated from the conventional boards, leading to a significant decrease in the transfer rate of electric signals.
To avoid the problem that conventional boards have, much effort has been made to manufacture boards that are of a high multi-layer structure and of excellent thermal stability. In the boards, semiconductor chips are bonded onto heatsinks while binding to bonding pads in the form of steps.
There are disclosed various methods for establishing heatsinks in printed circuit boards. For example, Japanese Patent Publication No. Hei. 10-116933 discloses a multi-layer printed wiring board for mounting IC, in which a heatsink is fixed firmly on a laminated structure by soldering, with IC being fixed firmly on the heatsink by use of a resin adhesive. Furthermore, Japanese Patent Publication No. Hei. 10-116932 discloses a method for preparing a multi-layer printed wiring board for mounting IC, in which a multilayered BGA is heated at 200° C. for 1 hour to prevent the board from being bent, followed by heating the BGA in a reflow furnace to cure a thermosetting resin adhesive, thereby fixing a heatsink onto the board. Heatsinks used in the above methods are prepared by plating copper foil with Ni and then with platinum.
Generally, a BGA board equipped with a heatsink is manufactured by bonding individual BGA boards to a strip-type heatsink that is blackened at the side onto which the BGA board is bonded, with the other side being plated with Ni. A detail description will be given of the manufacture of a heatsink-equipped BGA board in conjunction with FIG.
1
. With reference to
FIG. 1
a
, there is illustrated the pre-bonding of a BGA
5
to a heatsink
3
through an adhesive
2
. To this end, the adhesive
2
is coated on the heatsink
3
, followed by the application of heat and pressure by use of a hot steel plate
1
. In this regard, a jig
4
is employed to accurately apply the adhesive
2
to a defined part of the heatsink
3
. Thereafter, main-bonding is accomplished by pressing an individual BGA
5
against the resulting structure obtained from the pre-bonding step, with a provision of heat by use of a hot steel plate
6
, as shown in
FIG. 1
b
. The heatsink-equipped, strip-type BGA board thus obtained is shown in a plane view in FIG.
2
.
When a heatsink is bonded to a BGA board as described above, there are generated problems, including contamination of the Ni-plated side, poor bonding reliability, and inapplicability of individual heatsinks.
Furthermore, Japanese Patent Publication No. Hei. 10-178122 discloses an IC mounting multilayer printed wiring board which causes no breaking of wire resulting from cracking in an inner layer conductor wire. In the IC mounting multilayer printed wiring board constituted by laminating a plurality of resin substrates, the coating plated at the wall of a through hole is 8-35 &mgr;m thick while a conductor wire spatially distant from an external lead pin by the coating plated in the through hole is 25-70 &mgr;m thick, thereby preventing the wire breaking caused by the cracking at the plated coating of the through hole and at the conductor wire. The IC mounting multilayer printed wiring board, however, suffers from the disadvantage of being out of the permitted range of thickness deviation or being distorted.
Therefore, there remains a need for a method that can be used to laminate individual heatsinks and can prevent the distortion of multilayer printed wiring boards when a BGA board is bonded to the heatsink.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to avoid disadvantages encountered in the prior art, and provide a method for preparing the high performance BGA board which enjoys the advantages of using individual heatsinks, preventing the Ni-plated side of the heatsink from being contaminated and damaged, and having a reliable bonding state.
It is another object of the present invention to provide a method for preparing the high performance BGA board which enjoys the advantage of preventing BGA boards from being deviated in thickness from the permitted range and distorted upon bonding.
It is further object of the present invention to provide a jig applicable to the method for preparing a high performance BGA board.
These objects can be accomplished by providing a method for preparing a high performance BGA board, comprising the steps of:
a) providing an individual BGA board laminated structure;
b) providing an individual heatsink for dissipating heat of the BGA board laminated structure;
c) pre-bonding an adhesive layer to the BGA board laminated structure or the heatsink by use of a pre-bonding jig; and
d) main-bonding the BGA board laminated structure or the heatsink, to which the adhesive layer is previously stuck in the c) step, to the corresponding heatsink or the BGA board laminated structure, respectively, by use of a main-bonding jig.
To accomplish above objects, another method for preparing a high performance BGA board according to the invention may be provided, the method comprising the steps of:
a) providing an individual BGA board laminated structure;
b) providing an individual heatsink for dissipating heat of the BGA board laminated structure;
c) pre-bonding which comprises establishing a first set of pins for arranging the BGA board laminated structure on a pre-bonding jig of a strip-type, placing the BGA board laminated structure onto the pre-bonding jig under the guidance of the first set of pins, forming an adhesive layer covered with a cover sheet on the BGA board laminated structure in a pattern fitting to the heatsink followed by removing the cover sheet from the adhesive layer, attaching the heatsink to a flexible tape and then arranging the flexible tape-attached heatsink on the adhesive layer with the flexible tape being locked by a second set of pins established onto the pre-bonding jig, and lightly bonding the heatsink to the BGA board under pressure;
d) separating a resulting pre-bonded structure consisting of the BGA board laminated structure, the adhesive layer and the heatsink therefrom; and
e) main-bonding the pre-bonded structure using a main-bonding jig under pressure at a high temperature.
Furthermore, the objects of the invention can be accomplished by a jig for combining a heatsink with a BGA board laminated structure via an adhesive layer, the jig consisting of an upper and a lower plate to form a cavity, wherein the cavity is so defined that the BGA board laminated structure, the adhesive layer and the heatsink are arranged to precisely combine one another, and wherein the total thickness of the jig is smaller than that of the combination of the BGA board laminated structure, the adhesive and the heatsink by 20 to 40 &mgr;m.
REFERENCES:
Kang Jang-Kyu
Kang Myung-Sam
Park Keon-Yang
Mayes Melvin C.
Morgan & Lewis & Bockius, LLP
Samsung Electro-Mechanics Co. Ltd.
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