Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-08-23
2003-04-29
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S832000, C029S837000, C174S263000
Reexamination Certificate
active
06553660
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electronic device and a manufacturing technology thereof, and particularly to a technology effective for application to an electronic device having electronic components mounted on a wiring board, which is suitable for use in each of different embodiments.
BACKGROUND OF THE INVENTION
There has been known an electronic device called an “MCM (Multi Chip Module)” as an electronic device. The MCM is one wherein a plurality of semiconductor chips each having an integrated circuit built therein are mounted or implemented on a wiring board to configure one integrated function. In order to speed up a data transfer rate of the MCM and downsize it, a flip-chip mounting technology for using semiconductor chips (flip chips) wherein protruded electrodes are respectively formed on electrode pads placed on a circuit forming surface, and mounting the same on a wiring board has actively been adopted for the MCM.
In the flip-chip mounting technology, various mounting or packaging methods or systems have been proposed and put into practical use. As one of them, there is known an ACF mounting or packaging system using a sheet-like anisotropic conductive film (ACF: Anisotropic Conductive Film) as an adhesive resin. The ACF mounting system is a method for using a semiconductor chip wherein stud bumps each comprising, for example, gold (Au) are respectively formed on electrode pads placed on a circuit forming surface as protruded electrodes, thermo-compression bonding the semiconductor chip in a state in which an ACF resin is being interposed between the semiconductor chip and a wiring board to thereby bond and fix the semiconductor chip to the wiring board, and electrically connecting connecting portions of wirings of the wiring board and electrode pads of the semiconductor chip respectively. The anisotropic conductive film is one obtained by mixing lots of conductive particles into an insulating-film resin in dispersed form. The ACF mounting has been described in Unexamined Patent Publication Hei No. 10(1998)-270496 (U.S. Pat. No. 6,208,525).
In addition to the ACF mounting system, there are known an NCF mounting system using a sheet-like non conductive film (NCF: Non Conductive Film) as an adhesive resin, an ACP mounting system using a paste-like anisotropic conductive resin (ACP: Anisotropic Conductive Paste) as an adhesive resin, etc.
On the other hand, soldering devices or electronic components mounted or packaged by soldering are known as surface mount devices (SMD: Surface Mount Devices) mounted on a wiring board in addition to the semiconductor chip. The soldering electronic components include passive components or parts and active components or parts. As the soldering passive components, may be mentioned, for example, chip capacitors, chip resistors, chip inductors, etc. As the soldering active components, may be mentioned, for example, semiconductor devices such as a BGA (Ball Grid Array) type, a CSP (Chip Size Package) type, a QFP (Quad Flatpack Package) type, a QFN (Quad Flatpack Non-Leaded Package) type, which respectively include packaged semiconductor chips, etc.
SUMMARY OF THE INVENTION
Meanwhile, the present inventors have developed an MCM wherein a semiconductor chip (hereinafter called a “compression mounted IC (Integrated Circuit) chip”) mounted by thermo-compression bonding as in the ACG mounting system, and soldering electronic components are placed on the same wiring board in mixed form. Upon the development of the present MCM, the present inventors have found out the following problems.
(1) The soldering electronic components include those whose post-mount heights (each corresponding to a height from one main surface of a wiring board to the top portion) are higher than that of the compression mounted IC chip. When such soldering electronic components high in height are mounted prior to the compression mounted IC chip, a thermo-compression bonding tool (thermo-compression bonding head) for thermo-compression bonding the compression mounted IC chip become easy to contact the already-mounted soldering electronic components upon mounting the compression mounted IC chip. It is therefore necessary to widen the interval between each soldering electronic component and its corresponding compression mounted IC chip. Further, this would lead to the inhibition of a size reduction in MCM.
When it is desired to collectively thermo-compression bond a plurality of compression mounted IC chips with a view toward improving productivity, it is necessary to use one larger than the compression mounted IC chip as a thermo-compression bonding tool. However, when soldering electronic components high in height exist within a range for the thermo-compression bonding tool, it becomes difficult to collectively thermo-compression bond the IC chips.
(2) A soldering paste material (corresponding to a semisolid soldering material obtained by mixing and kneading lots of solder particles and flux together) is supplied to connecting portions of wirings for the wiring board, soldering electronic components are thereafter mounted so that the connecting portions of the wirings for the wiring board and their corresponding electrode portions of the soldering electronic components are held face to face with one another with the soldering paste material interposed therebetween, and subsequently they are subjected to heat treatment to thereby melt the soldering paste material, whereby the mounting of the soldering electronic components is carried out. For the purpose of the supply of the soldering paste material, a screen printing method or a dispense method is used. The screen printing method is a method for transferring a soldering paste material placed on a screen mask to the surface of a substrate through each aperture or opening defined in the screen mask by means of a squeegee. The dispense method is a method for discharging a soldering paste material through a thin nozzle and applying it.
The screen printing method capable of collectively supplying the soldering paste material is suitable for the achievement of an improvement in productivity of the MCM. However, when the compression mounted IC chip is mounted prior to each soldering electronic component, it is difficult to supply the soldering paste material by means of the screen printing method upon the mounting of the soldering electronic components. The supply of the soldering paste material is carried out through the use of a screen mask called an “embossed mask” provided with at least one protruded portion at a portion of the already-mounted compression mounted IC chip so as to avoid the portion, whereby the supply of the soldering paste material by one operation is allowed. In such a case, however, it is necessary to set a plane size of the protruded portion of the embossed mask larger than that of the compression mounted IC chip to thereby produce a smooth protruded shape so that the squeegee can be slid smoothly. Therefore, the soldering electronic components cannot be placed in the neighborhood of the compression mounted IC chip, thereby leading to the inhibition of a size reduction in MCM.
(3) A radiator is selected for the MCM which needs to have high dissipation. Since the back of the compression mounted IC chip, which is opposite to its circuit forming surface, is kept bare, the radiator is mounted onto the back of the compression mounted IC chip with a thermal conductive sheet interposed therebetween, the compression mounted IC chip can obtain a high radiating effect. However, when the soldering electronic components higher than the compression mounted IC chip in post-mount height exist, the soldering electronic components interfere with the contact between the back of the compression mounted IC chip and the thermal conductive sheet, whereby the dissipation of the MCM is reduced.
An object of the present invention is to provide a technology capable of achieving an improvement in productivity of an electronic device.
Another object of the present invention is to provide a technology cap
Arbes Carl J.
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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