Internal-combustion engines – High tension ignition system – Having a specific ignition coil
Reexamination Certificate
2000-04-06
2001-11-27
Solis, Erick (Department: 3747)
Internal-combustion engines
High tension ignition system
Having a specific ignition coil
C123S647000, C257S795000, C257S787000, C257S789000, C438S127000
Reexamination Certificate
active
06321734
ABSTRACT:
This application claims priority of JP 11-99088, filed Apr. 6, 1999, the disclosure of which is expressly incorporated by reference herein.
BACKGROUND OF THE INVENTION
The present invention relates to a resin sealed semiconductor device, that is, a resin sealed electronic device and a method of fabricating the resin sealed electronic device and an ignition coil device for an internal combustion engine using the above resin sealed electronic device.
Various proposals to improve reliability of the resin sealed electronic devices have been made by reducing strains produced in the sealing resin in order to suppress occurrence of cracks.
Japanese Patent Application Laid-Open No.10-107182 discloses a resin sealed semiconductor device. The resin sealed semiconductor device in which electrodes formed on a board are electrically connected to a semiconductor chip through bumps, and a gap between the board and the semiconductor chip is filled with a sealing resin and the surrounding of the semiconductor chip is covered with the sealing resin, wherein when a height of the peripheral portion of the sealing resin covering the surrounding of the semiconductor chip from bottom end surface of the semiconductor chip is (b) and a distance between the outer peripheral edge of the peripheral portion and the bottom edge of the semiconductor chip in a plane being flush with the bottom end surface of the semiconductor chip is (a), an average value of (a/b) is smaller than 2; and the sealing resin is a resin material of an epoxy group composed of an epoxy resin and spherical particles made of a low thermal expansion inorganic material having a thermal expansion coefficient lower than that of the epoxy resin; and the sealing resin contains the inorganic material within the range of 50 to 80 weight % to the total weight.
Further, Japanese Patent Application Laid-Open No.9-246300 discloses a method of fabricating a semiconductor device. The method of fabricating a semiconductor device is one in which a chip is arranged on a board opposite to each other with a gap between them, and the gap between the chips and the board is filled with a lower layer side sealing resin, and the whole chip is covered with a upper layer side sealing resin, wherein the method of fabricating the semiconductor device comprises the first process of injecting a thermosetting resin before setting into the gap between the chip and the board; the second process of making the resin bring in a semi-set condition; the third process of disposing a thermosetting resin before setting so as to cover the whole chip; and the fourth process of completely setting the both laminated resins.
In the case where a flip chip is contained inside a conventional resin sealed electric device as described in Japanese Patent Application Laid-Open No.10-107182, an under filler material is initially injected and filled under the flip chip and then the under filler material is set, and after that the circuit board portion including the flip chip is sealed with a resin through transfer molding. Therefore, before sealing the whole circuit with the resin, there is the process of injecting, filling and setting of the under filler material. Most of liquid under filler materials have linear expansion coefficients near that of the solder in order to secure the reliability of the soldered portions, and such liquid under filler materials need to be stored at a low temperature and are heated up to room temperature when they are used. However, the pot-life of the liquid under filler material is short, and accordingly management of the liquid under filler material is troublesome because it needs to be run out within the pot-life period. Further, particularly, in a case where the size of flip chip is small and the bump height is low, it takes a very long time to inject and fill the under filler material, and to inject and fill the under filler material into the under portion of the bumps and to set the under filler material.
On the other hand, since the reliability of the electronic device may be deteriorated when the transfer molding resin is not bonded to the under filler material, control of setting the resin must be performed in order to improve bonding by making the under filler material bring in a semi-setting condition as described in Japanese Patent Application Laid-Open No.9-246300.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a resin sealed electronic device in which packaging of a hybrid circuit board mounting a flip chip capable of securing high reliability by a transfer molding resin without using any under filler material used in the conventional technology described above, and to provide a method of fabricating the resin sealed electronic device.
In detail, principal aims of the present invention are to solve the conventional problem that the contact between the transfer molding resin and the under filling material is poor, the problem on the process that needs injecting and filling the under filling material, and the problem that cracks occur in the sealing resin by thermal stress due to use of the under filler material.
The resin used for transfer molding can be let to flow below the flip chip by setting the linear expansion coefficient of the transfer molding resin to 3×10
−6
to 17×10
−6
and using a filler to be added to the resin which is selected so that the particle size of the filler becomes smaller than a value of a bump height after mounting the flip chip on the board minus 10 &mgr;m. In this case, the difference between a thickness of the transfer molding resin in the periphery of the flip chip and a gap (clearance) formed by the bump height under the flip chip is large, and at molding the transfer molding resin initially covers the whole body of the flip chip and then is impregnated into the bump portion. Therefore, a void is formed at a position near the central portion under the flip chip. However, the outer peripheral portion forming the bumps of the flip chip where the thermal stress value becomes high can be restrained from moving by the transfer molding resin, and by using the resin having the set linear expansion coefficient and the set filler particle size the thermal stress exerting on the bump portion can be reduced to a value smaller than that in the case where the under filler material having the linear expansion coefficient of 20 to 30×10
−6
. That is, the durable life-time can be improved.
The present invention provides a resin sealed electronic device which mounts a flip chip type monolithic IC on a hybrid circuit board through bumps, and is packaged with a thermosetting resin through transfer molding, wherein the thermosetting resin used for the transfer molding (hereinafter, referred to as “transfer molding resin”) has a linear expansion coefficient of 3×10
−6
to 17×10
−6
and contains a filler having a particle size smaller than a height of the bump by more than 10 &mgr;m, and the resin sealed electronic device is integrated in a unit including the hybrid circuit board mounting the flip chip type monolithic IC through transfer molding with the transfer molding resin.
The present invention further provides a resin sealed electronic device in which the size of the filler is smaller than 75 &mgr;m.
The present invention provides a resin sealed electronic device which mounts a flip chip type monolithic IC on a hybrid circuit board through bumps, and is packaged with a transfer molding resin, wherein the resin sealed electronic device is integrated in a unit including the hybrid circuit board mounting the flip chip type monolithic IC through transfer molding with the transfer molding resin, and the bump is restrained from moving by the transfer molding resin flowing around at transfer-molding.
The present invention provides a resin sealed electronic device which mounts a flip chip type monolithic IC on a hybrid circuit board through bumps, and is packaged with a transfer molding resin, wherein the resin sealed electronic device is integrated
Fukatsu Katsuaki
Kaminaga Toshiaki
Kobayashi Ryoichi
Shida Masami
Sugiura Noboru
Crowell & Moring LLP
Hitachi , Ltd.
Solis Erick
LandOfFree
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