Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1994-01-28
1998-04-14
Hampton-Hightower, P.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528 26, 528 28, 528 38, 528125, 528128, 528170, 528172, 528173, 528176, 528183, 528185, 528188, 528220, 528229, 528350, 526935, 428458, 4284735, 427154, 427155, 427358, 427240, C08G 7310, C08G 6926
Patent
active
057392633
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a polyimide film adhesive which has excellent heat resistance and low water absorption, which is suitable for use in electronics applications particularly as a material for mounting of semiconductors, which has excellent adhesion to silicon substrates and metals and which can be applied at low temperatures in a short period of time.
BACKGROUND ART
In recent years, while semiconductor chips have come to possess a higher function and a larger capacity and accordingly have become larger in size, the packages containing semiconductor chips are required to have an external form same as or even smaller than the conventional form so as to meet the demand for smaller electronic devices. In response to this trend, some new mounting methods allowing the high-density mounting of high-density semiconductor chips have been proposed. One is a LOC (lead-on-chip) structure proposed for memory devices, wherein a die pad-free lead frame and chips are fixed to each other with a double-coated adhesive tape. Meanwhile, in logic devices, a multi-layered lead frame structure has been proposed in which the electric source and the glands are provided in different frames and the metal plates for heat radiation are provided in a plurality of layers. While in the conventional methods, the chip area was too large to secure the area for inner leads, in the above new methods, semiconductor chips and a lead frame are bonded with a double-coated adhesive tape and can be accommodated in a package having the same external form as the conventional package although the chip area is larger due to the larger capacity of chips. In the new methods, it is possible to rationalize in-chip wiring and wire bonding, shorten the length of wire for quicker signal, radiate the heat generated by the higher consumption of electric power, and make smaller the size of a device.
In the devices employing the above new mounting methods, there exist various adhesion interfaces between same materials or between different materials, such as chip vs. lead frame, lead frame vs. plate, lead frame vs. lead frame and the like. Therefore, the reliability of a device is greatly influenced by the adhesion reliabilities of said interfaces. The adhesion reliabilities must withstand the temperatures employed during the assembling of a device and further must be sufficient when the device is under humidity or under humidity and heat. Further, adhesion workability is also an important item. In semiconductor apparatuses of COL or LOC structure, the semiconductor chips and the lead frame are fixed to each other with an adhesive. This adhesive is required to have an excellent adhesivity so that the adhesion interfaces do not cause peeling under humidity or under thermal stresses caused by reflow soldering, temperature cycle, etc. The presence of a large amount of volatile components in the adhesive is not preferable because, when it is applied with heating, the volatile components contaminate the working environment, leads, etc. Desirably, the adhesive can complete adhesion in a period of time as short as possible, in view of the mass productivity of a device.
As such an adhesive, there have heretofore been used paste-like adhesives and adhesives obtained by coating an adhesive on a heat-resistant base. As the adhesive, there are used thermosetting resins of epoxy resin type, acrylic resin type or rubber-phenolic resin type; however, they do not satisfy the requirements for a highly reliable adhesive, because they contain a large amount of ionic impurities, require a high temperature and a long time for thermosetting and are not productive, generate a large amount of volatile matters during thermosetting and contaminate leads, and are highly hygroscopic. Thus, no satisfactory adhesive has not yet been found.
Meanwhile, with respect to the heat-resistant film adhesive which is contact-bondable with heating, some film adhesives are known. For example, hot-melt adhesives of polyamideimide type or polyamide type are described in Jap
REFERENCES:
patent: 4916009 (1990-04-01), Hino et al.
patent: 5192619 (1993-03-01), Konotsune et al.
patent: 5300364 (1994-04-01), Hase et al.
patent: 5300627 (1994-04-01), Kunimune et al.
patent: 5604041 (1997-02-01), Choi
D. Wison et al, "Polymides", Chapman and Hall, 152-153, 1990, This is a book, No Month of Publication is Needed.
Okugawa Yoshitaka
Sakamoto Yushi
Suzuki Toshio
Takeda Toshiro
Tochimoto Takuya
Hampton-Hightower P.
Sumitomo Bakelite Company Limited
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