Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-07-14
2004-11-30
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S439000, C524S440000
Reexamination Certificate
active
06825249
ABSTRACT:
TECHNICAL FIELD
This invention relates to a laminating method of a film-shaped organic die-bonding material, a die-bonding method, a laminating machine and a die-bonding apparatus for the bonding of a semiconductor element (hereinafter referred to as “chip”) onto a support member such as a leadframe using the film-shaped organic die-bonding material.
BACKGROUND ART
As a method for bonding a chip on a leadframe, it has heretofore been the practice to feed a die-bonding material onto the leadframe and then to bond the chip onto the leadframe. As such die-bonding materials, Au—Si eutectic, solders, resin pastes and the like are known, for example. Among these, Au—Si eutectic has the problems that it is costly and has a high modulus of elasticity and requires vibrations at portions to be bonded. Solders involve the problems that they cannot withstand temperatures equal to and higher than their melting point and they have a high modulus of elasticity. Of resin pastes, silver paste is most common. Compared with other materials, silver paste is most inexpensive and has high heat-resistant reliability and a low modulus of elasticity, which means that silver paste is used most often as a bonding material for IC and LSI leadframes.
Reflecting the high densification and the move toward larger chips in recent years, it has however become increasingly difficult to evenly coat silver paste over an entire surface upon bonding. Unless resin paste can be coated evenly, voids occur in bonded parts and upon mounting, they cause package cracking during the course of soldering heat treatment. Occurrence of such voids has therefore become a problem.
Further, there has been an ever-increasing demand in recent years for high-density mounting to meet the move toward smaller and/or thinner electronic equipment. Replacing semiconductor packages of the conventional pin insertion type, surface-mount semiconductor packages suited for high-density mounting have come into mainstream use.
In the case of a surface-mount package, leads are directly soldered to a printed circuit board or the like. Therefore, using infrared reflowing, vapor phase reflowing, solder dipping or the like as a heating method, the package is heated in its entirety and is then mounted.
Here, the entire package is exposed to temperatures as high as 210 to 260° C. If moisture exists inside the package, package cracking (hereinafter called “reflow cracking”) occurs as a result of explosive vaporization of the moisture.
This reflow cracking significantly reduces the reliability of the semiconductor package to the extent that it has become a serious problem and the subject of technical attention.
The following is the mechanism of the occurrence of reflow cracking caused by a die-bonding material. In a semiconductor package, (1) the die-bonding material absorbs moisture during storage, (2) upon mounting the package by reflow soldering, the moisture is vaporized by heat, (3) destruction or separation of the die-bonding layer takes place due to the resulting vapor pressure, and (4) reflow cracking then occurs.
Under the current circumstances whereby sealing materials have been increasingly improved in reflow cracking resistance, reflow cracking which is caused by a die-bonding material has become a serious problem, especially in thin packages, leading to a strong demand for the improvement of reflow cracking resistance.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a laminating method, a die-bonding method, a laminating machine and a die-bonding apparatus, which make it possible to fabricate, with good productivity, semiconductor packages which are free from package cracking and have excellent reliability.
Another object of the present invention is to provide a semiconductor device, which makes use of a film-shaped organic die-bonding material, is free from reflow cracking and has excellent reliability, and a fabrication process thereof.
In the present invention, a film-shaped organic die-bonding material is used. This is in the form of a film made primarily of an organic material such as an epoxy resin, silicone resin, acrylic resin or polyimide resin (including an organic material added with a metallic filler or an inorganic filler). On a support member such as a leadframe, the film-shaped organic die-boding material is compression-bonded in a heated state. Further, a chip is placed on the film-shaped organic die-bonding material, followed by heating and compression-bonding. Namely, a die-bonding material is evenly applied to a part, which is to be bonded, by forming a resin paste into a film. Such a film-shaped organic die-bonding material requires application of pressure so that the film-shaped die-bonding material is reliably provided with wettability to the chip and leadframe.
A film-shaped organic die-bonding material useful in the present invention can be produced, for example, by dissolving or dispersing an organic material such as a polyimide or epoxy resin and optionally, a material, for example, an additive such as a metallic filler in an organic solvent to form a coating varnish, coating the coating varnish onto a carrier film such as a biaxially-stretched polypropylene film, causing the solvent to evaporate to form a layer and then peeling off the layer from the carrier film. One side of the layer, the side having been in contact with the air in a drying step in which the solvent was caused to evaporate (i.e., the side being a side opposite to a side where the layer was in contact with the carrier film), will be referred to as the “side A”, while the side at which the layer was in contact with the carrier film will be referred to as the “side B”.
This invention provides a laminating method, die-bonding method, laminating machine and die-bonding apparatus for a film-shaped organic die-boding material, which are free from voids and feature good productivity and which are useful for applying the film-shaped organic die-bonding material to an actual assembly step for semiconductor devices.
The laminating method according to the present invention for a film-shaped organic die-bonding material comprises mounting and tack-bonding a film-shaped organic die-bonding material of a predetermined size on a chip-mounting support member at a predetermined position thereof and then pressing the die-bonding material against the support member, whereby the die-bonding material is compression-bonded on the support member.
The die-bonding method according to the present invention comprises mounting and tack-bonding a film-shaped organic die-bonding material of a predetermined size on a chip-mounting support member at a predetermined position thereof and then pressing the die-bonding material against the support member and compression-bonding the die-bonding material on the support member, thereby laminating the film-shaped organic die-bonding material of the predetermined size on the chip-mounting support member at the predetermined position thereof; and heating a chip and compression-bonding the chip on the film-shaped organic die-bonding material at a predetermined position thereof, the die-bonding material being located on the support member.
A first laminating machine according to the present invention comprises a feeder for feeding a film-shaped organic die-bonding material over a predetermined constant length, a punching device for punching out the film-shaped organic die-bonding material, a film tack-bonding device for placing and tack-bonding the punched-out film-shaped organic die-bonding material on the support member, and a film compression-bonding device for pressing the tack-bonded film-shaped organic die-bonding material against the support member so that the tack-bonded film-shaped organic die-bonding material is compression-bonded on the support member.
A second laminating machine according to the present invention comprises a feeder for feeding a film-shaped organic die-bonding material over a predetermined constant length, a cutter for cutting out the film-shaped organic die-bonding material, a film t
Kageyama Akira
Kaneda Aizou
Kikuchi Tooru
Kotato Akio
Maekawa Iwao
Cain Edward J.
Griffin & Szipl, P.C.
Hitachi Chemical Co. Ltd.
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