JPH0589721A - Conductive adheive and bonded body using the same - Google Patents

Abstract

PURPOSE:To provide a conductive adhesive which causes no warpage in a bonded body when a semiconductor chip is bonded on a lead frame via a conductive adhesive layer, as well as the bonded body free of warpage using the conductive adhesive. CONSTITUTION:A conductive adhesive contains silver particles and spherical particles and spherical silica 4 spherical diameter of which is controlled in a filler part, the spherical diameter of the spherical silica 4 being designed to be larger than that of the silver particles. In a bonded body such that a semiconductor chip 1 is bonded to a lead frame 3 by the conductive adhesive, the spherical silica 4 in the conductive adhesive 2 are oriented in one layer, and the film thickness of the conductive adhesive 2 is controlled to a predetermined thickness by the spherical diameter of the spherical silica 4. Therefore, the consumption of the conductive adhesive can be reduced by adjusting the film thickness to the minimum resisting warpage, as well as causing no warpage in the bonded body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive used for semiconductor chips, particularly large-sized semiconductor chips, and an adhesive body using the conductive adhesive.

[0002]

BACKGROUND OF THE INVENTION Conductive adhesives are used primarily in the semiconductor industry to connect semiconductor chips to leadframes and serve both mechanical and electrical connections. To bond the semiconductor chip and the lead frame, a conductive adhesive is applied to the lead frame in multiple points, the semiconductor chip is placed, and a scrub pressure is applied to the semiconductor chip to lead the conductive adhesive. Spread it with a constant thickness between the frame and the semiconductor chip,
It was adhered by curing at a temperature of 150 to 200 ° C. for 1 to 2 hours.

[0003]

Since the silver paste or the like used for the conductive adhesive is expensive, the cost will increase if the conductive adhesive layer is thicker than necessary in bonding the semiconductor chip and the lead frame. It will be hard. However, when the thickness of the conductive adhesive layer is made too thin, the semiconductor chip 1 is interposed via the conductive adhesive layer 2 provided on the lead frame 3 as shown in the sectional view of the warp of the semiconductor chip in FIG. The one to which was adhered had a warp.

In recent years, by making a package smaller and thinner, using a lead frame material of copper in order to attach importance to thermal conductivity due to the thinner package, and using a large chip, In particular, the above-mentioned problem of warpage has occurred. Therefore, it is an object of the present invention to provide an adhesive body that does not warp when a semiconductor chip is bonded onto a lead frame via a conductive adhesive layer. Moreover, this invention aims at providing the adhesive body which does not warp using the adhesive agent.

[0005]

In order to solve the above-mentioned problems, the conductive adhesive of the present invention comprises silver particles and spherical silica having a controlled spherical diameter in the filler portion which is a particle component in the adhesive. The spherical diameter of the spherical silica is larger than that of the silver particles. Further, the present invention is characterized in that, in a bonded body in which a lead frame and a semiconductor chip are bonded to each other via a conductive adhesive layer, spherical silica is contained in the conductive adhesive layer so as to form one layer. An adhesive body using a conductive adhesive as defined below.

[0006]

According to the present invention, the conductive adhesive contains silver particles and spherical silica having a controlled spherical diameter in the filler portion, and the spherical diameter of the spherical silica is made larger than that of the silver particles. The thickness of the conductive adhesive layer can be controlled to be constant by the spherical diameter of silica. Therefore, I
The adhesive body in which the C chip is adhered to the lead frame via the conductive adhesive layer can be controlled to have an appropriate thickness of the conductive adhesive layer, and the adhesive body does not warp.

[0007]

Example 1 Regarding occurrence of warpage of an adhesive body in which a semiconductor chip 1 is adhered onto a lead frame 3 via a conductive adhesive layer 2, various kinds of conductive adhesives having different material compositions are used,
The relationship of the warp with the thickness of the conductive adhesive layer was investigated. The conductive adhesives used in this experiment were the following three kinds of conductive adhesives (1), conductive adhesives (2), and conductive adhesives (3).
Is.

The composition of the electrically conductive adhesive (1) is a mixture of bisphenol A type epoxy resin and novolac type epoxy resin as a main component, phenol novolac resin as a curing agent, butyl cellosolve acetate as a solvent, and reactive dilution. Γ-Glycidoxypropyltrimethoxysilane was used as the agent, and a mixture of tetraphenylphosphonium and tetraphenylborate was used as the reaction accelerator. This conductive adhesive (1) is classified as a solvent type.

In the composition of the conductive adhesive (2), bisphenol A type epoxy resin was used as the main component, amine was used as the curing agent, phenylglycidyl ether was used as the reactive diluent, and imidazole was used as the reaction accelerator. .. This conductive adhesive (2) is classified as a solventless type using an amine compound as a curing agent. The composition of the conductive adhesive (3) uses bisphenol A-based epoxy resin as the main component, acid anhydride as the curing agent, phenylglycidyl ether as the reactive diluent, and zinc octylate as the reaction accelerator. I was there. This conductive adhesive (3) is classified as a solventless type using an acid anhydride compound as a curing agent.

The compositions of these conductive adhesives are tabulated in FIG. 4M-DRAM size lead frame 3 prepared using the conductive adhesives (1) to (3)
The experimental results of the warp of the adhesive between the semiconductor chip 1 and the semiconductor chip are shown in FIG.
This is shown in FIGS. In these graphs shown in FIGS. 4, 5 and 6, when the thickness of the conductive adhesive layer is plotted on the horizontal axis and the warp is plotted on the vertical axis with the peripheral portion of the lead frame as the bottom surface, the central portion is in the vertical direction. It was shown as the height which was transformed into. In these experimental data, there is a difference in the amount of deformation of the conductive adhesive in the vertical direction depending on the film thickness of the conductive adhesive layer, and depending on the type of material, but generally, it is shown in FIG. The tendency of the deformation can be shown in a graph in which the horizontal axis represents the thickness of the conductive adhesive layer and the vertical axis represents the warp vertically deformed. That is, when the thickness of the conductive adhesive layer is thin, the amount of deformation of the adhesive body rapidly increases, but when the thickness of the conductive adhesive layer is large, the amount of deformation decreases, and when the thickness becomes a certain amount, the amount of deformation It can be seen that is constant.

Therefore, in the present invention, the use of the minimum thickness of the conductive adhesive layer at the time when the magnitude of the warp starts to become a practical problem does not affect the amount of the conductive adhesive used. It was realized that it can be reduced and it is an economically advantageous means. In FIG. 7, when the thickness of the conductive adhesive layer is A μm, the amount of the conductive adhesive is the smallest, which is economically advantageous.

However, the control of the thickness of the conductive adhesive layer has hitherto been carried out by controlling the supply amount of the conductive adhesive, but it is difficult to finely control the supply amount. is there. In the present invention, in order to control the thickness of the conductive adhesive layer, it is possible to use spherical silica in which the spherical diameter contained in the filler portion, which is the particle component of the conductive adhesive, is controlled to a certain size. To control the film thickness to a constant value. That is, the spherical diameter of the spherical silica is set to a value approximately equal to the thickness of the target conductive adhesive layer, and the spherical silica is blended in the conductive adhesive in an amount such that the spherical silica does not overlap in the conductive adhesive layer. To do. The contents of silver particles and spherical silica contained in the conductive adhesive of the present invention were determined as follows.

FIG. 8 is a graph showing the relationship between the silver particle content of the conductive adhesive on the horizontal axis and the volume resistivity on the vertical axis. The volume resistivity of the conductive adhesive is generally required to be at least 10 ⁻³ Ω · cm or less. Therefore, from FIG. 8, the content of silver particles is 70% by weight.
You can see that we have to do the above. In order to prevent the spherical silica from overlapping in the conductive adhesive layer, that is, to make the spherical silica one layer, the addition amount thereof is 10% by weight or less in the conductive adhesive.

FIG. 1 shows an adhesive body of a lead frame and a semiconductor chip of this embodiment. Reference numeral 1 denotes a semiconductor chip, which is bonded to a lead frame 3 via a conductive adhesive layer 2. The portion shown in the circle in FIG. 1 is an enlarged view of the conductive adhesive layer 2, and in the conductive adhesive layer 2 made of silver particles, epoxy resin and other additives, compared to silver particles. The spherical silica 4 having a large diameter is arranged in a single layer.

The present invention can be applied not only to large semiconductor chips, but also to all sizes of semiconductor chips capable of preventing warpage.

[0016]

As described above, according to the present invention, since spherical silica whose spherical shape is controlled to a certain size is contained in the conductive adhesive, variations in the thickness of the conductive adhesive layer in the assembly process are caused. It was possible to obtain an adhesive body of the semiconductor chip and the lead frame, in which there was no variation in warpage.

[Brief description of drawings]

FIG. 1 shows an adhesive body of a lead frame and a semiconductor chip of this embodiment.

FIG. 2 is a sectional view showing a warp of a semiconductor chip.

FIG. 3 shows the composition of the conductive adhesive used in this example.

FIG. 4 shows an experimental result of warpage of an adhesive body between a lead frame and a semiconductor chip.

FIG. 5 shows an experimental result of warpage of an adhesive body between a lead frame and a semiconductor chip.

FIG. 6 shows an experimental result of warpage of an adhesive body between a lead frame and a semiconductor chip.

FIG. 7 shows a general tendency of warpage of an adhesive body between a lead frame and a semiconductor chip.

FIG. 8 is a graph showing the relationship between the silver content of the conductive adhesive and the volume resistivity.

[Explanation of symbols]

 1 Semiconductor Chip 2 Conductive Adhesive Layer 3 Lead Frame 4 Spherical Silica

Claims (2)

[Claims] 1. A conductive adhesive comprising a filler part containing silver particles and spherical silica having a controlled spherical diameter, wherein the spherical silica has a larger spherical diameter than that of the silver particles. 2. An adhesive body in which a lead frame and a semiconductor chip are adhered via a conductive adhesive layer, wherein the conductive adhesive layer contains spherical silica in a single layer. An adhesive body using the conductive adhesive according to claim 1.