JPH034030Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to improvements in semiconductor bonding thin wires. In conventional semiconductors such as ICs, LSIs, and hybrid ICs, thin Au wires or Al-Si wires of about 15 to 60μφ are used to electrically connect electrodes formed on semiconductor elements such as Si chips to lead frames and substrate leads.
Fine alloy wire is used. The former thin wire is widely used because it can be applied to highly productive heat fusion bonding methods and ultrasonic thermocompression bonding methods and has corrosion resistance, but its drawback is that it is extremely expensive. On the other hand, the latter thin wire is cheaper than Au wire, but it cannot be heat fused in the atmosphere, so it has poor productivity and is easily corroded, leading to failures such as disconnection when using semiconductors. . Particularly in semiconductors molded with general-purpose resins such as epoxy resins, corrosion of Al wires has been a major problem due to the moisture permeability of the resins and chlorine contamination. Some attempts have been made to use Cu or Cu alloy wire instead of this Al alloy wire, but Al
Although it was slightly improved over alloy wire, it was a big problem in practical use. Furthermore, attempts have been made to use this alloy wire coated with Ag, but this has caused severe migration in resin-molded semiconductors, causing short circuits. Note that migration also occurs in the above-mentioned Cu or Cu alloy wire, but it is lower than that in the Ag wire. The present invention was developed as a result of extensive research in view of the current situation, and the discovery of a practical thin bonding wire that is economical and has high performance. That is, in the present invention, the outer periphery of a core wire made of Cu or Cu alloy wire is coated with Pd or Pd alloy either directly or through an intermediate layer. As shown in Fig. 1, which explains one example of the present invention with drawings, Cu, Cu-Sn, Cu-In, Cu-Ni, Cu-
Pd, Pd-Ni,
A coating layer 2 of Pd-CO or the like is provided. In the present invention, the thickness of the coating layer 2 is not particularly limited, but is preferably 0.01 to 2 μm.
0.02 to 0.5μ is preferable from the economic point of view. By providing a coating layer of this thickness, corrosion resistance and strength can be improved. That is, the present invention uses Cu wire or Cu wire.
This makes more effective use of the conductivity and strength characteristics of alloy wire. In particular, the present invention can have the additional effect of exhibiting performance comparable to expensive Cu alloy wire even when using an inexpensive pure Cu wire as the core material. In other words, pure Cu wire usually has better conductivity than Cu alloy wire, but is inferior in strength. However, in the present invention, we have developed a wire that uses pure Cu wire as a core material but has high conductivity and strength. It is ideal because Cu and Pd form an alloy and strengthen, especially in the bonding area. Moreover, the one shown in FIG. 2 is one in which an intermediate layer 3 is provided and a covering layer of Pd or a Pd alloy is provided. That is, since the intermediate layer uses a metal such as Ni or Co, which is inexpensive and can improve corrosion resistance and diffusion deterioration, the coating layer 2 of Pd or Pd alloy can be made thinner, such as 0.02 as described above. A sufficient effect can be achieved with a thickness of about 0.5μ. The thickness of the intermediate layer is not particularly limited either, but it is usually about 0.02 to 0.1 .mu.m. In the present invention, the intermediate layer and the covering layer may be formed by vacuum plating, mechanical pressure bonding, etc., but electroplating is most advantageous. Next, embodiments of the present invention will be described in detail. EXAMPLE Oxygen-free copper wire (20 μΦ) was coated with the metals or alloys shown in Table 1 by electroplating to obtain thin bonding wires of the present invention and comparative thin wires. The bonded thin wire obtained in this way was attached to a 16-pin lead frame (made of Cu-0.15 Sn-0.01P alloy).
After the chips were die-bonded, wire bonding was performed using an atmospheric heat fusion method. The bonding conditions were 10% _H2 - _N2 atmosphere, temperature raised to 190℃, first bonding pressure 50g, second bonding pressure.
I went with 80gr. The strength of the bonding obtained in this way was measured using a pull-raster, and then the IC molded with epoxy resin was held at 130°C with a pressurizer at saturation pressure for 2000 hours with 12V applied to determine the probability of disconnection and short circuit. The probability was measured. The results are shown in Table 1.

[Table] As is clear from the above table, the thin bonding wire for semiconductors of the present invention does not break or short-circuit and has excellent strength like the conventional Au wire (Comparative Example 3). Further, although the Cu wire (Comparative Example 1) did not cause short circuit, when the IC was destroyed and observed under an electron microscope, migration of Cu was observed. In contrast, no trace of this was observed in the thin wire of the present invention. As described in detail above, the present invention has remarkable effects such as providing a bonding thin wire with low cost and high performance in place of the expensive Au wire.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing one example of the semiconductor bonding thin wire of the present invention. 1... Core wire, 2... Covering layer, 3... Intermediate layer.

Claims (1)

[Claims for Utility Model Registration] (1) A thin bonding wire for semiconductors, characterized in that a coating layer of Pd or Pd alloy is provided on the outer periphery of a core wire of Cu or Cu alloy, either directly or via an intermediate layer. (2) The thin bonding wire for semiconductors as set forth in claim 1 of the utility model registration claim, characterized in that the intermediate layer is made of Ni, CO, or an alloy thereof.