JPH01257357A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To improve a close adhesion property of a lead frame with reference to a resin after a resin sealing operation by installing and forming a Cu-plated layer containing Ag on a whole face or a resin-sealed part on the surface of the lead frame. CONSTITUTION:A Cu-plated layer containing Ag is formed on a whole face or a part on the surface of a lead frame 1. That is to say, sinde Ag is contained in the Cu-plated layer, it is possible to form an oxide film whose close adhesion property with reference to a substratum is good even when the layer is oxidized due to heating at a die bonding operation. In addition, it is especially preferable that an amount of Ag to be contained in the Cu-plated layer is 0.1-10wt.%. By this setup, it is possible to solve a conventional problem that the moisture creeps from a part between a resin 2 and the lead frame 1 after a resin sealing operation and that a semiconductor device operates defectively.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lead frame for a semiconductor device, and more particularly to a lead frame for a semiconductor device that has improved adhesion to a resin after resin encapsulation. .

[Prior Art] Semiconductor devices such as transistors and ICs are generally assembled by the following method.

First, a semiconductor element is mounted on a lead frame, and the semiconductor element is thermally bonded (die bonded) to the lead frame using Au-3i eutectic, Ag paste, solder, etc. Next, the electrode part of the semiconductor element and the lead frame are connected. After wiring with Au or AIt wires, the semiconductor element portion and the wiring portion are sealed with metal, ceramics, resin, or the like. Finally, the outer lead portion is assembled by soldering or solder plating.

Cu alloys and Fe-Ni alloys are generally used as lead frame materials, and after the entire surface of the lead frame is plated with Ni, the wire bonding area and die bonding area are partially coated with Ag. , directly on the die bonding part of the lead frame or on the base C.
What is used is U plating followed by partial Ag plating. Among these, in the case of the former case where the entire surface of the lead frame is plated with Ni, the solder layer on the outer lead part tends to peel off due to the heat effect when the semiconductor device is used. Currently, lead frame materials that are partially Ag-plated directly or after base Cu plating are widely used.

In addition, as a method for sealing a semiconductor device, there is a hermetic sealing method using metal, ceramics, glass, etc. as a sealing material;
Resin sealing methods using epoxy resins, silicone resins, etc. have been adopted, but resin sealing methods have become mainstream in terms of mass productivity and quality stability, and are expected to increase in usage in the future. has been done.

However, in the resin sealing method, since voids exist between the polymer main chains of the resin, water molecules easily permeate through these voids, making it difficult to protect the semiconductor element in a completely airtight state.
It has the disadvantage of being inferior in airtightness compared to sealing methods using metals, ceramics, etc. In recent years, by improving resin materials and improving sealing technology, it has reached a level comparable to the hermetic sealing method described above. However, there is still a problem in that moisture intrudes into the semiconductor device and causes corrosion around the semiconductor element and electrode portion, which tends to cause malfunction of the semiconductor device.

In particular, lead frames in which the die bonding area is partially plated with Ag after direct or base Cu plating on the surface of the Cu alloy have Cu exposed in the resin-sealed area, so heating during die bonding may cause The Cu surface is oxidized, forming an oxide film that easily peels off. Since the resin is in close contact with the surface of the Cu alloy through this easily peelable oxide film, moisture infiltrates into the interior of the resin seal.

Conventionally, large amounts of expensive inert gas and reducing gas have been used to prevent Cu from oxidizing during die bonding. The use of this gas has been a major obstacle to cost reduction, and there has been a desire to develop a surface treatment technology that provides good adhesion to the substrate during heating during die bonding.

[Problems to be Solved by the Invention] The present invention is directed to a resin seal in which Cu is exposed in the resin seal part, which has poor airtightness in the resin seal part despite being excellent in mass productivity and quality stability. This was made to solve the problems of fixed-type lead frames for semiconductor devices,
This was done for the purpose of providing a lead frame for a semiconductor device at a low cost with improved adhesion between the lead frame and the resin after resin sealing.

[Means for Solving the Problems] The present invention provides a lead frame for a semiconductor device in which a semiconductor element is mounted and resin-sealed, in which Cu metal containing Ag is used on the entire surface of the lead frame or in the resin-sealed portion. There is a gist in a lead frame for a semiconductor device, which is characterized by being provided with a bonding layer.

[Function] The present inventors have discovered that the main path for moisture intrusion into a resin-sealed semiconductor device is through the bond between the lead frame and the resin.
Focusing on the fact that the amount of moisture infiltration depends on the adhesion between the lead frame and the resin, it is important to improve the adhesion between the lead frame and the resin in order to prevent moisture intrusion. I thought there was. Therefore, we investigated the factors on the lead frame side that affect the adhesion with the resin, and found that a lead frame surface with good adhesion to the substrate and a relatively thick oxide film is suitable. As a result of extensive research into Cu plating, which has excellent adhesion to resin, it was found that the objective could be achieved by providing a Cu plating layer containing Ag on the entire surface or part of the lead frame surface.

That is, by incorporating Ag into Cu plating,
This makes it possible to form an oxide film that has good adhesion to the substrate even if it is oxidized by heating during die bonding.

In addition, in the present invention, Ag contained in the Cu plating layer
The amount is particularly preferably 0.1 to 10 wt%. The reason why the preferable lower limit of the Ag content is set to O.1 wt.% is that O.twt.% is the lower limit at which adhesion to the resin can be particularly preferably exhibited. In addition, the reason why the preferable upper limit of the Ag content is 10 wt% is that although it does not mean that the effect of improving adhesion with the resin cannot be achieved even if it exceeds 10 wt%, the effect that increases the cost due to the increase in the content is not enough. This is because they cannot be obtained. This point will be described more specifically in the following examples.

[Example] The present invention will be specifically explained below with reference to Examples.

Cu-2wt%5n-O as lead frame material
, 1wt%Fe-0,03wt%P alloy was used to prepare a specimen having the shape shown in FIG. 1 by etching.

This test piece was subjected to a commonly used plating pretreatment (alkaline degreasing - electrolytic degreasing - pickling), and then plating was performed under the following conditions.

Plating conditions> 1) Example liquid composition of the present invention: Copper pyrophosphate 100 g/It Potassium pyrophosphate 350 g/I Ag ion 10-110000 pp Temperature: 50°C Current density: 4 A/dm" Plating thickness 20. 5μm 2) Conventional example liquid composition: CuCN 30g/ftNaCN
30g1ft N a2 co3 15 g/fl Temperature
: 40°C Current density: IA/dm2 Plating thickness = 0.5 μm After plating, the Ag content in the plating of each test piece was analyzed, and then heated (350°C in air for 5 minutes) assuming die bonding. The plating surface was oxidized. Thereafter, as shown in FIGS. 2(a) and 2(b), epoxy resin 2 was molded on lead frame 1 by transfer molding under the following conditions.

Resin molding conditions> 1. Resin epoxy resin: (EME6100 manufactured by Sumitomo Bakelite) 2. Molding conditions Preheating temperature: 90℃ ゛Mold temperature: 175℃ Resin injection pressure 70kg/crn” Injection time = 20 seconds Curing time = 90 seconds Bot cure: The adhesive strength of the sample molded at 175° C. for 8 hours or more was measured to evaluate the adhesion to the resin.

Measurements are made after resin molding and by pressure shoe test (
2 after 121°C, 100% RH, 2 atm, 500 hours)
An Instron type universal test m (Autograph manufactured by Shimadzu Corporation) was used for the measurement.

The adhesive strength was determined by fixing the resin part 2 to a jig processed to fix the resin, and pulling one of the lead parts of the lead frame 1 parallel to the resin bonding surface at a speed of 25 mm/7 minutes.
This value was obtained by measuring the maximum load before peeling.

The results obtained from the above tests are shown in Table 1.

In Table 1, samples No. 1 to No. 7 are examples of the present invention, and especially No. 1 to No. 5 have an Ag content of 0.1.
~10%, No, 6°No, 7 is for other cases. No. 8° No. 9 is a conventional example for comparison.

For Examples No. 1 to No. 5, the weight was 23.0 to 24.7 kg/crn' after resin molding, and 19.5 to 20.3 kg after pressure shoe test.
/err? It showed high adhesive strength.

Although Example No. 6 is slightly inferior to Examples No. 1 to No. 5 due to the low Ag content in the Cu plating, it exhibits very good adhesive strength when compared to the conventional examples described below. Ta.

On the other hand, Example No. 7 had a high Ag content, and exhibited a value equivalent to that of Examples No. 1 to No. 5 in terms of adhesive strength.

In addition, when similar tests were conducted on conventional examples No. 8 and No. 9, it was found that the Cu plating that does not contain Ag in No. 8 had a weight of 12.5 kg/cm" after resin molding, and 10 kg/cm" after the pressure cutter test. It has an adhesive strength of .5kg/crn" and is No.

9 Cu alloy plating after resin molding 12.8kg/c
rn”, 9.8 kg/c after pressure hookah test
In terms of adhesive strength of rn', both exhibited much lower adhesive strength than the examples of the present invention.

Note that the Cu plating containing Ag in the present invention may be either electrolytic plating or electroless plating.

Table 1 [Effects of the Invention] As described in detail above, the present invention solves the conventional problem of moisture infiltrating between the resin and the lead frame after resin sealing, causing malfunction of the semiconductor device. It has become possible to provide a lead frame for a semiconductor device at a low cost that can solve these problems, and thereby it has become possible to greatly improve the reliability of the semiconductor device.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the shape of the lead frame of the present invention;
2(a) and 2(b) are a plan view and a side view of the lead frame shown in FIG. 1 sealed with resin. 1...Lead frame, 2...Resin. (a) (b)

Claims (2)

[Claims] (1) A lead frame for a semiconductor device on which a semiconductor element is mounted and sealed with resin, characterized in that a Cu plating layer containing Ag is provided on the entire surface of the lead frame or on the resin-sealed part. Lead frame for equipment. (2) The lead frame for a semiconductor device according to claim 1, further comprising a Cu plating layer containing 0.1 to 10 wt% of Ag.