JPH0523064B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lead frame material that has excellent adhesion to resin and solderability, for example in a resin molded IC. Currently, 42 alloy (42Ni−) is used as a metal material for lead frames.
Fe) Copper alloys and pure iron systems are used, but
42 alloy is often used in MOS type ICs due to its thermal expansion compatibility with Si chips and lead strength. In order to protect the IC elements from the outside, they are generally hermetically sealed with an envelope made of ceramic or resin. Ceramic molds with excellent moisture resistance are used for highly reliable products, but they have the disadvantage of increasing the cost of the package. On the other hand, the resin-sealed type has been used in large quantities in recent years because of its excellent productivity and low cost, but it still has the drawback of being inferior in moisture resistance compared to the ceramic type. In order to solve this problem, research on the resin side and examination of sealing conditions are also being conducted.
Various improvements have also been made on the lead frame material side. The purpose of the present invention is to provide a lead frame that has both properties of adhesion between 42 alloy and resin and solderability.As a result of research on both of these properties, the oxide film on the surface of the lead frame and the material composition are patented. The claimed invention is based on the discovery that an alloy with better resin adhesion and better solderability than conventional alloys was obtained. The reasons for the limitations of the present invention will be described below. If Ni is less than 30% or more than 50%, the coefficient of thermal expansion becomes too large and the compatibility with the Si chip deteriorates, so Ni is limited to 30 to 50%. Si and Mn are elements that form an oxide film with excellent adhesion to resin on lead frames, but Si
If the total of
If it exceeds this value, the oxide film will become thicker and will easily separate from the base metal. When the Mn/Si ratio exceeds 10, the surface oxide becomes Mn-rich and the adhesion with the resin deteriorates, while when it is less than 2, there are many Si-based inclusions that cause plating defects in the lead frame. To become
The Mn/Si ratio was limited to 2 to 10 with Si+Mn of 0.2 to 1.5%. Al is an element that promotes oxide film formation,
If it is less than 0.001%, the effect will be small, and if it exceeds 0.1%, the oxide film will become too thick and the solderability required for lead frames will deteriorate, so we limited it to 0.001 to 0.1% as a range for good resin adhesion. . The thickness of the surface oxide film was determined by analyzing Si, Mn, and Al in the depth direction with an ion microanalyzer, and was limited to 20 to 150 Å because the adhesiveness with the resin is weak below 20 Å, and if it exceeds 150 Å. This is because the solderability deteriorates. Next, specific examples will be shown in Examples. The alloy whose chemical composition is shown in the table was melted in a 7 kg high-frequency vacuum induction furnace, and then a strip with a thickness of 0.25 mm was obtained by forging, hot rolling, and cold rolling. Adhesion with resin is 0.25mm thick x 25mm x than the above material
A 25mm sample was taken and heat treated in 900°C x _3mmH2 gas. Then, as shown in the figure, a resin molding thin plate jig 2 (with an 11φ hole) was placed on top of the sample 1, and heated to 168°C x 2mm on a hot plate 3.
Powder resin 4 was cured. After cooling to room temperature, sample 1
was fixed and the thin plate jig 2 for resin molding was pulled in the direction of the arrow to measure the adhesion strength. Also, for solderability, the same sample as the resin adhesion test was used.
Good solderability was achieved if the solder wetted more than 90% of the area after immersion in a molten solder bath heated to 240°C for 2 seconds. The results of the characteristic evaluation are shown in the table. As is clear from the table, the alloys of the present invention exhibited approximately twice as much adhesion strength with the resin as the comparative alloys, and had excellent solderability when the oxide film thickness was 150 Å or less. As described above, the present invention provides a resin molded package with a predetermined solderability, increases the adhesive strength between the resin and the leads, and greatly improves the reliability of the package, which has great industrial effects. It is. 【table】

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the resin adhesion strength test. 1...Sample, 2...Thin plate jig for resin mold,
3...hot plate, 4...resin.

Claims (1)

[Claims] 1 In Ni30~50 (weight% and below are the same)-Fe alloy, Si+Mn0.2~1.5% (however, Mn/Si=2~
10), A10.001~0.1%, which is an alloy containing impurities that are unavoidable during manufacturing, and the thickness of the surface oxide film is 20~150 Å.Adhesion with resin and solderability. Excellent lead frame material.