JPH0142502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a material for lead frames of semiconductor devices such as ICs and LSIs. Traditionally, many ICs and LSIs were manufactured using ceramic packages, but as a result of constant price competition, more and more products are being manufactured using lower-cost plastic molds, and we believe that this trend will become even stronger in the future. It will be done. Of course, lead frame materials are also required to be as inexpensive as possible. Kovar alloy (29Ni-16Co-Fe) was preferred as a lead frame for ceramic packages due to its coefficient of thermal expansion and sealing properties, but as the price of Co increased, 42Ni-Fe alloy was increasingly used. It became like that. However, since Ni is also expensive,
There was a strong demand for the emergence of inexpensive materials. Proposals that meet this demand include, for example (34-
40) Use of Ni-(2~10)Cu-Fe alloy (JP-A-Sho
56-33457), (25-50)Ni-(1-25)Cu-
There are leads for Fe alloys (Japanese Patent Application Laid-Open No. 56-50550), but these have been developed by replacing some of the Ni with Cu within the limits that do not significantly change the coefficient of thermal expansion or corrosion resistance of the 42Ni-Fe alloy.
The idea is to change your clothes. The present inventor has discovered that the material for lead frames used in the manufacture of electronic devices using plastic molds is
Considering that it should have properties that are appropriately selected from a different perspective than materials for ceramic packages, and should also be cheaper, we did not consider replacing the conventional Ni with Cu, but instead created the desired properties by adding an appropriate amount of alloy components. Research aimed at finding a balance between characteristics and price led to the present invention. The lead frame material of the present invention has Ni: 15%
It is characterized by being made of an alloy containing less than 25% Cu and 4% or more and 30% or less, and the balance being substantially Fe. Apart from price, the properties required for lead frame materials used in plastic molds are corrosion resistance, plating and solderability, punching workability, strength and bendability, thermal conductivity, and a coefficient of thermal expansion close to that of Si. , as well as heat resistance strength. The Fe-Ni-Cu alloy having the above composition has a good balance of these properties. That is, the corrosion resistance is considerably high due to the presence of Ni, the plating and soldering properties are significantly improved by the addition of Cu, and the strength and bendability are also high. Thermal conductivity and heat resistance strength are not bad, and the coefficient of thermal expansion shows a satisfactory value. The punching workability is much better than those with high Ni content such as 42Ni-Fe alloys. Ease of punching is an important factor because it makes the processing process into a lead frame advantageous and greatly contributes to reducing the manufacturing cost of the entire electronic device. The alloy components mentioned above were selected from this point of view, but to supplement the explanation, Ni is 15%
If it is not added in an amount exceeding 25%, the metal structure will become unstable and the dimensions may change due to transformation during heating and cooling after molding into a lead frame, such as at the temperature of a plastic mold. Not only does it reduce conductivity, but it also goes against the purpose of manufacturing at low cost. Furthermore, Cu cannot improve plating and solderability unless it is 1% or more, and 4% or more is required to fully obtain these effects. This may cause cracking during rolling into sheets. When manufacturing the lead frame material of the present invention, there is virtually no problem with impurities when alloying components are added to pure iron, but even when impurities are difficult to avoid when other manufacturing methods are used, the following The ingredients have been found to be acceptable up to the indicated limits. C: up to 0.3%. Si and Mn: up to 3%. However, the total amount must not exceed 3%. The suitability of the lead frame material of the present invention for plastic molded semiconductor devices is shown by data showing improvements in punching workability and plating performance. Example A material having the composition shown in the table below (the remainder being substantially Fe) was melted and rolled into a sheet with a thickness of 5 mm, and the surface was cleaned by pickling. Punching workability was evaluated by the length of the sheared surface and the size of the burr when a thin plate with a thickness of 0.25 mm was punched using a carbide die with a clearance set to 7% of the plate thickness. Plating properties were determined by cutting the above pickled sheet into test pieces of 3 cm x 10 cm, first applying a Cu base plating (thickness of 1 μm), and then performing Ag plating (thickness of 4 μm) thereon.
This plating test piece was placed on a hot plate at 450° C. for 5 minutes, then taken out, and the presence or absence of blisters on the front and back sides was counted. For comparison, similar tests were conducted on 42Ni-Fe alloy and other materials outside the scope of the present invention. The results are also shown in the table. 【table】

Claims (1)

[Claims] 1 Ni: more than 15% and less than 25% and Cu: 4% or more
A lead frame material comprising an alloy containing 30% or less Fe, with the remainder being substantially Fe. 2 The alloy further contains 1 to 3 types of C: 0.3% or less, Si: 3% or less, and Mn: 3% or less (however, Si and
The total amount of Mn is limited to 3%. ) The lead frame material according to claim 1, which contains the following.