JPS6154863B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an IC lead frame material made of an Fe--Cr alloy that is inexpensive and has excellent adhesion to resin and plating properties, for example in a resin molded IC. [Prior art] The lead frame material used for this purpose is required to have excellent plating properties, corrosion resistance, and lead pin strength in the packaging process (plating, bonding resin encapsulation, etc.) or in use. required. Conventionally, this kind of material is 42
Although alloy (41Ni-Fe) is widely used, it has the disadvantage of high cost because it contains a large amount of Ni, which is an expensive raw material. However, in recent years, with the strict requirement to reduce the cost of products, there has been an increasing demand for materials that are cheaper than before and have the minimum necessary characteristics, and pure iron and stainless steel (SUS410, SUS430) are being considered. However, these alloys have advantages and disadvantages; pure iron easily rusts in the atmosphere and therefore has poor corrosion resistance, while stainless steel has excellent corrosion resistance but has the disadvantage of significantly poor plating properties. The present inventor has proposed Fe-
We proposed a lead frame material (Japanese Patent Laid-Open No. 57-50457) that is made of a 6-10% Cr alloy and is inexpensive and has excellent corrosion resistance without impairing plating properties. [Problem to be solved by the invention] ICs are sealed with ceramic or resin to protect their elements from the outside, but the disadvantage of resin-sealed types is that they are less moisture resistant than ceramic types. ing. However, in recent years, there has been a trend toward smaller and thinner packages due to the demand for higher density packaging, and there is a stronger desire for improved moisture resistance than ever before. However, conventional materials have poor adhesion to the resin, allowing water to enter through the gap between the lead and the resin.
There are problems such as corrosion and disconnection of Al wiring on the element. [Means and effects for solving the problems] From the above viewpoint, the present invention improves the drawbacks of conventional Fe-Cu alloys and improves the adhesion with resin from the material standpoint. Research on adhesion and plating properties revealed that when the oxide film on the lead frame surface and the material composition were within the claimed range, resin adhesion was significantly improved compared to conventional alloys, and a product with good plating properties was obtained. It is based on the discovery that The reasons for the limitations of the present invention will be described below. The Fe-Cr alloy that is the subject of the present invention must have the plating properties and corrosion resistance required for a lead frame material, and if the Cr content exceeds 10%, plating with good adhesion cannot be obtained. , also 6%
If it is less than Cr, the corrosion resistance will be significantly inferior, so it is limited to 6 to 10% Cr. If a large amount of C is contained, it forms carbides and causes corrosion, so the content is set to 0.1% or less. Si and Mn are elements that form an oxide film with excellent adhesion to resin on lead frames, but Si
If the total of Mn and Mn is less than 0.2%, the oxide film formed will be thin and will not be effective in improving adhesion to the resin, and if it exceeds 1.5%, the oxide film will become thick and the adhesion of plating will deteriorate. When the Mn/Si ratio exceeds 10, the surface oxide becomes Mn-rich and the oxide film easily separates from the base metal, while when it is less than 1, Si-based inclusions become a source of plating defects in the lead frame. Since the ratio increases, Si + Mn is 0.2 to 1.5% and Mn/Si ratio is 1 to 10.
limited to. 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 0.2%, the oxide film will become thick and the plating properties will deteriorate, so it was limited to 0.001 to 0.2%. 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 80 to 250 Å because adhesiveness with the resin is weak below 80 Å, and if it exceeds 250 Å. This is because the plating properties deteriorate. Furthermore, in the present invention, in order to obtain even better corrosion resistance without impairing the plating properties of the basic alloy,
One or more of Ni, Mo, Nb, V, and W may be contained, and if the amount alone or in combination is less than 0.2%, it will have no effect on corrosion resistance, while if it exceeds 3.5%, the plating properties will deteriorate. 0.2 to 3.5 because the molding processability of
%. [Example] The following is an explanation based on an example. After melting and casting the alloy shown in the table in a high frequency induction furnace,
Forged and hot rolled at temperatures above ℃, thickness 3
Rolled into a mm plate. Furthermore, cold rolling and annealing were repeated to obtain a thin plate material with a thickness of 0.25 mm.

【table】

〔effect〕

The results of the characteristic evaluation are shown in the table. As is clear from the table, alloys 1 to 8 of the present invention have approximately twice as much adhesion strength to the resin as the comparative alloys, and also have excellent plating properties when the oxide film thickness is 250 Å or less. Obtained. Furthermore, it can be seen that all of the alloys of the present invention have superior corrosion resistance compared to general pure iron, and can provide good plating properties equivalent to that of Alloy 42. As described above, the lead frame material of the present invention is a material that is inexpensive, has good plating properties, and high resin adhesion, and greatly improves the reliability of resin molded packages, which has great industrial effects.

[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. Cr6 to 10% by weight, C0.1% or less, Si+
Mn0.2-1.5% (Mn/Si=1-10). A10.001~0.2
Contains % balance Fe and unavoidable impurities
An IC lead frame material made of Fe-Cr alloy with excellent adhesion to resin and plating properties, characterized by a surface oxide film with a thickness of 80 to 250 Å. 2 Cr6-10% by weight, C0.1% or less, Si+
Mn0.2~1.5% (Mn/Si=1~10), A10.001~0.2
%, further contains 0.2 to 3.5% of one or more of Ni, Mo, Nb, V, and W, singly or in combination, and the balance is Fe and unavoidably mixed impurities.
In Cr-based alloys, the thickness of the surface oxide film is 80
An IC lead frame material with excellent adhesion to resin and plating properties, characterized by a thickness of ~250Å.