JPS629658A - Manufacture of alloy-base belt material for lead frame - Google Patents

Abstract

PURPOSE:To simplify substantially the manufacturing process of a lead frame, by plating Ni and/or Cu onto belt-shaped alloy source material and then by rolling it. CONSTITUTION:Since it may be satisfactory to plate only on one face of alloy belt source material on account of the original purpose of an underlayer for Ag plating, it is not desirably considered to plate onto both faces because of material being wasted. However, since plating only onto one face of the alloy belt source material requires to mask the other face, it may be rather desirable to plate onto both faces of the alloy belt source material if the required material and labor are considered. After the alloy belt source material 1 is plated with Ni and/or Cu in this way, it is cold-rolled after being annealed if desired. Thus the alloy belt source material with a thickness of 0.4-1.0mm can be rolled into a thickness of about 0.25-0.125mm to provide alloy-base belt material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to an alloy strip base material used in IC lead frames.

[Background of the invention]

K, which manufactures this type of lead frame, anneales and/or cold-rolls the alloy strip base material if desired, and as shown in FIG. Slit several alloy strips aυ, α3, (13, α fathom). If desired, perform annealing after slitting, then punch or photo-etch the lead frame into the shape shown in Fig. 3 (2 ) The lead frame (2) is connected to the silicon chip (3) by a thin wire (4) at the tip end of each bottle Cυ as shown in FIG.

[Conventional technology]

Conventionally, the tip of the pin Qυ of the lead frame (2) (
Co., Ltd.) was plated with 1 to 0.5 μm thick K An. However, since Au is expensive, recently Ag has been used instead of Au.
A method of plating is being considered. Lead frame(
2) materials include 42Z Ni steel and 29Ni-17
Kovar, which is a Co steel, is used, but since such a material has poor Ag plating properties, as shown in Figure 4, 1 to 5 μm of Ni or Cu is first applied as the base plating (5).
Thick plating, and then 1-3μ thick Ag plating (6)
is being carried out.

[Interim point that the invention attempts to solve]

However, performing the plating process on the lead frame (2) twice as described above requires a very complicated and time-consuming process.

[Means for solving problems]

As a means to solve the above-mentioned conventional problems, the present invention provides a lead frame for use in which one or both surfaces of an alloy strip raw material are plated with KNi and/or Cu and then rolled to a predetermined thickness. A method for manufacturing an alloy strip base material is provided.

The invention will be explained in detail below.

The material of the alloy strip raw material used in the present invention is 4
Kovar is a 2% Ni steel or a 29Ni-17Co steel. The alloy strip raw material is plated with Ni and/or Cu, and the thickness of the plating layer is usually 2 to 7 microns. The plating may be applied to one side or both sides of the alloy strip raw material. From the viewpoint of its original purpose as a base for Ag plating, it is sufficient that the plating is applied only to one side of the alloy strip raw material. It is considered undesirable to apply plating to both sides because it wastes material, but in order to apply plating to only one side of the alloy strip raw material, the other side must be masked. Considering the required materials and labor, it is preferable to perform blood precipitation plating on both of the alloy strip raw materials. After the alloy strip raw material has been plated with Ni and/or Cu in this way, it is cold-rolled while being annealed if desired. Further, if desired, annealing is performed again and then cold rolling is performed. In this way it is usually 0
．． 0.25 to 0.1 alloy strip raw material with a plate thickness of 4 to 1.0 mm
The alloy strip base material is obtained by rolling to a thickness of approximately 25II11. The alloy strip base material thus obtained is slitted as shown in FIG. 1 to divide it into several alloy strips. In the figure, (1) is the alloy band base material, (5) is the base plating layer which is Ni and/or Cu plating, αυ, α
4. α3. (I is an alloy band. The width of the alloy band (5) is made to approximately match the width of the lead frame, but the annealing strain formula etc. are taken into consideration. The alloy bands αυ, α3 divided in this way
, Q3, If desired, annealing is performed on the α-shape after slitting to remove distortion during slitting. - The alloy strip thus obtained is punched or photoetched to produce a lead frame (2) as shown in FIG. 3.

For the frame (2) K obtained as described above, it is only necessary to apply kAg plating (6) to the tip of each bottle Qυ as shown in FIG. After applying Ag plating (6), if the base plating (5) is Cu plating, it is desirable to remove the exposed Cu plating part by elution with an elatin solution, etc. because Cu tends to rust. Effects and Effects of the Invention In the present invention, since the base plating treatment is applied to the alloy strip base material which is thicker and therefore shorter than the alloy strip base material, the processing area is correspondingly reduced and the plating processing cost is reduced. is reduced. Although the thickness of the plating layer cannot be reduced to a certain level, for example, 1 μm or less, the thickness of the plating layer can be reduced to 1 μm or less by rolling after plating. Since the alloy strip material has a simple shape, it is easy to plate it, and the number of parts to be plated is much smaller than before, so continuous processing is possible. The manufacturing process will be greatly streamlined.

Example 1 Copal material 1. Pull out a coil of raw alloy strip material with a thickness of 120 mm and a width of 120 mm from one end, put masking material on the back side of the drawer, and immerse it in a plating bath to apply Ni plating to a thickness of 6 μm on the surface. When the thickness is reduced by 0.25wK by rolling, the Ni plating layer becomes approximately 1.5μ.
It becomes thick. Three alloy strips having a width of 37 layers are cut out from the alloy sheet thus obtained by slitting. The obtained alloy strip is punched into the shape of a lead frame, and then degreased with trichloride and then pickled. K like this
A 3μ thick A
Good bonding properties were obtained when Aura with a diameter of 30 μm was bonded after g plating.

Example 2 A coil of alloy strip raw material made of 42SNi steel, 90.3 ms thick, 310 sa + width is pulled out from one end, a masking material is applied to the back side, and immersed in a plating bath to coat the surface with 3 μ thick C.
Apply U plating. After plating, annealing is performed, followed by cold rolling, and after repeating the annealing and cold rolling, the thickness is finally reduced to 0.254 μm, resulting in a Cu plating layer of approximately 2.54 μm.

Twelve alloy strips having a width of 24.6 sag were cut out from the alloy sheet thus obtained by slitting. The obtained alloy strip is annealed to eliminate distortion caused by slitting, and then punched into a lead frame shape, followed by degreasing with trichlene and then pickling. After applying Ag plating with a thickness of 3μ to the predetermined parts of the lead frame treated in this way, the exposed Cu plating portion was removed with an etching solution, and then a thin Au wire with a diameter of 30μ was bonded, resulting in good bonding. was gotten.

[Brief explanation of drawings]

1 is a perspective view of an embodiment of the present invention, FIG. 2 is a perspective view of a conventional example, FIG. 3 is a plan view of a lead frame, and FIG. 4 is a sectional view taken along line AA in FIG. 3. In the figure (1)... Alloy strip base material, (5)... Base plating patent applicant Daido Steel Co., Ltd. 71-1) Figure 2

Claims (1)

[Claims] A method for producing an alloy strip base material for a lead frame, which comprises plating Ni and/or Cu on one or both surfaces of the alloy strip raw material and then rolling it to a predetermined thickness.