JPS5943973B2 - Manufacturing method of lead frame material for Ag plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to Fe-Ni-
The present invention relates to a method for manufacturing a lead frame material made of a Co-based alloy.

As is well known, the sealing material used for lead frames of semiconductor integrated circuit devices and lead wires of various vacuum tubes is Fe, also known as Kovar, which has a composition of 29% Ni, 17% Co, and the balance is Fe. -Ni-Co
alloys are known.

A method for obtaining a material for a lead frame, such as a thin flake material, from an alloy ingot of such a Fe-Ni-Co sealing alloy is to cold-work the alloy ingot, such as rolling, to form a thin plate. The common method is to slit the thin plate and cut it into narrow widths, and when processing the material obtained in this way into lead frames at the user stage, punching or, in rare cases, etching is used. Generally, the above-mentioned material is processed into the shape of a lead frame, and the surface thereof is further plated with Ag. However, when the surface of the Fe-Ni-Co alloy lead frame obtained as described above is directly plated with Ag, the adhesion of the plating layer is poor. The Ag plating layer ``swells'' due to the heating temperature during the wire bonding process to the lead frame.
Problems such as ' may occur or the plating layer may peel off occur.

Therefore, conventionally, as a pretreatment for Ag plating, it was necessary to perform strike plating (short-time high current density plating) on the material surface with Cu or Ni, etc., which complicated the plating process and increased lead frame manufacturing costs. There is a problem in that the metallurgy becomes high, and even if Ag plating is applied after strike plating, the adhesion of the plating layer is not always reliably and sufficiently good.
Further, depending on the use of the lead frame, strike plating may have to be avoided, and in such cases it has been almost impossible to improve adhesion. Furthermore, since the lead frame material is usually thin, about 0.5 mm thick or less, it is susceptible to distortion due to residual stress caused by cold rolling in the material manufacturing process, especially during slitting and subsequent processing. Another drawback is that the flaky material often warps during punching or the like, making it unsuitable as a material for lead frames. The object of the present invention is to provide a method for manufacturing a lead frame material for Ag plating that can effectively solve the above problems.

That is, the manufacturing method of this invention uses 26% to 32% Nl and 5% to 19% COl, which are normally used as lead frame materials.
%, the balance being Fe. After cold rolling, the Fe-Ni-CO alloy has a composition of 480% in a reducing atmosphere.
It is characterized by heat treatment at a temperature of ℃ to 650℃ for 25 minutes or more, and by performing a prescribed heat treatment after cold rolling, the adhesion of Ag plating in the subsequent lead frame manufacturing process is improved. This makes Ag
Eliminating the need for strike plating as a pretreatment for plating,
At the same time, distortion is reduced. The manufacturing method of this invention will be explained in detail below.

The Fe-Ni-CO alloy targeted by this invention may be any alloy that is generally used as lead frames of semiconductor integrated circuit devices, and therefore its composition range is Nl
It may be 26 to 32%, CO1 5 to 19%, and the balance Fe.

Fe--Ni--CO alloys outside this range are not normally used as lead frame materials and are therefore outside the scope of this invention. In the manufacturing method of the present invention, an alloy ingot having the composition range described above is cold-rolled until it reaches the final thickness of the desired lead frame, and then rolled at 480°C in a reducing atmosphere such as a hydrogen stream. ~650℃ for 25 minutes or more, preferably 500℃ or higher for 3 minutes.
Heat treatment for 0 minutes or more.

Here, if the treatment temperature is less than 480° C. or the treatment time is less than 25 minutes, a sufficient effect of improving the adhesion of the plating layer in the subsequent Ag plating cannot be obtained, and a sufficient strain removal effect cannot be obtained. Furthermore, at a processing temperature exceeding 650° C., the adhesion of the plating layer will no longer be improved, nor will the strain removal effect be improved, and on the contrary, there is a risk that the material will soften and deform. Further, although the upper limit of the treatment time is arbitrary, it is usually desirable to set it to 4 hours or less, since each effect will not be further improved even if it exceeds 4 hours. When creating a lead frame from the material obtained in this way, it is usually cut into thin pieces using a slitting process, then punched into a lead frame shape, and then the surface is plated with Ag. administer.

In this Ag plating, there is no need to perform strike plating with Ni or Cu as a pretreatment, as will be clear from the test results described later. Next, examples and comparative examples of the present invention will be described.

Example 1 A Fe-Ni--CO alloy ingot having a composition of 29% Ni, 17% CO, and the balance Fe was cold-rolled to obtain a thin plate material with a thickness of about 0.25.

This thin plate material was heated at a temperature of 500°C for 30 minutes in a hydrogen stream.
Heat treated for minutes. Example 2 A thin plate material was obtained in the same manner as in Example 1, and this thin plate material was heat-treated at a temperature of 600° C. for 4 hours in a hydrogen stream.

Comparative Example 1 A thin plate material was obtained in the same manner as in Actual Proportion 1, and this thin plate material was not particularly heat-treated.

Comparative Example 2 A thin plate material was obtained in the same manner as in Example 1, and this thin plate material was heat-treated at a temperature of 400° C. for 30 minutes in a hydrogen stream.

Comparative Example 3 A thin plate material was obtained in the same manner as in Example 1, and this thin plate material was heat-treated at a temperature of 500° C. for 10 minutes in a hydrogen stream.

Comparative Example 4 A thin plate material was obtained in the same manner as in Example 1, and this thin plate material was heat-treated at a temperature of 600° C. for 10 minutes in a hydrogen stream.

Thirty test pieces of 50 mm x 50 cod (thickness: 0.25 mm) were cut out from the materials obtained in each of the above examples and comparative examples, and each of the ten test pieces had a thickness of 0.5 μm. After applying Ni strike plating, 3
Ag plating with a thickness of μm was applied, and Cu strike plating with a thickness of 0.5 μm was applied to each of the other 10 test pieces, and then Ag plating was applied in the same manner. 3 directly without strike plating
Ag plating with a thickness of μm was applied.

The Ag plating adhesion of each of these Ag-plated test pieces was determined in their original condition, and they were heated under conditions similar to those used during wire bonding in integrated circuit device assembly work (heating at 500 C in the atmosphere using an electric furnace). The adhesion of the Ag plating after heating for 5 minutes was observed using a stereomicroscope with a magnification of 20 times. The observation results are shown in the table below. In the table, the number of defects indicates the number of test pieces in which poor adhesion occurred among the 10 test pieces, and the dimension (μmφ) in the defect details column indicates the size of the blisters that occurred, and the score in the defect details column also indicates the size of the blisters that occurred. indicates the number of blistering points in each defective test piece. As is clear from the table, the first test piece obtained according to the example of the present invention showed no blistering or peeling of the Ag plating layer even when Ni or Cu strike plating was not applied as a pretreatment for Ag plating. Furthermore, the Ag plating layer does not blister or peel even when heated in the same way as heating during wire bonding in the normal semiconductor integrated circuit device assembly process.
The adhesion of the plating layer is extremely good.

In addition, F of the same composition as each of the above-mentioned examples and comparative examples was used.
e-Ni-{'o alloy with a thickness of 0.25m7! L, width 3
FIG. 1 shows the change in strain amount when a 0 mm coiled thin plate is cold rolled and no heat treatment is applied to it, and when the heating temperature and heating time are varied in a hydrogen stream.

Here, the amount of strain d indicates the amount of warpage of the coiled thin piece with respect to the plane in the width direction B perpendicular to the rolling direction A. As is clear from Figure 1, over 480℃,
The material that has been heat treated for 25 minutes or more has a significantly reduced strain compared to the amount of strain of the untreated material (marked 8 in Figure 1).
μn1 or less. The allowable strain limit when used as a lead frame material is 50μ per 30mm width.
m or less, it is clear that this value is fully satisfied by the heat treatment described above. As mentioned above, the reason why the adhesion of Ag plating is improved by the predetermined heat treatment in a reducing atmosphere is thought to be that the surface of the material is cleaned by heating in a reducing atmosphere.

As is clear from the above description, according to the present invention, the adhesion of Ag plating when manufacturing a lead frame is significantly improved.Therefore, there is no need to perform strike plating as a pretreatment for Ag plating, so the plating can be improved. The manufacturing process becomes simpler and the manufacturing cost of the lead frame becomes much cheaper, and even if strike plating must be avoided depending on the application, the adhesion of the plating layer can be reliably improved, and distortion can also be eliminated. Various effects can be obtained, such as:

[Brief explanation of drawings]

FIG. 1 is a graph showing the change in the amount of strain when the heat treatment conditions in the manufacturing method of the present invention are changed, and FIG. 2 is a schematic diagram showing the measurement position of the amount of strain.

Claims (1)

[Claims] 1 Ni26-32% (weight%, same below), Co15
A Fe-Ni-Co alloy with a composition of ~19% Fe and the balance Fe is cold rolled, and then reduced to 480 ~ 6% in a reducing atmosphere.
A method for producing a lead frame material for Ag plating, which is characterized by heat treatment at a temperature of 50°C for 25 minutes or more.