JPS6235548A - Lead frame - Google Patents

Abstract

PURPOSE:To improve plating workability, solder bondability and resin sealability by working a single crystal metal at 90% or less of workability. CONSTITUTION:The material of a lead frame may be other material (e.g., phos phorus bronze) heretofore used, but is preferably Fe-Ni alloy. In the Fe-Ni alloy, the weight ratio of Fe:Ni is not particularly limited, but is preferably 60:40-50:50. The working may be conventional hot rolling or cold rolling. The workability means (sectional area of single crystal)-(sectional area of final product)/(sectional area of single crystal). The workability is 90% or less and may be at 0 deg.C. If the workability is 90% or more, it is considered that the property of the single crystal is lost and preferably result is not obtained. This lead frame is obtained by working the single crystal metal at 90% or less of the workability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to lead frames, particularly Fe--Ni alloy lead frames.

[Prior Art] Conventionally, lead frames used in ICs and the like have been obtained by forming a polycrystalline ingot, hot-rolling, cold-rolling, acid washing, etc., and punching out a strip, followed by etching.

However, lead frames manufactured from polycrystalline materials have poor plating processability, such as flame plating, and are prone to peeling. Further, after heating for bonding, the material is deeply oxidized in the thickness direction due to grain boundary oxidation, resulting in poor solder adhesion. In addition, since the oxidation state of the oxide film is uneven, the adhesion of the oxide film is not good and the sealability with the resin is poor.

[Object of the Invention] An object of the present invention is to provide a lead frame free from such drawbacks.

[Structure of the Invention] The gist of the present invention resides in a lead frame formed by processing a metal single crystal with a processing degree of 90% or less.

The lead frame material may be other conventionally used materials (e.g. phosphor bronze), but is preferably a Fe--Ni alloy. F in Fe-Ni alloy
The weight ratio of e:Ni is not particularly limited, but is preferably 6.
The time is from 0:40 to 50:50.

The processing may be conventional hot rolling, cold rolling, etc.

In this specification, the degree of processing means ((cross-sectional area of single crystal) -
(cross-sectional area of the final product))/(cross-sectional area of the single crystal). In the present invention, the degree of processing is 90% or less, and may be 0%. If the degree of processing is 90% or more, good results cannot be obtained. This is considered to be because the properties of the single crystal are impaired. The lead frame of the present invention is obtained by processing a metal single crystal at a processing degree of 90% or less.

Note that the present invention is also applicable to materials other than Fe--Ni alloys such as phosphor bronze.

[Effects of the Invention] The lead frame of the present invention has the following advantages. There are fewer grain boundaries and fewer defects due to inclusions, so
Plating workability is extremely good.

Since the oxide film is thin and uniform after heating for bonding, solder adhesion and resin sealability are good.

The lead frame of the present invention can be advantageously used in ICs and the like.

[Example] Examples and comparative examples are shown below.

Examples 1 to 3 A single crystal material of Fe-Ni (42% by weight Fe, 58% Ni heavy and total alloy) or Pa-N1 (38% by weight Fc, 62% by weight Ni) alloy was cold rolled (or cold rolled finished). Zuni)
The strips were punched out and etched to produce a lead frame.

The plating workability, solder adhesion, and resin sealability of this lead frame were evaluated.

Plating workability was evaluated as follows.

The lead frame was degreased with trichlene, washed with 6N hydrochloric acid for 10 seconds, and then 5 g of AgCN/(!+100 g of KCN
/Q+=C0s30g/ρ in solution with current 2, O
Strike plating is applied by applying current for 1 minute at "A/di", AgCN+00g/ρ+KCN85g/
Main plating was performed by applying current for 10 minutes at a current of 8 A/dm in a solution of 115 g of f2+KO). This was heated at 4508 C in the air for 10 minutes, and blistering of the plating was observed to evaluate plating workability. .

The above plated and heated sample was used for evaluation of solder adhesion and resin sealability. ZnC (!220g/ρ+
Using a flux of NH, CCI 00g/Q, 28
Solder adhesion was evaluated by measuring the wetted area after immersion in a solder eutectic bath at 0° C. for 5 seconds. The lead frame was sealed using a commercially available epoxy resin for IC lead frames, a pressure nail test was performed, and the peeled area was measured to evaluate resin sealability.

The composition and rolling ratio of the alloy and the test results are shown in Table 1.

Comparative Examples 1 and 2 Lead frames were obtained by repeating the example except for using a polycrystalline material. No rolling was performed. Next, a test was conducted in the same manner as in the example. The compositions and test results of these alloys are shown in Table 1.

Table 1 It can be seen that the lead frame of the present invention is superior to conventional lead frames in terms of plating workability, solder adhesion, and resin sealability.

Claims (1)

[Claims] 1. A lead frame formed by processing a metal single crystal with a processing degree of 90% or less. 2. The lead frame according to claim 1, which is formed by processing a Fe-Ni alloy single crystal at a working degree of 90% or less.