JPH01212790A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To improve the thermal exfoliation resistance of the outer lead part of a lead frame for a semiconductor device at the time of soldering by plating the lead frame with an Ni alloy contg. a specified amt. of Zn or Cu. CONSTITUTION:A lead frame for a semiconductor device made of copper deoxidized with P is subjected to pretreatment such as alkali degreasing and plated with an Ni alloy obtd. by adding 0.5-10wt.% Zn or 1-10wt.% Cu to Ni or an Ni alloy such as Ni-Zn, Ni-P-Zn, Ni-Co-Zn or Ni-B-Zn. A lead frame for a semiconductor device having superior thermal exfoliation resistance of the outer lead part at the time of soldering is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead frame for a semiconductor device, and more particularly to a lead frame for a semiconductor device in which the solder heat peeling resistance of the outer lead portion is improved.

[Prior Art] Semiconductor devices such as transistors and ICs are generally assembled by the following method.

That is, a semiconductor element is thermally bonded to a semiconductor element bonding portion of a lead frame for a semiconductor device via an adhesive layer such as Au-5t, Ag paste, or a metal solder such as solder. After that, after wiring between the electrode part of the semiconductor element and the lead frame for the semiconductor device with Au or AJ2 wire, the semiconductor element part and the wiring part are sealed with metal, ceramics, resin, etc., and finally the actuator lead The parts are soldered or solder plated to complete the assembly of the semiconductor device.

Cu alloys are often used as lead frame materials for semiconductor devices, and the entire surface is plated with Ni in order to impart oxidation resistance and suppress diffusion of Cu, and then this Ni plating is applied. The surface is further partially plated with Ag.

When the above-described semiconductor device is assembled and used using the semiconductor device lead frame material having the above-described structure, solder often peels off at the outer lead portion. This is because the soldering or solder plating part of the outer lead part is affected by heat under the conditions in which the actual semiconductor is used, and the Ni plating on the lead frame surface and the solder on the Ni plating surface. The constituent Sn forms and grows a Ni-3n alloy layer (Nis Sn, Nis 5n4), and by bending the outer lead part, the Ni-3n
The solder has peeled off starting from the alloy layer.

If solder peeling as described above occurs, there is a risk that the semiconductor will malfunction and the entire semiconductor device will develop into trouble, and there is currently a desire for an improvement measure that will prevent solder peeling.

To date, methods to improve the above have been considered, such as chemically dissolving and removing the Ni plating on the lead portion before soldering the outer lead portion, or applying partial Ni plating only to areas other than the outer lead portion in advance. However, this method increases the number of processing steps and costs, and is not an effective improvement measure.

[Problems to be solved by the invention] The present invention solves the problems of the prior art explained above, and
The present invention provides a lead frame for a semiconductor device, which is plated and has an outer lead portion with good solder heat resistance and peelability.

[Means for Solving the Problems] The present invention provides a semiconductor lead frame having a Ni plating layer or a Ni alloy plating layer, the Ni plating layer or the Ni alloy plating layer containing Zn: 0.5 to 10% (
There is a gist in a lead frame for a semiconductor device, which is characterized in that it contains Curl (weight% or less) or Curl to 10%.

[Function] Solder peeling in lead frames with conventional Ni plating or Ni alloy plating is caused by the soldering applied on the Ni plating or the Sn constituting the solder plating due to the heat effect during semiconductor use. Ni Metsuki and Ni-3
This is thought to be a phenomenon in which an n alloy layer is formed and grown, and the solder layer peels off starting from the inside of this Ni-3n alloy layer.

The present inventors believe that by modifying the properties of the Ni-3n alloy layer,
Based on the idea that the above-mentioned solder peeling could be eliminated, we conducted extensive research on elements to be added to Ni plating.

As a result, Z is added to the Ni plating layer or Ni alloy plating layer.
It was confirmed that this objective could be achieved by containing n: 0.5 to 10% or curl to 10%.

The reason for adding Zn or Cu and the reason for limiting the range will be explained below.

In the present invention, it has not yet been fully elucidated why the inclusion of Zn or Cu in the Ni plating layer or Ni alloy plating layer contributes to the modification of the Ni-5n alloy layer. Since it has the property of easily diffusing into the plating and solder, it is thought that the formation of the Ni-5n alloy layer is suppressed and the properties of the Ni-3n alloy layer are modified. Moreover, when Cu is contained, Ni-
5n (Ni3 Sn, Ni35n4) alloy layer is formed and Ni-Cu-5n [(Cu-Nt)3s
It is considered that the formation of the Ni-5n alloy layer occurred, resulting in a change in the properties of the Ni-5n alloy layer.

First, regarding the Zn content, if the Zn content is less than 0.5%, no improvement in solder heat resistance and peelability is observed. Moreover, when the Zn content exceeds 10%,
Although it has the effect of improving solder heat resistance and peelability, the soldering properties are poor and good soldering cannot be obtained. Therefore, Zn
The content was 0.5 to 10%.

In addition, as the Ni plating containing Zn of the present invention, N
i-Zn, N1-P-Zn, N1-C.

-Zn, N1-B-Zn and the like. Further, the same effect can be obtained regardless of the presence or absence of base plating, full-surface plating, or partial plating.

Next, regarding the Cu content, if the Cu content is less than 1%, no improvement in solder heat resistance and peelability is observed. Moreover, when the Cu content exceeds 10%, the hardness of the plating film increases, which deteriorates the bending workability of the actor lead portion. Therefore, the Cu content was 1 to 10%.

In addition, as the Ni alloy plating containing Cu of the present invention, Ni-Cu, N1-P-Cu, Ni-B-Cu, N
1-Co-P-Cu and the like. Moreover, the same effect can be obtained regardless of the presence or absence of base plating, and whether the entire surface is plated or partial plating is performed.

The present invention will be specifically described below with reference to Examples.

[Example] Example 1 Phosphorus deoxidized copper (plate thickness 0.5 m) was used as lead frame material.
Using the -numerical transistor-shaped specimen of m), after performing the commonly used pretreatment [alkaline degreasing, φ electrolytic degreasing and pickling], plating was performed under the conditions shown below. The plated specimen was analyzed for Zn content using EPMA and subjected to a solder heat resistance peeling test.

The solder heat resistance peeling test method involves heating a plating sample assuming a semiconductor assembly process (350°C x 5 minutes in air and 20 minutes).
0°C x 48 hours), and then the outer lead part was soldered under the conditions shown below to create a solder heat peeling test piece.
After heat aging for 200 hours, 400 hours, and 500 hours, bend the actor lead part with a radius of 0.5R.
The sample was bent back by 90 degrees, and the presence or absence of peeling of the solder layer at the bent portion was observed using a stereomicroscope (20x magnification). In addition, for each specimen, the solder surface condition after soldering was also visually observed.

(Plating conditions) Liquid composition (1) Ni SO4' 6 H20240g / lN1
Cj22 ・6H2040g/JlZnSo4 ・7H
200~5g/λ Hs BOs 30g/fl temperature
Temperature: 55℃ Current density: 2A/drn” Plating thickness: 1.5μm Liquid composition (2) NiSO4・6H20150g/flNiCjZ
2・6H20150g/j2ZnSO4' 7H200
~5g/jZH3P03 2g/λH
3PO410g/j2 Temperature 60℃ Current density 2A/drri” Plating thickness 1.5μm (soldering is a condition) Solder composition 60%5n-40%pb soldering temperature
260° C. Immersion time: 5 seconds Flux: Table 1 shows the results of tests for active flux and above.

In Table 1, No. 001 to No. 006 are examples of the present invention, No. 7. No. 8 is a comparative example outside the scope of the present invention, No.
,9. No. 10 is a conventional example.

Examples No. 001 to No. 016 of the present invention all exhibited solder heat resistance and peelability for 500 hours or more, and also exhibited good soldering properties. In addition, No, 5. Similar good results were obtained even when the plating base composition was N1-P alloy plating instead of Ni plating, as in Example No. 6.

On the other hand, No.7. Looking at the comparative example No. 8, Z
N017 with an n content of 0.13% had a low Zn concentration, so it exhibited better solder heat peeling resistance than the conventional example, but peeled off after 400 hours. Also, Z n fH13
% No. 8 does not cause solder peeling even after 500 hours,
Soldering showed poor results in sex.

Also, No. 9. In the conventional example No. 10, the soldering properties were good, but peeling occurred after 200 hours in terms of solder heat resistance and peelability.

Example 2 Phosphorus deoxidized copper (plate thickness 0.5 mm) as lead frame material
) was subjected to a commonly used pretreatment [alkaline degreasing, electrolytic degreasing, pickling], and then plating was carried out under the conditions shown below. The plated specimen was analyzed for Cu content using EPMA and subjected to a solder heat resistance peeling test.

The solder heat resistance peeling test method involves heating a plating specimen assuming a semiconductor assembly process (350°C x 5 minutes in air and 200°C
℃ x 48 hours), and then soldering was carried out on the outer lead part under the conditions shown below to prepare a solder heat resistance peelability test piece. After heat-aging this test piece at 150°C for 100 hours, 200 hours, 400 hours, and 500 hours, the outer lead part was bent back by 90 degrees with a radius of 0.5R, and the solder layer at the bent part was The presence or absence of peeling was observed using a stereomicroscope (x20 magnification). In addition, the occurrence of cracks in the plating layer at the bent portion was also observed.

(Plating conditions) Liquid composition (1) NiSO4・6H20240g/u Ni Cf12・6)! 20 40g/ACu
CJ12・2H200~2g/fl.

H2BO330g/u Temperature 55℃ Current density 2 A/drn” Plating thickness
1.5μm Liquid composition (2) NiSO4・6H20150g/uNiCIt
2 ・6H20150g/βCuCJ22 ・2H2
00~2g/IHs POs 2
g/pH3P O410g/J2 Temperature 60℃ Current density 2 A/drrf' Plating thickness 1.5μm (soldering is a condition) Solder composition 60%5n-40%pb soldering temperature
Rice soaked at 260°C for 5 seconds Flux: Table 2 shows the test results for active flux and above.

In Table 2, No. 1 to No. 8 are examples of the present invention, and No. 9. No. 10 is a comparative example outside the scope of the present invention; No. 11. No.

12 is a conventional example.

Regarding No. 1 to No. 8 which are examples of the present invention,
Both have good solder heat resistance and peelability even after 500 hours.
It also has good bending workability. Also, No, 6~N
Similar good results were obtained even when the plating base composition was N1-P alloy plating instead of Ni plating, as in Examples o and 8.

On the other hand, No.9. Looking at the comparative example of No. 10,
No. 9 had a low Cu content of 0.5%, so although it was better than the conventional example, some peeling occurred after 400 hours. Further, N0010 has a Cu content of 12%, and although the solder heat resistance and peelability do not cause peeling even after 500 hours, the bending workability is poor.

Also, No. 11. In conventional example No. 12, cracks due to bending were slightly generated, but peeling occurred in 200 hours regarding solder heat peeling resistance.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a lead frame having better solder heat peeling properties than conventional ones, and as a result, Ni plating can be applied to the entire surface or only the necessary portions after the entire surface is Ni-plated. The conventional plating method of applying Ag plating can be used, eliminating the need for dissolving and removing Ni plating in the outer lead plating and eliminating the need for costly partial plating, reducing process costs and reducing costs in the semiconductor assembly process, as well as semi-equipment. This contributed to improving the reliability of the system.

Claims (1)

[Claims] A semiconductor lead frame having a Ni plating layer or a Ni alloy plating layer, wherein the Ni plating layer or Ni alloy plating layer contains Zn: 0.5 to 10% (same weight % or less) or Cu: 1 to 10%. A lead frame for a semiconductor device characterized by containing %.