JPS63249361A - Semiconductor lead frame - Google Patents

Abstract

PURPOSE:To prevent exfoliations due to long time heating after coating with tin or solder, by constituting at least a three-layered structure in which a nickel- plated layer is interposed between a copper alloy and a copper-plated layer. CONSTITUTION:A copper alloy is plated with nickel and copper after a prescribed cleaning treatment such as alkali degreasing, electrolytic-degreasing, pickling and rinsing. Usual electroplating is applied to said nickel plating and copper plating, and another dry plating such as electroless plating and vacuum metallizing is applicable. By providing at least a three-layered structure in this manner in which a nickel-plated layer is interposed between the copper alloy and a copper-plated layer, the exfoliations of plated layer can be prevented even in the case of employment under a high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objective of the Invention) The present invention is directed to peeling off a copper alloy material for electronic parts by applying tin or solder coating and then heating it for a long period of time. (hereinafter referred to as heat peeling).

(Conventional technology and problems) In the field of copper alloy lead frames, the inner leads are conventionally plated with precious metals such as gold and silver to improve wire bonding properties, but there are problems with productivity, economy, quality, etc. From this point of view, there is a tendency to use copper plating instead of the above-mentioned precious metal plating such as gold and silver.

On the other hand, the outer lead portion of a lead frame is coated with solder or tin by electroplating, hot-dip plating, etc. for the purpose of mounting on a board. However, when tin or solder is coated on a lead frame that is directly plated with steel on the above-mentioned copper alloy, there is a problem that the tin or solder peels off from the base material due to the high temperature and long-term thermal history during use, resulting in poor contact. .

Furthermore, as the IC mounting method is currently shifting from the pin insertion type to the surface mount type, the peeling resistance of tin or solder required for this surface mount type has become even more important.

(Structure of the Invention) The present invention relates to a lead frame having at least a three-layer structure in which a nickel plating layer is interposed between a copper alloy and a copper plating layer.

(Detailed Description of the Invention) The copper alloy that is the base material of the semiconductor lead frame contains Sn;
~8wt%, P; 0.03~0.35wt%, balance Cu
and unavoidable impurities, or phosphorus containing 0.05 to 2 wt% of one or more of Mn, Ni, Si, Cr, Zr, and In as subcomponents in addition to the above components, with the remainder being Cu and unavoidable impurities. Bronze-based copper alloy, Sn; 0.1
~3 wt%, Ni; 0.1 to 10.0 wt%, balance Cu and unavoidable impurities or Mn as a subcomponent to the above components; Q, 5 wt% or less, Fed, 1 wt% or less,
Cu-8n-Ni based copper alloy containing PO, 1 wt% or less of one or more kinds, the balance being Cu and unavoidable impurities; 1. O~4°0wt%, balance Cu and unavoidable impurities or P as a subcomponent in addition to the above components; 0.
01~0.1wt%, Zn: O-05~O-3w
Cu-Fe based copper alloy containing one or more types of t% and the balance consisting of Cu and inevitable impurities, and Sn; 0
°3-2wt%, Fed, 5-3. Owt%, balance Cu
and unavoidable impurities or additional subcomponents to the above components: pro, 03 to 1.0 wt%, Zr; 0.05 to 1 wt%
%, Co1wt% or less, and the remainder is Cu and inevitable impurities.Cu-3n-F
It is applied to copper alloys that are prone to thermal peeling such as e-series copper alloys, but it is also applied to other copper alloys for lead frames in consideration of safety as lead frame materials with heat peeling resistance. be able to. After the copper alloy described above is subjected to predetermined purification treatments such as alkaline degreasing, electrolytic degreasing, pickling, and water washing in a known manner, nickel plating and copper plating are applied according to the present invention. The nickel plating and copper plating are usually performed by electroplating, but there is no problem in plating by other plating methods such as electroless plating or dry plating such as vacuum evaporation. The thickness of the nickel plating is not particularly limited in the present invention, but is between 0°1 and 2°.
It is preferably about μ. The reason for this is that if it exceeds 2μ, workability tends to deteriorate, and if it is less than 0.1μ, the effect on heat-resistant peeling becomes weak. There is no particular limit to the thickness of the copper plating, and the thickness is determined depending on the use as a lead frame material.

Next, typical examples of electroplating bath compositions and plating conditions for nickel and copper plating are described below.

Copper plating copper sulfate bath sulfuric acid copper 150-240 g/
QWit 61 30”1
00g/12 Brightener Appropriate amount Bath temperature 20~60℃ Current density 1~10 A/da", Copper pyrophosphate plating Copper pyrophosphate 63~105 g/R copper
Minutes 23-38g/Ω Potassium pyrophosphate 240-470g/Q Ammonia water (specific gravity 0.88) 2-6+ fl/
Q Potassium nitrate ・8～16□gIQ gloss
Appropriate amount of agent bath temperature
50~60℃PH H8,2~8.8 Current density 0.9~7 A/dm" Nickel plated Watt bath Nickel sulfate 240~330 g/Q Nickel chloride 45 gIQ Yes
Acid 30-38 g/Q bath
Temperature 40~70℃ Current density
2-10 A/da” Wood bath Nickel chloride 200-300 g / Q Hydrochloric acid 30-45 g /
Q bath temperature: 40-60°C Current density: 2-10 A/dm" (Effects of the present invention) According to the present invention, a nickel-plated and copper-plated material is coated with tin or solder by electroplating or hot-dip plating. The plated layer does not peel off even during use at high temperatures.For example, no peeling occurs even when a 90'' bending peel test is performed after being held at a temperature of 150°C for 1000 hours.

Next, embodiments of the present invention will be described.

(Example) Example 1 A phosphor bronze strip was subjected to alkaline degreasing, electrolytic degreasing, pickling and neutralization, and then 1μ nickel plating was applied. The handling copper plating is 1
After that, the pot or solder was electroplated, hot-dip plated, and after electroplating, hot-dip plating of 1μ or more was applied. The bath composition and plating conditions are as follows.

Nickel plating bath composition 1 Wood bath nickel chloride 240 g/Q salt
Acid 40gIQ bath
Temperature 25℃ Current density JJE
S A/da” Bath composition 2 Watt bath Nickel sulfate 330 g/Q Nickel chloride 45 g/Q
Acid 38g/Q temperature
degree 45℃ current density 5
A/da” Copper plating bath composition 3 Sulfuric acid steel bath Sulfuric acid steel 210 g / Q Sulfuric acid 100 g / Q bath
Temperature: 30℃ Current density
5 A/da” Bath composition 4 Copper pyrophosphate bath Copper pyrophosphate 80 g / Q Potassium pyrophosphate 300 g / Q Aqueous ammonia (specific gravity 0.88) 4+* Q / Q Potassium nitrate
12g/Ω bath temperature
50°C Current density 5 A/d+++z Tin plating bath composition 5 Tin sulfuric acid bath Sulfuric acid Tin 70 g/fl
Sulfuric acid 100g/Q
Cresol sulfonic acid 100 g / Q gelatin 2 g / Q Beta naphthol 1.5 g / Q bath temperature 20 °C Current density 3 A /
dm” Bath composition 6 Hot dip tin plating tin bath Temperature 240℃±5℃Flux
25% Rosin Metacool Solder Plating Bath Composition 6 Phenolsulfonic Acid Bath Stannous Phenolsulfonate 200 g / Q Lead Phenolsulfonate 40 g IQ Phenolsulfonic Acid 150 g / Q Bath Temperature 20 °C Current Density
3 A/da” Bath composition 8 Hot-dip solder plating Sn/Pb 6G/40 Temperature 235°C ± 5°C Flux
After heating the thus plated sample in the atmosphere at 150°C for 1000 hours, 9
A peel test was conducted using a 0° bending test. The results are shown in Table 1, and no peeling occurred.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that nickel plating was not performed. As a result of the peel test, peeling occurred in all samples. Similar to Example 1, the results are shown in Table 1.

Example 2 and Comparative Example 2 Samples were prepared in the same manner as in Example 1 and Comparative Example 1 using phosphor bronze in which 1 wt % of each of one or more of Mn, Ni, Si% Cr, Zr, and In was added. As a result of the peel test, the nickel plated sample did not peel off, while the non-nickel plated sample did peel off. Note that since this was the same result as Example 1 and Comparative Example 1, the list was omitted.

Margin below

Claims (1)

[Claims] 1) A semiconductor lead frame having at least a three-layer structure in which a nickel plating layer is interposed between a copper alloy and copper plating.