JPH0310035A - Copper alloy for electrical and electron ic parts - Google Patents

Abstract

PURPOSE:To obtain the copper alloy for electrical and electronic parts having improved peeling resistance of an Sn (alloy) layer, whisker resistance of Sn plating, heat resistance and migration resistance without deteriorating the characteristics of phosphor bronze by limiting the contents of Sn, P, Ni and Zn. CONSTITUTION:A copper alloy contg., by weight, >2.5 to 9.0% Sn, 0.03 to 0.35% P, 0.1 to 1.0% Ni, 1.0 to 5.0% Zn and the balance substantial Cu is prepd. The copper alloy is suitable, e.g., to terminals and connectors used for the public, industry or automobiles.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to copper alloys for electrical and electronic parts, and more specifically, for example, copper alloys for terminals and connectors used in consumer, industrial, and automobile applications. Regarding alloys.

[Prior art] Cheap brass is generally used as a material for terminals and connectors, but since brass has a fatal defect of causing stress corrosion cracking, it is used in cases where reliability is required. Phosphor bronze has been widely used.

However, phosphor bronze also has the following problems, and improvements are required. In other words, materials for terminals and connectors are often plated with Sn or an Sn alloy such as solder, but if there is a temperature rise in the usage environment, diffusion may occur between the alloy and the solder. occurs to form an alloy layer. If the alloy is phosphor bronze,
This alloy layer formation causes the Sn or Sn alloy layer to peel off. Such a peeling phenomenon causes a circuit failure in electronic devices, etc., and significantly impairs their reliability. This peeling phenomenon is caused by Sn
Alternatively, when the Sn alloy layer is provided by a reflow plating method, the alloy layer grows due to heating during reflow, and this is more likely to occur than when the Sn alloy layer is provided by a bright Sn plating method.

On the other hand, when bright Sn plating is applied to phosphor bronze, it is known that acicular single crystals of Sn called whiskers grow from the plating surface, causing problems such as short circuits between terminals. Reflow plating is an effective method for preventing the generation of whiskers, but for the reasons mentioned above, applying the flow plating method to phosphor bronze is disadvantageous in terms of peeling. Preventive measures are desired.

The temperature increase in the above-mentioned usage environment causes not only the peeling phenomenon but also the deterioration of mechanical properties, that is, the contact force decreases due to stress relaxation due to thermal effects, resulting in an increase in contact resistance, causing electrical connection failure. Phosphor bronze does not have sufficient heat resistance, and in recent years, the temperature of environments in which it is used, such as the engine compartment of automobiles, has been increasingly rising, and there has been a strong demand for improved heat resistance of phosphor bronze.

Further, when moisture infiltrates between electrodes such as terminals or adheres due to dew condensation, Cu ions are exposed, further reduced by the potential between the electrodes, and deposited as metal Cu. As a result of this elution/precipitation phenomenon being repeated, the deposited Cu grows and short-circuits between the electrodes. This phenomenon is called migration, but phosphor bronze is a copper alloy that is prone to migration, and as electrical and electronic components become smaller and the pitch between electrodes becomes smaller, it becomes necessary to improve migration resistance. Problems to be Solved by the Invention] The present invention has been made in view of the problems of phosphor bronze explained above, and the present invention aims to improve the peeling resistance of Sn or Sn alloy without deteriorating the properties of phosphor bronze. Gender, Sn
The purpose of the present invention is to provide a copper alloy with improved plating whisker resistance, heat resistance, and migration resistance.

[Means for Solving the Problems] The copper alloy for electrical/electronic parts according to the present invention is characterized by Sn: 2.5 to 9.0 wt% (excluding 2.5%), Pro, 03-0.35wt%, Ni: 0
．． 1-1.0wt%, Zn: 1.0-5.0wt%
, and the remainder substantially consists of Cu.

This will be explained in detail below.

First, the components and component ratios of the copper alloy for electrical/electronic parts according to the present invention will be explained.

Sn is an element that improves mechanical properties, that is, strength, elongation, springiness, and formability by being dissolved in Cu, and these properties are insufficient at 2.5 wt% or less, and at 9.0 wt% Even if it exceeds %, the improvement in properties is relatively small and is uneconomical, and it also limits productivity such as processability. Therefore, the Sn content is set to 2.5 to 9.0 wt%.

However, 2.5% is excluded.

P is a deoxidizing agent that deoxidizes the molten metal, improves drainage properties, and obtains a healthy ingot. If it is less than 0.03 wt%, the effect is small, and if it exceeds 0.35 wt%, the effect will be reduced. becomes saturated, causing problems such as deterioration of solder peeling resistance. Therefore, the content of P is 0.03 to 0.35w
It is assumed to be t%.

Ni improves heat resistance by forming an intermetallic compound with P. The intermetallic compound of Ni and P is Cu-5n-
By being uniformly and finely distributed in the Zn matrix, Zn acts as an obstacle that prevents the movement of dislocations due to the compound itself or the stress field around it. As a result, the stress relaxation phenomenon caused by the movement of dislocations is suppressed, and the heat resistance as a terminal/connector material is improved. In addition, Ni, P
In order to obtain a uniform and fine distribution of the compound that brings out such effects, the following manufacturing process is desirable.

That is, the manufacturing process includes a solution treatment step in which Ni and P are dissolved in solid solution, a subsequent cold rolling step, and an aging precipitation step in which Ni and P compounds are precipitated.

When the amount of Ni is O, less than 1 wt%, P is 0.03 to 0.3
Even if the content is 5 wt%, the above effects due to Ni and P compounds are small, and even if the content exceeds 1.0 wt%, P is 0.03
Since it is ~0.35 wt%, the effect is saturated and it is uneconomical. Therefore, the Ni content is 0.1 to 1.0 wt%
shall be. As is clear from the above explanation, the ratio of Ni to P is preferably in the range of 2 to 10 in consideration of the formation of intermetallic compounds.

Zn is an element that prevents Sn or Sn alloy from peeling off. The peeling phenomenon of the Sn or Sn alloy layer in the Cu-3n-P-Ni system is as follows.

That is, due to mutual diffusion of Cu and Sn by heating, ε phase (Cu3S n) and η phase (C
An intermetallic compound layer of uaSns) is formed. As the diffusion progresses further, many voids, which are assumed to be due to the Kirkendahl effect, are formed around the interface between the base material and the ε phase, leading to peeling. It has been found that the addition of Zn is extremely effective in suppressing the formation of ε phase and voids and preventing peeling.

Zn is also effective in preventing the generation of whiskers in Sn plating, and is also effective in preventing migration.

If Zn is less than 1.0 wt%, the above effects will be small, and if Zn is contained in more than 5.0 wt%, the above effects will be saturated, and the solder wettability and stress corrosion cracking resistance will tend to decrease. . Therefore, the Zn content is 1.0 to 5.0w.
It is assumed to be t%.

[Example] Next, the copper alloy for electric/electronic parts according to the present invention will be explained by using an example.

A copper alloy having the components shown in Table 1 was melted in the air while covered with charcoal using a Kributol furnace, and then cast into a cast iron booksold to produce an ingot measuring 45mmtx80mmwx20mmj2. These ingots were solidified by 2.5 mm on each of the front and back sides, and then hot-rolled at a temperature of 815° C. to a thickness of 10 mm except for No. 4, and then quenched in water from a temperature of 650° C. or higher. After removing the scale, it was cold rolled to 0.64mmt, heated at a temperature of 500℃ for 2 hours, and then cold rolled to 0.32mm.
mt board material was obtained and further heated to 350℃ using a salt bath.
Heating was performed at a temperature of 20 seconds. Regarding No. 4, the ingot was solidified and finished to a thickness of 10 mm, and then cold-rolled to a thickness of 0.64 mm while annealing at 550°C for 2 hours at a thickness of 4 mm and 1.5 mm. The board was finished using the same process as the others.

These plates were tested using the method shown below.
The results shown in Table 2 were obtained.

(1) Tensile strength and elongation are J cut parallel to the rolling direction
Measurement was carried out using an IS13 B test piece.

(2) The stress relaxation rate is 0, 3 cut out parallel to the rolling direction.
A test piece of 2mmtxlOmmwx80mmjl was attached to a cantilever test jig, and the maximum surface stress was 80% of the proof stress.
After bending the test piece so that
The ratio of the relaxed stress to the initial stress was calculated. Second
The table shows the values after 500 hours.

(3) Solder peeling is 0.32mmtx20mmwx50
After molten solder plating with 603n-40pb solder on a mmj2 test piece at a temperature of 230±5℃ using a weakly activated flux, after heating at a temperature of 150℃ for 500 hours, a 2mm
It was bent back by 180 degrees with radius R, and the presence or absence of peeling was examined.

(4) Migration test is 0.32mm t x
3 mmw x 80 mml test pieces were prepared, and two pieces were made into a set as shown in Figure 1 (1 is a test piece, 2 is an inch-thick polyethylene resin, 3 is a battery, 4 is an electric wire, 5 is a clip, and 6 is a 15 mm diameter A DC voltage of 14 V was applied to the test piece 1 using the energizing method shown in (a), and a dry-wet cycle test of 5 minutes of immersion and 5 minutes of drying was performed until 50 cycles were completed. The maximum leakage current value was measured using a Memory Hicorder 8802 manufactured by Shirakubi Denki.

(5) Whisker resistance test is 0.32mmtX50mm
Sn was applied directly to the wx100mA test piece under the conditions shown in Table 3.
After plating, the test piece was set in a concave cross-section jig with an inner width of 94 mm as shown in FIG. 2, compressive stress was applied, and the test piece was left indoors.

For whisker measurement, whiskers generated within a compressive stress surface of 20 mm x 50 mm were observed using a stereomicroscope.

The results after 6 months are shown in Table 2.

As is clear from Table 2, the alloy No. t~4 of the present invention was improved in tensile strength, stress relaxation rate, solder peeling, maximum leakage current, and whisker generation compared to the phosphor bronze of Comparative Example No. 015. I can see that On the other hand, in Comparative Examples No. 6, Zn is added, so solder peeling, maximum leakage current, and whisker generation are improved, but since Ni is not added, the stress relaxation rate is inferior.

[Effects of the Invention] As explained above, since the copper alloy for electrical/electronic parts according to the present invention has the above-mentioned structure, the peeling resistance of the Sn or Sn alloy layer, the heat resistance, and the Sn plating are improved. It has the effect of being excellent in whisker resistance and migration resistance.

[Brief explanation of drawings]

Figure 1 is a diagram of the equipment used to examine migration resistance.
FIG. 2 is a diagram of an apparatus for examining whisker resistance. rock surface

Claims (1)

[Claims] Sn: 2.5 to 9.0 wt% (excluding 2.5%),
P: 0.03-0.35wt%, Ni: 0.1-1.0
%, Zn: 1.0 to 5.0 wt%, and the remainder substantially consists of Cu.