CN1848305B - Lead wire for electronic parts and flat cable composed of the lead wire - Google Patents

Abstract

The invention discloses a conductor of electronic part, which comprises the following parts: conductive base (1), Sn alloy coating layer (2) with Sn and Bi, Cu, Ag or Sn and Zn on the positive layer of conductive base (1), upper coating layer (3) with Zn coating layer, Ag coating layer, SnZn alloy coating layer, SnAg alloy coating layer or SnBi alloy coating layer on the surface of Sn alloy coating layer (2), wherein the density of Bi, Cu, Ag or Zn is 0.1-15%; the total thickness of Sn alloy coating layer (2) and upper coating layer (3) is 0.5-20 mum.

Description

Lead wire for electronic parts and flat cable composed of the lead wire

technical field

The present invention relates to a lead wire for electronic components and a flat cable using the lead wire. More specifically, the present invention relates to lead wires and flat cables for electronic components that do not use toxic lead and have an effect of preventing short-circuit causes.

Background technique

Sn (tin) plating is widely used as a protective film for improving solderability or a protective film for an anti-corrosion coating in parts for weak current industries, parts for electronic industries, and the like.

It is known that whiskers (whiskers) occur in Sn (tin) plating, and for example, in flexible flat cables in which the intervals between flat cables are extremely small, the whiskers may cause short circuits.

As measures to prevent this short circuit, there are methods of performing heat treatment such as annealing treatment, and replacing the Sn plating with another plating protection film such as gold plating or SnPb alloy plating.

However, just performing such conventional heat treatment cannot sufficiently prevent generation of whiskers. Furthermore, gold plating and the like do not generate whiskers, but are expensive, and SnPb alloy plating is not preferable from the viewpoint of environmental protection because lead is used. Therefore, in recent years, SnBi (bismuth) alloy plating has attracted attention (for example, refer to Patent Document 1), but it is still insufficient in terms of preventing generation of whiskers.

Patent Document 1: Japanese Unexamined Patent Publication No. 2002-30468

Contents of the invention

Therefore, the present invention is proposed in view of the above-mentioned problems, and its object is to provide a lead wire for electronic parts that has a tin-based plating layer, does not contain a toxic substance lead at all, is low in cost, and can reliably prevent whiskers from occurring. The wires make up the flat cable.

In order to solve the above-mentioned problems, the wire for electronic parts of the present invention is to form a Sn alloy containing at least one element in Bi, Cu (copper), Ag (silver), and Zn (zinc) on a conductive substrate. coating, and form Zn coating, Ag coating, SnZn alloy coating, SnAg alloy coating, or SnBi alloy coating on the upper layer. Here, it is preferable to further perform heat treatment such as reflow treatment on the lead wire for electronic components to form an alloy layer in which tin is diffused.

Furthermore, it is preferable that the total thickness of the Sn alloy plating layer and the Zn plating layer, Ag plating layer, SnZn alloy plating layer, SnAg alloy plating layer, or SnBi alloy plating layer on the upper layer is 0.5 to 20 μm.

Moreover, this invention manufactures a flat cable using these lead wires for electronic components. Here, after being rolled into a flat cable, it is preferable that the total thickness of the above-mentioned Sn alloy plating layer and its upper layer Zn plating layer, Ag plating layer, SnZn alloy plating layer, SnAg alloy plating layer, or SnBi alloy plating layer is 0.1-3 μm, and it is preferable to apply Heat treatment such as annealing treatment.

Because the wire of the present invention and the flat cable using it form a Sn alloy coating containing at least one element in Bi, Cu (copper), Ag (silver), and Zn (zinc) in an amount of 0.1 to 15% by weight on the conductive substrate , so lead-free and beneficial to environmental protection, and the effect of suppressing whiskers can be obtained. At the same time, since Zn plating, Ag plating, SnZn alloy plating, SnAg alloy plating, or SnBi alloy plating are formed on the upper layer, it can be more reliably Prevents the occurrence of whiskers.

Moreover, since heat treatment such as reflow treatment and annealing treatment is performed, tin diffuses into the upper layer of Zn plating, Ag plating, SnZn alloy plating, SnAg alloy plating, or SnBi alloy plating to form an alloy layer, so its electrical properties can be maintained.

Moreover, since the total thickness of the Sn alloy coating on the wire and its upper Zn coating and Ag coating is 0.5 to 20 μm, in addition, after rolling into a flat cable, the above-mentioned Sn alloy coating and its upper Zn coating, Ag coating, SnZn alloy coating, Since the total thickness of the SnAg alloy plating layer or the SnBi alloy plating layer is 0.1 to 3 μm, generation of whiskers can be reliably prevented while maintaining the same electrical characteristics.

Description of drawings

FIG. 1( a ) is a cross-sectional view of the lead wire of the first embodiment, and FIG. 1( b ) is a cross-sectional view of the lead wire of the second embodiment.

2( a ) is a cross-sectional view of the flat cable of the third embodiment, and (b) is a cross-sectional view of the flat cable of the fourth embodiment.

Symbol Description:

A, B-wire

C, D-flat cable

1- Conductive substrate

2-Sn alloy coating (bottom coating)

3- Upper coating

4-alloy layer

Detailed ways

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing a conductive wire, and FIG. 2 is a cross-sectional view showing a flat cable. FIG. 1( a ) is a cross-sectional view of the lead wire of the first embodiment, and FIG. 1( b ) is a cross-sectional view of the lead wire of the second embodiment. 2( a ) is a cross-sectional view of the flat cable of the third embodiment, and (b) is a cross-sectional view of the flat cable of the fourth embodiment. The symbol 1 in the figure represents the conductive substrate, 2 represents the Sn alloy plating layer (underlayer plating layer), 3 represents the upper layer plating layer, and 4 represents the alloy layer.

As shown in Figure 1 (a), the wire A of the first embodiment is made of a conductive substrate 1, covered with a Sn alloy coating (undercoat coating) 2 of Sn and Bi, Cu, Ag or Sn and Zn on it, and The upper layer 3 is composed of Zn plating, Ag plating, SnZn alloy plating, SnAg alloy plating, or SnBi alloy plating formed on the upper layer.

As the conductive substrate 1 , copper wires or copper alloy wires such as brass and phosphor bronze can be used, and iron wires such as CP wires whose surface is covered with copper or copper alloys can also be used.

Bi, Cu, Ag or Zn in the Sn alloy plating layer 2, in the case of containing multiple kinds, set its average concentration to 0.1 to 15% by weight. In addition, the Sn alloy plating layer 2 and the upper layer plating layer formed on it The total thickness of 3 is set within the range of 0.5 to 20 μm.

By containing at least one of Bi, Cu, Ag, or Zn in Sn, although the occurrence of whiskers can be prevented to a certain extent, when the above-mentioned content is less than 0.1% by weight, the effect of preventing the occurrence of whiskers cannot be obtained sufficiently. , and when greater than 15% by weight, the hardness of the Sn alloy coating 2 increases, and defects such as cracks and ruptures are likely to occur, and the cost also increases.

In the present invention, by further forming an upper layer coating 3 made of Zn coating, Ag coating, SnZn alloy coating, SnAg alloy coating, or SnBi alloy coating on the Sn alloy coating 2, it is possible to prevent crystallization more reliably without losing its electrical characteristics. The occurrence of whiskers. However, if the upper layer plating layer is too thick, the electrical characteristics will be lowered, so it is preferably 2 μm or less, more preferably 0.5 μm or less. For example, in the Zn-Sn alloy plating layer 2 and the Zn plating layer thereon, the Zn concentration in the entirety of the Sn alloy plating layer 2 and the upper layer plating layer 3 may exceed 15% by weight. This also applies to other embodiments described below.

Next, the wire B in the second embodiment is to implement the Sn alloy coating 2 of the first embodiment and the upper layer coating 3 of the Zn coating, Ag coating, SnZn alloy coating, SnAg alloy coating, or SnBi alloy coating on the upper layer. Heat treatment such as reflow treatment changes the wire into the tin-diffused alloy layer 4 .

Next, the flat cable C in the third embodiment is a cable produced by a drawing calender using the conducting wire A, and the flat cable D in the fourth embodiment is a cable produced using the conducting wire B by a drawing calender.

The total thickness of the Sn alloy plating layer 2 and the upper layer plating layer 3 after rolling into a flat cable is preferably 0.1 to 3 μm, more preferably 0.3 to 0.7 μm.

Among them, the flat cable D in the fourth embodiment is produced by subjecting the flat cable C to heat treatment such as electrical annealing.

(Example 1)

After pretreatment such as electrolytic degreasing and pickling, the copper wire (conductive substrate) with a diameter of 0.6 mm is subjected to Sn Bi alloy plating using plating chemicals produced by Ishihara Pharmaceutical Co., Ltd. (Japanese name: Ishihara Pharmaceutical Co., Ltd.) to form a Sn alloy plating layer (bottom plating).

Next, Zn electroplating is performed to form an upper layer plating layer, and a lead wire having a double-layer structure plating layer is formed. Moreover, the stretching calender produced by SAIKAWA Corporation (Japanese name: サイカワ) performs stretching, calendering, and electrification annealing to make flat cables.

(Example 2)

After pretreatments such as electrolytic degreasing and pickling on the copper wire (conductive substrate) with a diameter of 0.6 mm, Sn Zn alloy electroplating is carried out using electroplating chemicals produced by Nippon Metal Plating Co., Ltd. A Sn alloy plating layer (underlayer plating layer) is formed.

Next, Zn electroplating is performed to form an upper layer plating layer, and a lead wire having a double-layer structure plating layer is formed. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(Example 3)

After pretreatments such as electrolytic degreasing and pickling, the copper wire (conductive substrate) with a diameter of 0.6mm is subjected to Sn Cu alloy plating using a plating solution produced by Uemura Industry Co., Ltd. (Japanese name: Uemura Industry) to form a Sn alloy plating layer (bottom plating).

Next, Zn electroplating is performed to form an upper layer plating layer, and a lead wire having a double-layer structure plating layer is formed. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(Example 4)

After pretreatments such as electrolytic degreasing and pickling are performed on a copper wire (conductive substrate) with a diameter of 0.6mm, Sn·Ag alloy plating is performed using electroplating chemicals produced by Ishihara Pharmaceutical Co., Ltd. to form a Sn alloy plating layer (underlayer plating layer).

Next, Zn electroplating is performed to form an upper layer plating layer, and a lead wire having a double-layer structure plating layer is formed. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(Example 5)

After pretreatments such as electrolytic degreasing and pickling are performed on a copper wire (conductive substrate) with a diameter of 0.6 mm, Sn Bi alloy plating is performed using plating chemicals produced by Ishihara Pharmaceutical Co., Ltd. to form a Sn alloy plating layer (underlayer plating layer).

Next, Ag electroplating was performed using a plating solution produced by Meltex Corporation (Japanese name: Meltex), to form an upper layer plating layer, and constitute a lead wire having a double-layer structure plating layer. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(Example 6)

After pretreatments such as electrolytic degreasing and pickling, the copper wire (conductive substrate) with a diameter of 0.6mm was subjected to Sn Bi alloy plating using plating chemicals produced by Ishihara Pharmaceutical Co., Ltd. to form a Sn alloy layer (bottom plating layer).

Next, a Sn·Zn alloy plating layer was formed using a plating solution produced by Nippon Mining Metal Plating Co., Ltd. to form a lead wire with a double-layer structure. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(Example 7)

After pretreatments such as electrolytic degreasing and pickling are performed on the copper wire (conductive substrate) with a diameter of 0.6mm, Sn Zn alloy plating is performed using the plating solution produced by Nippon Metal Plating Co., Ltd. to form a Sn alloy layer (bottom plating layer).

Next, using a plating solution produced by Nippon Mining Metal Plating Co., Ltd., a Sn·Zn plating layer with a Zn concentration (%) higher than that of the underlying plating layer was formed to form a lead wire having a double-layered plating layer. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(Embodiment 8)

After pretreatments such as electrolytic degreasing and pickling are performed on the copper wire (conductive substrate) with a diameter of 0.6mm, Sn Zn alloy plating is performed using the plating solution produced by Nippon Metal Plating Co., Ltd. to form a Sn alloy layer (bottom plating layer).

Next, a Sn·Bi alloy plating layer was formed using a plating solution produced by Ishihara Pharmaceutical Co., Ltd., to form a lead wire having a double-layer structure of the plating layer. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(Comparative examples 1 to 3)

After pretreatments such as electrolytic degreasing and pickling are performed on a copper wire (conductive substrate) with a diameter of 0.6mm, Sn plating is performed using plating chemicals produced by Ishihara Pharmaceutical Co., Ltd. to form a wire with a Sn plating layer. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(comparative example 4)

After pretreatments such as electrolytic degreasing and pickling are performed on the copper wire (conductive substrate) with a diameter of 0.6mm, the same as in Example 1, the Sn Bi alloy electroplating is carried out using the electroplating chemicals produced by Ishihara Pharmaceutical Co., Ltd. to form an alloy coating of wires. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

(comparative example 5)

After pretreatments such as electrolytic degreasing and pickling are carried out to the copper wire (conductive substrate) having a diameter of 0.6mm, the same as in Example 2, the electroplating chemicals produced by Nippon Mining Metal Plating Co., Ltd. are used to implement Sn.Zn alloy electroplating to form a alloy-coated wire. Then, stretching, rolling, and electrical annealing were performed by the above-mentioned stretching calender to produce a flat cable.

In order to evaluate each of the flat cables of Examples 1 to 8 and Comparative Examples 1 to 5 above, they were laminated, fitted with Sn-plated connectors subjected to reflow treatment, and left at room temperature for 1000 hours. Hours later, the occurrence of whiskers was confirmed and evaluated with a scanning electron microscope manufactured by Hitachi, Ltd.

The evaluation results of each Example and Comparative Example are shown in Table 1 below.

The thickness of the bottom layer plating, the thickness of the top layer plating, and the total thickness in Table 1 are the thicknesses in the wire before being rolled into a flat cable, and the maximum length (μm) in the whisker evaluation is the length of the longest whisker among the generated whiskers , and the occurrence rate (%) is (the number of whisker-generating conductors)/(the total number of evaluation conductors).

Table 1

The following results can be obtained from Table 1.

(1) In any of Examples 1 to 8, the maximum whisker length was 20 μm or less, and the whisker generation rate was 10% or less. From this, it can be seen that even compared with Comparative Examples 4 and 5, generation of whiskers can be reliably prevented.

(2) From Comparative Examples 1 to 5, it can be seen that the maximum whisker length in any of them is 50 μm or more, and the whisker generation rate is 20% or more. Comparing Comparative Examples 1 to 3 with Comparative Examples 4 and 5, it can be confirmed that the Sn-Bi alloy coating and the Sn-Zn alloy coating have the effect of preventing the generation of whiskers, but compared with Examples 1 to 8, the effect is inferior It is found that the effects of Comparative Examples 4 and 5 are insufficient.

Claims (6)

1. electronic component-use lead is characterized in that:

Form the Sn alloy layer of at least a element among Bi, the Ag contain 0.1～15 weight %, the Zn on conducting base, layer is formed with Zn coating, SnZn alloy layer or SnBi alloy layer thereon,

The combination of the coating on described Sn alloy layer and upper strata thereof is selected from

The combination of SnBi alloy layer and Zn coating,

The combination of SnZn alloy layer and Zn coating,

The combination of SnAg alloy layer and Zn coating,

The combination of SnBi alloy layer and SnZn alloy layer,

The combination of SnZn alloy layer and SnZn alloy layer and

In the combination of SnZn alloy layer and SnBi alloy layer any.

2. electronic component-use lead according to claim 1 is characterized in that:

This electronic component-use lead is implemented the heat treatment that reflow is handled.

3. electronic component-use lead according to claim 1 and 2 is characterized in that:

The aggregate thickness of the Zn coating on described Sn alloy layer and its upper strata, SnZn alloy layer or SnBi alloy layer is 0.5～20 μ m.

4. flat cable that uses each described electronic component-use wire producing in the claim 1～3.

5. flat cable according to claim 4 is characterized in that:

After rolling into flat cable, the aggregate thickness of the Zn coating on described Sn alloy layer and its upper strata, SnZn alloy layer or SnBi alloy layer is 0.1～3 μ m.

6. flat cable of claim 4 or 5 described flat cables being implemented the heat treatment of annealing in process and forming.

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