Gold finger gold plating quality problems and measures

1 Introduction

In connector plating, due to the high electrical performance requirements of the contact pairs, the gold plating process occupies a significant position in the connector plating. At present, except for some of the ribbon connectors using selective gold plating process, the rest of the needles The gold plating in the hole of the hole part is still carried out by barrel plating and vibration plating. In recent years, the volume of the connector has been further miniaturized, and the quality of the gold plating in the hole of the pinhole part has become increasingly prominent. The quality requirements are also getting higher and higher, and some users have even reached a very critical level of appearance quality of the gold layer. In order to ensure the quality of the gold-plated connector of the connector, these common quality problems are always the key to improve the gold quality of the connector.

2 Causes of Quality Problems in Gold Plating

2.1 gold layer color is not normal

The gold color of the connector is inconsistent with the color of the normal gold layer, or the color of the gold layer of different parts in the same accessory product is different. The reasons for this problem are:

2.1.1 Impact of gold plating raw material impurities

When the impurities added by the chemical added to the plating solution exceed the tolerance of the plating solution, the color and brightness of the gold layer will be quickly affected. If the organic impurities affect the appearance of the gold layer, the gold layer will have a dark and hairy appearance. Check the darkness and hairflower position is not fixed. If the interference of metal impurities will cause the current density of the effective range becomes narrower, Haoer trough test shows that the current density of the test piece is not bright or the high-end plating is not bright Reflected on the plated parts is the coating red or even black, the color change in the hole is more obvious.

2.1.2 Gold plating current density is too large

Due to the calculation of the total area of the plating tank parts, its value is greater than the actual surface area, so that the gold plating current is too large, or the amplitude is too small when using vibration plating, so that all or part of plating gold plating plating in the tank is rough, visual gold Redness.

2.1.3 Aging liquid aging

If the plating liquid is used for a long time, excessive accumulation of impurities in the plating solution will inevitably cause the gold layer to be abnormally colored.

2.1.4 Change in Alloy Content in Hard Gold Coatings

In order to increase the hardness and wear resistance of the connector, the gold plating of the connector is generally a hard gold plating process. Among them, gold and cobalt alloys and gold-nickel alloys are used more often. When the content of cobalt and nickel in the plating solution changes, it will cause Gold plating color change. If the cobalt content in the bath is too high, the color of the gold layer will be reddish; if the nickel content in the bath is too high, the metal color will become light; if the change in the bath is too large and the same ancillary products are different When the parts are not gold plated in the same tank, there will be different colors of the gold layer of the same batch of products provided to the user.

2.2 can not be plated in the hole

When the thickness of the external surface of the plated part reaches or exceeds the specified thickness value after the pinning process or pinning process of the connector is completed, the inner hole of the wire hole or the hole of the plug is thin or even has no gold layer.

2.2.1 Plating pieces are inserted into each other during gold plating

In order to ensure that the jacks of the connectors are somewhat flexible when the jacks are used during plugging and unplugging, most types of jacks have a tongue and groove design at the mouth during product design. The plating parts are constantly turned during the plating process. The jacks are inserted into each other at the opening so that the power lines of the plug-in parts are screened and the plating in the holes is difficult.

2.2.2 Plating Parts End to End When Plating

Some types of connectors have a pin whose outer diameter is slightly smaller than the hole size of the wire hole when the pin is designed. During the plating process, part of the pins will form end-to-end contact, resulting in no gold plating within the hole. (See illustration) The above two phenomena are more likely to occur during vibration gold plating.

2.2.3 Concentration of blind hole is larger than that of electroplating process

Since there is a distance from the bottom of the hole at the bottom of the tongue and groove of the jack, this distance objectively forms a blind hole. Similarly, there is such a blind hole in the solder wire hole of the pin and the jack, which is to provide wire welding. When the hole diameter of these holes is small (usually less than 1 mm or even less than 0.5 mm) and the blind hole concentration exceeds the hole diameter, it is difficult for the bath to flow into the hole. It is difficult to flow into the hole. Outflow, so the quality of the gold layer in the hole is difficult to guarantee.

2.2.4 Gold plated anode area is too small

When the volume of the connector is small, the total surface area of the single-slotted plating is relatively large, so that when the small-sized pinhole pieces are plated, if the number of single-slot plating is large, the original anode area is insufficient, especially when the platinum-titanium mesh is used. Too long use time When the platinum loss is too much, the effective area of the anode will be reduced, which will affect the plating ability of the gold plating, the plating hole will not be plated.

2.3 poor adhesion of plating

When the plating adhesion of the connector is inspected after plating, sometimes the front portion of the pin end of the pin is bent or the peeling of the pinhole hole of the pinhole is sometimes caused at the time of bending. (2001 hours) Tests revealed that the gold layer had very fine blistering.

2.3.1 Incomplete treatment before plating

For small pinhole parts, if the trichloroethylene ultrasonic degreasing cleaning cannot be used immediately after the machining process is completed, the subsequent conventional plating treatment will be difficult to remove the dry oil from the holes, so that the plating inside the holes The binding force will be greatly reduced.

2.3.2 Incomplete activation before substrate plating

A wide variety of copper alloys are used in the connector base material, and trace metals such as iron, tin, antimony and tin in these copper alloys are difficult to activate in a general activation liquid, and if they are not activated by using a corresponding acid, electroplating is performed. At this time, the oxides of these metals are difficult to bond with the plating layer, thus causing the phenomenon of high-temperature blistering of the plating layer.

2.2.3 The bath concentration is low

In the case of nickel plating using nickel sulfamate nickel plating bath, when the nickel content is lower than the process range, the quality of the hole plating of the small pinhole parts is affected. If the gold content of the pre-plating bath is too low, then the gold plating hole There is a possibility that no gold plating is possible. When the plated part enters the thick gold plating solution, the nickel layer in the hole of the plating layer in the hole metal layer is passivated. As a result, the gold layer in the hole has a poor bond strength.

2.3.4 Sleeveless pin electroplating does not reduce the current density

When plating slender pins, if electroplating is usually done using remote current density, the plating on the tip of the needle will be much thicker than on the needle bar. Observing the needle under a magnifying glass will sometimes result in a match head shape (see Figure 3). The coating on the neck, which is the top of the front end of the pin, is inferior to the gold plated coating. This phenomenon is unqualified. This phenomenon is easy to occur when the gold plating is vibrated.

2.3.5 Incorrect adjustment of vibration frequency of vibrating gold plating

When vibrating electroplated connectors are used, if the vibration frequency is not properly adjusted during nickel plating, the plated parts will pulsate too quickly. The easy-to-open double-layer nickel will have a great influence on the bond strength of the coating.

2.4 How to solve quality problems

Some types of connectors have a pin whose outer diameter is slightly smaller than the hole size of the wire hole when the pin is designed. During the plating process, part of the pins will form end-to-end contact, resulting in the inside of the wire hole being plated without gold. (See illustration) The above two phenomena are more likely to occur during vibration gold plating.

2.4.1Concentration of blind hole is larger than that of electroplating process

2.4.2 Gold plated anode area is too small

When the volume of the connector is small, the total surface area of the single-slotted plating is relatively large, so that when the small-sized pinholes are plated, if the number of single-slot plating is large, the original anode area is insufficient, especially when the platinum-titanium mesh is used. Too long use time When the platinum loss is too much, the effective area of the anode will be reduced, which will affect the plating ability of the gold plating, the plating hole will not be plated.

2.4.3 poor adhesion of plating

2.4.4 Incomplete treatment before plating

2.4.5ncomplete activation before substrate plating

2.4.6The bath concentration is low

2.4.7 Sleeveless pin electroplating does not reduce the current density

2.4.8 Incorrect adjustment of vibration frequency of vibrating gold plating

3 How to solve quality problems

At present, there are many companies in the country that provide patented electroplating gold processes. The gold plating processes of Shiplion, Angkelron, and Enthone are used for the relatively stable quality of gold-plated coatings on connectors. In addition, many of China’s older generation of electroplating work have used their rich experience in electroplating on the basis of foreign advanced gold-plated formulations developed a number of more practical gold plating process. It is suggested that domestic users may use their gold plating process after agreeing to use the effect.

4 Conclusion

In the gold plating process of connectors, there are many factors affecting the quality of plating. With the rapid development of China’s electronics industry, some new quality problems will arise. However, as long as we start from the various links in the manufacture of connectors, find the root cause of these problems, adopt scientific management methods for various production processes, and adopt advanced electroplating equipment and techniques as far as possible, these quality problems will be solved.