Gold Plating Board Gold Plating Quality Problems and Measures

1. Reasons for the quality problems of gold plating

1.1 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:

1.1.1 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 and the phenomenon of blooming, the Hall effect test 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 part is the coating red or even black, the color change in the hole is more obvious.

1.1.2 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 tank rough, visual gold Redness.

1.1.3 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.

1.1.4 Change in Alloy Content in Hard Gold Coatings

In order to improve the hardness and wear resistance of the connector, the gold plating of the connector is generally a hard gold plating process. Among them, a gold-cobalt alloy and a gold-nickel alloy are used more frequently. 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.

1.2 can not be plated in the hole

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

1.2.1 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 openings so that the power lines of the plug-in parts are screened and the plating in the holes is difficult.

1.2.2 Plating parts are connected end to end during gold 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. The above two phenomena are more likely to occur when the gold plating is vibrated.

1.2.3 Concentration of blind hole is larger than that of plating 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, the bath is difficult to flow into the hole, and the plating solution flowing into the hole is difficult to reach. Outflow, so the quality of the gold layer in the hole is difficult to guarantee.

1.2.4 Gold plated anode area is too small

When the volume of the connector is relatively 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 high, the effective area of ​​the anode will be reduced, which will affect the ability of the gold plating deep plating, plating will not be plated into the hole.

1.3 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.

1.3.1 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.

1.3.2 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 general activation liquids, and if they are activated without using the 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.

1.2.3 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 may be no gold plating. 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 has been passivated. As a result, the gold layer in the hole is naturally poor in binding force.

1.3.4 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 plating on the neck, which is the top of the front end of the pin, is ineligible for the gold plating test. This phenomenon is easy to occur when the gold plating is vibrated.

1.3.5 Incorrect adjustment of vibrating plated frequency

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 has a great influence on the bond strength of the coating.

2, the solution to quality problems

2.1 From the product design to eliminate the factors that affect the quality of plating

First of all, when designing a connector, product design must take into account the possible impact on the electroplating process, and try to avoid the potential for plating quality due to improper design considerations.

2.1.1 For a socket with a slotted shape, when the tongue and groove is used, first open the lip from the edge of the mouth to the center of the mouth and open it at a 45-degree angle, and then proceed vertically downwards along the center of the mouth. If it is a cross-shaped opening, The hole can be closed first so that the width of the chain of the notch is less than the thickness of the wall of the jack, so that the phenomenon of mutual insertion of the jacks during gold plating can be reduced and avoided.

2.1.2 When designing, the needle bar size of the pin should always be slightly larger than the hole size of the weld line or extend the milling hole length of the weld line to avoid the end-to-end contact during plating.

2.1.3 Design a lateral through hole at the bottom of the blind hole to allow the plating solution to enter and exit the hole during plating.

2.2 The use of scientific electroplating process management methods

2.2.1 Strengthen the quality control of electroplating, especially the quality of gold salt.

Pay attention to every batch of gold salt used. In addition to routine physical and chemical testing, you should sample it for Haoer bath test. For the plating tank. Haoer tank test method: Take 12 grams of gold salt in the sample, add 100 grams of potassium citrate formulated as 1 liter bath, heated to 50 °C adjusted PH5.4-5.8 for] Haoer tank test The normal result is 250 milliliters of Haoer’s trough test sample. The bright range of 0.SA current plating for 1 minute should be more than half of the current density by the low-end area, the whole test piece should be uniform golden yellow, otherwise it should be determined Gold salt can not be used normally.

2.2.2 The number, surface area, and total current of each plating are calculated and recorded before plating so that the cause can be found after quality problems occur.

2.2.3 According to the gold plating production situation, analyze and adjust the plating solution in a timely manner to ensure that the plating bath composition is in the optimum range of process, and the nickel plating solution is treated with at least activated carbon every month. When the plating liquid is used for more than 70 cycles, it is necessary to consider re-assembling the new plating liquid, and discard the old plating liquid after recovering the gold.

2.2.4 Ensure that there is sufficient anode area for gold plating. When the platinum-titanium mesh used in the electroplating process often contains a large number of bubbles and the gold plating cannot be plated for a long time, replacement of a new platinum-titanium anode should be considered.

2.2.5 Add an ultrasonic degreasing cleaning procedure to the small pinhole parts before plating.

2.2.6 The beryllium bronze connectors shall be boiled with 1:1 hydrochloric acid solution for 10-30 minutes before plating, fully remove the oxides and then enter the normal electroplating process. Brass shall be added to the activation solution before nickel plating. A certain amount of hydrofluoric acid or the use of fluorinated fluoride salts is used to prepare the activation solution to ensure the activation of trace metals in the copper alloy of the substrate.

2.3 Electroplating with advanced electroplating equipment and advanced gold plating process

2.3.1 After removing the unfavorable factors of product design, the quality of the gold-plated coating of the connector is obviously stronger than that of barrel plating using vibration plating equipment.

2.3.2 (1) Using a commutation pulse plating power source for gold-plated plating power supply, the quality of the inner hole of the deep-hole part is more obvious than that of the DC plating. (2) The PPR (Periodic Pulse) is used.

When power is supplied, the key is the ratio of the forward and reverse currents. The ratio of time to time must be chosen. Otherwise, the best results cannot be achieved.

2.3.3 At present, many companies in the country have provided patented electroplating gold processes, such as the plating process of Shipley, Angkelron, and Enthone, for the relatively stable quality of gold-plated connectors for 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.

3, the 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 technologies as far as possible, these quality problems will be solved.