PCB Electroplating Process And Common 8 Major Problems

PCB electroplating process

PCB application field is very wide, large to the aviation military industry to household electronics, are inseparable from its figure, the use of copper to connect the components on the circuit board to play a conductive effect. If the circuit board is exposed to air for a long time, not only will the circuit board oxidize but it will lose solderability due to corrosion.

So it is necessary to use special technology to protect the circuit board, PCB electroplating process operation flow:

Acid → full plate copper → pattern transfer→ acid degreasing→ secondary countercurrent rinsing→ micro-etching→ secondary acid → tin plating→ secondary countercurrent rinsing→ acid → pattern copper plating→ secondary countercurrent rinsing→ nickel plating→ secondary water washing→ citric acid → gold plating→ recovery→ 2-3 pure water washing→ drying.

There are three kinds of common PCB electroplating technology: oxide film, organic painting, and electroplating technology, among which most PCB manufacturers will choose electroplating technology, of course, there are also factories that choose the other two technologies.

So what are the differences between these three PCB electroplating processes?

1. Oxide film technology: It can protect the circuit board from erosion, but it cannot guarantee the solderability of the product;
2. Organic painting technology: The change of its concentration, chemical composition and curing cycle is not suitable for long-term use, and there may be unpredictable deviations in weldability after long-term use.
3. Electroplating technology: The standard operation that can effectively ensure the solderability of the product and protect the circuit from erosion plays a pivotal role in the printed circuit board. And it is a standard operation requirement for the printed circuit board to provide a soldering protective layer by plating a layer of metal with solderability on the printed circuit board.

The 8 most common electroplating problems in proofing circuit board factories

1. As an electroplating manufacturing device, in addition to the hanging color and the contact conductive part of the product, the rest of the hanger should be coated with insulating materials to reduce current loss and metal loss, ensure the effective area of the product electroplating, improve the effective current of the product, and make the hanger durable.
2. Most of the quality problems caused by the production process of PCB electroplating are caused by improper pre-plating treatment of metal products, which is closely related to the quality of pre-plating treatment in terms of the flatness, adhesion, corrosion resistance and other properties of the plating layer. The surface condition before plating and its cleanliness are important links to obtain high-quality coating, and it is difficult to obtain a smooth and bright coating on the rough surface of the plate, and the coating has many pores, which reduces the anti-corrosion performance.
3.  In the acid bright copper plating process, the use of electrolytic copper anode is easy to produce copper powder and cause rough coating, and the consumption of brightener is fast. So copper anode containing a small amount of phosphorus (0.1~0.3%) should be used, which can significantly reduce copper powder. However, if a copper anode with too high phosphorus content is used, the anode dissolution performance will deteriorate, resulting in a decrease in the copper content of the plating solution.
4.  Poor anodic dissolution during cyanide copper plating will lead to oxidation and consumption of a part of cyanide on the anode, and more free cyanide will be produced on the cathode due to the discharge of copper cyanide ions, which will increase the content of free cyanide in the plating solution.
5. The reason why chromium soluble metal is not used as the anode for chrome plating is that it is easy to dissolve in the chrome plating process. The current efficiency of anode metal chromium dissolution is higher than that of cathode metal chromium deposition. With the electroplating process, it is inevitable that the chromium content in the plating solution will become higher and higher, resulting in the inability to achieve normal plating results.

   

   6. Some brown films are produced in the chrome plating layer, mainly caused by insufficient sulfate, and the temperature of the bath solution is too low or interfered by impurities (such as Cl-), which will produce brown films in the chromium plating.

   7. The phenomenon of coating peeling after nickel plating and chromium plating is due to poor pre-plating, which is related to the condition of the plating solution and the phenomenon of double nickel.

   8. Two problems that need to be paid attention to in bright nickel plating, industrial raw materials are impure, such as zinc and nitrate, nickel sulfate contains copper, and anode nickel plate contains iron and other impurities. And copper and chromium brought in from the product or hanging gear that is contaminated in the production process, improperly cleaned, and so on. Decomposition products of organic additives. These are harmful impurities of bright nickel plating, which should be eliminated with care.

   

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