Printed circuit board

The difference between PCB sink gold process and gold plating process

A, the difference between gold-sinking and gold-plated boards

Second, why use gold-plated board

With the integration of IC higher and higher, IC feet also more and more dense. And vertical spray tin process is difficult to become fine pad blow flat, which brings difficulty to SMT placement; In addition, spray tin board life (shelf life) is very short. And gold-plated board just solves these problems: 1 for surface mount process, especially for 0603 and 0402 ultra small table sticker, because the pad flatness is directly related to the quality of the solder paste printing process, to play a decisive influence on the quality of the later re-flow welding, so, the whole board gold-plated in high density and ultra small table sticker process is often seen. 2 in the trial production stage, by the influence of factors such as component procurement is often not The board comes immediately solder, but often have to wait for weeks or even months before use, gold-plated board life (shelf life) than the lead-tin alloy

gold many times longer so we are happy to use. Besides, the cost of gold-plated PCBs in the sample stage is comparable to that of lead-tin alloy boards.

But as the wiring becomes more and more dense, the line width, spacing has reached 3-4MIL. therefore brings the problem of gold wire short circuit.

As the frequency of the signal gets higher, the more obvious the impact on the signal quality due to the skin effect causing the signal to be transmitted in multiple plating.

Skin effect is: high frequency of alternating current, the current will tend to concentrate on the surface of the wire flow.

According to calculations, the skinning depth is frequency dependent.

Other disadvantages of gold-plated plate in the sink plate and gold-plated plate difference table has been listed.

Third, why use sink plate

In order to solve the above problems of gold-plated board, the use of gold-plated PCBs mainly have the following characteristics.
1, because the crystal structure formed by the sink gold and gold plating is not the same, the sink gold will be more yellow than gold plating, the customer is more satisfied.
2, because the crystal structure formed by the sink gold and gold plating is not the same, sink gold is easier to weld than gold plating, will not cause poor welding, causing customer complaints.
3, because the sink gold board only pads have nickel gold, skin effect in the signal transmission is in the copper layer will not have an impact on the signal.
4, because the crystal structure is more dense than gold plating, it is not easy to produce oxidation.
5, because the sink gold board only pads have nickel gold, so will not produce gold wire caused by micro short.
6, because the sink gold board only pads have nickel gold, so the line of solder resist and copper layer of the combination is more solid.
7、 The project will not affect the pitch when making compensation.
8, because the crystal structure formed by sink gold and gold plating is different, the stress of the sink gold board is easier to control, for products with bonding, more conducive to the processing of bonding. At the same time is also because the sink gold than gold plating soft, so the sink gold plate to do gold finger not wear-resistant.
9、 The flatness and life expectancy of the sinker plate is as good as that of the gold-plated plate.

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