The difference between PCB gold sinking process and gold plating process

Now the production of gold plate is rarely, in the actual trial process, 90% of the gold plate can be replaced by gold plate sinking gold plate, gold plate welding poor is his fatal shortage, is also the direct cause of Princecircuit to give up gold plate! In the process of use, because the electrical conductivity of gold is small and widely used in the contact road, such as keyplate, gold finger plate, gold plate to sink the most fundamental difference is that gold is hard gold, gold is soft gold, from the electrical performance analysis!

First, the difference between gold plate and gold plate

Two, why use gold plate

As the integration of IC becomes higher and higher, the IC feet are more and more dense. The vertical tin-spraying process is difficult to flatten the thin pad, which brings difficulties to SMT mounting. In addition, the shelf life of the tin spray plate is very short. And the gold-plated plate is good to solve these problems: 1 for the surface mounting process, especially for 0603 and 0402 ultra-small table paste, because the flatness of the welding pad is directly related to the quality of the solder paste printing process, and plays a decisive influence on the quality of the reflow welding behind, so the whole plate gold-plated in high density and ultra-small table paste process often see. 2 In the trial production stage, affected by components procurement and other factors are often not the board to weld immediately, but often have to wait for a few weeks or even a month to use, the shelf life of the gilded plate is better than that of the lead tin

Gold is many times longer so everyone is happy to use it. Moreover, the cost of gold-plated PCB at the sampling stage is almost the same as that of lead-tin alloy plate.

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

With the increasing frequency of signals, the impact of signal transmission in multiple coatings caused by skin effect on signal quality becomes more obvious:

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

According to the calculation, skin depth is related to frequency:

The other disadvantages of gold plate are listed in the table of differences between gold plate and gold plate.

Three, why the use of gold plate

In order to solve the above problems of gold-plated plate, the use of gold-plated PCB has the following characteristics:

1. Because of the different crystal structure formed by sinking gold and gold plating, sinking gold will be more yellow than gold plating, and customers are more satisfied.

2, because the crystal structure formed by gold plating and gold plating is different, gold plating is easier to weld, will not cause poor welding, cause customer complaints.

3, because the gold plate only has nickel gold on the pad, the signal transmission in the skin effect is in the copper layer will not affect the signal.

4. Because of the denser crystal structure of gold plating, it is not easy to produce oxidation.

5, because the gold plate only has nickel gold on the pad, so it will not be produced into gold wire caused by short.

6, because the gold plate only has nickel gold on the welding plate, so the welding on the line and the combination of copper layer is more firm.

7, the project will not affect the spacing when making compensation.

8, because of the gold and gold plating formed by the crystal structure is not the same, the stress of the gold plate is easier to control, for the products of the state, more conducive to the processing of the state. At the same time, because the gold is softer than the gold, so the gold plate is not wear-resistant gold finger.

9. The flatness and service life of the gold plate are as good as that of the gold plate.

Note:

One, what is gold plating: the whole plate gold plating. Generally refers to [electroplated] [electroplated nickel gold plate], [electrolytic gold], [electric gold], [electric nickel gold plate], there is a soft gold and hard gold (generally used as gold finger) distinction. The principle is to dissolve nickel and gold (commonly known as gold salt) in the chemical solution, the circuit board immersed in the electroplating cylinder and through the current on the copper surface of the circuit board to generate nickel gold coating, electronickel gold because of its coating hardness is high, wear resistance, not easy to oxidize the characteristics of the name has been widely used in electronic products.

Two, what is gold deposition: through the method of chemical REDOX reaction to generate a layer of coating, generally thick, is a kind of chemical nickel gold deposit method, can reach a thicker gold layer, usually called gold deposition.