Why "gold" on the PCB?
Why do you want to "stick gold" on the PCB? Is there a "golden finger" on your PCB board?
Surface treatment of PCB board:
Anti-oxidation, tin spray, lead-free tin spray, immersion gold, immersion tin, immersion silver, hard gold plating, full plate gold plating, gold finger, nickel-palladium OSP: lower cost, good solderability, harsh storage conditions, time Short, environmentally friendly technology, good welding and smooth.
Tin spraying: Tin spraying plates are generally multilayer (4-46 layers) high-precision PCB samples, which have been used by many large telecommunications, computer, medical equipment, aerospace companies and research units in China. ) Is the connection part between the memory module and the memory slot. All signals are transmitted through the gold finger.
Gold finger: It is composed of many golden yellow conductive contacts. Because the surface is plated with gold and the conductive contacts are arranged like fingers, it is called a "gold finger". Gold fingers are actually coated with a layer of gold on a copper-clad board through a special process, because gold is extremely resistant to oxidation and has a strong conductivity. However, due to the expensive price of gold, most of the current memory is replaced by tin plating. Tin materials have been popular since the 1990s. At present, almost all "golden fingers" of motherboards, memory and graphics cards are used For tin materials, only some high-performance server / workstation accessories will continue to use gold plating, which is naturally expensive.
In fact, there are two types of gold plating processes: one is electroplated gold and the other is immersion gold.
For the gold plating process, the effect of tin on it is greatly reduced, and the effect of tin on Shen gold is better; unless the manufacturer requires binding, otherwise most manufacturers will choose the immersion gold process! Generally common In the case of PCB surface treatment is the following: gold plating (plated gold, immersion gold), silver plating, OSP, tin spray (lead and lead-free), these are mainly for FR-4 or CEM-3 and other plates In terms of the paper base material, there is also a rosin-coated surface treatment method; if the tin is not good (the tin is not good), the reasons for the production of the solder paste and other patch manufacturers and material technology are excluded.
Here only for PCB problems, there are several reasons:
1. During PCB printing, is there an oil-permeable film surface on the PAN bit, which can block the effect of tin; this can be tested by tin drift test.
2. Whether the lubricating position of the PAN bit meets the design requirements, that is, whether the pad design is sufficient to ensure the supporting role of the part.
3. Whether the pads are contaminated, which can be obtained by the ion pollution test; the above three points are basically the key aspects for PCB manufacturers to consider.
The advantages and disadvantages of several methods of surface treatment are their own strengths and weaknesses!
In terms of gold plating, it can make PCB be stored for a long time, and the temperature and humidity of the environment is relatively small (relative to other surface treatments). Generally, it can be stored for about one year; tin sprayed surface treatment is second, OSP is again Pay attention to the storage time of the two surface treatments at ambient temperature and humidity.
In general, the surface treatment of immersion silver is a bit different, the price is high, and the storage conditions are more demanding. It needs to be treated with sulfur-free paper packaging! And the storage time is about three months! In terms of the effect of tin, immersion gold, OSP, Spraying tin and so on are actually similar. Manufacturers mainly consider cost performance!