There are gold and copper in the circuit boards of mobile phones and computers. Therefore, the recycling price of used circuit boards can reach more than 30 yuan per kilogram. Than selling waste paper, glass bottles, scrap iron are more expensive.
From the outside, the circuit board has three main colors: gold, silver, and light red. Gold is the most expensive, silver is cheap, and light red is the cheapest.
It can be seen from the color, hardware manufacturers have no cut corners,
In addition, the circuit inside the circuit board is mainly pure copper. If exposed to air, it is easily oxidized. The outer layer must have the above protective layer. Some people say that gold is copper, and that's wrong.
Gold:
Large gold plating on the circuit board
The most expensive gold is true gold. Although only a thin layer, it also accounts for nearly 10% of the cost of the circuit board. Some places on the coasts of Guangdong and Fujian specialize in the purchase of scrapped circuit boards, stripping gold, and the profits are considerable.
The reason why gold is used is two purposes. One is to facilitate welding and the other is to prevent corrosion.
The golden finger of the memory strip that was 8 years ago is still glittering. If you change to copper, aluminum, or iron, it will not be able to use rust for a long time.
The gold-plated layer is used in a large number of components such as circuit board component pads, gold fingers, and connector springs.
If you find that some circuit boards are all silver, it must be cut corners. The industry term is called "costdown."
Most motherboards for mobile phones are gold-plated boards. Computer boards, audio systems, and small digital circuit boards are generally not gold-plated boards.
A circuit board four years ago is still golden
8 years ago memory finger gold finger.
iPhone X's circuit board, all exposed gold plating.
Silver
Gold is gold, silver is silver?
Of course not, it's tin.
The silver plate is called spray plate. Spraying a layer of tin on the outside of the copper wire can also help with soldering. However, it cannot provide long-term contact reliability like gold.
The tin spray plate has no effect on the already welded components, but the reliability is insufficient for long-term exposure to air in the pads, such as ground pads, bullet pins, and the like. Long-term use is easy to oxidize and cause poor contact.
The circuit boards of small digital products, without exception, are tin spray plates. There is only one reason: Cheaper
Small digital products like to use tin plate
Light red:
OSP, organic flux film. Because it is organic, not metal, it is cheaper than the tin spraying process.
The only effect of this organic film is to ensure that the inner copper foil is not oxidized before welding. When heated during welding, the film evaporates. Solder can bond the copper wire and components together.
However, it is very resistant to corrosion. An OSP board could not be soldered after being exposed to the air for a long time.
Many computer motherboards use the OSP process. Because the board area is too large, you cannot afford gold plating.
OSP circuit board, light red
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