Can the surface technology of PCB circuit boards be determined by color?

Do you know that PCB experts can judge what the surface technology of PCB circuit boards is based solely on the surface and color. The outer layer of our common circuit boards mainly comes in three colors, namely gold, silver, and light red.2 oz copper thickness in mm Gold is the most expensive, silver is cheaper, and light red is the cheapest.

You may not believe it, how can you tell? I'm so familiar that I can't even tell. Isn't this bullshit?

So let's take a look at how experts see it.

1. Gold

Gold is the most expensive, this is true gold. Although there is only a thin layer of gold on the PCB, it accounts for nearly 10% of the cost of the circuit board.

In fact, the use of gold has a purpose, firstly to facilitate welding, and secondly to prevent corrosion (gold has good corrosion resistance).

The gold plating layer has now been widely used in components such as solder pads, gold fingers, connector shrapnel, and other positions on circuit boards. In consumer electronics, most mobile phone motherboards are gold plated (which is why you often hear cries of recycling old and broken phones, because of gold, you understand). However, computer motherboards, audio systems, and small digital circuit boards are generally not gold-plated.

2. Silver

Don't think that silver is silver, in fact, this silver is not silver, but a softer metal - tin.

A silver circuit board is also called a solder spray board. Spraying a thin layer of tin on the outer layer of the copper circuit can help with welding, but it cannot provide long-term contact reliability like gold.

Solder spray plates have little effect on already welded components, but for solder pads that have been exposed to air for a long time, their reliability is still not perfect. Long term use can easily oxidize and rust, leading to poor contact.plated through hole vs via The circuit boards of small digital products are generally tin coated.

3. Light Red

OSP (Organic Soldering Protective Film) is even cheaper than the tin spraying process because it is an organic substance, not a metal. The only function of this organic thin film is to ensure that the inner copper foil is not oxidized before welding.

This thing will evaporate when heated during welding, so soldering tin can weld copper wires and components together.

Due to its non corrosion resistance, an OSP circuit board cannot be soldered after being exposed to air for about ten days. Many of the computer motherboards we commonly use use use OSP technology.