Mr. High Speed member - Huang Gang.
Normally, there will only be one surface treatment for a PCB board, and Mr. High Speed does not take the usual path, and insists on making a variety of surface treatments on the same PCB board!
Is it just for fun?Of course, this is also one of Mr. High-speed's ideas, which is to see if the board factory can achieve it through some special processes!
But there is definitely more than this idea, Mr. High Speed made it to study the high-frequency performance of the cable under different surface treatments. On the same board, the plate and the trace length are consistent, and under this premise, the difference in the high-frequency loss of the trace obtained by different surface treatment processes can be well obtained.
Hurry up and see the results to see if the loss ranking in everyone's mind is ......It's a long way off!
Surface treatment classification
Why do you need to do surface treatment?The most basic purpose of PCB surface treatment is to ensure good solderability or electrical properties. Because copper oxidizes easily in the air and cannot maintain its properties for a long time, other treatments are required to avoid oxidation while maintaining solderability.
We see the different colors on the pads of the PCB board, which are actually the presentation of different surface treatment processes, mainly in the following categories.
Immersion silver plate
Immersion silver is a process in which silver is deposited onto the surface of PCB pads. This method deposits a silver plating on the surface of the pad by replacing copper (Cu) with silver (Ag).
Advantages and disadvantages coexist, the advantage is high weldability and flatness, and the disadvantage is high storage requirements and easy oxidation.
Immersion gold plate
Immersion gold is a thick, electrically good nickel-gold alloy wrapped on the copper surface, which is a common surface treatment process.
The benefits mainly include a flat surface and a long shelf life.
The disadvantage is that the cost is higher and the welding strength is average.
Green oil board
Green oil refers to the ink coated on PCB copper foil, also known as liquid photoinduced solder mask, which is an acrylic oligomer. It can be said that it is one of the most common surface treatment processes!
The advantages include high stability, low cost, and a wide range of applications!
Immersion tin plate
Similar to the immersion silver process, it is a metal surface that is deposited through a chemical displacement reaction and applied directly to the base metal (copper) of the circuit board.
The advantage is that it has a high flatness and is suitable for fine-pitch devices, and the disadvantage is that it has a short shelf life.
OSP board
OSP is to chemically grow an organic film on a clean bare copper surface. An aqueous organic compound is used that selectively binds to copper and provides an organometallic layer to protect the copper prior to welding.
The advantage is that the process is simple and reworkable, and the disadvantage is that it is not suitable for PTH holes and has a short shelf life.
Losses for different surface treatments
After the test is de-embedded, the results of the loss of the traces with different surface treatments under the same length are obtained, and I am not surprised, I didn't expect that the difference between them is so big, right, and the quality of their loss is arranged in a way that everyone has guessed
Questions in this issue. What kind of surface treatment loss ranking do you think you are surprised by?