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What are the advantages and disadvantages of common PCB surface treatment? aiming at this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

After a PCB board is drawn, it will be sent to the PCB board factory for proofing or mass production, and a PCB processing process description document will be attached when issuing an order to the board factory, one of which is to indicate which PCB surface treatment process is selected, and different PCB surface treatment processes will have a greater impact on the final PCB processing quotations, and different PCB surface treatment processes will have different charges. Then we should have a certain understanding of the processing process of PCB, which can not only save costs, but also make the design of PCB more reasonable.

First of all, let's talk about why the PCB surface is specially treated.

Because copper is easily oxidized in the air, the oxide layer of copper has a great impact on welding, it is easy to form false welding, virtual welding, serious will cause the pad and components can not be welded, because of this, PCB in the production and manufacturing, there will be a process, in the pad surface coated with a layer of material to protect the pad from oxidation.

At present, the PCB instant noodle treatment processes of domestic plate factories are as follows: tin spraying (HASL,hot air solder leveling hot air leveling), tin deposition, silver deposition, OSP (anti-oxidation), chemical gold deposition (ENIG), electroplating and so on. Of course, there will be some special PCB surface treatment processes for special applications.

Compared with different PCB surface treatment processes, their costs are different, of course, the occasions used are also different, only the right, not expensive, there is no perfect PCB surface treatment process can be suitable for all application scenarios (here we are talking about the cost-effective, that is, with the lowest price can meet all PCB application scenarios), so there are so many processes for us to choose, of course, each process has its own advantages. Since the existence is reasonable, the key is that we should know them and make good use of them.

The following is an example to illustrate the advantages and disadvantages of PCB surface treatment process and applicable scenarios.

Bare copper plate

Advantages: low cost, smooth surface, good weldability (without oxidation).

Disadvantages: easily affected by acid and humidity, can not be put for a long time, need to be used within 2 hours after unpacking, because copper is easily oxidized in the air; can not be used in double panels, because the second side has been oxidized after the first reflow soldering. If there is a test point, tin paste must be printed to prevent oxidation, otherwise there will be no good contact with the probe.

Tin spray plate (HASL,Hot Air Solder Levelling, hot air leveling)

Advantages: low price, good welding performance.

Disadvantages: not suitable for welding fine gap pins and too small components, because the surface smoothness of the tin spray plate is poor. Tin beads (solder bead) are easy to be produced in PCB processing, and short circuits are easy to be caused by fine gap pin (fine pitch) components.

When used in the double-sided SMT process, because the second side has passed a high temperature reflow soldering, it is very easy to spray tin to remelt and produce tin beads or similar water droplets affected by gravity to form spherical tin spots, resulting in more uneven surface and thus affecting the welding problem.

Tin spraying process used to play a leading role in PCB surface treatment process. In the 1980s, more than 3/4 of PCB used tin spray process, but the industry has been reducing the use of tin spray process over the past decade. Tin spraying process is dirty, smelly and dangerous, so it has never been a favorite process, but tin spraying process is an excellent process for larger components and wires with large spacing.

In the PCB with high density, the flatness of the tin spraying process will affect the subsequent assembly, so the tin spraying process is generally not used in the HDI board. With the development of technology, tin spraying process has appeared in the industry, which is suitable for assembling QFP and BGA with smaller spacing, but the practical application is less.

At present, some factories use OSP process and gold leaching process instead of tin spraying process; technological development also makes some factories adopt tin deposition process and silver deposition process. Coupled with the trend of lead-free in recent years, the use of tin spraying process is further restricted. Although there has been so-called lead-free tin spraying, this will involve the compatibility of the equipment.

In addition, there are surface treatment processes such as OSP, Shen Jin, Shen Yin and Shen Tin, all of which have their own advantages and disadvantages and use different scenes.

This is the answer to the question about the analysis of the advantages and disadvantages of common PCB surface treatment. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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