PCB Tech - What are the conditions of use for PCBA wave soldering?

Selective wave soldering carrier

I didn't expect it, there are still many circuit boards still undergoing the wave soldering process. I thought the wave furnace had already been put into the museum! However, most of what is going now is the PCBA selective wave soldering (Selective Wave Soldering) process, rather than the earlier process of soaking the entire panel in a tin furnace.

The so-called selective wave soldering of PCBA still uses the original tin furnace, the difference is that the board needs to be placed in the tin furnace carrier/tray (carrier), and then the parts that need wave soldering are exposed and tinned, and the other The parts are covered and protected with a carrier, which is a bit like putting a lifebuoy in a swimming pool. The place covered by the lifebuoy will not be exposed to water. If it is replaced by a tin stove, the place covered by the carrier will naturally not There will be tin stains, and there will be no problems with remelting tin or dropping parts.

But not all boards can use the PCBA selective wave soldering (Selective Wave Soldering) process. If you want to use it, there are still some design restrictions. The most important condition is that the parts selected for wave soldering must be compatible with Other parts that do not need wave soldering have a certain distance, so that the solder furnace carrier can be made, otherwise the solder furnace carrier cannot be used for wave soldering.

PCBA selective wave soldering carrier and circuit design considerations:

1. When the solder pins of the traditional plug-in are too close to the edge of the carrier, the problem of solder insufficiency is likely to occur due to the shadow effect.

2. The carrier must cover the parts that do not need to be soldered with a tin furnace.

3. It is recommended to keep at least 0.05" (1.27mm) of the edge wall thickness of the broken hole of the carrier to prevent the penetration of soldering into the parts that do not need to be soldered with a tin furnace.

4. It is recommended to keep at least 0.1" (2.54mm) away from the edge of the broken hole of the carrier for parts that need to be soldered by a tin furnace to reduce the possible shadow effect.

5. The height of the parts of the furnace surface should be less than 0.15" (3.8mm), otherwise the furnace carrier will not be able to cover these high parts.

6. The material of the soldering furnace carrier (carrier) must not react with the solder, and it must be able to withstand repeated high thermal cycles without deformation, not easy to absorb heat, and be as light as possible, with less thermal shrinkage. The current comparison Many people use aluminum alloy materials, and some use synthetic stone materials.

PCBA selective wave soldering tray carrier design considerations 1

PCBA selective wave soldering tray carrier design considerations 2

In fact, almost all PCB boards were designed using traditional INSERTION operations when they first came out. All the boards needed to go through wave soldering, and the boards at that time were only single-sided. Later, after the invention of PCB, The mixed use of PCB and wave soldering began to appear, because at that time there were still a large part of the parts that could not be converted to the PCB process, that is to say, there are still many traditional plug-in parts, so the board must be designed. The plug-in parts are arranged on the same side, and then the other side is used for wave soldering, and the PCB parts on the wave soldering side must be fixed with red glue to prevent the parts from falling into the soldering furnace when passing through the wave soldering furnace Now, almost all boards have adopted the PCB process on both sides, but it seems that there are still very few parts that cannot be completely replaced by the PCB process, so this type of PCBA selective wave soldering has emerged as the times require Process.