Layout Design For Printed Circuit Board Assembly

The design of PCB should start with determining the layouts of the SMT (Surface Mount Technology) and DIP (Dual In-line Package) on the both sides of PCB. Different ways of assembly correspond to different processing, and also have different requirements for production lines. In the actual designing process, to ensure a higher straight-through rate of PCB soldering, the assemble ways that we preferably recommend are 1, 2, and 3 points listed in the table below.


Assembly Types


PCB Design features and
Processing Technology

1 Single mix single mix

It has SMD as well as THC(plug-in)on one side: firstly using reflow soldering to solder SMD, and then manually soldering (wave soldering) THC.

2 TOP mix BOT attach simple SMD only TOP mix BOT attach simple SMD only

To attach BOT (solder paste) through reflow soldering first, and then turn the panel over and attach TOP (solder paste) through reflow soldering. In the end, turn the panel over again and go through wave soldering after adding carrier to BOT.

3 Single side with THC Single side with THC All THC on one side with wave soldering.
4 Single side with SMD Single side with SMD All SMD on one side with reflow soldering.
5 Two sides with SMD

 Two sides with SMD

All SMD on both sides with double-sided reflow soldering.

Note 1: To avoid only a few SMDs on the B side of panel with wave soldering (2 and 5 assembly ways), which adds the assembly process.

Note 2: Simple SMD refers to the R, L and C devices of Package 0603, 0805 and 1206, and devices of Package SOT-23.

Note 3: When soldering the second side, the components solder joints on the first side will melt again, and they will attach to the bottom of PCB just by the surface tension, and those heavy ones are about to fall off. Therefore, when designing the layout of devices, try to place heavier elements on A side and lighter devices on B side.


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Posted by Candy Xu

Candy Xu

Candy has helped numerous startups and makers get their hardware across turbulent seas of the market into their customers' hands. Having studied engineering, she's all round equipped to solve problems in all aspects of our services.