Introduction to PCB Assembly

Some of you might have heard of the term PCB Assembly & thought, "What's that"?

This editorial is meant to shed some light on the subject.

The whole process of manufacturing electronic devices is a long & complicated.
The beginning point for all electronics is in the material - Silicon or any other semiconductor.
Through lots of long & pricey tidy room processes, these "wafers" are transformed in to "smart" electronic microprocessors & chips.

These chips cannot do anything by themselves, & need to be integrated onto a printed circuit board (PCB) in order to be able to do something in the finish (like operate your computer or phone).

Now, there is a immense number of companies that design these chips & sell end-products. However, these companies cannot afford to buy all the equipment necessary to assemble their chips onto PCBs in order to devise their end-product.

This is what PCB Assembly companies are for. These (EMS) companies have lots of Surface Mount Assembly lines, & offer PCB Assembly services to other companies who are not interested in doing this themselves.

The PCB Assembly process consists of lots of different processes:

Solder Paste Printing - In the work of this process the preliminary solder paste is printed onto the PCB using a stencil. This is fundamentally the binding material of the devices to the PCB.

SMT Pick & Place Assembly - This is the heart of each PCB Assembly line. This process takes all the individual chips & exactly places them on their designated place on the PCB.

Reflow/Through-hole curing - After placing the chips onto the solder paste, the boards go through a conveyor oven to melt the solder & bind the chips to the PCB.

Conformal Coating - Some boards need a protective lacquer coating. Conformal "Selective Coating" machines quickly & exactly provide a layer of protective coating on the PCBs.

AOI & AXI - Automatic Optical Inspection & Automated X-ray Inspection. These processes are key to confirming that no mistakes have been made in the work of the assembly process

Reworking if needed - If any mistakes or defects are found, some devices can be reworked. Reworking consists of heating the board or tool, & removing it from the PCB so that a replacement can be placed in its stead.