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How does a PCB Assembly process work?

By pcbpower      November 29,2016

PCB Assembly process flow:

An analysis of the stages of PCB Assembly:

Solder Paste Printing:

Solder paste is applied onto the PCB through a stencil printer with optical alignment or a simple pin-registration system.

The print quality is verified before proceeding to the next step.

SMD Stencil Printer

SMD Stencil Printer

PCB Power offers a SMD stencil printer with a simple pin-registration system for a fast and precise set-up and low-cost frameless stainless-steel stencils, suitable for proto & small quantity PCBs with SMD.

For further details follow the link: http://www.pcbpower.com/products/soldering-solutions/

Component Placement:

Placement of the small SMT components is performed by a pick and place machine since Placement by hand is a critical one and hence unadvisable in case of SMT technology. A double sided surface mount assembly on the other hand requires Glue dispensing to hold the components in place on the opposite side.

PCB Power provides the camera-assisted manual pick and place device power-placer which is a camera-assisted manual pick and place device designed and priced for prototype and small series assembly.

Power-placer makes component placement quicker and works wonders with our other soldering-equipments put together saving both your time and cost.

For further information follow the link: http://www.pcbpower.com/products/soldering-solutions/

Pick N Place Machine

SMD Reflow Oven

Reflow Oven:

Once the component placement is done, place the assembled PCB onto the reflow oven conveyor belt. Reflow soldering melts the solder applied during the solder paste process and connects the component joints permanently through controlled heat.

The term “reflow” refers to the temperature above which a solid mass of solder alloy is certain to melt (as opposed to merely soften). If the temperature is dropped below, it stops the flow of the solder and if again it is raised, it causes the solder to flow again – hence the term “re-flow”.

PCB Power offers a SMD Reflow Oven for proto & small quantity PCBs with SMD.

SMD reflow oven maintains a constant temperature across the board with total user control throughout the soldering process.

For details follow the link: http://www.pcbpower.com/products/soldering-solutions/

Manual Insertion:

Before the insertion process, it is important to have the component leads cropped to an appropriate length. If they are too short, they may not extend into the through-holes far enough to form a good solder joint. If they are too long – the component may fail to sit on the board in the correct position. Once cropped, the leads are bent in to a particular shape to provide stress relief.

Components are inserted into the board. To hold them in place on the board, we often perform lead clinching process or use jigs.

Wave Solder:
In wave solder process, a conveyer moves the PCB through the different zones. As the PCB is passed over a molten ‘wave’ of solder, via a mechanical conveyor driven system, a connection is made between the electronic component leads, the PCB pads/holes and the solder itself forming an electrical connection.

Cleaning:
After the soldering process, the flux residues found around the solder joints are removed with solvents and/or de-ionized water through cleaning stage. If a “no-clean” solder paste has been used for solder paste printing, the flux residues need not be removed after the soldering process.

Final Inspection:
This stage involves the verification of the assembly quality with the available inspection machines, such as x-ray and conventional AOI machine. There should be no shorts, no solder bridges between solder balls, and no loose solder balls under or around the component or component leads.

Touchup/Rework:
If a defect is observed after assembly, a touch-up or rework will be carried out by removing the defective part and replacing it by a new one. Some of the common defects observed after board assembly are:

  • Wrong part
  • Reversed polarity
  • Misaligned part
  • Shorts/bridging/excess solder
  • Opens / insufficient solder
  • Non-wetting / Un-reflowed solder