Understanding The Printed Circuit Board Assembly Process

We thought it necessary to revisit this topic due to high amount of inquiries regarding the assembly process and the changes that do take place in the industry. Although this article is elementary and answers the basic questions, it allows one to gain a bit of a better perspective on the process of the printed circuit assembly.

A Printed Circuit Board (PCB) is the base for wiring and supporting surface-mounted, socketed components in electronics. In circuits where there is a need for find conductive traces (such as computer systems), these PCBs are made through the photolithographic process. This is similar to the way conductive paths are made for processors just that it is on a much larger scale.

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PCBs can have up to twelve layers depending on the complexity of the electronic devices involved. Printed circuit boards are commonly colored green but there is no specific rule or standard defining this color code. Printed Circuit Board Assembly (PCBA) is the finalized board that is obtained after all the components have been mounted on the printed circuit board. These components may include resistors, capacitors, integrated circuits (ICs), and others depending on the application of the electronic device. In order to ensure a mechanical connection between the board and components, the PCBA for smart devices must undergo reflow furnace heating.

Things Needed for PCBA:

Given below are a list of electronics and associated consumables that are necessary for printed circuit board assembly:

  1. Printed Circuit Board (PCB).
  2. Electrical components such as resistors.
  3. Soldering flux.
  4. Soldering materials such as wire, preforms, bar, and paste.
  5. Soldering equipment such as wave soldering machine, soldering station, SMT and testing tools.

Once the above listed equipment is available, all materials can now be put through the assembly process for forming the PCBA.

PCBA with Thru-Hole Electronics:

Components that have leads coming out through tiny holes in the printed circuit board for soldering are known as thru-hole electronics. The soldering for these components must be done through the wave soldering process. Wave soldering is the process in which the solder bar is put through high temperature until it melts. This molten solder remains in the heat bath until waves form. The thru-hole electronic components are passed over the molten solder through the use of a conveyor belt to integrate them onto the PCB.

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The wave soldering process can be broken down in the following steps:

  1. Soldering of the thru-hole components on the PCB.
  2. Application of the flux.
  3. Preheat the PCBA.
  4. Clean the board for any residues.
  5. Test the PCBA for proper functionality. If there is any fault in the soldering, it is sent back for a rework job. In the rework, the component is reattached using hand soldering.

PCBA Surface Mount Technology (SMT):

This is an assembly process for surface mount devices. These are components that do not have leads or legs unlike the thru-hole electronic devices. Through this process, the SMDs are directly mounted on top of the surface of the printed circuit board. Generally, surface mount electronic components are smaller and easier to install than thru-hole components. The equipment and material required for this assembly process is different than that of the thru-hole components.

Conclusively, PCBA is the finalized board that is integrated into machines and systems. The assembly process for PCBA involves a range of different electronics that have to be assembled to manufacture these devices that are commonly used in many households.

For more information and question contact Giltronics Associates customer support.

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