PCB Assembly Process

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When PCB assembly processes or electronic assembly, welding, production or manufacturing of electronic circuits, PCB printed circuits are performed, the methods to achieve a robust, consistent and reliable welding, must be known.

Why should you inspect the PCB?

After welding, the assembled card must be inspected. The inspection criteria for electronic assemblies, established by common agreement between the assembler and the customer or user, must be used. This is to achieve both satisfaction and product duration.

In the world, the IPC 610 Standard of Acceptability of Electronic Assemblies is used to verify the quality of the manufacture of electrical and electronic assemblies, as a quality standard for electronic products.

The standard collects a series of criteria and requirements for visual quality. These are to verify the manufacturing quality of the electrical and electronic assemblies. As a quality standard for electronic products, the standard collects a series of criteria and requirements for visual quality.

The IPC 610 was developed by the IPC (Association Connecting Electronics Industries). These criteria are independent of the process used (manual, with soldering iron, wave, reflux, selective, pin-in-paste).

When can the standards be used for the different electronic assembly processes?

They apply for tin-lead solder, as lead-free, with certain differences, for welding THT (Though Hole Technology or insert) type components and welding SMD or SMT components (Surface Mount Devices, Surface Mount Technology, or surface mount components).

It is important to keep in mind that the assembly is the result of a good design; therefore you must consider the design standards of IPC 7351 pads, design of PCB printed circuits IPC 2221 and several more.

Important recommendations in PCB assembly processes

Prior to any PCB assembly or welding process, it is recommended:

  • Designthe PCB with manufacturing orientation DFM, DFA assembly (design for assembly), DFT tests (design for test), DFC cost (Design for cost), or DFR reliability (Design for reliability).
  • Knowthe characteristics of the inputs to be used: tin / lead for welding, flux, cleaners compatible with flux and welding.
  • Have and demonstrate the abilityto handle assemblies, ESD (protection against electrostatic discharge), preparation, tin / lead welding technique, cleaning and storage of electronic circuits.
  • Understandthe complexity of the type of electronic product to which circuit welding is to be performed and the required skill. For this, the IPC has specified three kinds of products:
  • Class 1: General or consumer products, such as televisions, cell phones, toys.
  • Class 2: Industrial electronics equipment such as controls, machinery, automation.
  • Class 3: High reliability equipment or products, such as medical or military.
  • Use suitable tools suchas: soldering station or soldering iron with temperature control, stereoscopic microscope, magnifying glass, lamp, antistatic tweezers, work table, mat and antistatic gloves.
  • Use the main standards that regulate the qualityof electronic products, apart from design standards and iec standards, IPC standards such as IPC-A-610 Acceptability of Electronic Assemblies, and J-STD-001 technical welding standard Requirements for Soldered Electrical and Electronic Assemblies.  Understand how to perform a visual inspection of the assembly within the PCB assembly process, and apply the criteria of inspection criteria of electronic assemblies, to accept or reject any defects that may be found.
Hattie B. Trosclair

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