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What is PCB Tinning?

Published in PCB Surface Finish 2 mins read

PCB tinning is essentially the process of applying a layer of solder onto the exposed copper areas of a printed circuit board.

According to the provided reference, the concept of PCB tinning is to apply a soldering coating on the copper traces, pads, and vias, which will aid the soldering process later during PCBA. This coating serves a crucial role in preparing the board for the assembly stage where electronic components are attached.

Why is PCB Tinning Performed?

The primary goal of applying a solder coating (tinning) is to protect the underlying copper and enhance the board's solderability. Without a protective layer, copper is susceptible to oxidation, which can significantly hinder the ability of solder to properly wet and form strong connections.

The reference highlights several key benefits of PCB tinning:

  • Protection Against Oxidation: The solder coating forms a barrier, preventing the copper from reacting with the air and forming oxides.
  • Improves Solderability: A clean, solderable surface ensures that molten solder flows easily and creates reliable joints during assembly.
  • Helps with Solder Bridging: A consistent solderable surface finish can help prevent unintended solder connections between adjacent pads or traces (solder bridges).
  • Avoids Need for Repair and Rework: By ensuring good solder joints from the start, tinning helps minimize defects, reducing the time and cost associated with fixing issues later in the production process.

How PCB Tinning Aids PCBA

During the PCBA (Printed Circuit Board Assembly) process, components are soldered onto the PCB. The presence of a pre-applied solderable coating on the pads and vias ensures that when solder paste is applied and reflowed, or when wave soldering is used, the solder wets correctly to the intended areas. This creates robust electrical and mechanical connections for the components.

Tinning ensures the surface is ready to accept solder, making the assembly process more efficient and reliable.

Benefits at a Glance

Here is a quick overview of the advantages provided by PCB tinning, based on the reference:

Benefit Description
Oxidation Protection Shields copper from environmental degradation.
Improved Solderability Ensures solder wets well for strong joints.
Manages Solder Bridging Helps prevent unwanted solder connections.
Reduces Rework Minimizes defects during assembly, saving time.

In summary, PCB tinning is a vital surface finish treatment that prepares the copper features of a bare board for successful and reliable component assembly by providing protection and optimizing solderability.