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The Advantages of PTH Assembly

7th July 2014

PTH assembly is a method of making electrical circuits that uses pin-through-hole (PTH) components. These are inserted into a printed circuit board through drilled holes. The leads, or ends, of the components are attached to specific pads on the other side of the board with molten metal solders

PTH assembly was the technique that replaced standard assembly techniques in the 1950s, when a second generation of computer technology was being developed. It continued to be in common use until the 1980s, when it was replaced by surface-mount technology.

However, one of the continuing advantages of PTH assembly is that the mechanical bonds that connect the components to the circuit board are much stronger than those produced by surface-mount methods. In the event of any faults, the connections can also be repaired individually by hand rather than by replacing an entire circuit board. But they are also more expensive.

As a result, PTH assembly methods are usually reserved for use with bulky components, such as large package semiconductors that need a high mounting strength to sustain high stresses or in electrolytic capacitors.

This type of assembly remains very common for use in power supplies, electronic modules and the assembly of LED applications. However, a demand for circuit board configurations with increasing component densities, a wide range of board thicknesses in one application, ever-changing board surface finishes, changing electrical power demand, reliability and ongoing concern about the lead content in metal solder (some 90 per cent of solder metal is a tin-lead alloy) can provide serious challenges to design and process engineers using PTH assembly methods.

The call for lower costs, less equipment, fewer manufacturing processes and higher profit yields has made life even more difficult.

As a result, process and design engineers have evolved a mixed technology that uses through-hole and surface mount methods together. Machines have been designed that use both surface mount and through-hole technologies in a two-phase process. This allows for flexibility in the assembly and the ability for hand-soldering and repair while also proving a cost-effective and automatic assembly method. However, a challenge remains in developing lead-free solder methods that minimise the dissolution of copper in tin-silver-copper solder alloys.

If you need more information on through-hole technology and PTH assembly, feel free to contact us here at Trizo. We are only too happy to answer your queries and create a product that suits your exact requirements.