Through-hole technology - Leading PCB Assembly Manufacturer

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Through-hole (leaded) resistors

The first PCBs used through-hole technology, mounting electronic components by leads inserted through holes on one side of the board and soldered onto copper traces on the other side.

Boards may be single-sided, with an unplated component side, or more compact double-sided boards, with components soldered on both sides.

Horizontal installation of through-hole parts with two axial leads (such as resistors, capacitors, and diodes) is done by bending the leads 90 degrees in the same direction, inserting the part in the board (often bending leads located on the back of the board in opposite directions to improve the part's mechanical strength), soldering the leads, and trimming off the ends. Leads may be soldered either manually or by a wave soldering machine.

Through-hole manufacture adds to board cost by requiring many holes to be drilled accurately, and it limits the available routing area for signal traces on layers immediately below the top layer on multi-layer boards, since the holes must pass through all layers to the opposite side.

Once surface-mounting came into use, small-sized SMD components were used where possible, with through-hole mounting only of components unsuitably large for surface-mounting due to power requirements or mechanical limitations, or subject to mechanical stress which might damage the PCB (e.g. by lifting the copper off the board surface

The process of building electrical circuits using through-hole technology involves inserting pin-through-hole (PTH) components via holes drilled into printed circuit boards (PCBs). The ends, or leads, are then attached with molten metal solder using reflow or wave soldering tools to pads on the other side. Another name for this procedure is through-hole assembly.ContextPoint-to-point construction and other early methods of electronics assembly were superseded by Through Hole technology. From the second generation of computers in the 1950s until surface-mount technology became prevalent in the late 1980s, every component on a standard PCB was a through-hole component.

SMT is seen to be a superior choice for complicated boards because the THT method is more costly and takes longer. THT is typically a preferable option for big components that may be exposed to high temperatures, strains, and vibrations, such as transformers and high-power industrial PCBs. Making the decision is typically difficult, therefore combining the two processes to reap the rewards of each is the best course of action. The strength and dependability of THT can be achieved during assembly by combining the two techniques, all while maintaining the overall cost and efficiency advantages of SMT.