Through hole manufacturing

Another name for “through hole” components is “conventional” components. These components are mounted manually. Automated machines do exist (sequencers) but these are huge and expensive.

Manual mounting is expesive, why do we do that anyway ?

In some cases there is no alternative for a through hole component. When the size is too large, when mechanical stress is too high or when power dissipation is too much. With some components the SMD type can be bought only in reels of at least 1,000 pieces, while all you need is 100 pieces. In those situations through hole components are selected. The less the better, but sometimes you can’t do without.

What does the through hole production process look like ?

Bending and cutting

The preparation for production means bending the lead to the correct pitch (hole distance) and cutting the leads to the appropriate length. Most components are delivered on paper tape that can be handled by a cutting and bending machine.

Mounting

All components are manually placed in the PCB. The leads are fit into the holes and extend about one millimetre.

Wave soldering

The pcb with all components positioned is placed on the wave soldering machine. Flux is foamed to the bottom of the PCB in order to clean the contacts and improve the quality of the solder joints. Next the pcb and the components are heated to 100°C. During the heating the flux will clean the contacts by etching and also a thermal shock is prevented. Now the pcb is transported over the solder wave. Liquid solder is pumped against the bottom of the pcb. Because of the turbulence in the liquid solder the contacts are well wetted and the solder fills the gaps between the holes and the leads. The result is a strong and reliable joint.

Inspection

The joints are optically inspected for correct soldering.

The pcb is now ready to be tested.