The quality is decisive!
THT means Through Hole Technology, in other words components, where the legs are positioned through the holes in the PCB and then soldered. These components can be assembled on both sides of the PCB, similar to the SMD technology.
The constant and reproducible quality of the automatic lead-free process can not be reached by hand soldering, e.g. of discrete components on the cards which already contain SMD components. Discrete components are accurately soldered lead-free under nitrogen atmosphere with precision solder nozzles. The lead free soldering preserves the environment, there are less heavy metal contents of the products and their residues.
The cards may already be SMD assembled on both sides. The selective temperature sequence and the monitored solder wave height allow the processing of all solderable and discrete components. Additionally, this technique also provides perfect soldering joints formed by the peel-off function. For the manual assembly the products are placed on tables. Nimble fingers are then fitting one position after the other through the entire batch.
Selective soldering - Whenever quality is crucial!
Especially in compact assemblies is a double-sided arrangement of complex SMD components (BGA, fine pitch) compulsory.
However, the use of SMD technology for connectors and large components is often inappropriate. For good mechanical stability, THT components are therefore used. For the soldering, a system is needed which supplies consistent results without affecting the previously assembled SMD components.
From the smallest soldering joints to the most massive fixation soldering of connectors are processed. Even both-sided component arrangements are possible without problems with 2 solder passages.
The selective solder system enables a consistently high quality of THT soldering joints.
Therefore, we do not have any hand soldering joints and experiments with solder masks on wave soldering systems. Small CNC-controlled nozzles automatically apply the flux and the solder at the right place. Also between already assembled components.