Ask Helena & Leo

Question: Can a PTH component (resistor, fuse, or solid wire) be reliably soldered in-line with stranded wire? Similarly to a wire lap joint, but with a component between the two wires. Is there an IPC standard that covers this situation? I have looked at IPC A 620, but could not find anything to address this process.

Answer: There is nothing on this concept in the IPC documents, be it either the IPC-A-610 Acceptability of Electronic Assemblies, or the IPC-A-620 Wires and Terminals  Section of the document.

Lap solder joints are an acceptable joint as seen with all the surface mount components, especially with gull wing components.

The document you should be referencing though is the J-STD-001 which describes the wetting necessary to make a good solder joint. Specifically Section 4, Paragraph 4.18.

The intent is to get good wetting between the wire and the component. The problem you may face is overheating the component when connecting the wire to the component itself and from your description you are soldering 2 wires to each component, one wire at each end. This will be a tremendous amount of heat applied to the component and that may impact it physical characteristics and could change the value of the component and its tolerances. So, make sure this is tested to verify no damage has been done to the particular device.