Question: I have a couple of questions regarding cup terminals. J-STD-001, IPC-A-610 and IPC-A-620 all require solder to be “visible” in the inspection hole (if present). Is there a more specific requirement to this? If you had a situation where solder is “visible” in the inspection hole but there is also a void or “unfilled” portion of the hole; would that be acceptable for Class 3?
Secondly, when soldering a small gauge wire in a large solder cup, I don’t see in J-STD-001, IPC-A-610 or IPC-A-620 where there is a requirement for a “filler wire” to be used for Class 3. (As top-route bifurcated terminals/wires require.) What is the difference between the two, why would one need the filler wire and the other would not?
Answer: Great question and I’m not sure I’ve got the full answer, but here is what we do know.
Let’s start with the inspection hole. Its prime purpose is to see if the wire is fully inserted into the connector. I also believe this is for the crimping of the pin onto the wire, and all the literature I looked at emphasizes that the inspection hole cannot be destroyed during the crimping operation to make sure the wire is still visible in the connector pin.
I also found a portion of a document from ESA PSS-01-718 Issue 1 (October 1987) Titled 7. Assembly of Connectors to RF Coaxial Cables. In the discussion under assembly it states that the inspection hole shall be filled with solder. I’ve attached the latest version for you now Titled: ECSS-Q-ST-70-18C 15 November 2008. Check out paragraph 5.5.1 g1 here.
As for the two wires in the bifurcated terminal, this is to make sure the wire is soldered to the post of the terminal and adding an additional non functional piece of wire is to secure the wire against the post when making the solder joint.
As for the wire in a cup, completely different story, as the cup should be sized to the wire being used. The only important items in this situation are that the wire is inserted to the depth of the cup and that the solder fills 75% of the cup, which is very similar to soldering a wire into a plated through hole.