Some components as depicted in the below picture have different shape in their pins.
I wonder to know is it because the manufacturer wants to tell us from where should we assemble it in the board ?
Electronic – Why do some components have their through-hole pins flattened/pressed near the housing
componentspcb-assembly
Related Solutions
I have two possible explanations:
- The 'knuckles' are there intentionally to avoid the pins going all the way through the PCB.
Most of the times it is not desired that the pins are going all the way through the PCB. - They are a remnant of the production process (see picture below).
First the pins are a part of one single metal sheet and are cut after the dies and the casings are added. The cutting leaves the knuckles.
I was told to cut the leads to length before soldering. There was an IPC standard around on which basis we were taught that. I don't remember which standard it was exactly.
A reference I found is this document by IPC.
[...] The next part of the through-hole solder joint is the component lead. [...] Either way the leads are formed – usually with a 90 degree bend – and trimmed to the correct length. After the lead is trimmed, it may be clinched or bent over to hold the component in place during the rest of the assembly process. [...] The last part of the connection is the solder joint. [...]
So to prevent parts from falling off, you bent the already trimmed leads over (in a direction where it doesn't cause problems). And after that you solder them.
It is probably taught that way just as @GummiV mentioned in the comment, that the force and shock of the trimming might cause the joint or the PCB to be damaged.
I actually managed to break of a fragile ring with the track once because I was trimming after soldering, so I think the advice of the IPC is quite sound.
There are also frames around which help you in the assembly of through hole boards. You can put the board in, put all your components in from the top, then put down a lid and turn the whole thing around to solder on the bottom side.
Looks something like this:
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Best Answer
These flat strips are there because the manufacturer uses the same package for the SMD component. To turn it into SMD, they put a plastic spacer below the can, then bend the pins aside and cut the round wire ends off.