Electronic – What are the ‘knuckles’ on through-hole LEDs and photodiodes for

hardwareledpcb-assemblythrough-hole

I am using an IR LED and a photo diode, and I have designed the PCB according to the specifications that I found on the datasheet – i.e. hole sizes for the pins being 0.6 mm. However, on these components there are 'knuckles' (see below image) and these are wider than the hole size they quote for the pins.

Enter image description here

So the issue is the component doesn't go low enough into the board because of these knuckles.
Why are they there? How can I know how wide they are in order to make my holes account for this?

Best Answer

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.

enter image description here

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