What is the proper way to solder the compnents; resistors, caps, diodes etc. to a pcb. Flush or off a little?

What is the proper component positioning when soldering resistors, diodes, caps to a circuit board, flush or just slightly above the board? I want to get a good solder bond on both sides of the pad.  I'm building a Nixie tube clock kit.


seandogue6 years ago
There is a minimum bend radius dictated by IPC standards. See IPC 610 or the current iteration for specifics.

Do NOT simply fold the leads over. This can lead to mechanical failure of the wire.
Bond strength isn't affected by the distance from the board. Most components when fitted by hand, are usually a little bit spaced off the board automatically. Don't cut the excess length off through the joint though.

I usually try to leave a little bit of length on the leads, because...
 

The tree which does not bend with the wind, will be broken by the wind.

I read that on a fortune cookie once. 

What this proverb means for circuit construction is that you might, on occasion, want to un-solder some component  from a circuit board, and then maybe solder it back.   Or maybe at some date in the far away future, you, or someone else,  might want to use the parts on your circuitboard for some other application.  Having a little bit of length in the leads can help in this regard.  

Or maybe you have a too tall electrolytic capacitor that you'd rather have lie flat.  Extra length in the leads can help.

Of course there is such a thing as too much freedom.  I don't want you making any of those spaghetti-looking "hippie" circuit boards with leads so long they're in danger of shorting against each other.  Or I mean its your board, you can do that if you want to.  I think little extra length on the component leads is good, as long as everything stays "neat".

It should be possible to get a good solder fillet around the lead on both sides of the pad if the component is flush or slightly lifted. If there is a good solder joint on at least one side, it should be good electrically.

Functionally, there is not going to be any real difference. If your PCB will experience high levels of vibration, then you would not want it lifted far of the board, especially if it is a more massive component. For example, anything like a large electrolytic capacitor or transformer or inductor should not be standing off the board on long leads.