How to choose drill size with known pin diameter?

When I order PC boards, I specify the finished hole size, and let the board shop determine the required allowance for plating. Normally, the smallest size I specify for component leads is .030 (for TO92 transistors), but usually use .035" for most parts (ICs, 1/4W resistors, etc.)

The finished hole size should be at least .010" larger in diameter than the lead.

On Tue, 31 May 2005 16:30:17 -0500, Michael Noone wroth:

Some board manufacturers will deliver boards with specific hole diameters after plating. Some manufacturers only drill the original hole with the specified diameter and it's up to you to determine the finished, plated, hole diameter.

In short, pick a manufacturer based on other criteria, and then work with them to get the proper finished hole diameter. If they only drill the original hole to what you specify, they can tell you what the build-up due to plating will be.

Jim

Hello Michael,

In addition to Jim's explanation: You should also find out what the manufacturer of your part specifies as the ideal hole diameter after plating. Else you might find that drill position tolerances and other deviations jam up the part, IOW it won't insert unless you force it. Also, solder may need to wick into there.

Regards, Joerg

I choose pin dia +0.015" for finished diameter and +0.01" for plating thru, so with your 0.02" pins the drill diameter is 0.045". Now the cheap board house(Olimex) has only ... 0.039, 0.043, 0.051, ... without extra charge available, so I choose 0.043".