On 05/04/2010 23:40, Chris wrote:
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> As others have pointed out, it is dependant on many other factors. If you are doing surface mount parts, the pad needs to be about 10 mils greater in width than the leg (rough number).
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> For through holes, I prefer a pad that is as big as I can make it. Small rings are hard to solder and can easily lift off the backing. I try not to get much smaller than a 15 mil ring. So, if your hole is 50 mils, it would be 50 + 15 + 15 = 80 mills in diameter. This is still a rough number but it works for me.
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> Small rings are hard to solder and provide very little surface area for the solder to exists. I have found that anything smaller than 10 mills in width often lead to troubles as mentioned above.
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> What can help is also to make the pads oval in shape, this provides for better copper to backer adhesion and easier soldering. But again, watch your sides (narrow width) so that you still have some material there after drilling.
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I often use teardrops.
Leon
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Leon Heller
G1HSM