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enlarging smd pads

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MrDEB

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designing a board and after soldering 6 other boards for a 18f2221 soic pkg pic and wonder if making the 2mm height pads 3mm high higher. Then while soldering it might be easier??
current pads are .6 wide and 2mm height going for .6mm x 3mm
will post results after I get boards back from board house.
 

Ian Rogers

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designing a board and after soldering 6 other boards for a 18f2221 soic pkg pic and wonder if making the 2mm height pads 3mm high higher. Then while soldering it might be easier??
current pads are .6 wide and 2mm height going for .6mm x 3mm
will post results after I get boards back from board house.
I always do.... I cant stand it when the part covers the pad and you cant get to it.. As long as it doesn't touch other tracks you can do what you want!!
 

JonSea

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A document everyone should be aware of is the Microchip Packaging Reference. Other companies have similar reference manuals. This is a good place to check pitch and center-to-center pad spacing.

As Ian said, the pads can always be longer than the minimum distance - just be sure to extend outward from the center and don't change the internal gap.

I would keep the pads symmetric across the chip - don't make the pads on one side longer than on the other. This would make it harder to judge where the chip should be on the pads and if you're reflow soldering, weird things can happen if the pads are different sizes.
 

ronsimpson

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I would keep the pads symmetric across the chip
Here is a screen shot of a micro board I did late last year. (32 bit ARM) The leads reach out to the outside edge of the pad. I hand soldered the parts. There is no place for the solder iron to touch the pad. (or a test probe) Inside the green circle the pad is made longer for hand soldering. (used paint to show what I wish I had done but forgot)
upload_2017-3-28_6-53-55.png
 
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