Making surface mount pads bigger for convenience is OK?

Community PCB Design
1

Hello,

I am going to put 0805 footprints into Cadstar…as well as many other footprints as per the schematic.

-However, even though the PCBs will be reflow soldered, the first prototype PCB will be hand soldered by myself, just so i can test it to see that all is OK.

-Now the reflow soldering footprints are a bit small for my hand soldering skills, so i intend to extend the 0805 pads by 0.4mm

-that is, the overall length of the 0805 footprint will be 2 x 0.4mm = 0.8mm longer than it would normally be.

…with such a bigger footprint, do you think this will cause a problem for the pick-and-place machines?, and be a problem for the reflow soldering process?

2

You may experience tombstoning - when in doubt, stick with the manufacturer recommended footprints; especially if you’re doing large volumes. Note that the footprints in cadstar may not be optimal!

That said - soldering 0805s shouldn’t be a problem with the standard footprints - I do 0402s with standard footprints by hand all the time.

–David Carne

3

As Busonerd says - if you have larger pads you can have tombstoning, also excess solder paste & solder balls etc.

Or things may well run just smoothly, but it is best to design for the optimum manufactured board with least potential for problems.

If you are likely to be making a low volume prototype batch then having a production batch once all testing is done

and the production batch is likely to be changed slightly (or in other words - you will be having a 2nd tooling at the manufacturer)

Then a way to have larger pads for hand soldering and correct sized pads for production is to use the alternatives.

Lay the board out with alternative’s I.E. “0805 (hand soldering)” (the large pads) then when you are satisfied that everything is OK

and you have made any slight changes - you can choose options\replace and select the “production” alternative (the correct size).

Then you may have a very slight amount of tracking to do.

If you download Mentors free IPC7351 LP Viewer it will give you all the std pad dimensions for the components you are using

to aid you making them.

Perhaps you need to change your soldering iron bit to a smaller one or get a hot air rework/soldering station for SMT.