Smt

[KrashKing405]

Anyone able to make a board using SMT chips? I ordered the wrong package, got the smt version of the A3977, and the A3986 on accident.

[Cooper]

Hi there,

I can use SMD A3977 and A3986. Do you have questions about mounting?

Cooper

[KrashKing405]

I don't have the skills right now to use them, looking for someone to mount them on a board for me.

[Cooper]

Sorry, I'm very far away from your city.

Cooper

[KrashKing405]

I can see that . Anyone have non-SMT chips they'd trade me?

[pastera]

Do you have the right footprint for the board or do you need an adapter board made?

I can mount the parts but it would probably be cheaper to just buy the correct parts than to ship the stuff across country.

Aaron

[KrashKing405]

Would be nice to find someone to swap chips with.

[pminmo]

3977 and 3986 only come smt

[KrashKing405]

Oh, I thought there was a PLCC package for the A3977.

[pminmo]

plcc is surface mount, you can get a socket for a plcc, but the package is smt.

[KrashKing405]

Ah, ok. Makes sense then, thanks. Anyone want some A3977 and A3986 chips?

[rstringer]

Hi..

I ordered 5 A3977 chips from Allegro and the ones I got originally were almost normal DIP, only small with gull shaped leads. I couldn't find a board layout for that option so I re-ordered for the square SMT chips so I have both. If you go to the Allegro web site you can request samples and they will send you chips--that's how I got mine....and they are free. No questions asked if you order them through your work and indicate you are working on an evaluation project.

As for SMT soldering, it's no more difficult than regular soldering if you use a couple of techniques I'll describe here.

a. You need some type of good or decent, at least, magnifier so you can see the leads.

b. make a small solder ball on two opposite corners of the package pads, use about .020 (or even .010 if needed) solder and a very fine soldering iron tip and flux liberally with liquid flux, don't use paste--don't drown it, but use enough so the solder is less likely to bridge.

c. use tweezers to put the part down and align.

d. heat the pre-applied solder until it adheres to the lead on one corner, using the tweezers to hold the part in alignment.

e. repeat for the other pre-applied solder pad.

f. now you have the part secured flat to the board and can solder the remaining leads, again, use flux.

g. check for bridges and use solder wick to clean them up and maybe remove areas where you have big globs of solder.

VOILA!!! now you have a professional-looking SMT solder job...and it wasn't hard at all. The keys are being able to see what you are doing and using fine-tipped irons and very fine solder. I did surface mount soldering repairing Nokia cell phones for 7 years and it doesn't take long to become proficient at it, just have patience and don't try to get ahead of yourself.

Hope this helps...

Ron Stringer