Replacing as15-f chip

[audiofreak19]

Hey how are you all replacing the as15 chip. Do you use hot air or soldering iron. I'm trying to use my hot air station but for some reason it's not melting the solder paste. It melts it slightly but not into liquid solder. I tried using my iron but kept getting one or two bridges on each side that I couldn't get rid of.

[mmartell]

Re: Replacing as15-f chip

I've not done one of these yet but have replaced the buffer ic on a Samsung buffer board must be sorta similar.

I would use your iron with lots of flux and drag solder after you tack the corners. Any bridges can be cleaned up with a little braid. Good luck.

[audiofreak19]

Re: Replacing as15-f chip

Ok thanks for the tip. I changed the temp to 600f just out of anger and it finally melted it into solder and went on the legs but had a lot of bridges so I'm using my iron now to try and remove them.

[Glitcher]

Re: Replacing as15-f chip

Just use lots of flux and you can use solder wick to remove the bridge. I move the solder tip parallel to the IC leg pins so it doesn't bridge as much.

[audiofreak19]

Re: Replacing as15-f chip

Ok. Yea I need to up grade my soldering iron too. I think that also might be part of the problem. I'm just using a craftsman plug in. I'm gonna see if I can snag a hakko soldering station from work.

[budm]

Re: Replacing as15-f chip

600f (315c) is OK.
http://www.hakko.com/english/lead_free/pages/

[audiofreak19]

Re: Replacing as15-f chip

I just pulled the chip off again. I might try to reflow it again since before I was at like 450f.

[stj]

Re: Replacing as15-f chip

didnt i tell you not to use solder paste but to use good flux to flow the existing solder!
also, reflowing lead-free solder needs about 310'
so 600 is about right.

[audiofreak19]

Re: Replacing as15-f chip

There wasn't much solder left on the pads. I did that and it did stick but there wasn't much solder on ther to the point that it didn't even flow ontop of the edges of the feet

[audiofreak19]

Re: Replacing as15-f chip

It was on there. But I was afraid to leave it that way incase the chip got warm and possibility of melting the solder and it either coming off or one of the legs loosing contact.

[stj]

Re: Replacing as15-f chip

if taking the old chip off took all the solder with the chip then you probably didnt use enough heat.

if you need more solder on the pads you do it before you add a new chip - then you dont end up with bridged pins.

[audiofreak19]

Re: Replacing as15-f chip

Ok I think I will add solder to the pads and then put the chip on and reheat the solder on the pads.

[whatusername]

Re: Replacing as15-f chip

it is a P.I.T.A. i have tried this 3 times using both soldering irons and rework station hot air and still had to buy another board taking it off is easy but getting it back on where there are no false contacts after it warms up is incredibly hard. if u figure out the secret please update i would love to know cuz YouTube makes it look so easy and it most definitely isn't

[stj]

Re: Replacing as15-f chip

there are a few tricks.
i wouldnt call them secrets.

take the old chip off,
put flux on the board & re-melt the solder so it's all nice & flat.
clean burned flux off.

take "new" chip.
if it's not really new, put flux on the legs and put it down upsidedown.
use the air to flow and flatten any old solder on the legs.
clean the flux after with a soft brush and IPA

now you have a clean chip & pcb.

put the chip on the board and make sure it's straight.
then melt the solder on one of the end pins wih an iron just to hold it in position.
check you got it right and then repeat on the oposite corner.

now paint all around it with flux,
and heat 2 joined sides while gently pressing on the corner with a long thin metal thing with a thermally insulated handle - unless you like burns on your hand!

when the solder melts, the chip should drop onto the pads on that edge.

now get your magnifier and check it's still inline and didnt go off-center.

if it's good then repeat on the other 2 linked sides.
it should now be 100% down and alighned.

if your unhappy with the look of any of the soldering, re-flux it and reflow it in one go using a swirling motion with the air.

like our resident DJ recently said - it's all in the wrist!

now 2 other things.
1: if the chip is large it helps to warm he underside of the board first.
2: clean off the flux once your done - flux absorbs moisture and becomes conductive.
also if the flux uses a thermally activated corrosive agent - some do, then it's gonna stay corrosive after it cools.

[audiofreak19]

Re: Replacing as15-f chip

Thanks for the tips.