Tips and techniques for SMD solder and desolder

[Lino]

I have in the past used a gas iron with a hot air blower tip to desolder
remove smd (100pin) chips successfully and resolder using solder paste.
There are differences in opinion about what is the 'best' technique with the
highest success rate...other suggestions I have heard are to cut the legs of
the old chip with a sharp knife etc
would like to hear some different opinions.

cheers
Lino

--

 

[Nigel]

A knife is risky to you and the pcb, and doesn't solve the problem of the IC
being glued to the board.

You might be interested to read about this product
http://www.chipquikinc.com/

Basically, it mixes an alloy with the solder to reduce the melting point,
allowing all sides to remain molten simultaneously, for easy removal of the
IC.

There's also a review of it in the June 2003 edition of the magazine
"TELEVISION and home electronics repair"


"Lino" <savvy@hotmail.com> wrote in message
news:bgn6a6$74q$1@enyo.uwa.edu.au...
I have in the past used a gas iron with a hot air blower tip to desolder
remove smd (100pin) chips successfully and resolder using solder paste.
There are differences in opinion about what is the 'best' technique with the
highest success rate...other suggestions I have heard are to cut the legs of
the old chip with a sharp knife etc
would like to hear some different opinions.

cheers
Lino

--

 

[DHarper]

I use a Dima reflow oven ( 100% success rate ). . or just flux the hell out
of the ic run your iron back and forth over the leads and lift with a pair
of tweezers. Just becareful there you may lift a pad. We have a repair
stations, but you could use a heat gun or one of those air paint remover
things. Careful there too they can and will burn the board. and yes you CAN
cut the legs of your going to scrap the ic.


I think the main thing is to becareful. generally SOIC's I can take off with
a soldering iron and flux. flux the leads run the iron over them and lift
the side with tweezers them do the same to the otherside. If I have to
rework fpga qfp's fine pitch etc I always use the reflow oven. it is to easy
to damage the leads and the pads.

As for resoldering, just flux and solder with the iron. if its a qfp tack
the corners and solder the rest. I only use solder paste in the initial run
because well... stencils don't allow a redo on an assembled board.


Good luck!

 

[DHarper]

I use a Dima reflow oven ( 100% success rate ). . or just flux the hell out
of the ic run your iron back and forth over the leads and lift with a pair
of tweezers. Just becareful there you may lift a pad. We have a repair
stations, but you could use a heat gun or one of those air paint remover
things. Careful there too they can and will burn the board. and yes you CAN
cut the legs of your going to scrap the ic.


I think the main thing is to becareful. generally SOIC's I can take off with
a soldering iron and flux. flux the leads run the iron over them and lift
the side with tweezers them do the same to the otherside. If I have to
rework fpga qfp's fine pitch etc I always use the reflow oven. it is to easy
to damage the leads and the pads.

As for resoldering, just flux and solder with the iron. if its a qfp tack
the corners and solder the rest. I only use solder paste in the initial run
because well... stencils don't allow a redo on an assembled board.


Good luck!