Surface mount repair

[mroberts]

Trying to fix my car central locking remote, and discovered that all four pins on one side of a surface mount IC have come loose.

Is there an easy (non-soldering) way to fix this ? I'm not confident I could re-solder them without toasting the chip.

Otherwise, any tips for re-soldering without melting it ?

 

[kchriste]

Is there an easy (non-soldering) way to fix this ?

Not a reliable one!

Otherwise, any tips for re-soldering without melting it ?

Use a temperature controlled iron at around 650 degrees and just flow solder onto all the pins/pads without worrying about shorts. Then allow it to cool for a minute and use solderwick to remove any shorts/bridges. The key is to not apply the heat to the part/PCB for more than 5 seconds at a time. 5 seconds is a longer time than you realize and is plenty for what you need to so.

 

[mneary]

Try to find the cause of the problem.

Make sure (really sure) that everything is clean. Use an excess of flux and fairly small soldering tip. It's not necessary to use a tip that's smaller than the contacts. Try first on something that doesn't matter, to give you confidence.

You'll be OK.

 

[Sceadwian]

For reworking stuff like this flux is your best friend (just don't make the mistake of using plumbers flux)

 

[mroberts]

Try to find the cause of the problem.

I'm not sure what you mean - half the pins on one of the ICs aren't contacting the board.

 

[Sceadwian]

Are there solder pads underneath? Not all pins have to be connected. A quick picture wouldn't hurt (digital cameras are a godsend)

 

[mneary]

If half of the pins aren't connected, it would be a good idea to determine why. Is it by design? Manufacturing defect? Did it ever work? Did it overheat? Did moisture dissolve some of the leads?

 

[3v0]

If you have a pic-em-yourself junkyard I would visit it to see if I could find a replacement. You could at least look at similar units to see if the pins were supposed to be connected.

If the chip is visible without removing covers or screws (out in the open) you could visit a dealership and ask to see a replacement part. Most partsmen are up to that sort of thing if they are not in the middle of a rush. Take yous along so you can compare them.

 

[jbelectric777]

just a question for the experts. do those cold solder irons work at all ? i was going to buy one at RS but the guy said they dont work for component level work.

 

[Sceadwian]

I have one, it's good for me for quick and dirty jobs usually just desoldering something real fast as I don't have a location to set up a proper soldering station as yet. There's a lot of arcing at the tip and the power output is pretty low, but at the very least it will do in a pinch as a quick and dirty task light (it has a white LED in front) and if you touch wires to either side of the tip you get a quick and dirty access to the batteries (6 volt power supply) I use it to test small motors. I would not recommend it for a hobbyist for a primary soldering tool. You'd be better off spending the 20 bucks on a cheap soldering iron. There's supposed to be a cold solder plus which uses one more AA battery, which actually increases the power output quiet a bit. On a fresh set of batteries it will generate 60 watts, but keep in mind it applies a voltage to what it's touched to, the combination of the current flowing through the work material and the tip itself generate the heat. I wouldn't recommend using it on sensative IC's they say the tip is made out of a patented substance, but it's really just graphite with some kind of binder (pencil lead basically) I told my fiance I just couldn't see myself spending 20 bucks on it, but it'd make a good gift. I got one that Christmas =) Good gift, poor intentional purchase