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-   -   Replacing Surface Mount ICs (https://www.hometheatershack.com/forums/diy-repair-maintenance/47890-replacing-surface-mount-ics.html)

lcaillo 07-17-11 08:51 PM

Replacing Surface Mount ICs
 

Replacing surface mount ICs can be very difficult, but those who are willing to practice a bit, who are good with a soldering iron, and are patient and careful can replace many (not BGA chips) without expensive equipment.

Removal

One method is to cut the pins off at the IC. This has the advantage of not having to apply as much heat and minimizes damage to the traces, which can be fragile and easily damaged. The chip is destroyed, of course, but this is not an issue if you are sure that it needs to be replaced. There is the risk of cutting traces below the IC if you are not careful. Once the pins are cut and the chip is removed, it is easy to remove the pins with just a little heat and not damage the traces at all. Once can heat the pin and pull it off of the land in the direction of the center of the chip with the iron and then simply lift it away.

Another method is to lay a large bead of solder all the way around the perimeter of the IC, bridging all of the pins on each side. This takes a lot of solder, but is also a rather safe method. The mass of solder stays hot long enough to heat all of it and keep it melted at the same time, yet keeps the temp from going too high. The flux from all of the solder tends to aid in clearing the chip and solder from the lands as well. I use 63/37 lead eutectic solder because of the lower melting point on all chips, even those in lead free boards. The trick is to not be shy about using too much solder. Once you have melted a large bead across all of the pins on each side, melt each side in turn until all are melted, then lif off the chip. Remove the excess solder so that the lands are just tinned with wick or a vacuum device.

Once the chip is removed, you need to tin the lands leaving a small amount of solder on each with no bridges. Align the chip so that pins are precisely located on each location, then solder two opposing corners. Go over each pin with a small pick and a magnifier to assure the they are aligned perfectly. Apply a bit of liquid flux designed for electronics then gently heat each pin or pair of pins until the solder joint is made. Pulling the iron tip from the chip straight away along the pin will drag any excess solder and lay it where it belongs or pull it off on the tip.

Go back and check for bridged pins with a magnifier, then test all adjscent pins with a meter for shorts. Some pins may be connected to the same part of the circuit, so confirm connections with a schematic. I also suggest confirming continuity between each pin and some part of the circuit to which it connects.

I will try to take some pictures of the process and post them this week.




crujones 04-30-12 03:40 PM

Re: Replacing Surface Mount ICs
 

Thanks Icaillo!
I like the first method of clipping all the leads off the IC. I use a pair of "Fiscars" clippers with the fine point. I will try your other method tonight on a Boss RC-20... Wish me luck:)
Cheers,

loach71 08-14-12 09:50 AM

Re: Replacing Surface Mount ICs
 

Could you folks upload some photos of suggested tools and techniques for SMT repair? I am an old thru-hole electrical engineer and am leery about working on SMT board without the right tools.:help:

lcaillo 08-14-12 07:44 PM

Re: Replacing Surface Mount ICs
 

This is a very large topic. Perhaps if you were more specific about what kind of components and what tools you do have we might have some suggestions. There are likely lots of videos on you tube on the matter.




soldering iron 02-01-13 02:40 PM

Re: Replacing Surface Mount ICs
 

It could be helpful to use a solder wick , place it over solder joint and heat with soldering iron. That way solder wick will absorb most of solder. Then you can use hot-air gun which has nozzle big enough to heat all pins on IC.

Paxonator 06-29-14 04:23 PM

Re: Replacing Surface Mount ICs
 

Thanks for the tips. Always looking to improve my soldering skills.

bluecatfish 12-09-14 10:59 AM

Re: Replacing Surface Mount ICs
 

Thanks for the very helpful information.


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