CHIP QUIK Product Release - SMD Removal Kits

31/03/2011

 Removing SMDs The Safe Way!

The new, smart way to remove SMDs is with a special solder made by Chip Quik The solder is an alloy of tin, lead, indium, and bismuth. Bismuth is a heavy metal that's one step above lead on the periodic table, and is the most diamagnetic of all metals with a thermal conductivity lower than any other metal, except mercury. 

When tin and bismuth are "amalgamated," it reduces the melting point of the solder to a very low 136 °F, as opposed to the 361 °F melting point of 60/40 solder. When you meld the two together —- that is, melt the new solder with the old — the resultant alloy has a melting point of about 150 °F (well below the boiling point of water). At temperatures this low, it's nearly impossible to damage the solder pads.

 

 

 

The procedure is easy and painless. It involves four easy steps, which are outlined in the video. The process starts by applying a drop of flux from the included syringe to each lead of the part to be removed. 
Next, melt a dab of Chip Quik solder on each to the leads using a small (30W) soldering iron — just pretend like you're soldering the chip in place rather than removing it. Be liberal with the Chip Quik solder, and don't worry about solder bridges (slipovers). 
Once the leads are treated, apply heat to the leads until the new solder is molten, and lift the SMD off the board using a dental tool or vacuum pick. 
After the part is removed, you'll notice an unsightly mess left behind. This is solder "ash," a result of the interaction between the ChipQuik solder and the old solder, which has to be removed to expose the pad underneath. Clean-up is done with a cotton swab dipped in flux, followed by an alcohol wipe. The Chip Quik SMD-1 SMD Removal Kit contains enough solder to remove 8-10 44-pin SOIC packages.

SMD Replacement
What's left is a clean footprint, ready to accept the new SMD. The new part can be soldered in place using any number of techniques. 
With a pair of tweezers and magnifier, carefully align the new SMD in place so that it lands squarely on the pads. Let it set for a few hours to harden the paste. Use a low-wattage iron — about 15 watts — with the smallest chisel-tip you can buy. Begin by tacking down two or three of the corner leads. This prevents the chip from shifting while you heat the remaining leads.
A trick of the trade is to heat the bottom side of the circuit board to about 150 °F with a hair dryer or hot air gun before soldering the chip. This reduces the amount of time it takes for the solder to reflow when touched by the soldering iron, thereby lowering the heat transferred to the IC and reducing the risk of damage. 
Another trick is to drag the solder tip parallel to the body of the IC (perpendicular to the leads) at a rate just slow enough to melt the solder along the way. 
Never touch the pads or the pins; let the ball of solder carry the load of the work for you. Combining these two techniques minimizes chip heating and all but eliminates solder bridges.
The final step is to clean up the board using rubbing alcohol and a solder brush or a CFC-free solvent, a hydrofluoroether, azeotrope formulation with trans-1, 2-dichloroethylene and ethanol. This mixture is well-suited to defluxing and degreasing tasks, and is intended to replace ozone-depleting compounds.

And It's Done!
Really - that's it. Sound too simple to be true? Try it and find out for yourself now!