Chip Quik, Inc.
. JUNE 2004 SMD REWORK "YOU CAN DO IT"
. The Chip Quik SMT Rework Newsletter
REWORK SOLUTIONS
.
THE CHIP QUIK SMD REMOVAL KIT

Included in each Chip Quik SMD 1 kit is a special low temperature removal alloy that has excellent wetting ability and melts at 136deg.F (58deg.C), a special paste flux in a syringe used for solder & desolder, alcohol pads for clean up, and complete instructions. The kit will remove 8-10 SMD's depending on the amount of leads.The SMD 1 is the basic starter kit. The complete line of Chip Quik products are illustrated on the Chip Quik Web site and on the card that comes in the SMD 1 package.




PLEASE PASS THIS INFORMATION ON TO ALL OF YOUR TECHNICAL ASSOCIATES
A TYPICAL REWORK SITUATION

In a typical rework situation, an engineer designing a prototype board may have to change an SMD, install a test socket or adapter, replace a chip component, lift some SMD pins for test access, run tests with different SMD components, run a QC analysis after removing a failed component, etc. A technician may have to change a defective SMD, install an upgrade modification, repair a poor solder connection, remove components from a board, make a field repair on location, troubleshoot an inoperative board, etc. A contract manufacturer may have to change a component due to a production error, touch up solder joints after inspection, repair a board after going through the ATE (automatic test equipment), etc. These examples fall into the category of low volume rework. Fast, safe, easy, and affordable rework is needed. To send the board out to a rework specialist or to hire a trained technician would not be practical and/or economically feasible.

As you can see, becoming proficient at SMD solder/ desolder rework is to your advantage. You will save time and money. Also, you become less dependent on others. Best of all, fewer boards will be scrapped.

HOW DO I SAFELY REMOVE THAT SMD?
The removal procedure is included in the Chip Quik instructions in four simple steps. For learning purposes, I will explain the procedure in full detail. First, apply paste flux generously to all the pins of the SMD to be removed. Flux is important because it removes oxidation and enhances wetting. Secondly, use a solder iron set at 500 to 600Deg. F with a flat chisel tip. The size of the tip will depend on the size of the chip leads. With the solder iron, melt Chip Quik low temperature alloy (136Deg.F) along each side of SMD. Thirdly, continue running the iron along pins until a bead of alloy is formed all around the chip. Maintain the alloy in a molten state long enough to combine with the interconnect solder (melts at 361deg.F) between the pin and the pads. Once the Chip Quik mixes with the interconnect solder, we now have a molten mass of a new alloy with a low melting temperature below 200deg.F. At this new low melting temperature the pins stay in a molten state long enough to easily remove the Chip. In most cases the chip will easily slide off the pads when it is fully molten. Finally, when the SMD is held down with an adhesive, applying pressure with a dental pick will pop off the chip. As long as all the pins are released, you will not lift any pads. This procedure will eliminate all potential damage to the PCB.

*This is the basic Chip Quik SMD Removal Method. It is simple, safe, and affordable.

CLEAN PADS THOROUGHLY FOR NEW SMD


It is of the utmost importance to thoroughly clean all of the pads prior to installing the new SMD. In order for the new chip to seat correctly on the pads, we need coplanarity. This means that the adjacent pads are of equal height. Additionally, this will help the resolder procedure.

All remaining alloy should be removed from the pads in order not to allow any foreign material to remain. This will insure the integrity of the new solder joint.

To clean pads, run a soldering iron with a wide tip along all pads while polishing them with a swab dipped in Chip Quik paste flux. This procedure will do an excellent job. I do not recommend solder braid in this application because of the high temperature risk of lifting pads. Clean up all the remaining residue with Isopropyl Alcohol. You are now ready to solder on the new SMD.

FUTURE CHIP QUIK NEWSLETTER SUBJECTS


*HOW TO SOLDER THE CHIP BACK ON (in detail including which method is best for you, how to choose the right equipment, and which tools are the best.)

*CHOOSING THE CORRECT SOLDER IRON AND TIP (which includes, what determines a good solder iron , how the right iron can prevent PCB damage, and heat transfer theory.)

*OTHER UNIQUE REWORK METHODS (which includes hot air pencil, preheat, convection, and conduction, etc,)

*SOLDER, FLUX, CLEANING CHEMICALS (solder paste, paste flux, flux removers, etc.)

THE NEXT CHIP QUIK NEWSLETTER WILL EXPLAIN IN FULL DETAIL HOW TO SOLDER ON THE THE NEW SMD.


.    email: chipquik@aol.com
   voice: 1-508-477-2264
   web: http://www.chipquik.com
Chip Quik, Inc. 195 Falmouth Road Bld. 1C Mashpee MA 02649