The Chip Quik SMT Rework Newsletter

OCTOBER 16 2004

...HOW TO RESOLDER THAT SMD CHIP....

REWORK SOLUTIONS

THE CHIP QUIK SMD REMOVAL KIT
HOW DO I SOLDER THE NEW SMD TO THE BOARD
A QUALITY SOLDER IRON WITH THE CORRECT TIP WILL MAKE THE DIFFERENCE
READY TO RESOLDER THE SMD TO THE CIRCUIT BOARD
A FEW TIPS TO HELP IMPROVE THE REWORK PROCESS

THE CHIP QUIK SMD REMOVAL KIT

Included in each Chip Quik SMD 1 kit is a special low temperature alloy that has excellent wetting ability and melts at a low temperature of 136deg.F (58deg.C), a special paste flux in a syringe used for both solder and desolder, alcohol pads for clean up and instructions. The SMD 1 will remove 8-10 SMD's. Also Chip Quik alloy and flux is avilable in larger quantities.

Please click on to the links below for some of the latest articles on Rework and Remanufacturing. As you can see, being proficient at SMD solder desolder is to your advantage.

REMOVE ALL SMD'S SAFELY WITH A SOLDER IRON

The popularity of Chip Quik continues to grow as more technicians and engineers experience how safe and easy SMD rework can really be. If you have not tried Chip Quik yet, Chip Quik, Inc. will send an evaluation sample and literature anywhere in the world simply by filling out the simple request form on the Chip Quik Web Site. After about 3 weeks, a follow up e-mail is sent asking the simple question "how did Chip Quik work out for you?". The response has been overwhelming as the testimonials continue to pour in. In the reply our only request is to please spread the Chip Quik word to all of your technical associates. This has proven to be one of our best marketing tools to develop a global market. Best of all, fewer boards are being scrapped because of Chip Quik.

HOW DO I SOLDER THE NEW SMD TO THE BOARD

The most widely asked question is "now that I have safely removed the chip and cleaned the pads, how do I reinstall the new SMD". Suprisingly enough the biggest challenge has always been to safely remove the chip without inflicting damage to the pads and adjacent components.Chip Quik has solved that problem. Replacing the SMD requires some skill but is not that difficult. Most of us already own the necessary tools and equipment to do the job. You can do it.

A QUALITY SOLDER IRON WITH THE CORRECT TIP WILL MAKE THE DIFFERENCE

An important factor in installing the new chip is to use a solder iron that will maintain its temperature and heat delivery. A quality iron will maintain its set temperature even when it is inserted into a solder joint with various thermal loads. This is done by having the heater element and a sensor right in the tip. The temperature is continuously sampled and corrected thus accurately maintaining the set temperature. The result is that you can now effectively operate at a lower temperatures applying heat for less time to the solder joint. The real benefit is a better solder joint without inflicted damage. By using a good iron you can perform quality solder joints at 600deg.F and you can remove SMD's with Chip Quik at less than 500deg.F. Use a flat chisel tip wide enough to cover the pins and pads for good heat transfer. There are various tips available to perform drag soldering. One type is the mini-wave tip which has a little indented reservoir that holds molten solder in like a bubble. When dragged across the pins, the correct amount of solder is released on demand. Theoretically the tip never never touches the pins but rides on a wave of solder.This works great on fine pitch SMD's where the pins can easily be bent. Start with the traditional chisel tip then try the mini-wave. To desolder the tip is not as critical. I recommend using a different tip for solder and desolder.

READY TO RESOLDER THE SMD TO THE CIRCUIT BOARD

Before starting this step, it is important that the pads are clean and the solder on each pad is level. Apply paste flux generously on all pads. A paste flux helps to keep the chip from moving. Also it does not run when the board is tilted. Place the chip on the pads using good lighting and magnification to insure that the leads are centered on pads on all sides. Carefully hold the chip in place with a pick or tweezers. With a clean tinned iron tack solder in 3-4 locations so chip will not move. At this point check for placement accuracy. Now apply solder to the tip and slowly drag solder long the pins applying more solder and flux as needed. You will find that the solder will wick into each pin pad connection to form perfect solder joints. If a solder bridge is formed, it can be easily removed with solder braid. Clean solder joints with an acid brush and a good flux cleaner. Inspect all solder connections for for defects. Try this method, it's easy.

A FEW TIPS TO HELP IMPROVE THE REWORK PROCESS

Using solid core 63/37 solder will form a better and cleaner solder joint. Use a good no clean tack rework flux that is non-corrosive and non-conductive.There are many good flux cleaners available but when using a no clean flux, isopropyl alcohol will work quite well. The potential for pad damage increases when using solder braid with a poor solder iron set higher than 600deg.F. As already mentioned a good quality iron will allow you to do the same job at a lower temperature and also help preserve the tip. Another safe method to clean pads after a Chip Quik SMD removal is to run the iron along the pads following it with a swab dipped in flux while carefully brushing off each pad.

Hopefully this information will help improve the your solder desolder rework skills. In future articles I will cover other rework subjects of interest. To mention a few: Conduction, Convection, Preheat,Solder Paste, and Difficult Solder Joints. Please pass this Newsletter information on to all of your technical associates