Solder paste, solder flux, and best of all their low temp solder alloy removal stuff. Melt it into the connections to an SMD and it forms a crumbly alloy that allows the parts to just lift off after it is cool.
Steve Greenfield
----- Forwarded Message ----
From: Marv Cohen <
chipquik@...>
To:
alienrelics@...Sent: Tuesday, October 23, 2007 5:00:39 PM
Subject: The CHIP QUIK® SMT Rework Newsletter ∗NEW∗ (An Alternative To The Solder Iron)
OCTOBER 2007 ∗∗∗∗AN ALTERNATIVE TO THE SOLDER IRON∗∗∗∗
The CHIP QUIK® SMT Rework Newsletter
∗ HOW TO REWORK A PCB WITH A PREHEATER & A HOT AIR PENCIL
∗ REWORK ON A PCB WITH A BOTTOM PREHEATER
∗ USING CHIP QUIK® WITH PREHEAT FOR SAFE SMD REMOVAL
∗ ∗∗∗COMPLETE PREHEAT HOT AIR SYSTEM∗∗∗ Part # SMDSYSTEM3..... $475.00 free shipping in USA
∗ COMPLETE HOT AIR SYSTEM for $475.00
________________________________
HOW TO REWORK A PCB WITH A PREHEATER & A HOT AIR PENCIL
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With multi layer PCB's and the increased density of surrounding components near the SMD's, there is a heat sink effect that draws heat away from the pads. The incorrect way of overcoming this problem is by increasing the applied temperature, resulting in an increased potential for damage to the PCB board and components. When soldering in these dense areas, bottom side preheat has many advantages that will overcome this problem.
SETTING UP THE PCB FOR RESOLDERING THE SMD......... Place the PCB in a horizontal fixture that allows the preheater to be placed under the PCB rework area at the correct height. The preheater will blow focused hot air under the PCB. The heater is set at the correct temperature to maintain the bottom of the PCB at a constant 300°F.(150C). At this safe low temperature the risk of thermal damage has been eliminated, including the bottom side components directly under the heat. The heat will be transferred through the board, to the pin / pads and to the SMD. This safe temperature is maintained on the board throughout the rework process.
PREPARING FOR THE SOLDER PROCESS: Check pads on PCB board for coplanarity (equal height) and clean tinned pad surfaces with a good cleaning solvent. Using a syringe apply a thin bead of solder paste 63/37 w/flux along all of the pads. The amount of paste dispensed will depend on the size of the nozzle. It will take some practice to judge just how much paste to apply for different size SMD's. Carefully place the SMD directly into the paste on the pads. Use magnification to insure accurate pin / pad placement on all sides. Once the SMD is set in place, be careful not to move it.
USING A HOT AIR PENCIL AND BOTTOM HEAT: Apply bottom heat and wait until solder paste starts to activate. This will be visible when the flux in the solder paste starts to smoke. Now set the air pencil for low air velocity and a temperature of 500°F(260C). With the solder pencil slowly move from pin to pin and apply heat. Watch as each individual pin / pad solder joint as it is formed and then move on to the next. If a solder bridge is formed, apply more paste flux and heat again. If this does not work, use solder braid while heating with the hot air pencil. Clean all connections with an acid brush and flux cleaner. Check with magnification for accuracy. Place preheater on cool air and allow rework site to slowly go back to room temperature. This method works quite well with fine pitchcomponents.
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∗ CHIP QUIK® ON-LINE STORE (International)
∗ CHIP QUIK® Complete Line of Power Strips∗∗ 20 Models
∗ CHIP QUIK® Complete Line of Magnifier Lamps∗∗ 16 Models
∗ CHIP QUIK® SMD 291 No Clean Paste Flux 10cc
∗ CHIP QUIK® Lead-Free Solder / Desolder Kit NEW!
∗ CHIP QUIK® SMD Rework Previous Newsletters
We at Chip Quik, Inc. are committed to bringing you quality rework products. All products that we sell are tested and evaluated in our own lab. A NEW REWORK CHALLENGE FOR THE ENGINEER & TECHNICIAN
SMD Rework has become a greater challenge since the introduction of the latest PCB's. The new boards have multi layers and an increased density of surrounding components near the SMD's resulting in a heat sink effect that draws away the applied heat from the solder pads. This makes the required heat delivery to the solder joint even more difficult to maintain. The incorrect way of overcoming this problem is by increasing the applied temperature. Higher temperatures result in a greater potential for damage to the PCB and adjacent components. There is a better method.
REWORK ON A PCB WITH A BOTTOM PREHEATER
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SMD rework does offer an alternative choice other than the traditional solder iron. When applying heat to a solder joint, a certain amount of time is required to transfer the applied heat to the thermal load (solder joint). This time is determined by the efficiency of the heating device and the thermal conduction of heat to the solder joint. A quality solder iron is the most efficient device because the heat makes direct contact with the solder joint. A safe alternative method is the use of hot air for PCB bottom preheat. Hot air convection does not have as good heat transfer as direct contact but does offer some advantages, especially for higher volume rework and thermal processing.
THERMAL PROCESSING: When soldering a PCB, a certain amount of time is required to bring the temperature of the joint from ambient (room) temperature to reflow. The safe rework challenge is to apply the controlled heat only on the joint for as little time as possible. Longer heating periods will allow damaging heat to be transferred to undesired areas, causing board delamination and damage to adjacent and underside components. As you can see the control of the temperature in a specific location for a controlled amount of time will determine the quality of the rework and reduce the potential for inflicted damage. This controlled temperature process is called thermal profiling.
BOTTOM SIDE PCB PREHEAT Bottom heating the PCB under the site where the rework is to take place will allow the temperature to be gradually raised to a safe point prior to reworking the SMD. This is done by placing the PCB in a horizontal bracket and applying focused hot air from a preheater directly under the site to be reworked. The distance below the PCB and the focused heat must be controlled to deliver a safe temperature just below reflow. For traditional boards the temperature is 300° F. (150C. By focusing hot air under the PCB, the heat will gradually transfer through the board to the pads and to the SMD component to be reworked. This gradual rising temperature slope of controlled hot air will prevent damage to some of the more sensitive components. Now whatever rework that is done on the top side of the board will be enhanced. Soldering, de- soldering and solder removal will be safer, faster and more efficient.
»
USING CHIP QUIK® WITH PREHEAT FOR SAFE SMD REMOVAL
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Due to the low melting temperature of Chip Quik® removal alloy (136°F.)(58C) an SMD can be removed using bottom heat only. With the PCB bottom heated to a safe bottom temperature of 300° F(150C), apply flux to all leads of the SMD. Now apply Chip Quik low temperature alloy to all the pins. The removal alloy will easily become molten because all the pin / pad connections are now preheated to 300° F. The applied CHIP QUIK® alloy will melt and fuse into each individual pin /pad connection resulting in a new low temperature alloy with increased thermal mass. While in this molten state the SMD can easily be removed.
CLEAN UP............ Clean the pads with a swab dipped in flux while the preheat is still being appied. This clean up method is much better and safer than with solder braid. You are now ready to install the new SMD.
»
∗∗∗COMPLETE PREHEAT HOT AIR SYSTEM∗∗∗ Part # SMDSYSTEM3..... $475.00 free shipping in USA
________________________________
»
COMPLETE HOT AIR SYSTEM for $475.00
________________________________
AN ALTERNATIVE TO THE SOLDERING IRON AT AN AFFORDABLE PRICE
-------------CHIP QUIK ON-LINE STORE-------------- »
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