How to efficiently remove components from printed circuit boards

How to Efficiently Remove Components from Printed Circuit Boards

You may need to remove all the components from a printed circuit board for rework, repair, upgrade, salvage or other purposes. But how do you do it in the most efficient way? It’s a simple process if you keep in mind that most printed circuit boards (PCBs) have both active and passive components that are attached to the PCB in one of two ways: surface-mounted or through-hole.

Surface mounted devices (SMDs) are electronic components that are soldered to the PCB surface by their miniscule metallic surface terminals. Common examples of SMDs are passive parts such as resistors are capacitors, or active parts such as ICs. Through-hole components have leads that are inserted through padded holes and are then soldered to the pads on the bottom side of the PCB. Common examples of through-hole components are resistors, capacitors, relays, inductors, transformers and more.

To remove SMDs and through-hole components from a PCB, use the following procedure: Preparation 1. Don personnel protective equipment (PPE) such as safety glasses and gloves.

2. Set the PCB on a work surface that is both horizontal and dry. It is important that the PCB is set on a truly horizontal surface; when the PCB is heated, molten solder will be created and may move to adjacent

pads or tracing when set on a non-horizontal surface, which may cause short circuits on the PCB. Removing SMDs 3. Use a heat gun to remove the SMDs. After turning on the heat gun, position it approximately 15 centimeters above the PCB with its nozzle pointed down. In short order, the heat will melt the solder flux of the SMDs that are beneath the nozzle of the heat gun. Quickly remove these components by utilizing a tweezers. Collect them in a tray.

Repeat this procedure until all the SMDs are removed from the top side of the PCB. 4. After you have removed all the SMDs, allow the PCB to cool for up to three minutes. Power down the heat gun and properly stow it away in a safe place.

Removing Through-Hole Components 5. Energize a soldering iron and sets its temperature to 450oC. Obtain a 6-inch length of copper desoldering braid.

6. Select a desoldering starting point at the far edge of the board. Then touch the copper braid on top of a pad that as you place the tip of the soldering iron on the solder joint pad. In a matter of seconds, the solder flux should melt and flow into the copper braid. Follow this procedure for all pads.

7. After you have completed desoldering on the pads on the reverse side of the board, flip the PCB over and repeat the process again using both the heat gun and the soldering iron to remove any other components and residual solder.

8. When all SMD and through-hole components are removed, deenergize the soldering iron and properly secure it in a safe location.

Clean Up 9. Inspect the PCB and using swabs doused in alcohol, clean the pads on both sides of the PCB. After you have cleaned the pads, you should have removed all the components from the PCB. About Bittele Electronics Headquartered in Toronto, Canada, Bittele Electronics specializes in turnkey PCB assembly for electronics engineers requiring prototype or minimal volume PCBs. For more information, visit http://www.7pcb.com