SMD Jig - Prototype
This is the 3rd attempt at building a SMD jig to hold parts during assembly. I've tried different ideas with weights, spring pressure, etc with some success. Each of this jigs though could send the part flying across the workbench, it was difficult to adjust the pressure holding down the device. ICs were fine but small caps and resistors would take flight. Placement of these jigs was challenging because they were not stationary - the combination of a small part on a smooth PCB was a recipe for the part flying off the board.
Here's a prototype I put together in a couple of hours. The only parts I needed to purchase was the 6-32 all-thread and the knurled nuts. The remainder of the parts I had laying around. The base is a bamboo cutting board that's about 10"x6". The arm over the board is made from a scrap piece of 1"x3" pine that has been cut into the shape of an L. Light is provided by a re-purposed cheap, 9-LED flash light. I took it apart and attached it under the arm using a bent up coat hanger. The light is adjustable and is run off batteries. I wanted to keep cords running across the workbench to a minimum.
The all-thread has been turned down on one end to about 1/32th of an inch in diameter using a Dremel tool. The end was ground flat and smoothed. Using a 7/64th bit, I drilled a hole through the end of the arm and then used the all-thread to cut threads into the wood. This provides enough friction and stability so the business end of the all-thread is very stable. Here are a few photos during testing; click on the photos for higher resolution versions.
Turned down all-thread
Holding 0402 chip resistor
Holding SOIC-8 Chip
I tested the jig by holding a 0402 chip resistor and soldering it to the PCB; it worked like a champ. It took some practice to develop a feel when enough pressure has been applied to the part. The part to be soldered down doesn't need to be clamped forcefully, it just needs enough pressure to not move when the solder becomes molten and flows. I'm sure we've all experienced the tombstone affect when soldering. Another benefit of this approach is that the all-thread acts as a heatsink.