The circuit boards used in the counter top sterilizers of the medical and dental industries are subjected to a lot of stresses. The high moisture content in the air combined with the heating and cooling inherent in their operation puts them at higher risk of failure. One of the failure points is the board mounted fuse clips. Typically these fuses and clips must carry the current for the heating elements which are usually rated at 1,200 Watts. Here in the US where the mains are 120 Volts this translates to 10 Amps. As the environment interacts with the solder joints and metal of the fuse clips small increases in resistance leads to heat which eventually leads to more resistance and eventually heat and arcing damage to the circuit board.
In this short picture blog I will show my technique for repairing a damaged sterilizer circuit board using solder wick to replace the damaged circuit traces.
The circuit board in question arrived having already been patched by someone else in the field.
The first step is to remove the old fix and clean the board. As far as the circuit board itself we must remove any carbonization that has progressed so far that it now has a lower resistance.
I have used a small drill to open the original fuse clip holes to remove additional carbonization and to allow the solder wick to pass through. Next a small piece of solder wick is cut and anchored at one end with a little solder.
The wick is now looped through the fuse clip and down through the second fuse clip hole in the board. Pulling the solder wick tight straps the fuse holder against the board.
On the back side of the board we have pulled the wick tight and now we place the wick back over the pins of the clip, making small opening in the wick for the pins to pass through.
The extra wick is cut off and the wick is shaped and pushed tight against the board. The wick is tacked with a little solder.
When we are satisfied that the clip is in the proper position and the wick is down to the board the rest of the solder can be applied. Finally the work site is cleaned of excess flux.
The final touch is to put some protective masking on the repaired area to slow future damage from the heat and moisture.
I have no data to back this up but I suspect that this fix is more durable than the original boards construction.
John
Top Comments
Woah! This is highly Jugadeous plan.
Observed similar degradation of PCB traces inside TV Remote when alkaline batteries leaked out.
This definitely a trick I'll keep in mind. Thank you for such an awesome and detailed write-up!
Nice tip. For sure the joint will last longer and not vaporize on a downstream short :-)
This is a good solution too for building breadboards that have some significant power runs of 10A or higher. Its…