Small Electrical Continuity Test Probe

[dreinsdo]

Hello! I am currently designing an electrical continuity tester for a flex circuit. The circuit itself is a series of copper bars that are mechanically connected to traces through different buses. My idea is very basic: connect a trace to the test circuit (a power supply plus some sort of indicator), then sweep a probe across the bars. If continuity is present, the indicator will give a positive reading. I have attached a simple sketch to illustrate the basic concept. The dotted line arrow is to indicate the probe will sweep/translate across the circuit to contact each of the bars. The red dotted line indicates the primary area/components that this post is addressing.

Simple right? Here's the catch: the bars are .25mm wide at .55mm spacing (center to center, .3mm edge to edge). I am struggling with finding a viable solution for the probe. The probe needs to be translated across the electrode to contact each bar individually, without scratching/marring the copper bars. This will need to be done for thousands of cycles, so the probe solution needs to be repeatable. Can you offer any advice/direction/ideas on a probe for this tester? Please let me know if I can provide any further clarification. I appreciate any help I can get! Thanks all.

Also, please let me know if this belongs in a different forum.

 

[dreinsdo]

Try the attachment at the link below instead of the one above.

 

[MikeHalloran]

I wouldn't drag anything across a flex circuit, for fear of cutting the conductors, or worse, compromising their fatigue life in an undetectable way.

A quick search suggests that flex circuit testers are available commercially, and that they commonly translate a probe above the surface of the flex circuit, then press it down to make a test.

If you are considering a homebrew solution because of sticker shock, maybe you can find a rental/lease arrangement or snag some used machinery or rent some time on another outfit's test machinery or just farm out the test entirely.

Homebrewed stuff tends to get expensive quickly, because you get to climb a learning curve that someone else already ascended, you may build in reliability or operational issues from lack of experience, and you may just screw it up in any one of an infinity of ways and put your company at risk. If you're working on something that no one else has ever done, sure you want to keep it in house, but flex circuits are getting to be old hat now.





Mike Halloran
Pembroke Pines, FL, USA

 

[collies99]

Top side pressure with a rotary contact wheel, Connected to your indicator.

and probably should go on cct design forum.

 

[mcgyvr]

Why not just have the board house making the flex circuit do continuity testing (e-test)? They do flying probe/bed-of-nails tests all day long.. 100% e-test is "usually" thrown in for free with every circuit board we order.

Also what about circuit to circuit (trace to trace) shorts,etc... do you need to check for that?
How many conductors are in each flex pcb?
Why not just an individual indicator for each trace/circuit?
Just use some simple rounded point pogo-pins to contact each trace. (place flex circuit in tester..press down to engage pins..make sure all lights are on and done)