Using high current pulse in a trace to start chem. rxn

[TurboLS]

So the jist of the issue is that I am using a 1 oz. trace, approximately 7 thousandths wide and .5" long to supply a very short, high current (150A to sometimes 500A, 1V or less) pulse to a reactive multilayer to start a reaction. The problem is that sometimes, the trace "blows", charring nearby soldermask and creating a disconnect. The circuit is designed such that the current must pass through the thickness of the multilayer to reach ground.

I have current pulse properties that will never cause this blowing, but also be intermittent in starting the reaction.

I have current pulse properties that will always ignite the reaction, but sometimes blow the traces.

Some people have suggested I look at fusing requirements, but since most people assume a certain frequency above 0, or even DC, this analysis and prior work doesn't really apply to us.

Other things I have started looking into have been inductance when the reaction starts, potentially causing a momentary open circuit, which would cause arcing.

Any ideas on other resources to look into regarding high current pulsing of PCB's, especially those with Metallic Cores, such as Aluminum, would be fantastic. Thanks.

 

[itsmoked]

If it is just a specific trace having the issue why not fix that trace? Run 4 mil copper or better yet just leave that trace unsolder masked and lay a piece of bus wire down its spine?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[TurboLS]

thanks for the quick response. i did look at thickening the copper, but the problem with that is that the industry will not increase copper weight on the board. I have to accomplish my task by changing the shape of the trace and how it makes contact with the reactive material or, perhaps, change the contact resistance between the material and the trace via some kind of cleaning agent, increased pressure, or some other means. I am concentrating, in this case, on trace geometry.

So, in summary, I like your idea of increasing copper weight, but it cannot be done on the board during pre-preg. I may be able to accomplish the same effect by incorporating a copper bus bar into the ignition tool used to supply the pulse.

 

[itsmoked]

Why can you not just "check the box" and have the board be 2oz instead of 1oz? I can't imagine the price even changing.

Barring this I think have have too little info to help you much.

Got a photo of just the issue area/connector?

Keith Cress
kcress -

http://www.flaminsystems.com