Fusible traces can be designed to be consistent and fairly accurate, but more than trace width and copper thickness need to be considered. Are the coated with mask or bare? If they are bare what final finish?  Are they in free air or under a component. Are other circuits routed nearby? Routed over a plane? Layer to layer spacing? I believe there were a couple of other factors we identified but can't locate my notes on this.

As Karl suggest a smt fuse or polyswitch would be a better choice.

YMMV, 

Jeffrey A McGlaughlin, CID 

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Karl Bates
Sent: Thursday, October 04, 2012 3:01 PM
To: [log in to unmask]
Subject: Re: [DC] Trace Fuses

Sorry all again, have to remember not to send from my phone to this listserv.

Here is what I said:

It would seem strange to destroy a board at failure, instead of 
replacing a fuse.  
Would you risk failure of downstream components 
/circuits if the trace fuse doesn't work as planned. 
Not to mention the 
safety and liability of the product, to save a nickel and then be sued 
for 20 million?    
It is important to size the traces leading to a fuse 
also, as that could effect the fuse blow point.   
I have discussed 
it with several engineers over the years, and have always used the 
fuse.   
But please let us all know how it works out for your team.
Karl
 
 
Karl



> Date: Thu, 4 Oct 2012 11:15:04 -0700
> From: [log in to unmask]
> Subject: [DC] Trace Fuses
> To: [log in to unmask]
> 
> Does anyone have experience with designing a fuse into a PCB as a trace?I did a quick google on the topic and found a paper by Douglas Brooks (UltraCAD).Also found a CircuitCalculator to help with the equation. Just wondering what some of you have experienced with this sort of thing.
> 
> Bob McCreight, C.I.D.
> 
> 
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