Don't know if Class III can deal with an 0402 on the same leads, but the spacing sounds right.
For the etched solution, I've had a lot of experience with etched 2 mil thick brass foil (silver plated). Brass is a relatively poor conductor of heat, so if the irons are set to the proper temperatures you will be able to solder the second side without the first side re-melting. If you half-etch a tab into the design, your operators will thank you for the handle to ease the soldering pain. You can also design a simple bending fixture for pre-forming these leads while they are in a panelized format.
Wayne Thayer
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Barbara Burcham
Sent: Monday, February 02, 2009 9:56 AM
To: [log in to unmask]
Subject: Re: [TN] Jumper wire forming for fine pitch QFP?
You could have a jumper made by chemically etching the part. I have seen fine RF screens created, using this process and there are a lot of folks out there doing this.
It is not too expensive and can be made from numerous metals.
Barbara Burcham C.I.D.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Monday, February 02, 2009 8:03 AM
To: [log in to unmask]
Subject: Re: [TN] Jumper wire forming for fine pitch QFP?
Hi Steve
Not a dumb question. The short answer? Would it work? Absolutely.
Would it be legal per IPC-A-610 class 3? No way. So we could put it on the drawing, except it's a build to print project - we aren't the design authority. The mountain of difficulty involved in getting that approved... And product qualification? Can't claim qualification by similarity on that.
So the short answer is that putting an intentional solder bridge there is not an available option at this time. I'm stuck with the world's shortest jumper wire.
regards,
- Graham
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, February 02, 2009 9:05 AM
To: [log in to unmask]
Subject: Re: [TN] Jumper wire forming for fine pitch QFP?
Morning Graham,
Can I ask a dumb question? Why not just solderbridge the leads together?
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Monday, February 02, 2009 6:59 AM
To: [log in to unmask]
Subject: [TN] Jumper wire forming for fine pitch QFP?
Hello Technet
I've got a design where we have to run a jumper between two adjacent legs of a fine pitch part. So the jumper is a tiny piece of wire that runs down the leg, across the foot, bends around in a U, and back up the adjacent lead. We hand form this, and the operators are not liking it.
I'm pondering getting the machine shop to try to make something we could use to pre-form the wire for this, but it's a bit higher precision than they usually work to. The gap between component leads is about .012"
Does anything already exist in the tooling world to pre-form a wire in this manner? I don't want to re-invent the wheel if I can avoid it.
thanks,
Graham Collins
L-3 communications ES
Halifax Production Engineering
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