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A question arouses if it�s suitable with quality standards ... - Nov 12, 1999 by Wolfgang Busko

Wolfgang: Sure, stacking chip components is common practic... - Nov 12, 1999 by davef

As a CM, I have had customers stack components as a tempo... - Nov 12, 1999 by

Good suggestion Brian!!!! Two companies that screen ECOs o... - Nov 12, 1999 by davef

This is crazy... - Nov 12, 1999 by

I agree with Gordon!!... - Nov 12, 1999 by

Gordon and Bob I had to go back and read the previous posti... - Nov 12, 1999 by John Thorup

Back to Wolfgang's original request. Stacking chip compo... - Nov 14, 1999 by Jeff Ferry

Wolfgang Busko

#8555

patches | 12 November, 1999

A question arouses if it�s suitable with quality standards to solder a chip component onto another double-whopper-like to perform a patch. Often done in prototyping but is it also suitable for patches on boards already out in the field ?

Any suggestions ? Wolfgang

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davef

#8556

Re: patches | 12 November, 1999

Wolfgang: Sure, stacking chip components is common practice in prototyping, as you say, but it's not good practice for production work. Documentation:

* ANSI-IPC-275 does not allow stacking * MIL-STD-2000A does not allow stacking * J-STD-001B is unclear, fuzzy. You might be able to "lawyer" you way through this one. * Bellcore TR-NWT-000078 does not allow stacking

Issues:

* Loss of the ability to dissipate heat by the stacked-upon component. * Lower mechanical strength of the stacked structure.

Be careful if you have potential product liability issues.

My2�

Dave F

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Brian W.

#8557

Re: patches | 12 November, 1999

As a CM, I have had customers stack components as a temporary measure of incorporating an ECO. Most of the time, it includes using an adhesive to secure the component. Cost of material already in-house is the major factor when this occurs. Even though some standards don't allow this, the board drawing usually takes precedence over the standard. A better method is to secure the component to the board and run jumper wires if possible. If you have a large number of boards that need to be built, there is a company (and I cannot remember the name) that will take your boards and actually run a trace and put pads on the board for the component so you can surface mount it in the process.

If I can be of any further assitance, please let me know. Brian W.

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davef

#8558

Re: patches | 12 November, 1999

Good suggestion Brian!!!!

Two companies that screen ECOs onto unpopulated boards are:

ASI 8 Winn Ave Hudson, NH 03051 603-889-1999 www.additive.com Artie Desmaris Conductive Circuits 602.986.8939 fax0008 www.conductivecircuits.com

Dave F

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Gordon O'Hare

#8559

Re: patches | 12 November, 1999

This is crazy

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Bob P.

#8560

Re: patches | 12 November, 1999

I agree with Gordon!!

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John Thorup

#8561

Re: patches | 12 November, 1999

Gordon and Bob I had to go back and read the previous postings again after reading yours and I must say that I still don't understand...please enlighten us John Thorup

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Jeff Ferry

#8562

Re: patches | 14 November, 1999

Back to Wolfgang's original request.

Stacking chip components is just one of many unusual mods that are being added to IPC 7711 Rework of Electronic Assemblies. While some may deem this technique unacceptable, it is a relatively common practices .

The committee will also be adding other procedures with step by step instructions and illustrations showing component placed upside down, dip components stacked, and many more.

Stay tuned.

Jeff Ferry President - Circuit Technology Center Chairman - IPC Repairability Committee

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