Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Reliability of Reworked Pads/Traces?

Marc Ruggiero

#4618

Reliability of Reworked Pads/Traces? | 20 March, 2000

Hello,

I am looking for inputs (experiential or opinions) concerning field reliability of high-frequency RF boards that have had a trace or pad repair (or both), any package type. If anyone can comment on this subject, I would appreciate it.

We build an extremely high mix of complex PCAs, and I believe are unnecessarily scrapping assemblies that could be repaired and entered into service reliably. I am already pursuing this with our customers, but would like any "real life" tales of what has or has not worked for folks in the industry. Skill of the person(s) doing the rework is not as much of a concern as is long term RF performance. I plan to use IPC-7721 as my rework specification---any experience out there???

Cheers, mr

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#4619

Re: Reliability of Reworked Pads/Traces? | 21 March, 2000

Marc: Experimental evidence is rare. Published reports are rarer.

I can�t comment on the impact of rework on your RF boards. I can tell you that: � HF is pretty LF these days. � We allow three rework actions on each aboard. � IPC-7721 is a fine starting point for developing rework procedures. Good job Jeff!!

My 2� Dave F

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Erick Russell

#4620

Re: Reliability of Reworked Pads/Traces? | 29 March, 2000

Marc:

My experience found reliability IS a function of operator skill and attension to the process. Expecially for some RF assemblies. I worked with an engineer from Rogers to develope a process for reworking Pads for a special material. (I thing it was Rogers 2000?) it was a few years ago. We then did several peel tests to determine the reliability and found a process that worked well after several tries. I found the best method was using a Dry film epoxy backed replacement film. The surface preparation was critical. Cleaning the site with alcohol decreased the peel strength. (I thing it reacted to the epoxy)

Reworking on FR4 is much more forgiving and is reliable using Dry film or Liquid epoxy. There is also a bonding press you can purchase to help control the process. If you are reworking the on a Rogers Substrate, I have the contact name of the engineer who can suply the data and procedure. For FR4 I suggest you use the IPC procedures. There is an also excellent contract repair houses I can put in touch with that developed the procedures for the IPC.

I hope this Helps:

Erick

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