We have a customer who insists that circuit board assembly should not be re-worked in any way. They will not accept boards which have been re-worked. Board Talk
Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting.
Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up CEM Selection/Qualification, SMT Training/Seminars, Legal Disputes
Phil Zarrow
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis.
He has vast experience in SMT equipment, materials and processes.
Jim Hall
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics.
He is a pioneer in the science of reflow.
Transcript
Phil
Welcome to Board Talk. This is Phil Zarrow and Jim Hall, the Assembly Brothers, we're here to answer your SMT process questions. What is today's question, Jim?
Jim
Our question today comes from D.V.M. We have a customer who insists that circuit board assembly should not be re-worked in any way. They will not accept boards which have been re-worked. Is this practical?
Phil
What do we mean by repair, and what do we mean by rework?
Jim
The standard terminology that I've always accepted is that a reworked board is a design change, something where it was changed from the original configuration, a wire was added, a path was changed, a component was substituted, or something like that.
If that's the case, then the customer should have been involved in that decision from the beginning.
But, I'm assuming that this customer is using rework interchangeably with repair and they're talking about boards that have been manufactured to specification, but have a problem, a solder joint, a bridge, an insufficient or something like that that was then repaired before it was shipped to the customer.
Then how would you describe that, Phil?
Phil
It sounds like your customer is expecting to get the proverbial zero defects. We don't see a lot of that going around, and chances are you probably don't see it at your facility, either.
So, when we do repair, just how bad is it, because we've heard various documents and specifications that some customers will give no more than one repair or two, but let's talk about the single repair.
Typically, how much damage are we inflicting? We're going through a thermal excursion, or two thermal excursions.
Jim
Potentially, if there's a component removal and replacement or maybe three, if we're doing a pad cleaning operation with some solder wick, we're adding another cycle, so there are concerns.
IPC has a whole division that does nothing but certify repair technicians, and the basic accepted practice is that if your operators are certified, they know how to safely repair boards without damaging them. Now, the question is prove it and, unfortunately, there's very little data out there.
I would like to point out that the consortium for the aerospace and military people, which our good friend, Dave Hillman has produced some of the best, most comprehensive test data.
Now, the orientation was a comparison of lead-free and tin lead, but within this matrix, the consortium included, repaired assemblies
To the best of my knowledge, they did not find any reduction in reliability, and they did two different versions of thermal cycling. They did shock and vibration and a whole bunch of other military and aerospace related accelerated life testing, and they did not find any degradation of repaired assemblies.
Dave, if we're wrong, please contact us. But the point is this is the only known published data comparing un-repaired boards with repaired boards that I know of.
There is a concern because you are putting them through thermal cycles, you are handling it again, and so I understand your customer's concern. But, as Phil said, to expect zero defects from a process, particularly if you're doing through hole components.
Phil
One of the best safeguards you could have is to have a very well trained, well skilled repair tech who are IPC certified.
Don't take any chances here, and that should give your customer a little bit more of a comfort level, and yourself, too, for that matter.
Jim
Any other custom procedures and work practices, and work instructions that you've developed for your repair situation, showing that it is controlled, and that it is, to the best of your ability, done in a fashion that's not going to damage or reduce the long-term reliability of the product.
Phil
Very good. I think we handled that question pretty well. So, thank you for listening to Board Talk. Keep those questions coming.
On behalf of Board Talk, this is Phil Zarrow and Jim Hall saying that whether you're doing primary operations, secondary ops or re-work, whatever you do, don't solder like my brother.
Jim
And don't solder like my brother.
Comments
Whether allow any rework is depended on the agreement between manufacturer and customer. If rework is not allowed, then the quoted cost shall be higher which should consider the scrap factor. If there is no agreement, then rework shall be accepted if rework result is acceptable as per IPC acceptance criteria, no matter how many times of rework have been occurred. If long term reliability is a concern, then there should be the limitation listed on the agreement.
Tim Li, Vecture Inc
Best way to qualify rework or repair (or whatever) is to test the fixing method by some accelerated life test to check if product reliability after the operation is acceptable or not. If a qualification plan is well done for rework method, you can test if a specific component replaced twice or three times is reliable or not. Of course, this cost money, but you will learn all you need to know about reworked/repaired product after. This makes easier taking the decision and also conversation with the customers about acceptability of a reworked board.
By the wat I do not see much discussion about things that worse board final quality, as, for example, PCB copper dissolution, thicker intermetallic compounds layers after rework and other stuff that really defines if a rework/repair is or not good as a fresh and untouched product as it was produced and approved.
Glayson Figueiredo, Philips Medical Systems
"Zero Defect" EMS, MiNT Corporation. We had several customers that allowed NO REWORK. It boils down to simply of what would you rather have, a pacemaker implanted inside yourself, to be one which exceeds all tests standards flawlessly or the one which was reworked and then "passed" the tests?
Andy Mrozowski, fluid LLC (formerly MiNT Corporation)
How much reworks are authorized per component? I don't speak about repair but about rework. For BGA component, for example, if the component is reworked because the wetting isn't acceptable and after x-ray inspection, solder bridging is present, an other rework shall be performed. That to say 2 reworks. It's authorized? And any other rework of this bga component is allowed? IPC7711/7721 don't speak about this limit. Is there a standard who indicate that?
Jean-Noel LEVRARD, SAGEM group SAFRAN
It will be depend on the situation for Asia business pattern. Normally the supplier will not rework the PCBA if the cost is low and in high volume production. For high mix low volume PCBA, they will follow in-house rework procedure including testing.
We change many BGAs and are able to maintain quality without any customer complain. To ensure rework carry out without any issue, I think most important is the knowledge of Mfg Engineer and skill of rework operators.
Ridley Chan, Wincor Nixdorf Mfg Pte Ltd.
If we are now talking the correct terms of rework and repair. What are the thoughts on "No repairs"? If there is a lifted trace where nothing is separated or broken and it is repaired per IPC 7711/7721 is this acceptable for all product? If the repair is done correctly and functionality is restored can this repaired board be used in any space or military environment?
Arlis Greco
I'm a little concerned by Jim's definition of Rework, as he seems to be mainly describing Modification.
Rework:- The act of repressing non-complying product, through the use of original or alternate equivalent processing, in a manner that assures compliance of the product with drawings and specs.
Modification:- the revision of the form, fit and/or function capability of a product to satisfy new acceptance criteria.
Debbie Wase, Advanced Rework Technology Ltd
Rework-Touch-Up Function, Restores the assembly to full compliance to Print. Repair- "MRB" Issue to which the board will function but not meet all of the acceptance criteria of the documentation.
Joe Racz, Precision Graphics Inc.
It is always a good time listening to you guys.
Just a though after listening to your Board Talk relative to rework being acceptable or unacceptable.
Per IPC–T-50, I believe you have it mixed up between the terms repair and rework. Fixing a circuit board by adding a trace, fixing a pad and stuff like that is a repair, not a rework. Removing an icicle is a rework.
A repaired board or circuit will not look like the drawing although it does restore functionality without being in compliance, it does not look like the print. Rework on the other hand is the act of reprocessing noncomplying articles, through the use of original or alternate equivalent processing, in a manner that assures compliance of the article with applicable drawings or specifications.
I get the words mixed up myself, and over the years I've always wanted to eliminate those words and just say fix it. One example I was given to keep them straight was you put air in your tires when they have low pressure and that is a rework, you put a plug in the tire to stop a leak and that is a repair as it no longer looks like a new tire, it has a plug in it. So rework looks the same, and repair does not look the same.
Just my two cents.
Leo lambert, Vice President, Technical Director, EPTAC Corporation
I enjoy listening to Board Talk, however I must question the definitions you gave of rework and repair. They are opposite those used for military assemblies and the definitions listed in IPC-T-50. For military products, rework restores a nonconforming item to full compliance with the drawing/specifications. Repair restores functionality to the item, but does not result in full compliance to the drawing/specification. Repair requires customer concurrence. Otherwise, the information given in this episode was very helpful, as usual.
