We are experiencing delamination on printed circuit boards, is there a way to determine that this is caused by moisture or some other defect? Jim Hall and Phil Zarrow, The Assembly Brothers, answer this question and share their own experiences. 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 50 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 with Phil Zarrow and Jim Hall of ITM Consulting, the Assembly brothers. Coming to you today from the ITM Consulting failure analysis cave high atop Mount Rialto.
Jim what's our question of the day?
Jim
We actually have a similar question submitted by two listeners; the first one is from D.H.
We are experiencing delamination on our printed circuit boards causing scrap, is there a way to definitively determine that the delamination is being caused by moisture or some other type of defect? Is it possible to repair printed circuit assemblies with delamination?
Frank from Montreal has basically the same question but notes that he is processing his boards, reflowing them, very soon after receiving them so that they're not hanging around his shop. But had basically the same question; should he bake them and so forth.
Phil
There are a lot of aspects that come into play here, but in our allotted five minutes let's hit on the key ones.
First make sure that your fabricator is using laminates that pertains to the current specification. We've run into a number of people who are still fabricating to the IPC 1399 spec. That went out quite a few years ago.
Per our good friend Gary Ferrari, Dr. Design, basically any material being used these days, particularly for lead-free, should be conforming to IPC 4101/126 or /129 and this is basically high performance material with very high T sub G and T sub D decomposition temperatures and tolerances. Make sure you're using the right material.
Then once we get into your shop, you should be following IPC 1601 that covers the handling and care, and storage of circuit boards.
Make sure that you've done the proper due diligence and your design of experiment for your reflow profiles or your wave solder or selective soldering profiles and certainly your hand soldering is under control.
Jim, there is a way, I believe, of measuring whether you have absorbed moisture.
Jim I know that some people have determined that there is moisture in the board by weighting the board first then baking it per IPC 1601. That's the nice thing about 1601, it defines specific baking time cycles which has been a question throughout the industry for a long time until that came out.
I know that some people have weighed the board and then baked it and weighed it afterwards and the difference was the amount of moisture.
In terms of determining whether there was moisture and whether it was causing your problem that would be one thing to do. I'm not sure if that procedure is described in 1601 but you just need a very accurate scale.
In terms of repair, I imagine that the more sophisticated circuit board repair shops that repair damaged boards can repair a certain amount of delamination.
Delamination is really destroying the basic structure of the board.
I don't imagine that a badly delaminated board could be repaired. But it's something you can check with a professional circuit board repair service.
Phil
Like Circuit Technology Center and there's a number of others out there.
Jim
Make sure that your supplier is handling the boards properly and drying them and following the procedure so that they're not getting to you wet and that they're coming they are coming in the properly sealed packages.
Most boards are coming from overseas and there is storage times depending on whether your shipping by boat or by plane but in all cases, IPC 1601 will guide you about how to seal them and you should keep them sealed until you're ready to use them.
Phil
Yes, been there done that; I own a delaminated t-shirt.
You've been listening to Board Talk. Whatever you're doing and however
you're doing it, don't solder like my brother.
Jim
And don't solder like my brother.
Comments
IPC-1601 has been superseded by IPC-1602. With HDI designs more attention to increased bake times must be understood, Epoxy filled or plated shut laser see moisture about 30 times and there is significant uptake of moisture in the dielectric before the via is plated with copper. With the plated barrel and layers with high copper area retention (>85%) bake times need to be extended. Please see the following for an in depth conversation on Moisture "Let Me Vent, and You Should Vent With Me"
Gerry Partida, Summit Interconnect
The most likely cause is really the quality of the PCB. This includes quality of processing and materials. If the lamination of the PCB is inherently defective, then all hope is lost. Then, if the lamination is good, a pre-bake at 120 degree C, for 4 hours, to remove moisture, will eliminate moisture-caused delamination. Pre-bake has few rules, but the most important is: Do not just place a bundle in the oven. The moisture extraction works best if the boards are uncovered and arranged with an air gap between them, which allows the water vapors to be carried away.
Jaye Waas, Renkus-Heinz
In terms of root cause failure analysis, micro-sectioning across a delaminated area can reveal clues such as where the separation occurred, or material anomalies associated with the board fabrication (such as copper surface roughness, prepreg preparation.) DSC (differential scanning calorimetry) analysis can be used to measure the glass transition temp, which can be used to confirm whether specified board material was used. Ruling out obvious material quality issues may be helpful before you invest time and treasure in reviewing and/or overhauling your handling and thermal processes.
Alan Couchman, Process Sciences, Inc.
The cause of delamination is fundamentally the high temperature required for soldering. All of the observations made here were made by smart experienced folks trying mitigate the intrinsic realities of solder to the best of their abilities. The Occam Process was invented to eliminate, to the extent possible, the solder process. Might find interest in an article I recently published in Electronic Design titled "Solder: Is it really necessary for Electronics Assembly?" Solder will likely be around for many decades to come but it will be as a choice.
Joseph Fjelstad, Verdant Electronics
In my opinion, delamination occurs due to card manufacturing processes that do not meet the minimum product specifications, deficient purchasing processes where the requirements are not specified, new suppliers, unfortunately the delivery times, the difference in cost of materials between manufacturers. As we say cheap is expensive. I have also seen it when a wrong solder profile is made.
Roger Cespedes, Camtronics
If delamination occurred on outside layer or peripheral area, it might be affected by moisture absorption and it could be cured by baking prior to soldering. And if happened in deep inside area, it might be caused by too high z-axis expansion and it could be cured by using low CTE laminate.Most delamnation also comes from poor oxide treatment itself and insufficient drying after oxide treatment. Higher resin content of prepreg and CZ treatment are also good remedy avoiding delamination.
Jinho Lee, KETI
As of April 2020, I believe that IPC-1602 supersedes IPC-1601 Rev A 2016. This standard has some very good information on handling PCBs and briefly addresses the effects of baking on different surface finishes. If you are handling and shipping PCBs, I recommend getting a copy of IPC-1602. It is short (just over 20 pages including several Appendices) and packing with good information.
Stephen Wint, Astek Corporation
Consider your PWBs as MSL devices. Prior to solder, you have to check the level of humidity with a specific IPC-TM-650 method. But in my opinion it is cheaper to do baking.
Most of the suppliers don't use MBBs, so PWBs have humidity inside the 99% of the times.
But take care to do SMT process and PTH process in the same day.
If you wait 24h or more time prior to PTH soldering, blistering and delamination can occur, and in multilayer PWBs often you don't see it by eyes, nor by X-Ray. For Lead-Free soldering, my opinion is that baking is mandatory.
Pierpaolo Galli, Meta System SpA
In my experience much of the delamination I have seen is from using incompatible materials for the number of heat cycles or the reflow profile itself is flawed. Doing a good job of matching material to the use case is very important. Another consideration is moisture. Even the higher Tg materials are hydroscopic and a low temperature bake is advised, particularly now that profiles are peaking at 260C. Lastly, proper thermal relief of power and voltage planes must be considered; since inexperienced PCB designers can forget about the consequence of hand solder operations and thermally linking nearby components. Most delamination cannot be repaired, and in all cases violate IPC 6012 and 610. Delamination on a board edge such as a corner repair is possible; but this would be the only scenario.
