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What Causes Board Delamination?



What Causes Board Delamination?
We are experiencing delamination on printed circuit boards, is there a way to determine that this is caused by moisture or some other defect?
Board Talk

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

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.
Brad Fern, Medtronic, USA

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