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FR4 boards Delamination Cause?

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#54655

FR4 boards Delamination Cause? | 7 May, 2008

I have these boards that are a four layer FR4 material, we had been running them for quite awhile with no trouble, and then they started delaminating, I checked my Reflow oven profile and I was barely hitting the temps required for our paste, we then took the problem to our board house and they took responsibility saying that they might not have baked them properly and there apeared to be moisture between the layers of the board. They refunded us for boards that had problems, but the bad boards just kept on coming, we then swtiched to a different board-house and for the first 2,000 boards I didn't see any trouble, then I had one delaminate, I went through around another 1,000 good boards and then had one delaminate. I just want to see if there is something that I may be overlooking. could this be a defect in our design? seems like we would see more of a problem. and if this was a problem with the oven profile seems like it would be more consistant. So does everyone agree that this is likely the same problem from a different board-house. I just want second opinions before I persue reimbursments AGAIN. Thanks, Wayne

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#54659

FR4 boards Delamination Cause? | 7 May, 2008

Causes of Delamination ["Quality Assessment of Printed Circuit Boards" Lund, Preben; Bishop Graphics 1985 0137450354] The reason for delamination is epoxy starvation in the glass cloth layers or an incomplete curing of the base material. It has been reported that some manufacturers of laminates have reduced the lamination press cycle a little in order to increase production.

In multilayer boards, visible delamination may be due to poor lamination of layers or insufficient bonding of prepregs to the inner layer copper circuits. Here, the PCB manufacturer is in a way also the "manufacturer" of the base material.

Delamination may develop, however, in a board after assembly and soldering. There are several possible reasons for this: * Asymmetrical buildup of multilayer boards. * Faulty soldering techniques, such as skipping the baking which removes retained moisture from the board. (A 1 to 2 hour baking at 230*F immediately before assembly and soldering is highly recommended. * Lack of preheating as the first step of mass soldering.

A-600 has words to the effect: Delamination or blistering may occur in clad laminate materials either between plies of laminate, or between the laminate and the foil cladding. Any occurrence, either in the as-received condition or after routine thermal stress testing at receiving inspection is evidence of a major flaw, and the material should be rejected, since the defect will almost always propagate during the normal stresses of manufacturing.

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#54671

FR4 boards Delamination Cause? | 8 May, 2008

Hi Wayne,

I am just curious what material is being called out.

Are you just specing FR4 or are you calling out a particular IPC 4101 /

Some recommended laminates designed for Lead free assembly are: Isola 370HR Nelco 4000-11 or 4000-29 Iteq IT158 and IT180 Nan ya NP180 TU-662 and TU-722

I would stay away from Isola IS410 due to there have been issues of delamination with this material.

I would check with your board shop and have them tell you what material Manufacture and Grade is being used., Example:(ISOLA /370HR) also have them give you the TG & TD of Material. Your TG should be a Minimum of 150 Tg. with a Min. TD of 320 Td. for a 2 -6 layer and Minimum of 170 Tg. with a Min. of 340 Td. for 8 layer and up.

Just some suggestions,

Regards,

BoardHouse

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#54761

FR4 boards Delamination Cause? | 15 May, 2008

We have seen this problem before. We have ALWAYS found it to be a board vendor issue. Also, we tend to see it more during the summer months. Our solution has been to bake our PCBs @ 50 deg C for 1 hr prior to use. We use immersion white tin board finsh and have to be careful not to damage it during the bake cycle. Since doing this we havent seen the problem again.

P.S. Definitely go after reimbursement. Be sure to point out the cost of lost parts as well as lost line time which you will never get back.

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#54863

FR4 boards Delamination Cause? | 23 May, 2008

Wayne;

Several things.

1.check the vendors and see what black oxide they are using are they the same ? It might be that. 2.You should bake your pcbs before the thermal stress is applied. To remove moisture. At your shop. The process should be at least 45 minutes @ 150-175 F. 3.When you inspect the pcbs at incoming visually look at the oxide to determine if there is any streaking of the oxide. I should be no "stained appearance". Wayne: I got a question for you !! I need the names of several companies that sell assembly tables with all of the esd and wrist attachments and flooring (ESD) do you have any information on these types of business.

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#54864

FR4 boards Delamination Cause? | 24 May, 2008

Welcome to Chinese manufacturing!

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reflow oven profiler

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