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PCB Delamination

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#66478

PCB Delamination | 31 May, 2012

I have encountered PCB delam issue with high density PCB. PCB has 42 layers , 5 mm thickness ,laminate material is NelcoN4000-13EP,Tg 210C and Td 350C. Have pre-bake at 125 c for 12 hrs before assy.My reflow temp is standard with 243 peak and TAL is around 85s with possitive ramp at 1.7 c/s. Any advice are welcome..

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#66479

PCB Delamination | 1 June, 2012

If you think the root cause is excess moisture in the pcb then try to bake it for longer. Even longer then the manufacturers recommendation. It takes a long time for excess moisture to come out of a pcb. Try 24 hours , then 36 hours and see if there is a difference.

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aj

#66480

PCB Delamination | 1 June, 2012

could be down to board design also - are you seeing the delam in the same area all the time?

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#66488

PCB Delamination | 1 June, 2012

Post-reflow delamination is almost always caused by entrapped moisture. Here's more from the fine SMTnet Archives ... http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=64774

As Graham Cooper suggests in an earlier posting on this thread, baking boards to remove moisture takes a lot more energy than you'd think. Following on with this, Chris Hunt from NPL gave a presentation at IPC APEX 2012 about the results of his research ["Impedance Testing for Sensitivity to Delamination in Printed Circuit Boards" C.P. Hunt, M Wickham, O Thomas, L Zou, MAT 40, March 2010] on baking boards. It was: * Startling how long to took to bake boards * Amazing how ground planes affected the movement and concentration of moisture from the board during baking

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#66489

PCB Delamination | 1 June, 2012

You also need to get with the PCB manufacturer. Their is a lot that can go wrong with that many layers. If the manufacture is trapping that much moisture. you may have a hard time baking it out. Dave and Graham are right about the time and energy. It takes a long time for moisture to migrate out of the board. If it is trapped by large power and ground planes it may not bake out. Water does not pass through copper.

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#66490

PCB Delamination | 1 June, 2012

HI Guys, i am facing similar issues with this BT resin material too. PCB specs are 4 layers, Nelco400013, same Tg and Td. My PCB delam after reflow.

The PCB has both side mounted with SMDs. Initial mounting on the btm side after reflow, no delam. But after mounting topside, pass through the reflow and the PCB delam. LF process and max temp is 243 Degree C. Other than baking the PCB, is there other possible reason? Thanks!

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aci

#66496

PCB Delamination | 4 June, 2012

Sounds like the boards were not properly manufactured since you have baked them prior to assembly. We just had a customer return from China becasue of this issue. We have made 10K without issue. Let me take a stab and ask if they were made in the USA? If not try this: www.americancircuits.com

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#66497

PCB Delamination | 4 June, 2012

bwjm: Delamination can be attributed to several factors: * Entrapped moisture, processing solutions, and what not that expands when heated to normal soldering temperature * Excessive soldering temperature * Excessive laminating temperature * Defective laminate material * Problem in oxide treatment of innerlayer * Contamination at the laminate interface

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#66506

PCB Delamination | 4 June, 2012

There is sympthom that the delam only happen on area that near to via location.What does this try to relate to? It appears on both primary and secondary side even pass through with primary reflow process only.

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aci

#66512

PCB Delamination | 5 June, 2012

It's called pink ring.

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aci

#66513

PCB Delamination | 5 June, 2012

Definition: Pink Ring - A condition that can exist in multilayer printed circuit or wiring boards, in which the oxide around a through-hole inner layer interface is chemically removed, and there is a lack of adhesion of the inner layer to the dielectric substrate.

www.americancircuits.com

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#68630

PCB Delamination | 4 April, 2013

Okay, i got the concept. What are advantages of using pink ring? http://www.ccsintlcircuits.com/flexiblepcb.html

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