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..
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.
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
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.
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!
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
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
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.
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.