We used Isola 408HR in our designs and found delamination is common during Pb-free assembly. Our fabs said they can't do more to Iso 408HR, thye wish us to change other material. Do you use this type of material and see delamination is common?
We don't specify by manufacturer's material numbers, we list the criteria we need and let the vendor chose the material. I don't think we've used 408HR, it exceeds what we normally require. But I can tell you, based on the 408HR specifications most critical to surviving lead free soldering (Tg=200, Td=360, non-dicy, low CTE), you need a new assembly or fabrication vendor. There's no way that material should be delaminating under normal reflow and wave, even with multiple cycles. That's one of the more robust materials available! FR408 is far more common, rarely delaminates, and is lower rated.
Start with handling and storage. They may be collecting moisture at either tha fabriactor or assembler locations. Are they vacuum packed with humidity cards? Could also be poor curing by the fabricator.
That material is specific for it's electrical properties. If that's why you are using it in the first place, be very careful letting them change - it could affect your product performance.
I have specified that material on millions of boards. Have never seen or heard of a problem that was not caused by our depanelizing process (which was caused by poor fabs)
I agree with the answers here. I have always called out per the IPC Slash sheets, allowing the fab house to choose the best fit for material to the process. This holds them responsible for the Workmanship specification of the Slash sheets and other notes on the drawing.
I also agree HR408 should not be giving you lamination issues. So it could be uneven plane structures within your design, or a few other items. If it is planes, you may try adding copper theiving to the uneven layers.
Good Luck Yanfeng!
Thank all of you much.
We have 5 pcb partners(all of them be ranked on Top 20-50). However, They don't have experiences with Isola 408HR before, and they also found the delamination during process and they said they have put much effort to improve the process but failed. In our assembly lines, We aslo found the delamination and did adjust our reflow process .
We also use other materials such as Megtron-4 or Megtron-6, it's good . Due to cost issues with Megtron-4/6, We need to seek alternatives. Before using Isola 408HR, We have tried to use Nelco 40013, it also have delamination issues during reflow process.
Sorry. I may forgot to tell one important thing. all board with delamination be blind via type where fabs need to do 3 sequantial lamination. We prefer use blind via design instead of HDI for cost and versitility.