Multiple Laminate PCB - Page 1
Forum section: electronics / projects

author: Icarus
author_rank: Regular Contributor
timestamp: October 10, 2015, 06:42:38 pm
content: Is it posible to make such a pcb layer that half is FR4 and the other half is another material (such as R5580) ?

author: Dago
author_rank: Frequent Contributor
timestamp: October 10, 2015, 07:39:29 pm
content: Quote from: Icarus on October 10, 2015, 06:42:38 pmCouldn't find any info on what is R5580 but assuming it is some teflon substrate the answer is yes and this is very common for RF PCBs. They usually have the top layer made from teflon/ceramic substrate and the rest of the layers are from regular FR4 substrate.

author: Icarus
author_rank: Regular Contributor
timestamp: October 11, 2015, 09:26:01 am
content: I mean something like this

author: ovnr
author_rank: Frequent Contributor
timestamp: October 11, 2015, 09:32:01 am
content: Then no. Consider creating a sub-assembly for your RF section with castellated pads or something, then solder it onto your main board. You can't have a random slab of different material on the board - it's either all or nothing. Sure, you can have one side with one grade of board material and the other plain old FR4, but not only a section.

author: coppice
author_rank: Super Contributor
timestamp: October 11, 2015, 10:14:05 am
content: If you laminate things which have different expansion rates the structure will curl as it warms (e.g. bimetal thermostat strips). Do it with two thick layers and things break. You get away with a thin layer of copper on a thick layer of FR4, but two thick layers with different expansion rates means trouble. You can only put a BGA on an FR4 board because BGA packages have been designed to have a comparable expansion rate to FR4. So, it all comes down to the expansion rates of the materials you want to mix..

author: G0HZU
author_rank: Super Contributor
timestamp: October 11, 2015, 03:44:53 pm
content: The other option could be to have a complete top layer of an exotic laminate like Rogers 4350 and then have FR4 layers below this and maybe another final layer of Rogers at the bottom. But in the discrete areas you just want one layer of Rogers material you can have all the other layers removed or cut away, leaving just a single layer of Rogers material in certain pockets with a copper layer visible on the underside of the Rogers material.

author: daqq
author_rank: Super Contributor
timestamp: October 11, 2015, 05:57:56 pm
content: To the best of my knowledge no. Everything I've seen similar to that what you've shown was done in multiple boards, that were bonded together by various means, ranging from simple cables, connectors to bondwires.You can have the sub board glued or otherwise held in place, but it will have to be a separately made board.

author: SeanB
author_rank: Super Contributor
timestamp: October 11, 2015, 06:05:46 pm
content: For an idea of how to do it look at a Siemens Gigaset, where the main board is SRPB with 2 layers and a conductive carbon layer for the keyboard, which contains all the non RF side on the cheap paper board, with a multilayer FR4 board containing the RF section on top, covered with a soldered on steel can and joined with some solder pads using plated mouse bites along the edges.I have taken a few apart that suffered various failures, broken casings, broken speakers, dropped in the toilet, dipped in bleach........The older Panasonic phones used a similar setup, but the RF section was in a module that plugged into the main board. Made it easy to repair them, though I did run out of donor units eventually.

author: Icarus
author_rank: Regular Contributor
timestamp: October 11, 2015, 06:34:43 pm
content: Thanks, I guess best course is make another "mini" board