Carey, We have produced quite a few multilayer boards with many combinations of different dielectric materials. In most cases, you should not expect UL certification of the finished circuit board even if the raw materials are both UL rated. With RO4003 you will not get certified boards from any supplier because the material is not only missing a UL rating, but will burn if you put a match to it. RO4350 is basically RO4003 with a flame retardant filler. The electrical difference is that RO4350 has a dissipation factor is .004 instead of .002 with RO4003. When you are mixing dielectric materials in general you should be concerned with the following with regard to the stackup: 1. The first thing that should cause you concern is will the materials bond together. RO4350 can be bonded with FR4 prepreg to anything else that will stick to FR4 prepreg. However some PTFE based laminates will not bond to many prepregs. So you should consult your fabricator early in the design to ensure that the materials will hold together after lamination. 2. The next concern is warp. If the dielectric materials are not balanced about the Z-axis, the board will warp. The only question left is: "How much will it warp?". The warp will be dependent on differences in Tg and X-Y CTE of the different dielectric materials as well as other things. 3. Then other factors should be considered like: Can you supplier process the board through processes other than lamination. ie: plating, drilling, soldermask, etc. The largest cost component in a circuit board is the raw material (not including yield). RO4000 series laminates cost more to the tune of 3-5 times that of difunctional FR4. There is no RO4000 series prepreg yet so every board will have a different dielectric for the prepreg. On a 4 layer .062" multilayer the best stackup is: RO4350 / FR4 / RO4350 - little - no warp The price may be lower for a RO4350 / FR4 / FR4 board, but you will need to waive the 1% IPC warp specification and will have added costs in assembly trying to deal with a warped board. If you have any other question feel free to call. Darren Hitchcock (503) 359-2658 [log in to unmask] Carey Ritchey/KENT/COM/AUGAT <Carey_Ritchey/KENT/COM/AUGAT.AUG Wrote: | | FROM too long. Original FROM is 'Carey | Ritchey/KENT/COM/AUGAT | <[log in to unmask]>' | | ---------------------- Original Message Follows | ---------------------- | | Has anyone built a 4 layer mulitlayer PCB utilizing | Rogers RO4003/4350 materials for two layers and FR4 | for the other 2 Questions : what type of stack up | did you use we are imagining 0.020 RO double side | material FR4 prepreg and 0.020 FR4 double side for a | finished of aprox 0.062What happens to flammability | rating if you hybrid 94VO rated FR4 with non rated | RO4003Can we still expect UL approval if we utilize | FR4 and RO4350 which is 94VO ratedAlso what sort of | cost saving is to be expected by utilizing FR4 for | the non critical layers. *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************