On 6/12/06, Florian Voelzke wrote: > Vasile Surducan wrote: > > On 6/10/06, Rich Graziano wrote: > > > >>In my dumb way, I thought they were all compressed to the same thickness; > > > > > > No way. The thickness is a matter of layer numbers and technology (ie > > a RF board may be totally different because the epsilon of the > > material determine the route impedance for the same substrate > > material, industrial standard FR4). With a magnifier you can easily > > make difference between 6 or 10 layers standard board. 10 layers have > > bigger thickness than 6 layers. Between 2 and 4 layers could be no > > difference in thikness but is viewable on cross section even without > > magnifier. > > Yes and No... > > You can order PCBs in a big range of thickness - if you really want. > From very thin (below 0.5mm, 20mil) to very thick (beyond 3.2mm, > 125mil). The normally seen 1.6mm is just a standard thickness (at least > in europe). The thickness is usually not a direct result of the layer > number. > > A multilayer PCB consists of several base material sheets and prepregs. > By varying the number and thickness of these a large range of layers is > possible in a large range of PCB thickness. AFAIK a 10 layer board in > standard thickness should no problem at all. Let's count 6mil between two layers, 10 layer = 9x6mil = 55 mil (1.4mm) 1 oz per layer = 10 oz = 0.35mm total 0.9+0.35=1.75mm So you may do it at limit with only 0.5oz or with a perfect prepreg arrangement. Now, how easy you found 6mil prepreg, or when 0.5 oz is a good choice ? I think you was to generous with "no problem at all". greetings, Vasile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist