Vasile Surducan wrote: > 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 thicknes= s; >>> >>> >>>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 =3D 9x6mil =3D 55 mil (1= .4mm) > 1 oz per layer =3D 10 oz =3D 0.35mm total 0.9+0.35=3D1.75mm > = > 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 One possible arrangement for a 10 layer PCB is: - 5 base laminate sheets, double sided - 4 prepregs, one between each base laminate sheet - Thickness of base laminate: 0.15mm - Copper: 1 oz, 35=B5m - Prepreg: 0.1mm So you get: 5*(0.035mm + 0.15mm + 0.035mm) + 4*0.1mm =3D 1.5mm If I look at the material table of one german manufacturer = (www.andus.de), this is quite conservative. I could get base laminates = of 0.05mm and prepregs of 0.05mm. That results in 0.8mm for a 10 layer = board with 35=B5m copper. That would be thin. I do not know if this would = be easy to manufacture, though... Florian -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist