Homebrew PCBs

Jan,

The difference between G-10 and FR-4 is minimal and has to do with 
flammability. G-10 is not self extinguishing in a vertical flame test 
while FR-4 is. A strip of laminate is held vertically in a flame 
until it ignites. When the source of ignition (flame) is removed the 
G-10 will keep burning and the FR-4 will self extinguish. Check out 
the Underwriter Laboratories test specifications. If I remember 
correctly, this test is called the "UL 796 Vertical Flame Test".

I believe there are some slight differences in the velocity factor at 
very high frequencies between the two types. This may also depend on 
the specific vendor. G-10 laminate always has a white or grayish 
water mark and FR-4 always has a red water mark. G-10 laminate is 
kind of rare these days with most boards being made from FR-4. Hope 
this information helps.

Tom


--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> Can someone who know please explain the main difference between 
(apparently 
> older) G-10 and (apparently currently-used) FR-4?       Thanks.   
Jan Rowland
> 
> 
> [Non-text portions of this message have been removed]