On 17 Mar 2016 12:03:01 -0700, you wrote:
>Hi guys,
>
> I have been following this group for many months, and I am very excited to see the quality of the discussions presented here.
>
> I have not contributed until now because I had little to add. I made boards as a teenager in the '60s and then into the '70s. In those days I used G-10 board. A some point FR-4 crept in, and became the standard for PWBs. Recently, I have become interested in making boards again, and am delighted to have discovered this group.
>
> My 2 cents: I think the train has become derailed on the subject for G-10 vs. FR-4. It seems to me that the stated goal was to get boards that look like Don Lancaster's green G-10. There are several companies making unclad G-10 and FR-4. You only need to look at the websites to see that both are the same color when purchased as natural. The only difference between them is the addition of a small amount of Bromine to make
> the FR-4 boards flame retardant. Check this out: http://www.acculam.com/data-chart.html. Other places on this website (Accurate Plastics, inc) show samples of the material, and it can be seen that the color is the same. The color of the G-10 from American Micro Industries is the same.
>
> The "green" color is called natural. Back in those days, the only color that glass/epoxy boards came in was natural or "green." The shade did vary between manufacturers, probably because of differences in the epoxies they used.
>
> Since the color is the same and the goal is to provide the same looking boards, I think that the solution is to use FR-4, and specify "natural" color for the base material.
I like the name.
The main thing I saw between the two grades was exactly what you
mentioned, the addition of bromine to make the board less flammable.
I think that if the board is solder masked (and I don't remember if
they were or not), the color of the solder mask will generally
override the board color.
The thickness of the board also determines the depth of color as well.
Harvey
>
>(Another) Harvey