Homebrew PCBs

On Thu, 17 Mar 2016 21:09:42 -0700, you wrote:

>I just looked at some old boards that I still have.  They are about the 
>same color as the current material, maybe a shade or two darker.  To my 
>mind, it makes no sense to go to great expense to custom laminate copper 
>clad boards with current G-10 material, as they will come out looking 
>just like common FR-4.  My best guess is that the original boards were 
>0.062" thk, give or take a mil or two.  Back in the 1960's I was working 
>in an electronic surplus house in New York.  The only copper clad 
>material we ever had in those days was nominal 1/16" (0.0625).  I don't 
>remember any finished boards we received, including military surplus 
>having solder mask until much later. The military boards were covered 
>with a conformal coat of one sort or another.

Thinking of all the HP and Tek equipment I have that dates from that
time, I'll agree with you.  No solder mask (although I've seen some, a
different style, generally green if nothing else.  I think it was
likely spray paint, candy apple green or the like, and you either
soldered through it or you actually had a mask).  The conformal
coating was an epoxy dip.

Even military boards (of that time) did not have a silk screen (much)
or a solder mask as I remember.

And 1/16th was about right, unless you had a motherboard made that
someone was going to be plugging stuff in, and I've seen that be 1/8th
thick.  (old southwest technical stuff).

Harvey


>
>(Another) Harvey
>
>On 3/17/2016 12:17 PM, Harvey White madyn@... 
>[Homebrew_PCBs] wrote:
>>
>> 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
>>
>>