Liquid Photo-Imagable

-----Original Message-----
From: Doug [mailto:[log in to unmask]]
Sent: Friday, March 03, 2000 07:19
To: [log in to unmask]
Subject: Re: [DC] Cost of Different Colored Boards ...


Thank you Ron and others.

Remind me what LPI is again?

I'm working BC (Before Coffee ...)

Regards, Doug


Ron D Huston wrote:
>
> Doug;
> As a fabricator, here's the scoop;   its Yes and No as to whether there's
a cost difference.
>
> If your designs require the tolerances of LPI mask, then it will cost more
to change colors. The reason is that the LPI process is a BATCH process.
Every pcb, regardless of design, is flooded with mask using the same setup.
It is later exposed with your custom film in an exposure unit.   A color
change requires an extra silkscreen tear-down and setup...Actual costs vary
from shop to shop.   In our case, we build all proto's using LPI soldermask.
>
> On the other hand, if your design is tolerant of thermal mask, AND your
fabricator still uses it, then a color change makes no cost difference.  In
this case, every unique design requires a screen setup/tear-down so the
color of ink on the screen makes no difference.  However, if you ask for a
color that is not used often, then you may have to pay for the special
purchase whether you use it all or not.   Red, black and blue are common
enough alternative choices.
>
> As to whether a pcb shop charges for these costs or not varies.
>
> Hope this helps.   I think the different color on proto's vs production is
a good idea and its often used.  Cost or not, its worth the lack of
confusion of trying to read the fine print revision level in the copper
circuitry.