Homebrew PCBs

I'm not sure why this happens or if anyone else has experienced this but
sometimes ExpressPCB will  slightly shrink or enlarge the job being
printed.

 

Most of you probably know to print out the PCB layout on regular paper
and test the layout before wasting a board. Im just learning my lesson.


If anyone knows why Ive experienced this, please chime in.

 

 

Best Regards,

Steve Maroney

 

Business Computer Support, LLC

Mobile Phone:504-914-4704

Office Phone: 504-904-0266

Fax: 866-871-7797

From: expresspcb@yahoogroups.com [mailto:expresspcb@yahoogroups.com] On
Behalf Of Dennis
Sent: Thursday, July 15, 2010 7:04 AM
To: expresspcb@yahoogroups.com
Subject: [expresspcb] Re: Unplated hole

 

  


Well, there is more than one way to make a board. Plated through holes
are a bit of a trick though. The method I am familiar with is that the
double sided board is drilled before anything else. Then the board is
dipped in a catalyst solution that makes the fiberglass conductive. Then
the whole board receives a thin copper electroplating. Then the negative
etch mask is applied. Then the board gets electroplated with more copper
followed by tin. The tin also plates inside the holes. The etch mask is
removed. Then the board gets etched. The etchant used only dissolves
copper and not tin so the tin becomes a positive etch mask. Then you
have a board.

That works for simple double sided boards. I am not sure how the
multi-layer boards are made.

But if this process is used, the only way to make an unplated hole is to
drill it after the board is complete.

Dennis.

--- In expresspcb@yahoogroups.com <mailto:expresspcb%40yahoogroups.com>
, "Nick Alexeev" <kender_a@...> wrote:
>
> Hello Jim,
> 
> Before reading your post, I thought that drilling and plating occur
before copper is etched. I've got that idea from the PCB design book by
Craig Mitzner. Probably, I've interpreted the book incorrectly.
Probably, there's more than one sequence.
> 
> - Nick
> 
> 
> 
> --- Jim Drew wrote:
> 
> That is simply not true. I have been working with PCBs for 35 years,
so
> if someone tells you simple drilled holes are difficult and require a
> secondary drill, do not believe them! A non-plated hole is very simple
> to create and costs nothing extra. To create a non-plated hole, you
> simply pull back the copper from around the hole. This leaves a ring
of
> non-copper around the hole and no possibility of creating a hole
during the plating process.
> 
> 
> --- Nick Alexeev wrote:
> >
> > > ...
> > > - even a simple unplated hole drill!!
> > > ...
> >
> > By the way, an unplated hole is not that simple. Drilling holes
without
> > plating is an additional step at the end of the process. In fact,
PCB
> > fabs that take gerbers charge extra for unplated holes.
>





[Non-text portions of this message have been removed]

Are you sure it's the software, and not the printer?  My laser printer 
shrinks *everything* about 0.4%, which is enough to make big connectors 
not fit in their holes.

DJ Delorie pravi:
> Are you sure it's the software, and not the printer?  My laser printer 
> shrinks *everything* about 0.4%, which is enough to make big connectors 
> not fit in their holes.
>
>
>   
...and my one skew image too. (rectangle come out trapezoid). In small 
scale but as you say long items is hard to assemble. (and if drilling is 
made with CNC the alignment is nightmare)

On 18/07/2010 01:06, DJ Delorie wrote:
> Are you sure it's the software, and not the printer?  My laser printer
> shrinks *everything* about 0.4%, which is enough to make big connectors
> not fit in their holes.

And, it's likely to vary with humidity. Paper is very hygroscopic (I 
worked for Rank Xerox many years ago, and it was a problem, we even 
supplied some customers with heated storage cabinets). That might 
explain whi it's so variable.

Leon
-- 
Leon Heller
G1HSM

> On 18/07/2010 01:06, DJ Delorie wrote:
> > Are you sure it's the software, and not the printer?  My laser
> printer
> > shrinks *everything* about 0.4%, which is enough to make big
> connectors
> > not fit in their holes.
> 
> And, it's likely to vary with humidity. Paper is very hygroscopic (I
> worked for Rank Xerox many years ago, and it was a problem, we even
> supplied some customers with heated storage cabinets). That might
> explain whi it's so variable.


I run the sheet of paper thru the printer a couple of times to shrink it.

Open Notepad, press the space bar a couple of times and then hit print.

Then print the PCB.  You need to do it straight away, you can't leave it
until tomorrow.

Tony

--- In Homebrew_PCBs@yahoogroups.com, "Steve Maroney" <steve@...> wrote:
>
> I'm not sure why this happens or if anyone else has experienced this but
> sometimes ExpressPCB will  slightly shrink or enlarge the job being
> printed.
> 
>  
> 
> Most of you probably know to print out the PCB layout on regular paper
> and test the layout before wasting a board. Im just learning my lesson.
> 
> 
> If anyone knows why Ive experienced this, please chime in.
> 



I noticed that as well, though it was usually not enough to be a problem. Kicad as well as other packages I tried out did not do that, I suspect it is done intentionally with ExpressPCB as they do not really want people printing artwork to self etch boards, notice how it doesn't even let you go to the printer settings.

I am working with ExpressPCB for almost 3 years and have not seen such a problem.
I print the files on a pdf format, open them in Photoshop and inverse the colours, as well and flipping them in horizontal direction. Save them again in pdf format and then take them to digital image setting and get the films and manually produce them on laminate sheet process.
Check if your settings on printing to a pdf file is correct. Maybe it is on an A4 format and you try to print them on legal or vice versa, or other settings that force the print to be done on a percentage basis.
 


      

[Non-text portions of this message have been removed]