Homebrew PCBs

I took the Homebrew PCB Group Spiral Challenge, for my initial results see:

http://wa0uwh.blogspot.com/

or an on site search for; PCB


72 - Eldon - WA0UWH - CN88xc - http://WA0UWH.blogspot.com/

Did you try to fix the breaks and measure the resistance?  I think it
would be interesting to see if my calculations are accurate, and if so,
how the measured resistance compares to it relative to how much
bigger/smaller than "spec" the etched traces are.

OK, DJ

I did that, see the web page.

I will have more thoughts later, it is late.

Regards,
Eldon Brown

72 - Eldon - WA0UWH - CN88xc - http://WA0UWH.blogspot.com/



On Wed, Aug 3, 2011 at 7:19 PM, DJ Delorie <dj@...> wrote:

> **
>
>
>
> Did you try to fix the breaks and measure the resistance? I think it
> would be interesting to see if my calculations are accurate, and if so,
> how the measured resistance compares to it relative to how much
> bigger/smaller than "spec" the etched traces are.
>
>


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

Sweet!

Here's a tip: you know the track-to-track spacing is 20 mil (you did say
10/10 pattern, yes?).  Given that, you can calculate the actual DPI of
the photo (about 4300 dpi for the spot I was measuring).  Also measure a
track, and you can compute the actual track width (about 9.2 mil in some
spots, 7.1 in others).

But simply measuring pixels-of-copper vs pixels-of-space should
tell you how close to "perfect" you are.

Your ohms are a little high, some things that might cause that:

* pinholes cause "necks" in the copper which add resistance

* cleaning/scraping/sanding the copper might thin it somewhat

* thinner traces on average would increase it

If you just go by the ohms ratio, it says your average trace width is
18/23 * 10 = 7.8 mil, which sounds close enough.

Did you measure the high ohms between the two tracks?


Also, if you have a flatbed scanner, they're often useful for
high-accuracy PCB scans.

DJ,

I just realized via your last name and the Spiral Challenge URL, that you
are the owner/keeper of the Challenge. And, we may have chatted/email before
on other issues.

Thanks for the Challenge, and insight.

Yes, the resistance between traces is greater the several Meg ohms. I
updated the blog page a little.

I think with more attention to details, I could successfully produce a
flawless 10/10 Challenge board, using the Toner Transfer Method. Or maybe
even a higher resolution version with  smaller traces.

Perhaps a PCB Software Vendor, Transfer Paper Vendor, or an Industry Leader
would like to sponsor a Homebrew PCB Contest or a Formal Challenge.

It would be fun.

Thanks for your Homebrew PCB support and efforts.


Regards,
Eldon Brown

72 - Eldon - WA0UWH - CN88xc - http://WA0UWH.blogspot.com/

On Thu, Aug 4, 2011 at 10:08 AM, DJ Delorie <dj@...> wrote:

> **
>
>
>
> Sweet!
>
> Here's a tip: you know the track-to-track spacing is 20 mil (you did say
> 10/10 pattern, yes?). Given that, you can calculate the actual DPI of
> the photo (about 4300 dpi for the spot I was measuring). Also measure a
> track, and you can compute the actual track width (about 9.2 mil in some
> spots, 7.1 in others).
>
> But simply measuring pixels-of-copper vs pixels-of-space should
> tell you how close to "perfect" you are.
>
> Your ohms are a little high, some things that might cause that:
>
> * pinholes cause "necks" in the copper which add resistance
>
> * cleaning/scraping/sanding the copper might thin it somewhat
>
> * thinner traces on average would increase it
>
> If you just go by the ohms ratio, it says your average trace width is
> 18/23 * 10 = 7.8 mil, which sounds close enough.
>
> Did you measure the high ohms between the two tracks?
>
> Also, if you have a flatbed scanner, they're often useful for
> high-accuracy PCB scans.
>  ,___
>


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

Eldon Brown <eldonb46@...> writes:
> DJ,
> I just realized via your last name and the Spiral Challenge URL, that you
> are the owner/keeper of the Challenge.

Yup!  Hence my interest in your results :-)

> Yes, the resistance between traces is greater the several Meg ohms.

Whew :-)