Homebrew_PCBs

I have lurked here for a while and perhaps made one or two posts. But now is the time for action.

I go back a way and have made PC boards at home before, using high contrast negatives from artwork that I created. But just try to get such a negative today and even if you can, using two of them to make a double sided board is not the easiest thing. So, I must use more modern methods.

 

I am designing a board for a project and will ultimately be ordering between 50 and 350 of them in an initial order. This represents a significant expense for me and I do not want to place such an order until I am real sure that the foil is 100% OK. I can accept minor silk screen errors so that is not as important. So I need to make one or a few prototypes FROM THE VERY ARTWORK printed from the PC design program I choose. I haven't chosen it yet but am leaning toward a system called Design Spark. I haven't played with it yet, but it looks a lot like the software used by Advanced Circuits.

 

I know I can order several boards for about $65 with shipping but if there is a mistake, then I have to do it a second time and heaven forbid, a third. So am looking for a low cost method to do this at home. My time is precious, but I can spend some on this if it lowers the cost. I am looking for suggestions with specifics (like the model number of any equipment suggested) for doing this. I count expendables as project cost and equipment as capital expenses. So the equipment is easier to justify in my eyes. Sorry if I sound like a bean counter, but the equipment can be used on future projects while the expendables are gone with this one.

On Sun, 20 Jul 2014 21:45:12 -0400, you wrote:

>If you are only looking to develop one design, your design skills are
>solid, and your time is precious, you are *much* better off just paying the
>extra $$ to have them made at a local fab with quick turn-around.
>
>Although it is quite easy to make boards at home with modern techniques, it
>takes a fair bit of work to achieve anything close to what even
>lowest-grade commercial producer is capable of. Unless you are going to
>put a *lot* of time and effort into your homebrew techniques, you are going
>to wind up using different board layouts for those produced at home vs.
>those produced professionally anyway.

Let me amplify this a little for those who have not considered the
problem.

1) hand soldered boards with through holes generally want bigger pads
2) depending on your techniques, you may find that 10mil traces are as
thin as you want to go, commercial can use 8 easily.
3) you're not likely to do plated through holes (you can, and some do,
but not casually). That means that the vias are out from under chips
and are separate, with no plated through holes on through hole
components such as IDC strips and the like. A commercial layout would
eliminate some of these suddenly redundant vias. On the other hand,
if their process fails anywhere, it's likely to be a via, and if the
project works without vias under parts, you can easily fix the vias.
4) solder mask and silk screen, not always found in home projects.
5) you're likely to do double sided boards at best at home, you can do
more with a commercial house.
6) you can cut corners (and put things close to edges) where a
commercial house may not.

Harvey

>
>-p.
>
>On Sun, Jul 20, 2014 at 6:11 PM, palciatore@... [Homebrew_PCBs] <
>Homebrew_PCBs@yahoogroups.com> wrote:
>>
>>
>>
>> I have lurked here for a while and perhaps made one or two posts. But now
>is the time for action.
>>
>>
>> I go back a way and have made PC boards at home before, using high
>contrast negatives from artwork that I created. But just try to get such a
>negative today and even if you can, using two of them to make a double
>sided board is not the easiest thing. So, I must use more modern methods.
>>
>>
>>
>> I am designing a board for a project and will ultimately be ordering
>between 50 and 350 of them in an initial order. This represents a
>significant expense for me and I do not want to place such an order until I
>am real sure that the foil is 100% OK. I can accept minor silk screen
>errors so that is not as important. So I need to make one or a few
>prototypes FROM THE VERY ARTWORK printed from the PC design program I
>choose. I haven't chosen it yet but am leaning toward a system called
>Design Spark. I haven't played with it yet, but it looks a lot like the
>software used by Advanced Circuits.
>>
>>
>>
>> I know I can order several boards for about $65 with shipping but if
>there is a mistake, then I have to do it a second time and heaven forbid, a
>third. So am looking for a low cost method to do this at home. My time is
>precious, but I can spend some on this if it lowers the cost. I am looking
>for suggestions with specifics (like the model number of any equipment
>suggested) for doing this. I count expendables as project cost and
>equipment as capital expenses. So the equipment is easier to justify in my
>eyes. Sorry if I sound like a bean counter, but the equipment can be used
>on future projects while the expendables are gone with this one.
>>

On 7/20/2014 10:36 PM, Harvey White madyn@...
[Homebrew_PCBs] wrote:

>
> <snip>
>
> Let me amplify this a little for those who have not considered the
> problem.
>
> 1) hand soldered boards with through holes generally want bigger pads
> 2) depending on your techniques, you may find that 10mil traces are as
> thin as you want to go, commercial can use 8 easily.
> 3) you're not likely to do plated through holes (you can, and some do,
> but not casually)....<snip>
> 4) solder mask and silk screen, not always found in home projects.
> 5) you're likely to do double sided boards at best at home, you can do
> more with a commercial house.
> 6) you can cut corners (and put things close to edges) where a
> commercial house may not.
>

Hello--

I'll add a couple of additional points:

--If you create a design for fabrication by a commercial board house
and thus plan to invest some money in the design, you're likely to put
more thought into the board's layout and testability than if you're
making a board at home.

--Any piece of equipment for homebrewing PC boards entails
costs for materials and modifications. About the cheapest
approach would be the toner-transfer paper and flatiron
method.

--Once you have a layout that you think might be satisfactory, you can
create a mockup by stuffing components through a 1:1-scale paper layout
that's superimposed on conductive foam.

--You can visually troubleshoot the board's etch by copying the trace
and silkscreen layouts onto transparency film and stacking them together.
Use felt-tip marker pens to mark off traces after you've verified
point-to-point
continuity.

I've been contemplating the whole make-boards-at-home process and I'm
getting closer to going the commercial route... unless I can think of
additional
tasks for a router, laser engraver, and 3-D printer<g>.

73--

Brad AA1IP

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On Mon, Jul 21, 2014 at 4:49 AM, Brad Thompson
brad.thompson@... [Homebrew_PCBs]
<Homebrew_PCBs@yahoogroups.com> wrote:

> --Once you have a layout that you think might be satisfactory, you can
> create a mockup by stuffing components through a 1:1-scale paper layout
> that's superimposed on conductive foam.

Good advise that.
I do that for time critical designs, especially if I have new (to me)
components where I might have made a mistake when drawing them up.

> --You can visually troubleshoot the board's etch by copying the trace
> and silkscreen layouts onto transparency film and stacking them together.
> Use felt-tip marker pens to mark off traces after you've verified
> point-to-point
> continuity.

Alternatively you can check the gerber files in software such as
viewplot or viewmate, both free.
You can do a lot of checking in Designspark, but there is always a
(slim) possibility of errors in the gerber output.

Also it helps to see the same thing "in a different light" so to
speak. You get blind to errors you have stared at for days.
Looking at the design in a different tool, rotating it around and
mirroring it strangely lets you see things you missed before.




I agree with the general notion that homebrew PCBs are not a good way
to verify designs for production.

ST

On Sun, Jul 20, 2014 at 10:49 PM, Brad Thompson
brad.thompson@... [Homebrew_PCBs]
<Homebrew_PCBs@yahoogroups.com> wrote:

> I've been contemplating the whole make-boards-at-home process and I'm
> getting closer to going the commercial route... unless I can think of
> additional
> tasks for a router, laser engraver, and 3-D printer<g>.

I think you are looking at this the wrong way. You make PCBs at home
when you only want one of them. This can either be a 1-off for a
particular task or a prototype for a circuit. If you ever want much
more than 1 copy of a board, you are better off having it made
professionally.

The only thing you really need to spend any amount of money on to make
basic PCBs at home is a quality drill press and a set of carbide bits.

-p.

On Mon, 21 Jul 2014 00:09:12 -0400, you wrote:

>On Sun, Jul 20, 2014 at 10:49 PM, Brad Thompson
>brad.thompson@... [Homebrew_PCBs]
><Homebrew_PCBs@yahoogroups.com> wrote:
>
>> I've been contemplating the whole make-boards-at-home process and I'm
>> getting closer to going the commercial route... unless I can think of
>> additional
>> tasks for a router, laser engraver, and 3-D printer<g>.
>
>I think you are looking at this the wrong way. You make PCBs at home
>when you only want one of them. This can either be a 1-off for a
>particular task or a prototype for a circuit. If you ever want much
>more than 1 copy of a board, you are better off having it made
>professionally.

I can agree and disagree with this. For me, the advantage of making
the boards at home is simply cost. I can do a reasonably decent
double sided board, no silk screen or plated through holes, which I
can use if I want a "one of" or consider sending off to a board house
(not yet done that), if I know I want a lot, and the silk screen and
solder mask and plated through holes are worth the money.... They
generally are, but I use the home made stuff to verify the design.

"And that, Virginia, is why they have revision numbers on
drawings...."

The boards I'm doing are generally largish, 6.5 by 3.4 or so inches at
the latest, generally a microprocessor, I2C, and whatever else I need.
I'm generally happy to do the boards at home, since I do a lot of "one
of" designs, although I think that'll change.

I generally improve a design, or have to add something, or just have
to modify the design because the parts are no longer available (some 4
terminal 3.3 and 5.0 volt regulators are an example)...

Making do with toner transfer, laser printer, laminator, shear, and an
upside down drill press with a TV camera to view the boards.

Harvey

>
>The only thing you really need to spend any amount of money on to make
>basic PCBs at home is a quality drill press and a set of carbide bits.
>
>-p.

On Mon, Jul 21, 2014 at 12:39 AM, Harvey White madyn@...
[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> I can agree and disagree with this. For me, the advantage of making
> the boards at home is simply cost.

I don't think we are disagreeing at all. When you only want one board
it is generally cheaper to make it at home.

-p.

On Mon, 21 Jul 2014 00:44:38 -0400, you wrote:

>On Mon, Jul 21, 2014 at 12:39 AM, Harvey White madyn@...
>[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
>
>> I can agree and disagree with this. For me, the advantage of making
>> the boards at home is simply cost.
>
>I don't think we are disagreeing at all. When you only want one board
>it is generally cheaper to make it at home.

I was replying to the cost argument (and agreeing), and commenting on
the "more than one" and somewhat disagreeing.

Harvey

>
>-p.

Being sure your design is error free is always going to be an issue, it's a probability thing.  I have seen simple boards prototyped 4 times before the guy got it acceptable then I have seen them come out of the shoot 100% accurate.    There are two classes of errors, the first one is electrical and how your circuit works, nothing the pcb process can do to fix a bad electronic design, improper component choices or just bad engineering.  So the first thing is to make sure you circuit is correct and been prototyped some how if necessary and working.  The second thing is to carefully select all your components, picking a component that is built from unobtanium or not suited to the task is the first risk you must blunt.  Don't underestimate this risk, a part in stock may not be when you get your boards back.  Find alternate sources up front, best to use parts that have multiple sources.

Now we come to the PCB process.  First is the schematic and the component libraries,  I have always found that the libraries are a big source of error, very easy to get a pin switched around.  So one needs to be proactive and do a formal library check of all newly built components (twice and by a second person if you want to be sure).   The second major source of error is poorly captured schematic.  Its easy to miss wires have wires that look connected to nets but are not, bus numbering errors and the like.   Again double QA the schematic.  I most always name all nets, then print out an text based net list format and spot better 100% check the connectivity.   Once you are sure the schematic is correct and you have identified all your parts only  then is it time to do the PCB layout.

We have an entirely new set of issues with the layout,  first is the mechanical is the board shape correct, are all the mounting holes correctly located and of proper size?  Again it good QA that saves the day.   Again we have a big risk with the pattern library and its coordination with the component library in the schematic.  Is the clock on pin 1 or pin 11.  Easy to make a typo.   Is the pattern footprint correct, does it have proper size pads, holes.  Is the silk art and solder mask correct.  SMT helps a lot here as the number of different pattern types is reduced and more standardized.   Check Check and more checking.   Next do the placement and review it again --you got any component height issues with your housing?   Now you are down to routing -- plenty of places for errors here,  trace width, clearances, SI,  EMC.  Use the tools DRC checks but also use your mark 100 eyeball.  I have found nothing beats printing out the layout 2:1 and using a highlighter to trace it all out comparing to the schematic -- though that is a lot of work and may not be practical on more than a small board double sided board.  I have worked on 8 layer designs with thousands of nets and 70 pages of schematics, in this case the best you can do is a spot check but you are just forced to trust the tools.  In my experience the most risks are with the library and the component selection process, check these good an you have a good chance of making a 100% board the first time.

Check check and more checking -- then prototype if you are still unsure.   But a home built board is not really representative of what you would send to a commercial house to add a lot of value.    The costs on getting 1-3 boards these days is not all that bad unless you are talking multi layer.  Just get a couple of prototypes before sending in your order of 100's.  If nothing changes most houses will not charge a second NRE for the production order.
Craig

Great responses. Thanks to all.

As I said, I will order greater quantities from a commercial PCB
maker. I have no intention of making hundreds of them at home.

The home made boards, ONE, TWO, or at most THREE, would be ONLY to
verify the PCB layout. With that in mind, I would HAVE to make those
few, home brew boards DIRECTLY from the layout that I create in a PCB
design program. Otherwise, it is still prone to mistakes and
therefore useless.

Vias are a problem, but my circuit is simple so this may not be
overly difficult. First, I can probably solder some wires in vias
that are under the chips. Just use a close cutting pliers to trim
them as flat as possible. The specs for a -DW Plastic Small Outline
package, which I intend to use, show a 0.004" to 0.012" clearance
between the bottom of the package and the board. The copper thickness
will add a bit more to this. I would verify the connection(s) before
installing the chip. A little extra bending on the chip leads will
create a bit more space for them. Tedious, but possible. And this is
ONLY to verify the design.

Sounds like toner transfer may be the way to go. I could always get
laser/Zerox style copies made at a local service. I have the ability
to drill it, no problem there.

On Mon, Jul 21, 2014 at 5:49 PM, Paul Alciatore palciatore@...
[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> The home made boards, ONE, TWO, or at most THREE, would be ONLY to
> verify the PCB layout. With that in mind, I would HAVE to make those
> few, home brew boards DIRECTLY from the layout that I create in a PCB
> design program. Otherwise, it is still prone to mistakes and
> therefore useless.

You may have missed what some of us have been telling you. While you
can absolutely make boards at home to test the operation of your
circuit, the design of the boards you make given the constraints of
home construction are going to be sub-optimal to those designed under
the constraints of professional production.

There is nothing really wrong with that, but you might be able to save
quite a bit of money on your production run if you can get the
production boards on a smaller form factor.

-p.