Homebrew PCBs

To date component placement silk screens have been limited to black
using toner transfer. With colour laser printers you should be able to
toner transfer a vivid yellow.

Toner transfer has a couple of issues when nice readable paterns are
required. 

1. It is difficult to get a complete image due to the differing
heights of the copper and the missing copper. 

2. You need a very good paper that releases well and does not leave
any paper fibres or clay behind. 

Direct printing to the PCB using an inkjet printer and then toner
dusting could provide a better screen print.

Using direct printing the process requires baking the pigment ink such
that it goes brown. If you direct print the solder mask a black toner
will not be of much value. Yellow would be the colour to use and the
printing industry may even have a white toner they use as a base coat
for their photographic processes on transparent material.(To be confirmed)

A printer other than a pigment ink Epson may also be successful. This
 will depend on the binding characteristics of the toner once wetted
and then dried. Taking this thought one stage further, a water/alcohol
mix may  be usable through a dye print head if the toner stays bound
to itself and the PCB once dry. 

Although it would be better if the toner did not blow away once the
ink has dried, the method may not depend on any adhesion once dry.
Just keep the PCB horizontal and carefully get it up to temperature in
the next stage.

Once the PCB has been dusted the toner needs to be flowed. Ideally
this should be done using heat but no pressure. I don't know if it can
be done without pressure as the plastic particles in the toner need to
 get together if the final result is to be strong. 

I suspect having most of the ink liquid evaporated before applying the
higher melting heat would be best to stop boiling the ink as this will
move the toner. I would then evenly raise the temperature of the PCB
to prevent stress and then locally heat the toner to melting point. An
oven or heat gun are the tools to try here but over temperature will
likely burn the plastic and loose the vivid yellow/white that the
toner promises. 

Those with direct printing ability may like to give it a try and
report back. 

 
Warren

Warren,
Colored toner tends to be very expensive, especially when you have to buy
all 4 colors at once.

SEARS has small packets of  an electrostatic paint powder that works very
well. It comes in many colors. I have used the green for solder mask.

There are other ES paint powders, guys who make their own fishing lures use
some very bright colors (even white). BASS sports hops has small bottles for
around $6.

The craft stores have "embossing" powder that may work, but I haven;t tried
it yet.

I have been using a MARVY hot air embossing tool to fuse my toner dusted
pcbs. You can see the toner turn shiny and fuse.

Myc

On Sat, Oct 18, 2008 at 5:29 PM, warrenbrayshaw <
warrenbrayshaw@...> wrote:

>   To date component placement silk screens have been limited to black
> using toner transfer. With colour laser printers you should be able to
> toner transfer a vivid yellow.
>
> Toner transfer has a couple of issues when nice readable paterns are
> required.
>
> 1. It is difficult to get a complete image due to the differing
> heights of the copper and the missing copper.
>
> 2. You need a very good paper that releases well and does not leave
> any paper fibres or clay behind.
>
> Direct printing to the PCB using an inkjet printer and then toner
> dusting could provide a better screen print.
>
> Using direct printing the process requires baking the pigment ink such
> that it goes brown. If you direct print the solder mask a black toner
> will not be of much value. Yellow would be the colour to use and the
> printing industry may even have a white toner they use as a base coat
> for their photographic processes on transparent material.(To be confirmed)
>
> A printer other than a pigment ink Epson may also be successful. This
> will depend on the binding characteristics of the toner once wetted
> and then dried. Taking this thought one stage further, a water/alcohol
> mix may be usable through a dye print head if the toner stays bound
> to itself and the PCB once dry.
>
> Although it would be better if the toner did not blow away once the
> ink has dried, the method may not depend on any adhesion once dry.
> Just keep the PCB horizontal and carefully get it up to temperature in
> the next stage.
>
> Once the PCB has been dusted the toner needs to be flowed. Ideally
> this should be done using heat but no pressure. I don't know if it can
> be done without pressure as the plastic particles in the toner need to
> get together if the final result is to be strong.
>
> I suspect having most of the ink liquid evaporated before applying the
> higher melting heat would be best to stop boiling the ink as this will
> move the toner. I would then evenly raise the temperature of the PCB
> to prevent stress and then locally heat the toner to melting point. An
> oven or heat gun are the tools to try here but over temperature will
> likely burn the plastic and loose the vivid yellow/white that the
> toner promises.
>
> Those with direct printing ability may like to give it a try and
> report back.
>
> Warren
>
>  
>


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

Myc
That's good information. Colored toner is expensive but you can buy
single bottles of refill toner. Still may exceed some budgets.

I Googled for information, prompted by your remarks, and soon spotted
a preferable route when selecting a powder. Electrostatic powders come
in two varieties ThermoPlastic and ThermoSetting. Laser Printer toner
must be ThermoPlastic otherwise the "Toner Transfer" method would not
work. It will re-melt on reheating whereas the second will not as it
undergoes a molecular change during heating and curing. As board
soldering takes place after the silk screening the writing will likely
survive better if the Thermosetting powder is used. The sources you
list may not make it clear what type is on offer but a simple reheat
test should reveal the answer. 

As these powders melt between 160 and 210 degrees C they will all be
in the melt range in a SMD oven cycle so the ThermoPlastic will reflow
also. This may not be an issue but I feel that the more stable
ThermoSetting powder would be better especially when using a soldering
iron or heatgun, that may disturb the toner/ES powder writing. (ugly). 

For use as an etch resist the opposite is true. I suspect it would be
best to use the ThermoPlastic variety as it should be easier to remove.
(To quote Wikipedia) "Methylene Chloride is generally effective at
removing powder coating, however most other organic solvents (Acetone,
thinners, etc.) are completely ineffective."  

As Acetone takes off laser Printer toner easily the thermo plastic
being referred to could well be of another type. Something to be
discovered.

Plenty to go on with 
Warren


"Myc Holmes"  wrote:
>
> Warren,
> Colored toner tends to be very expensive, especially when you have
to buy
> all 4 colors at once.
> 
> SEARS has small packets of  an electrostatic paint powder that works
very
> well. It comes in many colors. I have used the green for solder mask.
> 
> There are other ES paint powders, guys who make their own fishing
lures use
> some very bright colors (even white). BASS sports hops has small
bottles for
> around $6.
> 
> The craft stores have "embossing" powder that may work, but I
haven;t tried

> it yet.
> 
> I have been using a MARVY hot air embossing tool to fuse my toner dusted
> pcbs. You can see the toner turn shiny and fuse.
> 
> Myc

Warren,
On a practical note, the SEARS ES powder works fine as a solder mask. the
particle size is a bit larger than the toner powder. It is cheap and
readily available..

I use a MARVY embossing tool for fusing. It is basically a hot air gun that
has low air flow. It also works great for smt. A hot plate should also work.

I use a green 3M scrubbie to remove the toner after etching. I found that
solvents tend to stain the pcb.

Myc



On Sun, Oct 19, 2008 at 2:30 AM, warrenbrayshaw <
warrenbrayshaw@...> wrote:

>   Myc
> That's good information. Colored toner is expensive but you can buy
> single bottles of refill toner. Still may exceed some budgets.
>
> I Googled for information, prompted by your remarks, and soon spotted
> a preferable route when selecting a powder. Electrostatic powders come
> in two varieties ThermoPlastic and ThermoSetting. Laser Printer toner
> must be ThermoPlastic otherwise the "Toner Transfer" method would not
> work. It will re-melt on reheating whereas the second will not as it
> undergoes a molecular change during heating and curing. As board
> soldering takes place after the silk screening the writing will likely
> survive better if the Thermosetting powder is used. The sources you
> list may not make it clear what type is on offer but a simple reheat
> test should reveal the answer.
>
> As these powders melt between 160 and 210 degrees C they will all be
> in the melt range in a SMD oven cycle so the ThermoPlastic will reflow
> also. This may not be an issue but I feel that the more stable
> ThermoSetting powder would be better especially when using a soldering
> iron or heatgun, that may disturb the toner/ES powder writing. (ugly).
>
> For use as an etch resist the opposite is true. I suspect it would be
> best to use the ThermoPlastic variety as it should be easier to remove.
> (To quote Wikipedia) "Methylene Chloride is generally effective at
> removing powder coating, however most other organic solvents (Acetone,
> thinners, etc.) are completely ineffective."
>
> As Acetone takes off laser Printer toner easily the thermo plastic
> being referred to could well be of another type. Something to be
> discovered.
>
> Plenty to go on with
> Warren
>
>
> "Myc Holmes" wrote:
> >
> > Warren,
> > Colored toner tends to be very expensive, especially when you have
> to buy
> > all 4 colors at once.
> >
> > SEARS has small packets of an electrostatic paint powder that works
> very
> > well. It comes in many colors. I have used the green for solder mask.
> >
> > There are other ES paint powders, guys who make their own fishing
> lures use
> > some very bright colors (even white). BASS sports hops has small
> bottles for
> > around $6.
> >
> > The craft stores have "embossing" powder that may work, but I
> haven;t tried
> > it yet.
> >
> > I have been using a MARVY hot air embossing tool to fuse my toner dusted
> > pcbs. You can see the toner turn shiny and fuse.
> >
> > Myc
>
>  
>


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