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
>
>
>
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