Homebrew PCBs

Hi Guys,

What temperature should I be trying to achieve to achieve a good transfer of toner to PCB? I have access to a good workshop (machine shop in the colonies!) together with metal and I am thinking of making a heated press to provide a uniform hot surface and pressure rather than clowning about with steam irons or modifying a printer or laminating machine. 

Regards,

Steve

Make a roller version then.  The advantage of a roller over a flat plate is that the pressure is applied where needed, relatively uniformly, with relatively low force requirement.  To achieve 200psi with a roller requires a few pounds (35+/-) of force - the contact area is extremely small (estimate 0.030x6.0 inches).  Over a 4x6 inch surface, a plate would have to be loaded with a force of 4800 lb to achieve the same 200psi, and the uniformity of application is far from guaranteed.  A hot diaphragm with a 200psi hydraulic chamber behind might be able to provide sufficient uniformity, but would have to be at least twice the size of the maximum working area (to reduce edge effects) with support to prevent blowout of the diaphragm.

Temperature seems to depend on the toner, but somewhere around 275F to 325F seems to work pretty well, near as I can tell.

HTH,
Donald.
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----- Original Message -----

> From: "Stephen" <squirrox@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, November 14, 2011 10:53:15 AM
> Subject: [Homebrew_PCBs] Toner transfer temperature?
> Hi Guys,
> 
> What temperature should I be trying to achieve to achieve a good
> transfer of toner to PCB? I have access to a good workshop (machine
> shop in the colonies!) together with metal and I am thinking of making
> a heated press to provide a uniform hot surface and pressure rather
> than clowning about with steam irons or modifying a printer or
> laminating machine.
> 
> Regards,
> 
> Steve
> 
> 
> 
> ------------------------------------
> 
> Be sure to visit the group home and check for new Links, Files, and
> Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
> 
> 
>

Donald H Locker <dhlocker@...> writes:
> Temperature seems to depend on the toner, but somewhere around 275F to
> 325F seems to work pretty well, near as I can tell.

I tend to use 345F or so for HP toners.  Most Brother toners need
360-375F.

New to the group...

Donald H Locker <dhlocker@...> writes:
>  Temperature seems to depend on the toner, but somewhere around 275F to
>  325F seems to work pretty well, near as I can tell.

I tend to use 345F or so for HP toners. Most Brother toners need
360-375F.
[DJ Delorie]

I wonder if those temps are absolute or if they depend of you're 
using an iron or a laminator.

To my question:

I'm using a modified laminator to transfer the toner to the copper.

I'm using a Brother HL-5170DN to print to thin glossy (not photo) paper.

The printing goes just fine, as does the toner on the copper.

But after etch, it looks like there were some pinholes in the toner: 
there are places in the copper where the copper is etched through in 
a point or right across a trace. If I were to tin the copper it would 
probably be OK to use.

What is the cause? The toner adheres just fine to both the paper and, 
apparently, the copper.

Suggestions?

Thanks,
Dave

Hmmm.  Maybe I need to calibrate my temperature sensor.

Donald.
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----- Original Message -----

> From: "DJ Delorie" <dj@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, November 14, 2011 2:15:15 PM
> Subject: Re: [Homebrew_PCBs] Toner transfer temperature?
> Donald H Locker <dhlocker@...> writes:
> > Temperature seems to depend on the toner, but somewhere around 275F
> > to
> > 325F seems to work pretty well, near as I can tell.
> 
> I tend to use 345F or so for HP toners. Most Brother toners need
> 360-375F.
> 
> 
> ------------------------------------
> 
> Be sure to visit the group home and check for new Links, Files, and
> Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
> 
> 
>

DaveC <davec2468@...> writes:
> I wonder if those temps are absolute or if they depend of you're 
> using an iron or a laminator.

Each toner "recipe" has a specific temperature at which it is plastic
(and sticky) but not liquid.  Ideally, you want to heat it to exactly
that temperature, so it sticks to the copper but doesn't deform.
However, that's harder than you'd think.  So, each one of us needs to
come up with a pattern of device + temperature + #passes that results in
the toner hitting that "plastic" state.  Lower temperature but more
passes?  Should work.  Higher temperature, fewer passes?  Should work.

> But after etch, it looks like there were some pinholes in the toner: 

I always get this, I suspect we just can't tell modern printers to put
down enough toner to make a really thick mask.

This is just speculation with a sprinkling of theory, but it seems to me
that the whole electrostatic attraction thing does better on edges and thin
lines than it does on large areas. Certainly I remember most photocopies
rapidly losing filled areas while the edges got "ringy"

Because of this (assuming it's true of course), I've never had a problem
with a "pit" breaking a trace, only in pours or large pads where they're
not electrically a problem.

I also noticed, after I posted the photo, that the genuine-toner board I
tried most recently is exhibiting what are clearly (air) bubbles under the
toner which have prevented adhesion (the one I posted to show what a
trapped hair could
do<http://groups.yahoo.com/group/Homebrew_PCBs/photos/album/809517956/pic/2133723863/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc>),
whereas I haven't had such a problem with the (much more empty) generic
toner I was using before.

So my theory is that the pitting *helped* by allowing trapped air to escape
thru the paper and got me better adhesion. I usually splash a bit of nail
polish on my bigger pour areas to alleviate the pitting.

PG

On Tue, Nov 15, 2011 at 4:59 PM, DJ Delorie <dj@...> wrote:

> **
>
>
>
> DaveC <davec2468@...> writes:
> > I wonder if those temps are absolute or if they depend of you're
> > using an iron or a laminator.
>
> Each toner "recipe" has a specific temperature at which it is plastic
> (and sticky) but not liquid. Ideally, you want to heat it to exactly
> that temperature, so it sticks to the copper but doesn't deform.
> However, that's harder than you'd think. So, each one of us needs to
> come up with a pattern of device + temperature + #passes that results in
> the toner hitting that "plastic" state. Lower temperature but more
> passes? Should work. Higher temperature, fewer passes? Should work.
>
>
> > But after etch, it looks like there were some pinholes in the toner:
>
> I always get this, I suspect we just can't tell modern printers to put
> down enough toner to make a really thick mask.
>
>  
>


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

Could just be the paper you're using.

I tried recently a board printed at the warehouse, on their slightly shiny paper (200gsm) and while it transferred surprisingly nicely (I thought it would just stay on the paper) there were quite a few holes where paper fibers were stuck in the toner and seemed to pull it off.

I haven't noticed that problem with old magazine pages, which are noticeably more shiny and much thinner.

I would try repeating the process with something known to work well, preferably something designed for it like Pulsar Pro even. If you get problems even with that you know it's something else.

(But even they admit you can get pinholes\pitting with that, which is why they also sell the green TRF, although I don't think I've ever seen anyone who said they had needed to use that as well)

--- In Homebrew_PCBs@yahoogroups.com, DaveC <davec2468@...> wrote:

> I'm using a Brother HL-5170DN to print to thin glossy (not photo) paper.
> 
> The printing goes just fine, as does the toner on the copper.
> 
> But after etch, it looks like there were some pinholes in the toner: 
> there are places in the copper where the copper is etched through in 
> a point or right across a trace. If I were to tin the copper it would 
> probably be OK to use.
> 
> What is the cause? The toner adheres just fine to both the paper and, 
> apparently, the copper.
> 
> Suggestions?
> 
> Thanks,
> Dave
>