<azonenberg>
given baking, a few layers cna be stacked
<bart416>
a micron isn't enough for a pcb
<azonenberg>
Why do you say that?
<bart416>
You need to be able to solder this
<bart416>
And it has to survive some shocks
<azonenberg>
You put power planes inside
<azonenberg>
on the back side*
<azonenberg>
this is just for interconnect layers
<azonenberg>
as an ILD
<azonenberg>
You could make the top surface thicker
<bart416>
If the heat goes through it might crack the glass though
<azonenberg>
As long as you heat relatively evenly, nope
<bart416>
Soldering irons don't do even
<azonenberg>
you'd want to use reflow
<bart416>
even with reflow
<bart416>
You'd need a professional oven to do this
<azonenberg>
re scratching, it can handle nearly 500g on a steel needle before scratching
<azonenberg>
so a soldering iron handled carefully wouldnt damage the film
<azonenberg>
The bigger issue is the price of the solution
<azonenberg>
idk the exact number but my guess is, "not cheap" :P
<azonenberg>
In any case i'll be pickign up some of that solution in a month or two
<azonenberg>
i have ideas for stuff using it
<bart416>
Actually I have a idea that might just work
<bart416>
Use a small layer of polymer to protect the metal against HF
<azonenberg>
Copper is resistant to HF
<azonenberg>
It wont etch
<bart416>
Mhhh, you sure?
<bart416>
Then there is no issue
<bart416>
I can spin coat glass on as well
<bart416>
Just need to melt it
<azonenberg>
200nm of this glass dissolves in 5% HF in 10 sec and 1% in around 100 sec
<azonenberg>
my 3% should be around 30 sec
<azonenberg>
and you dont want to do that
<azonenberg>
it'll cool unevenly and crack
<azonenberg>
unless you had a heated chuck and everything
<bart416>
mhhh, even if it's spinning in a vacuum?
<azonenberg>
And the viscosity would be so high it'd form a very thick layer, i'd guess
<azonenberg>
The sol-gel mixture i linked you to is a room temperature deposition process
<azonenberg>
then you heat treat after spinning to densify and harden it
<bart416>
micron density just isn't good enough
<bart416>
The mechanical properties of such a board would be crappy at best
<azonenberg>
Agreed, i wouldnt recommend it for anything serious
<bart416>
We need a polymer that can be attacked by something that doesn't eat away photoresist
<azonenberg>
I suggested the idea purely as a curiosity
<azonenberg>
They have photosensitive SU-8 epoxy polymer
<azonenberg>
it can be spin coated
<azonenberg>
not sure about the developer etc though
<azonenberg>
And its probably harder to get hold of
<bart416>
Yeah but SU-8 is hard to remove
<bart416>
Really really really hard
<azonenberg>
you dont remove it
<bart416>
Does it have good insolation properties?
<bart416>
*insulation
<azonenberg>
You expose, develop, and *then* harden it
<azonenberg>
And its a polymer, so i'd assume so
<azonenberg>
very few are conductive
<bart416>
I mean > 1000V
<azonenberg>
i've never actually worked with it
<azonenberg>
and no idea
<azonenberg>
i never do HV stuff
<azonenberg>
well, HV by that standard
<azonenberg>
I consider 5 to be "high" since most of my work is 3.3 lol
<azonenberg>
and i'm starting to do 1.2
<bart416>
Side advantage of SU-8 is that you could use it to prototype biomedical circuit boards as well
<azonenberg>
biomedical circuit boards? You mean for implants etc?
<bart416>
Yes
<azonenberg>
yeah, iirc su-8 is biocompatible
<azonenberg>
they use it for microfluidics etc
<bart416>
Well obviously for lab tests with non-human subjects
<bart416>
but it'd be possible
<bart416>
Though you'd have to use titanium instead of copper just to be safe
<azonenberg>
You can evaporate pretty much any metal that melts at a lower temperature than tungsten
<azonenberg>
in a filament evaporator
<azonenberg>
The guy i talked to has only failed to do like two metals
<bart416>
And cause this isn't nearly as precise you don't need to go hard vacuum either
<azonenberg>
i think platinum and nickel
<azonenberg>
And you need hard vacuum to evaporate
<azonenberg>
period
<azonenberg>
otherwise you get oxidation and all kinds of problems
<bart416>
You don't need to go down to the level for semiconductors
<azonenberg>
You still need 1E-6 torr ish
<azonenberg>
even if its just for SEM sample prep
<azonenberg>
otherwise the coating isnt even enough
<bart416>
This isn't SEM
<bart416>
It's a PCB
<azonenberg>
or can be contaminated with oxides
<bart416>
the features are easily 1mm
<azonenberg>
Only way to know for sure is to try it
<azonenberg>
And 1mm?
<azonenberg>
The board i'm designing now has 150um traces
<azonenberg>
on almost all of the signals
<bart416>
Lucky you that you can afford somebody to manufacture it like that
<azonenberg>
Afford? Its the cheapest process i could find
<azonenberg>
expresspcb
<azonenberg>
$100 for three 4-layer boards 3.8 x 2.5 inch
<azonenberg>
with silkscreen and soldermask
<bart416>
that's way over my budget for these sort of things
<azonenberg>
Or $55 for three 2-layer, tinned copper with no silkscreen or soldermask
<azonenberg>
i'm putting a lot of time into the design for the board and splurging on the fab because i'll probably be using it for my research
<bart416>
you know, for two layer boards seeedstudio is cheaper :P
<azonenberg>
I'm planning to move to another fab in the near future
<azonenberg>
once i learn gEDA enough to make serious boards with it
<bart416>
I feel dirty, just read wikipedia page on SU-8
<bart416>
"allowing fabrication of relatively thick (hundreds of micrometers) structures with nearly vertical side walls"
<bart416>
That sounds about right :D
<azonenberg>
Yeah, its almost transparent iirc
<azonenberg>
Which means you need high exposure energy (not much absorption)
<azonenberg>
But also you get very good resolution
<bart416>
Meh, I intended to use a laser :P
<azonenberg>
very vertical sidewalls
<azonenberg>
etc
<azonenberg>
I want to try doing vertical sidewalls using KOH in <110> Si
<bart416>
I don't need sub 10µm features so using a laser on a 2D moving platform should be easy enough
<azonenberg>
But first i need to debug my hardmasking
<bart416>
Assuming I have a way of sealing off the compartment with the laser I could keep the board in the vacuum while working on it eh
<azonenberg>
I see no reason to use vacuum
<bart416>
evaporation of copper
<azonenberg>
You dont pattern during evaporation
<azonenberg>
You evaporate a continuous film, spin coat PR, expose, develop, etch
<bart416>
No but that means it'd require human interaction
<azonenberg>
You are not going to be able to do the entire process continuously
<bart416>
I'd love to make a machine that does all of it
<azonenberg>
Yeah, but not in one chamber without breaking vacuum
<azonenberg>
Do you want to use the laser for exposure?
<bart416>
Why not?
<azonenberg>
Or for ablation?
<bart416>
exposure
<azonenberg>
You cant put the photoresist down in a vacuum
<bart416>
It's spincoated on so why not? :S
<azonenberg>
There's a solvent in the solution
<bart416>
The pump draws it out as well heh
<azonenberg>
the vapor pressure is high
<bart416>
I know cause I tried
<bart416>
I did that when I built that stm
<azonenberg>
It'd evpaporate insanely fast, i mean
<bart416>
Though I'm not sure if it'll work with SU-8
<azonenberg>
You wouldnt be able to coat it
<bart416>
Bah
<azonenberg>
The only way it'd work is if you had photoresist that was evaporatable
<bart416>
Does SU-8 really have that bad properties?
<azonenberg>
Not that i know of
<azonenberg>
It seems like a good idea
<azonenberg>
Anyway so you'd need evaporatable PR
<bart416>
Lets see if I can get my hands on another vacuum pump for starters
<azonenberg>
But most photoactivators are heat sensitive
<azonenberg>
So it wouldnt survive the process even if coated
<azonenberg>
it'd decompose
<azonenberg>
And you'd need an aqueous or solvent based developer
<azonenberg>
I'm not saying you cant automate the process - modern IC fabs are almost lights-out level automation
<azonenberg>
But i dont think you can do it without breaking vacuum
<bart416>
well, did you build a fillament evaporator already?
<azonenberg>
No
<azonenberg>
I've been borrowing time on one in the electron microscopy lab at my school's mat sci department
<azonenberg>
while saving up and seeking out parts to build one of my own
<azonenberg>
Its on the todo list but is a few months out
<azonenberg>
my next major purchases will be an oscilloscope/logic analyzer (for general purpose use, not specifically fab) and parts for a small fume hood
<azonenberg>
In case you havent guessed my plans are bigger than *just* basic home fab lol
<azonenberg>
The wishlist for my dream home includes a CNC machine shop and a class 1,000 clean room with a class 100 glove box (assuming that full class 100 is prohibitively expensive/difficult)
<bart416>
the clean room you could build yourself actually
<azonenberg>
I intend to
<azonenberg>
But it will require extensive enough modifications i cant do it in a rented apartment
<bart416>
Alluminium frames
<bart416>
Perspex windows
<azonenberg>
So it has to wait until i graduate and buy a place of my own
<bart416>
then a good filter and HVAC system to create positive pressure
<azonenberg>
I also wont have the budget for it until then :P
<azonenberg>
But yeah, thats basically the plan
<azonenberg>
except i was thinking of glass for the windows
<azonenberg>
wall materials are TBD, most likely plastic or masonry
<azonenberg>
the only thing i know for sure is drywall is out of the question :P
<bart416>
I'd use a plastic
<bart416>
Something scratch resistant
<bart416>
+ easier to seal
<azonenberg>
Hmm
<azonenberg>
But its not solvent resistant
<bart416>
Some are
<azonenberg>
Not many clear ones
<azonenberg>
polycarbonate and acrylic are both degraded by acetone
<azonenberg>
Which is what i'd use to clean up spatter from, say, a spin coating gone wrong
<bart416>
Ideally you'd use the same polymers they use to make glasses these days
<azonenberg>
I doubt those like acetone though
<azonenberg>
Also, arent many glasses these days still actual glass?
<azonenberg>
just with scratch resistant coatings?
<bart416>
Heh, I've gotten aceton splashes on mine, nothing wrong with that
<bart416>
Hell no
<bart416>
They're moving away from glass
<bart416>
too fragile
<azonenberg>
Interesting
<azonenberg>
doesnt wear glasses, as you can probably tell
<bart416>
+ polymers are thinner for the same effect
<azonenberg>
You mean higher refractive index?
<bart416>
Yes
<azonenberg>
in that case, use something insane like tantalum oxide :P
<bart416>
My glasses would be 5 times as thick without using a polymer
<azonenberg>
Polycarbonate - 1.5841.586
<azonenberg>
Fused quarts - 1.458
<azonenberg>
quartz*
<azonenberg>
Ta2O5 is around 2.14 lol
<azonenberg>
Thats almost as high as diamond
<azonenberg>
and about on par with cubic zirconia
<azonenberg>
In any case, off to bed with me - i've accomplished what little i could to tonight given i was also busy with work
<azonenberg>
1 part HCl / 6 parts H2O2, dilute the resulting mixture 4:1 with distilled water
<bart416>
CR-39
<azonenberg>
etches my copper film in a more reasonable 8-10 seconds
<bart416>
Read up on CR-39 quickly :P
<azonenberg>
i.e. controllable enough to probably not overetch
<azonenberg>
sec
<bart416>
That's what they use for glasses according to google heh
<bart416>
Most descriptions mention it's resistant to solvents
<bart416>
:D
<azonenberg>
Interesting
<azonenberg>
Yeah, polycarbonate and PMMA are the only two clear plastics i'm particularly familiar with
<bart416>
"Taking into account that CR-39, one of the most sensitive ion track detectors, can not be removed by any solvent without altering the replica materials, the technique had to be adapted for using with this material."
<bart416>
LOL
<azonenberg>
lol
<bart416>
I have a feeling it'll get the job done :')
<azonenberg>
cats "standby" to /home/azonenberg/bedroom/azonenberg/sys/power/state