azonenberg | lol duct tape | 01:42 |
---|---|---|
azonenberg_lab | Woot | 05:50 |
azonenberg_lab | Testing use of 1000nm evaporated Cu over 5nm Cr as a hardmask for KOH wet etch of <110> Si | 05:50 |
azonenberg_lab | early experiments are promising | 05:50 |
azonenberg_lab | but i need to leave it in the etch bath longer | 05:50 |
azonenberg_lab | the Cu isnt attacked visibly but the Si isnt etched by much either :P | 05:51 |
azonenberg_lab | surface is roughened, which indicates that etching is happening | 05:51 |
azonenberg_lab | (of the Si) | 05:51 |
azonenberg_lab | If this works out i may be able to ditch that Ta2O5 for good | 05:53 |
azonenberg_lab | Its been the main thing killing my yields lately :P | 05:53 |
azonenberg_lab | too finicky | 05:53 |
azonenberg_lab | aww... it didnt work, there are bubbles in the film | 06:03 |
CIA-67 | homecmos r114 | trunk/lithography-tests/labnotes/azonenberg_labnotes.txt | Today's lab notes | 06:04 |
bart416 | azonenberg, I think I have it ifgured out | 07:31 |
bart416 | Conductive ink | 07:32 |
azonenberg | For? | 07:32 |
bart416 | Then I can copper plate whatever I want | 07:32 |
azonenberg | Ooh | 07:32 |
azonenberg | Thats what i tried for via plating | 07:32 |
azonenberg | but i tried using it bare | 07:32 |
bart416 | If I find one that can be diluted in water | 07:32 |
azonenberg | i didnt try electroplating over it | 07:32 |
azonenberg | Doesnt have to be water - any common solvent | 07:32 |
azonenberg | ethanol, isopropanol, acetone | 07:32 |
azonenberg | find one that can be thinned with any of them | 07:32 |
bart416 | I'd like something that I could remove again though | 07:33 |
azonenberg | Same solvent again? | 07:33 |
azonenberg | i dilute my PR in acetone before spin coating it | 07:33 |
azonenberg | and strip with acetone after etching | 07:33 |
bart416 | So I can coat the plexiglass in it | 07:33 |
azonenberg | as long as its a solvent-evaporation process and not curing you're fine | 07:33 |
bart416 | copper plate | 07:33 |
bart416 | lithography | 07:34 |
azonenberg | acetone isnt compatible with plexiglass but some of the other solvents may be | 07:34 |
bart416 | remove copper with H2SO4 or another acid | 07:34 |
bart416 | then kill the ink with something that doesn't kill the plexiglass | 07:34 |
azonenberg | I like what you're thinking but must caution you that you may have adhesion problems | 07:34 |
azonenberg | copper is hard to stick to things sometimes | 07:34 |
azonenberg | if the ink peels off the surface it may not work well | 07:34 |
bart416 | well yeah, it'll be sandwiched between two layers of plexiglass | 07:34 |
bart416 | So it only needs to stick for a few hours | 07:35 |
azonenberg | Hmm | 07:35 |
azonenberg | Explain your process again? | 07:35 |
azonenberg | From beginning to end | 07:35 |
bart416 | ok, get the circuit on the plexiglass | 07:35 |
bart416 | drill holes where necessary, plate vias, etc... | 07:35 |
bart416 | then stick the plexiglass together | 07:35 |
azonenberg | So you want to use a single sheet of PMMA as your board substrate | 07:35 |
bart416 | That's easy enough | 07:35 |
azonenberg | this is two layers only? | 07:36 |
bart416 | no | 07:36 |
azonenberg | top and bottom of the sheet? | 07:36 |
bart416 | two layers / sheet | 07:36 |
bart416 | You can smash together several sheets though | 07:36 |
azonenberg | How thin are these sheets | 07:36 |
bart416 | How thin do you want them? | 07:36 |
bart416 | I was thinking of starting with 1mm | 07:36 |
azonenberg | Hmm, even that is a bit thick | 07:36 |
azonenberg | you really want like 250um | 07:36 |
bart416 | I'd rather first get the process to work than start with a fragile material ;) | 07:37 |
azonenberg | True | 07:37 |
azonenberg | But that means you have to deal with really high aspect ratios in vias | 07:37 |
azonenberg | or make the vias gigantically wide | 07:37 |
bart416 | that's why the ink needs to be diluted as well | 07:38 |
bart416 | so it can get in the via through a bath | 07:38 |
bart416 | I want it so I can throw the sheet in the bath for an hour | 07:38 |
bart416 | And it's coated | 07:38 |
azonenberg | Hmm | 07:39 |
azonenberg | An hour? | 07:39 |
azonenberg | You want something with low surface tension | 07:39 |
azonenberg | maybe mix a little surfactant in there | 07:39 |
azonenberg | submerge, pull out, blow dry, done | 07:39 |
bart416 | Just giving a random number :| | 07:39 |
bart416 | yeah ideally you'd have something that chemically binds with the acrylic | 07:39 |
bart416 | I was considering it | 07:39 |
bart416 | But how do I remove it again afterwards eh | 07:39 |
azonenberg | First of all, why do you want to remove it? | 07:40 |
bart416 | You want a conductive substrate on a pcb? | 07:41 |
bart416 | Looks like a bad idea | 07:41 |
bart416 | That's why to use plexiglass azonenberg | 07:43 |
bart416 | It won't die if you try to solder it | 07:43 |
azonenberg | Let me get this straight | 07:43 |
bart416 | and you can bond layers together with chloroform | 07:43 |
azonenberg | Isnt the idea, lay down conductive layer | 07:43 |
azonenberg | Electroplate copper | 07:43 |
bart416 | Etch | 07:43 |
azonenberg | spin/dip coat photoresist, expose, develop | 07:43 |
azonenberg | etch all the way through to the plexiglass | 07:43 |
bart416 | yes | 07:44 |
bart416 | I want the ink gone | 07:44 |
bart416 | or whatever I use to make the plexi conductive | 07:44 |
azonenberg | So you're talking about removing it from exposed areas | 07:44 |
azonenberg | It still seems like the best solution is to have your initial layer be evaporated copper | 07:44 |
azonenberg | a micron or so | 07:44 |
azonenberg | then electroplate that up to working thickness of 30um ish | 07:45 |
bart416 | Evaporation is expensive | 07:46 |
bart416 | And hard on large objects | 07:46 |
bart416 | + you can't get copper to stick to acrylic by evaporation | 07:46 |
azonenberg | Its not that expensive to run if you have the equipment already | 07:47 |
azonenberg | But define "large" | 07:47 |
azonenberg | are we talking PC mobo size/ | 07:47 |
bart416 | Yes | 07:47 |
bart416 | Anything smaller is pointless | 07:47 |
azonenberg | pointless?? | 07:47 |
bart416 | Yes | 07:47 |
azonenberg | Are you planning mass production or prototypes here? | 07:48 |
bart416 | Cause then you can stretch it out over a larger dual layer board | 07:48 |
bart416 | prototypes | 07:48 |
azonenberg | If you're doing prototypes, develop a 6- or 8-layer process | 07:48 |
azonenberg | and make 'em 3-4 inches across | 07:48 |
bart416 | 10 cm is already big | 07:48 |
azonenberg | The evaporator i've used has around a 6" wide disk as the usable area for coating | 07:49 |
azonenberg | if i were to build one of my own it'd be around the same size | 07:49 |
bart416 | I don't have access to an evaporator | 07:49 |
bart416 | And I'm not going to build one | 07:49 |
bart416 | We don't all go to some american university that gets 50 000 / year / student | 07:50 |
azonenberg | Building one doesnt have to be expensive | 07:50 |
bart416 | And most of the funding we do have goes to the stupid management & economy department for their stupid pointless trips | 07:50 |
azonenberg | Cheap vacuum pump as a roughing pump | 07:50 |
azonenberg | Homebrewed diffusion pump | 07:50 |
azonenberg | or off ebay | 07:51 |
bart416 | that alone would cost me over 200 euro | 07:51 |
bart416 | Not in the budget | 07:51 |
bart416 | chemicals I can get | 07:51 |
azonenberg | how? | 07:51 |
bart416 | plexiglas, how much square meter do you want? | 07:51 |
azonenberg | The more obscure chems have been my biggest expense | 07:51 |
azonenberg | or among the biggest alt east | 07:51 |
bart416 | Normal-ish chemicals (not for semiconductor use) I can get through college/university with academic discount | 07:52 |
bart416 | So that's not expensive at all | 07:52 |
azonenberg | Just out of curiosity | 07:52 |
bart416 | But a vacuum pump alone costs roughly 100 euro here | 07:52 |
azonenberg | See what it'd cost you to get 4 fluid ounces of 16% tantalum chloride in ethanol :P | 07:52 |
azonenberg | I'd be willing to bet a few hundred USD | 07:52 |
bart416 | now in milliliter like the civilised world uses? | 07:53 |
bart416 | the homebrew diffusion pump would set me back another 100 euro in materials at least | 07:53 |
bart416 | Not to mention toolbits to machine the materials | 07:53 |
azonenberg | You dont have anything suitable in the engineering department? | 07:53 |
azonenberg | To machine it, i mean | 07:53 |
bart416 | I have access to a cnc machine shop, just need to pay for the toolbits myself | 07:54 |
azonenberg | interesting | 07:54 |
azonenberg | they dont charge us for bits here | 07:54 |
azonenberg | just stock | 07:54 |
azonenberg | as in, we're expected to supply our own | 07:54 |
bart416 | Not at college/university | 07:54 |
azonenberg | oh, i see | 07:54 |
bart416 | Their cnc machines there are constantly in use and time on them is reserved from here till 2040 or something like that :S | 07:54 |
bart416 | Same for the rapid prototyping machines | 07:55 |
bart416 | + my point still holds | 07:57 |
bart416 | You can't evaporate copper on plexiglas | 07:57 |
azonenberg | diff substrate? | 07:57 |
bart416 | Name one that's readily available, cheap, easy to machine and heat resistant? | 07:57 |
azonenberg | stripping PR ont ork, you need acetone | 07:58 |
bart416 | the chloroform will attack the photoresist as well normally | 07:58 |
bart416 | so while bonding layers it will destroy the remains of the photoresist if there are any | 07:58 |
bart416 | maybe mylar | 08:03 |
bart416 | But that again brings the issue of how to coat it | 08:03 |
bart416 | Then again, mylar I could probably buy coated | 08:05 |
bart416 | buy coated mylar, electroplate with copper | 08:05 |
bart416 | etch | 08:05 |
bart416 | attack with whatever I want really | 08:05 |
bart416 | Actually that's the best thing I can come up with | 08:07 |
bart416 | buy mylar with a metal coat on it already | 08:07 |
bart416 | That's cheap, readily available and strong | 08:07 |
bart416 | Actually I'll settle on that | 08:10 |
bart416 | Mainly cause I can electroplate it | 08:10 |
bart416 | side bonus is that I could potentially laser cut thin sheets of mylar | 08:12 |
bart416 | never ever try to laser cut plexiglas ;) | 08:12 |
azonenberg | lol | 08:13 |
bart416 | what do you think about using mylar that already comes with a metalic layer? | 08:13 |
Action: azonenberg liek | 08:15 | |
bart416 | azonenberg, side bonus is that the industry actually uses mylar for this :P | 08:24 |
bart416 | My only issue with this is how to do vias | 08:24 |
bart416 | But maybe the fact that there are already metals available might act as a seed for the plating process | 08:25 |
bart416 | also tantalum chloride azonenberg | 08:27 |
bart416 | high purity powder? | 08:27 |
azonenberg | yes | 08:27 |
bart416 | So >99.8%? | 08:27 |
azonenberg | yep | 08:28 |
bart416 | Bit more than 100 euro / 10g | 08:28 |
bart416 | and with bit more I mean like a few cents, lol | 08:28 |
azonenberg | so 4 fl oz @ 16% solids =? | 08:28 |
bart416 | meh, that's up to you :| | 08:28 |
bart416 | catalog doesn't list liquid solution | 08:29 |
azonenberg | ondr if i got ripped off lol | 08:29 |
bart416 | academic pricing though | 08:29 |
bart416 | I doubt you can easily get this | 08:30 |
bart416 | A bit less pure it's 74 euro / 10g | 08:32 |
bart416 | (still 99.9%) | 08:32 |
bart416 | also, if I use regular electroplating I can finally get rid of that damned copper tubing I've been wanting to get rid off for ages | 08:57 |
azonenberg | ll | 09:00 |
bart416 | azonenberg, I think I found something suitable to power a portable railgun cheaply http://be.farnell.com/epcos/b41231a9568m000/capacitor-snap-in-100v-5600uf/dp/1839296 | 11:21 |
bart416 | I just did something scary | 11:52 |
bart416 | Mathz! | 11:52 |
bart416 | with 50 of those capacitors I should be able to speed up a bullet sized projectile to speeds in excess of a hunting rifle | 11:53 |
bart416 | total weight would be about 4kg | 11:53 |
bart416 | (this is assuming a gross lack of efficiency) | 11:53 |
berndj | bart416, i always thought you want to drive railguns with *thousands* of volts just to get over the inductance | 13:23 |
bart416 | berndj, depends on the design really | 13:26 |
berndj | and your level of ambition! | 13:28 |
bart416 | That too | 13:30 |
bart416 | lol | 13:30 |
bart416 | Nah, but the induction of a railgun isn't nearly as bad as you think | 13:30 |
berndj | oh? ok | 13:30 |
berndj | maybe it's more applicable when you're building one you hear about on the news | 13:30 |
bart416 | at least, haven't really had any trouble with that before | 13:30 |
berndj | as in, a very big one | 13:30 |
bart416 | Yeah, that's probably going to be bad | 13:30 |
berndj | i was doing some calcs for a spot welder the other day, that's also a bit depressing | 13:31 |
berndj | you need either a huge transformer or loads of copper | 13:31 |
bart416 | Yeah, and cooling is pretty nasty as well | 13:32 |
berndj | is it? i assumed you could manage that with a low duty cycle | 13:32 |
berndj | since the xformer windings are your first heat sink! | 13:32 |
bart416 | well yeah, I meant of the capacitor bank :P | 13:33 |
bart416 | We've tried to build some rapid fire coilguns at college | 13:33 |
bart416 | and the main point of failure is always the capacitor self destructing due to heat | 13:34 |
berndj | i was just gonna cheat and do mains -> bridge -> igbt crowbar as the "switch" | 13:34 |
berndj | self destructing due to one shot or a duty cycle issue? | 13:34 |
bart416 | well yeah, you're pretty much short circuiting a lot of them close to each other through a rail of copper | 13:39 |
bart416 | what do you expect to happen? :P | 13:39 |
berndj | to warm up, of course, but i've always assumed that a single discharge isn't enough to kill it? | 13:41 |
bart416 | with cheap chinese capacitors it is | 13:44 |
bart416 | Or it won't be able to build up enough charge until its cooled down again | 13:44 |
--- Mon Aug 22 2011 | 00:00 |
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