#homecmos IRC log for Thursday, 2011-09-22

swkhanazonenberg_work: that sounds good. i'm not sure were i can pick them up without alerting other group mates to what i'm doing00:37
swkhani should specify one thing. the furnace usually grows some iii-v semiconductor nanowires00:38
swkhanand the surrounding quartz will need to be cleaned. do you mind if i keep some of the pieces of silicon? like take a wafer and cut it into a bunch of pieces and try to grow the thermal oxide on some for you + send them to you and then keep some for myself so it looks like i'm doing something with it too?00:39
azonenbergJust got back from a meeting of the Capital District Microscopy and Microanalysis Society  (http://cdmms.org/)01:06
azonenbergI highly recommend similar groups if you can find any locally01:06
azonenbergthe lecture today was on microscopy of semiconductors, by a FA engineer at IBM01:07
kristianpaulcdmms know about your current work about homecmos?02:40
azonenbergkristianpaul: A few of the members do03:06
azonenbergi havent presented or anything03:06
azonenbergBut i've asked around for advice on sample prep etc03:09
azonenbergI actually just joined today03:09
azonenbergI know several of the members and wnated to join before but coudlnt make the last meeting03:09
azonenbergits usually every couple of months (3-5 times a year)03:10
azonenbergThey seem to be mostly focused on the various forms of electron microscopy but there is definitely interest in light microscopy as well as general sample prep techniques etc03:11
gkwhcHi, I'm new to semiconductor design & fabrication. I'd like to know if it will be hard to design/fabricate a simple logic/counter chip that runs on 0.005uA? Would this be a design problem or a fabrication problem, or both?04:55
azonenberggkwhc: Depends on what fab you're using, to start04:58
azonenbergThis channel is a little less about chip design (for now, at least) and more on building a working fab from scratch04:59
azonenbergif you're using a "real" process in a "proper" lab it's a lot more doable04:59
azonenberg5 nA is low, but for only a few gates on a low-leakage process tech it should be possible04:59
azonenbergOn 20 micron living room CMOS, i'd say most likely not04:59
azonenbergI'm focusing on MEMS right now but in a year or so i'll probably have made a working chip with a couple of gates on it (most likely a 74HC04 or similar in a 14-ball CSP BGA)05:01
azonenbergas in power, ground, six in, six out05:02
azonenbergIn terms of "a simple logic chip"05:02
azonenbergwhat are you starting from05:03
azonenbergpre-existing cell library, just arranging gates?05:03
azonenbergdrawing each transistor yourself?05:03
gkwhcazonenberg: I might be drawing each transistor for a greater learning curve05:12
gkwhci know a university that has proper equipments, but I am not sure if the 5nA is achieved through proper design or proper fabrication?05:12
azonenberggkwhc: Both05:17
azonenbergDo they have a course in vlsi design?05:19
azonenbergAnd/or fab techniques?05:19
gkwhcno, unfortunately05:20
azonenbergBut you say they have fab equipment?05:21
gkwhcwell, I am an undergraduate student. most people who operate the equipments are graduate students who have had proper training/knowledge of the manufacturing process05:22
azonenbergOh, i see05:23
azonenbergWell, you can always jump ahead in the theory05:23
azonenbergstart learning layout yourself05:24
azonenbergthere are a bunch of free tools for design, i linked to several on the project wiki05:24
gkwhcyes! i downloaded several of them05:25
azonenbergIf you hang out here we'll gladly discuss layout issues etc05:25
gkwhccan you suggest any getting-started ebooks/guides?05:25
azonenbergI'm a bit busy right now as i have homework due tomorrow morning05:25
azonenbergand hmm05:25
gkwhcah i see05:25
azonenbergwikibooks has a nice one on microfab but thats mostly fab processes05:25
azonenbergand less on the design05:25
azonenbergIt depends also on what you want05:26
azonenbergFor example, B0101 is interested in Josephson junctions05:26
azonenbergI'm doing MEMS but want to try CMOS at some point05:26
azonenbergYou want to do digital logic but are you more interested in MOS, bipolar, or not sure yet?05:27
gkwhcI am not quite sure yet - the only constraint is very low current consumption :)05:27
azonenbergWhat's your use case?05:27
gkwhcLearning-by-doing a watch/clock logic, like how the industry does it.05:29
gkwhcI mean, using a MCU is overkill05:29
azonenbergWell, there are a couple of things to do05:29
azonenbergThe first is to prototype your design in an FPGA or (better) a CPLD, using as few gates as possible05:30
azonenbergAt some point in the future you can then turn that into a netlist suitable for fab05:30
gkwhcI see05:30
gkwhcand then I will need to use the EDA software like Alliance or Magic to create the layout?05:31
gkwhcthanks :)05:40
azonenbergAnd then as for fab, well, there are a couple routes to go05:40
azonenbergSend it out to a commercial shop like MOSIS (expensive, doesn't teach you much, but will give you the best chance of working)05:41
azonenbergBuild it yourself in a proper lab (less expensive, you learn a lot, but you might screw it up)05:41
azonenbergand hack it up in a home lab05:41
azonenbergCheaper to operate (though equipment costs may be high as you get started), extremely educational05:41
gkwhcI was quite surprised to hear that  ahome lab is possible!05:41
azonenbergPossible, yes05:42
azonenbergSuccessful so far, no05:42
azonenbergThat's my best work to date05:42
azonenbergimaged in a SEM on campus05:42
azonenberg20 micron half-pitch copper wires on a silicon substrate05:42
gkwhcwow that is neat!05:42
azonenbergThe wiring turned out pretty well05:43
azonenbergThis is a long shot of the pattern http://colossus.cs.rpi.edu/~azonenberg/images/homecmos/2011-09-20/die_i4_002.jpg05:43
azonenbergand http://colossus.cs.rpi.edu/~azonenberg/images/homecmos/2011-09-20/die_i4_001.jpg is the whole chip05:43
azonenbergthe entire chip is around 2x3mm05:43
azonenbergof which the patterned area is around 0.5mm diameter05:43
azonenbergI am planning to do both etching of the silicon itself (for making MEMS devices) and doping (for transistors)05:44
azonenbergBut have not yet gotten that far05:44
azonenbergPhotoresist coating and patterning is being done at home, as is etching05:44
azonenbergI did the copper deposition on campus as well, i plan on building a vacuum coating rig05:45
azonenbergat home05:45
azonenbergBut the chamber hasnt arrived yet (ordered)05:45
azonenbergnice little 10x15 inch glass bell jar05:45
gkwhcmay I ask why do it at home if its possible on campus?05:45
azonenbergAnd i have to use it for somebody else's research project first05:45
azonenbergfirst, the on campus labs cost money to operate05:45
azonenbergeither out of my pocket or a grant05:45
azonenbergMine is relatively cheap to run05:46
azonenbergOnce the tooling is set up, that is05:46
azonenbergAnd the processes are potentially scalable to a hgih school chem lab etc05:46
azonenbergWhich is the ultimate goal05:46
azonenbergbring fab to the masses as much as feasible05:46
gkwhcoh yeah, I just found out that it costs money to go into the lab today05:46
gkwhcthats a good idea :)05:47
azonenberga HS science teacher should be able to build a comb drive in the classroom05:47
azonenbergThe second is that by doing all of the process development i have the fun of homebrewing it :p05:47
gkwhchaha definitely!05:47
azonenberghttp://colossus.cs.rpi.edu/~azonenberg/images/homecmos/2011-09-20/overview_001.jpg is an overview of all of the chips i was imaging in that session05:47
azonenbergNotice the patterned areas on the one at right are ~4x smaller05:48
azonenbergand there are a couple of them05:48
azonenbergThat was an experimental run of the 5 micron process05:48
azonenbergWhich was unsuccessful05:48
gkwhcfrom home?05:48
azonenbergThe pictures were taken in the older of the mat sci department's two SEMs05:48
azonenbergThe copper was deposited in the mat sci lab as well05:49
gkwhci see05:49
azonenbergI did all of the lithograpy (including photoresist coating, exposure, developing, and etching) at home05:49
gkwhcits rather hard for me to grasp how such is possible! since the patterns are layed on such a small scale05:50
azonenberggkwhc: My lab notes are in the google code repository under lithography_tests/labnotes/05:51
azonenbergThey go into pretty good detail on fab processes05:51
azonenbergtldr: print mask from layout tool on laser printer05:51
azonenbergoverhead transparency film05:51
azonenberg600 DPI05:51
azonenberg200 micron line width05:52
azonenberg(its actually not exactly 200, it's five pixels / 600 pixels per inch)05:52
azonenbergAnything <5 pix you run the risk of lines not being sharply defined on the printer05:52
azonenbergThen i stick the mask on top of the camera port of my microscope05:53
azonenbergand shine a halogen lamp through it05:53
azonenbergthe objective reduces the mask image appropriately (I usually use a 10x objective)05:53
azonenbergWhich gives me 20um lines05:53
azonenbergI tried the 40x objective for 5um lines but have so far had trouble getting consistent results05:53
azonenbergi always under/overexpose05:53
azonenbergthe window for proper exposure time is narrower than on the 10x since features are smaller05:54
azonenbergless margin for error05:54
azonenbergI'm confident i'll get there eventually05:54
azonenbergJust not there yet05:54
azonenbergFor such a hacked process, not in a cleanroom or anything close to it, i think its turning out decently05:55
azonenbergThe current roadmap calls for a working MEMS comb drive by end of this calendar year05:55
azonenbergand a working CMOS IC by the end of next year05:55
gkwhcthen its coming pretty soon!05:56
azonenbergThis is a spare-time project, i'm a PhD student (in computer science) who has classes to take, research to do, exams to grade, etc05:56
azonenbergSo work that would take a week or two of lab time, if that, takes months of calendar time05:56
azonenbergi try to get at least one or two nights a week of work in my lab05:56
azonenbergand then every month or two i do an imaging or evaporation run in the mat sci lab05:57
gkwhcah thats good scheduling05:57
azonenbergIt's rather rough05:57
azonenbergYou can see exact dates in the lab notes05:57
azonenbergWhcih reminds me i never wrote a lab report from my last SEM session05:58
gkwhcby the way, Ive been trying to find your lab notes but  couldnt find them..are they under http://code.google.com/p/homecmos/ ?05:58
azonenberggotta do that soon05:58
gkwhcazonenberg: Thank you soo much for the help & advices! Im gonna catch up on some sleep - its 2AM here!06:01
azonenbergPhotos from many of the lab sessions are at http://colossus.cs.rpi.edu/~azonenberg/images/homecmos/06:01
azonenbergI havent uploaded all of them yet unfortunately06:01
azonenbergand it is here too06:01
azonenbergwhere you at?06:01
gkwhcVirginia Tech :)06:02
azonenbergRPI here06:02
azonenbergi'm off to finish two more hw problems before class tomorrrow06:03
gkwhcbye! and thanks again!06:03
Action: azonenberg AFKs06:03
azonenberg_workWell... looks like I may not be getting much lab work done for a few days - homework to do, then busy all weekend16:26
azonenberg_workBut I want to do some KOH tests soon16:26
azonenberg_workhopefully sunday evening or monday16:26
azonenberg_workOr, if i'm lucky, tonight16:26
bart416azonenberg_work, we had a funny discussion today with some people at university16:41
bart416Writing a website in VHDL :P16:41
bart416Obviously integrated the web server into the fpga with only an external IC for the hardware layer of the network16:41
azonenberg_workbart416: lol16:50
azonenberg_workWould that be done with a softcore cpu (easy) or just raw tcp/ip/ethernet?16:50
azonenberg_workWould be fun to say the least16:50
azonenberg_workthe lowest i've gotten so far was a webserver in x86-64 asm (no libc, just linux syscalls)16:50
azonenberg_workbut i used the linux tcp/ip stack16:50
lekernelpeople did that already16:51
lekernelthere's a youtube video of it16:51
lekernelit's a pretty stupid thing to do however16:51
azonenberg_workMore of a stunt than useful16:52
bart416raw tcp/ip ofc17:17
bart416No OS17:17
azonenberg_worklol yeah17:17
bart416You have the hardware layer provided by the IC17:18
bart416But that's it17:18
bart416lekernel, it's still an interesting exercise17:18
bart416Especially if you would write a cross compiler17:18
bart416Say convert PHP to VHDL and then send it to whatever FPGA that you have17:18
azonenberg_workOh, lol17:19
azonenberg_workserver side scripting, not just static content?17:19
azonenberg_workbetter yet, no cross compiler17:19
azonenberg_workactually write HDL for the script :P17:19
bart416That'd be hard17:20
bart416But if you'd convert PHP it would actually be useful17:20
azonenberg_workreg[511:0] hdrs;17:20
bart416meh :P17:20
azonenberg_workinitial begin \ hdrs = "HTTP/1.1 200 OK\r\nX-Server: XC3S200A\r\n\r\n";17:21
bart416The latest in Cloud-HDL-Computing!17:22
bart416We could start a new cloud hype with this lol17:22
azonenberg_workOne thing's for sure, it would be fast17:22
azonenberg_workimagine having fifty webserver modules muxed into a giant output FIFO and an ethernet PHY17:22
bart416yeah, if you think about it, for a system that doesn't change often it'd actually be pretty effective17:22
azonenberg_workstore static html in block ram17:22
azonenberg_workyou could probably push Gbps of data without even trying too hard17:23
azonenberg_workthe NIC would be the bottleneck17:23
azonenberg_workhave preformed IP packets that you just patch up sequence numbers etc :p17:23
bart416Meh, 10 Gbps should be enough :P17:23
azonenberg_workXC6SLX75T plus GBIC slot?17:24
azonenberg_workOr ditch the SFP and just have a raw fiber connector17:25
bart416What we're actually considering doing is building a complete processor on transistor level (16 bit) without any help from software17:26
azonenberg_workwho's "we"17:26
bart416EE students17:26
azonenberg_workand you want to do it by hand, like the 4004 was?17:26
azonenberg_workor using cad but no synthesis?17:26
bart416by hand17:26
azonenberg_worki.e draw out cells, then place and route by hand?17:26
bart416No software17:26
azonenberg_workTHAT is just crazy lol17:26
bart416No PCBs though17:26
azonenberg_worki could understand doing it without synthesis17:26
bart416Just wiring17:26
azonenberg_worki thought you meant vlsi lol17:27
bart416Modules can be PCBs17:27
bart416You nuts?17:27
bart416We're with 7 people17:27
bart416It'd take us months17:27
azonenberg_workNot really17:27
azonenberg_workDo the design on paper, maybe start with HDL and hand synthesize17:28
bart416Keep in mind we also have classes17:28
azonenberg_workthen design a bunch of logic cells17:28
bart416I meant VLSI17:28
azonenberg_workcut and paste to form a reasonable (though perhaps not optimal) placement17:28
lekernelyou'd need inane amounts of transistors17:28
azonenberg_workdraw out routing17:28
lekernel4 bits could be feasible, but 16 ...17:28
azonenberg_workYou dont draw each transsitor by hand17:28
bart416That'd take months in the bit of time we have though azonenberg17:28
lekernelyou'd need a cabinet17:28
bart416Yes, we will need a cabinet17:28
bart416that's the point17:28
bart416We want to prove a professor wrong17:29
azonenberg_workWhy not use 7400 chips17:29
azonenberg_work... oh17:29
azonenberg_workThats a worthy excuse17:29
azonenberg_worki've done crazy things to prove faculty wrong17:29
bart416Cause with 7400 chips it's just stupid and anybody can do it17:29
bart416With 7400 series it takes almost no skill to make a small functional CPU17:29
azonenberg_workLike doing full functional programming (including passing a function as an argument to another function) in C17:29
azonenberg_workwhen he said it wasnt possible to do functional programming17:30
azonenberg_workOr writing an entire file system emulator (including the command line argument parsing) in x86 assembly17:30
azonenberg_work3000 lines in two weeks, including other homework17:30
azonenberg_workOr implementing an algorithm for solving the Towers of Hanoi puzzle (algorithm given to us) in x86 (which was the assignment)17:30
azonenberg_workBut doing it in 19 instructions17:31
azonenberg_workwhen he said <20 was impossible17:31
bart416We had a fun one17:31
bart416Random dice throw generator17:31
bart416But only 2 d latch flip flops17:31
bart416Not as easy as it looks17:31
bart416(and it has to be able to hold a *random* value and be able to reset)17:32
bart416Using only digital logic17:32
bart416And you're not allowed to make new flip flops17:32
azonenberg_workRandom number generator17:33
azonenberg_workUsing two dff17:33
bart416The random generator is easy17:33
bart416Just use the system clock17:33
bart416that was available17:33
azonenberg_workOk, if it has one17:33
azonenberg_workBut two dff17:33
azonenberg_workfor six values17:33
azonenberg_workyou only have two bits?17:33
bart416It's possible weirdly enough17:33
azonenberg_workOh, i believe you17:34
azonenberg_worki'm curious now17:34
azonenberg_workwas it a dynamic state?17:34
bart416I never found it myself either17:34
azonenberg_workthree bits, two in flipflops and one in motion?17:34
bart416I think he used the clock and somehow locked it as the final bit17:34
azonenberg_worklike a circular shift register17:34
azonenberg_workcrossed with a delay line17:34
azonenberg_workJust caught my pipelining bug17:40
azonenberg_workThe latest one, at least17:40
azonenberg_workSubject: test program busy-waits on UART data ready, then reads byte, adds one, echoes out uart17:40
azonenberg_workrepeats forever17:40
azonenberg_workSymptom: after processing 16 bytes (depth of the FIFO) it goes nuts and starts echoing the same value over and over17:41
azonenberg_workEventually traced it to a bug where issuing a conditional the clock after a memory read would give an incorrect value if you used the result of the memory read17:41
berndjbart416, cutting mylar tape?17:54
bart416What about it berndj?17:54
berndjazonenberg_work, i've actually got a pipe dream of a fully trustable computer that's consist of *only* 74*00's17:55
berndjmaybe not quite as trustable as relays as switching elements17:55
bart416Prepare for a very expensive project berndj :P17:55
mrdata"fully trustable"!17:55
berndjyes, a bit like "a little bit pregnant" :-/17:57
berndjbart416, i was referring to your no-software layout17:57
bart416How does that relate to mylar tape?17:58
Action: azonenberg_work needs to get some kapton tape17:58
bart416We have enough breadboards at college to model an entire x86 cpu on them I think17:58
azonenberg_workbart416: lol17:59
azonenberg_workmaybe an 808617:59
azonenberg_worknot an i7 :p17:59
berndjbart416, i thought that's how they did 4004-era chips17:59
bart416azonenberg, uhm the professor has a few cabinets in his office filled with boxes with nothing but breadboards...17:59
berndjand 8086 was about 35000 transistors IIRC, is that an "insane" number?17:59
azonenberg_workberndj: if you are going to do that18:00
bart41635000, meh18:00
azonenberg_workDesign custom PCBs for each 7400 chip18:00
azonenberg_workHave a few dozen of each sent out18:00
azonenberg_workand load them up with SOT23 mosfets18:00
berndjazonenberg_work, yes, i was going to do it like that, have an "adder" board that gets reused a few times etc18:00
mrdatawhat would a MEMS pressure sensor look like?18:00
bart416I'd guess a sort of membrane ish structure18:01
berndjoh, but i'd make it a (super slow) bit slice processor, taking 16 cycles to do a 16-bit ALU op18:01
azonenberg_workmrdata: Thats like saying what would a car look like18:01
azonenberg_workIt deends completely on the design18:01
azonenberg_workparallel membranes is one option18:01
bart416and using the capacity between the membranes as reference18:01
azonenberg_workThat would be my first thought18:01
bart416Looks the easiest way to go about it18:01
azonenberg_worki'd do it from two bonded wafers18:01
bart416But there might also be materials that change conductivity based on pressure I'd guess18:02
berndjif you used mosfets i guess you could have PCBs with nothing but transistors on them, right?18:02
berndjno resistors for bias etc18:02
azonenberg_workberndj: yes18:02
azonenberg_workDo CMOS18:02
azonenberg_worksot23 fets18:02
berndjhow many SOT23 could you fit on a board?  on the order of 1000?18:02
azonenberg_workberndj: i was thinking making them 4000 series actually18:02
Action: mrdata likes the parallel membranes; how hard would that be to make?18:03
azonenberg_worka wide (0.6 inch) dip14 etc18:03
azonenberg_workbut if you want to do more complex modules thats fine18:03
azonenberg_workmrdata: Hmm18:03
azonenberg_workLet's see, we need a framework18:03
azonenberg_worktwo parallel membranes with an air gap between them18:03
azonenberg_workBoth conductive, and insulated from their surroundings18:03
berndjazonenberg_work, ooh, you mean making little modules out of 7400-only, that emulate the other common logic functions?18:03
azonenberg_workAnd not touching18:03
azonenberg_workberndj: i was saying to make a DIP14 sized PCB with a few dozen sot23 (wide dip)18:04
berndjoh, lol18:04
azonenberg_workfor a 4x 2NAND etc18:04
mrdatahow small could it be made? what equipment would i want, to fab these?18:04
bart416mrdata, you could do this fairly large scale actually18:05
azonenberg_workmrdata: Well, let's see18:05
berndjhmm, to make a 7404 you'd need 12 transistors; can you fit them all?18:05
azonenberg_workBonded wafers is something i havent looked into18:05
bart416azonenberg, I'd do this large scale18:05
bart416Take mylar18:05
bart416Space it slightly18:05
bart416so you have maybe a mm in between18:05
azonenberg_workbart416: i am thinking mems:p18:05
bart416yeah, but if you have to make it at home18:05
azonenberg_workActually a pressure sensor would be a cool project once i do the comb drive18:06
azonenberg_worklet me see, i read an interesting paper on making membranes by KOH etch of silicon18:06
azonenberg_workwith heavy boron doping as an etch-stop layer18:07
azonenberg_workI have a slightly different idea18:07
azonenberg_workBottom wafer is the carrier18:07
azonenberg_workthe die has a ground terminal on it18:07
azonenberg_workand a big conductive disk18:08
Action: mrdata is thinking about the size of an LED18:08
azonenberg_workmrdata: yeah, thats doable18:08
azonenberg_workSo i was thinking of having a copper membrane18:08
azonenberg_workDeposited over silicon18:08
azonenberg_workthen you etch the silicon out from under it18:08
azonenberg_workleaving it around the edges to support the membrane18:08
azonenberg_workyou then place this framed membrane over another, stationary, conductor18:09
azonenberg_workapply pressure to the hole the membrane is in18:10
azonenberg_workand it will bow down18:10
azonenberg_workreducing plate separation18:10
mrdataand how would you etch the silicon?18:11
azonenberg_workKOH, thats easy18:11
azonenberg_workthe harder part is masking it18:11
azonenberg_workAnyway so the thinking is18:11
azonenberg_workBottom wafer, cover in copper18:11
azonenberg_workattach a ground terminal to the copper18:11
azonenberg_workTop die, cover top side in copper18:12
azonenberg_workflop over, put etch mask on bottom (material tbd)18:12
azonenberg_workput circular hole in the middle of this mask18:12
azonenberg_workoh, when you cover the top die in copper18:12
azonenberg_workdo it over thermal oxide18:12
azonenberg_workSo you have a circular hole in the mask18:12
azonenberg_workthen you KOH through the top wafer from bottom up18:12
azonenberg_workThis leaves us a big silicon die18:13
azonenberg_workwith copper over the entire top surface18:13
azonenberg_workinsulated from the silicon18:13
azonenberg_workby an oxide layer18:13
azonenberg_workthe center of the die is just a copper film with nothing under it18:13
azonenberg_workthats our sensing element18:13
azonenberg_workThen we bond this to the original bottom die18:14
azonenberg_workhook a wire up to each copper laye18:14
azonenberg_workBonding the dies together is a TBD problem18:14
azonenberg_workmake sense?18:14
azonenberg_workthe two unsolved problems in that process as far as i'm concerned are how to mask the KOH etch18:15
azonenberg_workand how to attach the wafers to each other18:15
azonenberg_workthe second i havent looked at much18:15
azonenberg_workthe first is something i am actively exploring18:15
mrdatai've etched aluminum with NaOH18:16
mrdatabut havent etched any silicon18:16
azonenberg_workmrdata: NaOH or KOH is simple enough to use, they are very similiar18:16
azonenberg_workThe hard part is masking them18:16
azonenberg_workAs they eat photoresist (among other things)18:17
mrdatasaponification, yeah18:17
azonenberg_workSo you basically need a metal or oxide hardmask18:18
azonenberg_workand they eat SiO2 as well - around 40x slower than Si but its a nontrivial rate18:18
azonenberg_worknormally they use silicon nitride but thats hard for an amateur to make18:19
mrdatado they eat vinyl?18:19
azonenberg_workmrdata: not sue18:20
azonenberg_worknever seen characterizatinos of that reaction18:20
berndjdo pretty much all SOT23's have the same pinout?18:21
Action: mrdata wouldnt assume so18:22
berndjor rather, is it less of a mess than through-hole devices18:22
azonenberg_workberndj: my guess is, no18:25
mrdatahmm... http://memscyclopedia.org/su8.html18:31
azonenberg_workmrdata: su-8 is fun stuff but its almost impossible to remove once patterned18:31
mrdataoh really18:32
azonenberg_workuseful more as a directly photosensitive structural material than a photoresist18:32
azonenberg_workits epoxy based18:32
azonenberg_workyou spin coat, expose, develop18:32
azonenberg_workthen i think anything that was hit by UV is now crosslinked18:32
azonenberg_workand super strong18:32
azonenberg_workanything that wasnt gets washed off18:32
berndjhmm, 2 SOT23s right next to each other already occupy 1/4 of a 300mil-wide DIP14 footprint :(18:36
azonenberg_workberndj: use a 618:36
azonenberg_workits gonna be big18:36
azonenberg_workalso, compnents on both sides18:36
berndjhmm, i didn't think of that18:36
azonenberg_worklook into transistor arrays18:37
azonenberg_worki think you can get like a TSSOP with 12 pins and four transistors18:37
azonenberg_workthey're technically ics, but might be ok to use since there is no connectivity on the die18:37
bart416SU-8 is also extremely expensive18:39
azonenberg_workbart416: how much18:39
azonenberg_worknever looked into buying it18:39
bart416Don't remember exact pricing18:40
bart416But remember, I looked at it for my home multi layer pcb project18:40
azonenberg_workbut is it more expensive than other semiconductor grade chemicals?18:40
bart416It's far more expensive than regular resist you'd use for semiconductor grade18:41
bart416Even when ordered with educational discount through the university18:41
bart416Chemical structure is fairly complex18:43
azonenberg_workIs the epoxy itself photosensitive or is it mixed with an initiator of some sort?18:44
bart416It's photoresist18:44
bart416check the pdf I linked18:45
bart416It mentions A complete SU-8 process consists of: spin coat, soft bake, exposure, post expose bake18:45
bart416and development18:45
azonenberg_worki know that much18:45
azonenberg_workwhat i meant was, chemically18:45
azonenberg_workis it one substance or two18:45
mrdataif you skip some of those steps, maybe it isnt permanent?18:46
azonenberg_workfor example DNQ-novolac resists are DNQ (photosensitive) + novolac (resin)18:46
azonenberg_workmrdata: no, the exposure makesi t permanent18:46
azonenberg_workPEB is just to smooth edges18:46
bart416Good question18:47
bart416And it's so complex that I don't even have a clue on how to synthesise it easily at home18:50
azonenberg_worki woudlnt even attempt i18:51
azonenberg_workheck, i wouldnt attempt DNQ personally18:51
azonenberg_workSome materials it just isnt feasible to homebrew18:51
bart416DNQ I'd be willing to try18:52
mrdataif i cant homebrew, then my post-apocalyptic MEMS lab will be ruined18:53
azonenberg_workmrdata: no, you cant homebrew SU818:55
azonenberg_workthat doesnt mean you cant do other stuf18:55
azonenberg_worki'm already doing alternate materials as i cant feasibly do CVD or RIE18:55
mrdatathen i'll have to take up bread baking18:55
bart416SU8 is complicated18:55
azonenberg_workmrdata: you could also become a nomadic warlord18:55
bart416IBM didn't even mention the composition in the patent18:55
bart416grrr >_>18:55
mrdatahmm... perhaps18:56
azonenberg_workpatent expired yet?18:56
bart416how long do US patents last?18:56
azonenberg_work17 years last time i checked18:56
mrdatadidn't even mention the composition??!? failure to disclose that would tend to invalidate the patent18:56
bart416It was issued Nov 21, 198918:56
azonenberg_workmrdata: actually, the patent might be more generic18:56
azonenberg_workand k, it should be expired now18:56
azonenberg_workSo thats a non-issue18:57
azonenberg_workThe composition is most likely a trade scret18:57
mrdataoh, as in, it's a base patent?18:57
azonenberg_workthat nobody has bothered to reverse engineer18:57
mrdatalet's reverse engineer a better one, then18:57
azonenberg_workOr that somebody has, but not published it18:57
bart416They mention some names18:57
azonenberg_workOr has, published it, and we havent found it :p18:57
bart416But nothing exact18:57
Action: mrdata decides to start with vinyl18:58
azonenberg_workAlternative solutions are a definite possibility18:58
bart416Homebrewing SU8 would be a worthwhile project on its own...18:58
azonenberg_worklol, yes18:58
berndjmrdata, re post-apocalyptic semi fab, what about bacterial cultures18:59
berndjplace mask, then feed them sunlight and starch / gelatine18:59
azonenberg_workberndj: lol18:59
bart416Mhhh, I wonder if I could get the chemicals they list in the example19:00
berndjsome kind of bacterium that photosynthesizes, of course19:00
mrdataberndj, yes, bacterial cultures19:00
mrdatathat's why bread19:00
mrdatasourdough, actually19:00
berndjlol, i just took a loaf of sourdough bread out the oven19:00
berndjbut how do you selectively kill it?  will UV-A do?19:01
berndjUV-B and C might be harder to do optics for19:01
mrdataseems probable that UV-A could kill it, yes19:01
mrdatabut KOH would also etch it, likely19:01
azonenberg_workberndj: I've done contact litho with UV-C19:02
azonenberg_workunshielded mercury vapor germicidal tubes19:02
berndj*post-apocalyptic optics19:02
azonenberg_workberndj: Mercury, vacuum, glass tube19:02
berndjhmm, the UV-C source i can still imagine, but what is the mask made of?19:03
azonenberg_workpost-apocalyptic? Harder19:03
azonenberg_worki used a laser printer + transparency film19:03
azonenberg_workhobbyist friendly but requires some infrastructure19:03
berndjsame stuff the bulb envelope is made of, i guess19:03
azonenberg_workYou could do chrome on glass, but have to pattern that somehow19:04
berndjyes, with a sharp-pointed rock19:04
azonenberg_workberndj: lol19:04
berndjmight want to reduce the mask though, which would need optics19:04
azonenberg_workI think you should get basic chemistry and machining working first19:04
bart416basic chemistry is hard without basic machining19:05
bart416You'd need to be able to blow your own glass instruments and grind your lenses19:05
berndjbut i think getting up to manually operated machine tools is a hard, but solved problem19:05
mrdatapost-apocalyptic optics could fall back to galileo19:05
berndjwith things like the gingery lathe and opensourceecology, you've got the metal supply and tool design covered19:06
berndjsoda-lime glass is probably *just* doable19:06
mrdatarenaissance glass making19:06
berndjbut something that works well in UV?  much harder19:06
bart416You need a blast furnace to make glass19:07
berndjyou need high-purity silica to start with19:07
mrdatain Venice. that's where they learned it19:07
berndjnot even - a blast furnace is for steel19:07
mrdata1000C should do19:07
mrdatafor a lot of stuff19:07
mrdatamaybe 1500C19:07
azonenberg_workConveniently 1200ish is all you need for semiconductor fab19:07
berndjyou'd need 1500C for steel19:07
azonenberg_workOnce you have the wafers, that is19:07
azonenberg_workCZ process would need more19:08
berndjdo you actually have to *melt* silicon to grow crystals?  or can you do it like with metals, and let the crystals grow in solid phase19:08
bart416berndj, to get high quality you need to go higher temperature than just melting19:09
azonenberg_workberndj: for large crystals you need full melt19:09
azonenberg_workeven for float zone19:09
berndjoh, but reflective optics is both UV-compatible and post-apocalypse-accessible19:09
bart416+ higher temperature allows you to get the impurities out of the material easier19:09
berndjhigher temperature almost always means faster19:10
bart416+ a blast furnace is easy to make anyway19:11
bart416And fairly easy to operate19:11
bart416It's pretty much fool proof19:11
berndjuhm, "blast furnace" has a specific technical meaning i don't think you mean to imply?19:11
berndja *blast* furnace is pretty far along in tech, afaict19:11
berndjbut if you mean just reaching the temperatures accessible in those, then yes19:12
bart416You are thinking too high tech19:13
bart416The early blast furnaces were easy in construction19:13
bart416And use19:13
berndjbut you don't need the "blast" part to melt sand anyway19:15
bart416Good luck melting sand with just coal19:15
bart416It sounds easy19:16
berndjoh, sorry, you're right; i was thinking of the bessemer process19:16
bart416Actually doing it is different :P19:16
bart416blast furnaces have been around for over two millenia :P19:17
bart416But with the extra oxygen flow you can get a serious amount of heat out of the coal easily19:18
mrdatacoal is good, that way19:18
bart416Is anything in that GVCS thing actually finished lol?19:21
berndjsome prototypes19:22
berndjbut there's a whoooole lot to do in not much time at all19:22
bart416If they'd be smart they'd throw a contest for engineering students19:23
bart416That would get a lot of designs done19:23
bart416Additionally I see a serious issue with their list19:25
bart416They don't have a metal extruder...19:26
bart416Good luck making pipes without that :P19:26
berndjbent and welded19:26
bart416That's impossible for many shapes19:26
bart416And gives horrible properties from a fluid dynamic point19:27
berndjhmm, maybe, but maybe round pipes are all the "pipe" the GVCS need?19:27
berndjfluid dynamics? what do you mean?19:27
bart416Weld joins created turbulence19:27
berndji doubt the GVCS needs hydraulics where such turbulence is an issue?19:28
berndjalso, don't weld like crap then :-P19:28
bart416Not to mention weld joins are horrible at containing pressure19:28
berndjyeah, there's that19:28
berndjand are hard to make gas-tight19:28
bart416Useless for high pressure hydraulics19:29
berndjwhich they *are* using19:29
azonenberg_workbart416: well done TiG welds are good with negative pressure19:29
bart416azonenberg, there you mention something important19:29
azonenberg_workin terms of vacuum gear etc19:29
bart416WEll done :P19:29
azonenberg_workBut these are, like, really well done ones19:29
azonenberg_worki am not that good, or even close19:29
bart416+ negative pressure is quite different19:29
bart416that'll try to compress the joint19:30
azonenberg_workin fact i dont even know TiG lol19:30
bart416positive pressure will try to pull it appart19:30
berndjazonenberg_work, auto-darkening filters really do make a big difference eh19:30
azonenberg_workMiG is on the get-good-at list first19:30
azonenberg_workberndj: yeah19:30
azonenberg_workgoing down to the shop to practice again tonight after office hours, actually19:30
bart416azonenberg, if you're ever in the area I think I need to teach you how to weld properly :P19:30
berndji tried mine the other day19:30
berndjby comparison, the fixed-shade helmet is like working blind19:30
azonenberg_workbart416: define"the area" :p19:31
bart416Belgium lol19:31
azonenberg_workberndj: agreed, i used a fixed shade 10 (i think) in the engineering processes class when i first took it19:31
azonenberg_workbart416: no plans to be in europe any time soon19:31
azonenberg_workberndj: and yeahm being totally unable to see until you strike the arc? Not my idea of a good working environment19:32
bart416could be worse :P19:33
azonenberg_workbart416: have you ever tried welding with a fixed shade helmet? :p19:34
azonenberg_workKeep it that way :p19:34
azonenberg_workThey'll protect you but are useless for actually getting work done19:34
bart416I have welded in a fire proximity suit though19:34
bart416The metalised foil makes is less than interesting lol19:35
azonenberg_workso... you were welding in extreme ambient heat?19:35
azonenberg_worklike inside a furnace or something?19:35
bart416Close to one19:35
azonenberg_workoh fun19:36
azonenberg_workArc, i assume?19:36
bart416Acetylene is too dangerous in high temperature environments19:36
azonenberg_worki woudl not want to bring acetylene anywhere near an environemnt that needed a fire suit19:36
bart416If you're standing 3m from molten metals you need one no matter what >_>19:37
azonenberg_workTrue that19:37
bart416somebody forgot to weld rings onto the metal we had to use so we couldn't lift it into the furnace with the crane19:37
azonenberg_workwait a minute, you were welding lifting attachments onto the furnace charge?19:38
azonenberg_worka few meters from a vat of molten metal?19:38
azonenberg_workThat would explain it19:38
azonenberg_workAny issues with shielding gas?19:38
azonenberg_workinterms of overpressure, spatter damaging the hoses, etc19:38
bart416You can't make the nicest of welds in such environment no19:39
bart416But it just has to hold19:39
azonenberg_workWhat i meant was, the equipment being damaged by ehe environment19:39
bart416No, it are only small spats of metal19:40
azonenberg_workOk, so it wasnt like 800C ambient temp19:40
azonenberg_workin air19:40
azonenberg_workor something crazy like that19:40
berndjthat would be insane19:40
bart416Are you nuts19:40
azonenberg_worksorry, i meant 800F19:40
azonenberg_workwhich is like 300C19:40
berndji think even that is nuts, no?19:41
bart416I wouldn't dare to enter 300°C ambient air, even with a fire proximity suit :|19:41
azonenberg_workThey have proximity suits, but then they have entry suits19:41
azonenberg_workwhich are designed for walking through flames for rescue ops etc19:41
bart416Advised use was up to 85°C19:41
bart416100°C for 5 minutes19:41
berndjwith a pack of ice in your backpack?19:42
azonenberg_workberndj: the entry suits are designed for very brief exposure19:42
azonenberg_workto extremely high temp19:42
berndjno doubt!19:42
azonenberg_worki think they can handle 1000F+ for a minute or so19:42
bart416berndj, the heat can't really go through the clothing19:42
bart416Your own body becomes a problem though19:42
bart416+ it's fairly heavy clothing19:43
berndjoh ok19:43
bart416Can't imagine what a 1000F+ one must weigh19:43
azonenberg_workbart416: those are not meant for extended wear lol19:44
berndjso you stay just as long as it takes for your body to heat your mini environment over what's tolerable19:44
bart416In the environment of a furnace it's tolerable for several hours actually19:44
bart416But you need to drink a lot19:45
bart416And be in a somewhat good physical condition19:45
berndjoh really? wow19:45
azonenberg_workbart416: you mean near a furnace19:45
azonenberg_worknot inside one19:45
bart416Inside, are you nuts?19:45
berndji suppose the fluid intake is a significant heat sink19:45
azonenberg_workI think the entry suits are rated for entry for shorttimes19:45
bart416I doubt even with fire entry suits that you'd survive that19:45
azonenberg_worklet me look one up19:45
azonenberg_workwe're not talking immersion19:46
azonenberg_workin molten metal19:46
azonenberg_workthis is for large ovens etc19:46
berndjimmersion in molten metal like the terminator!19:46
bart416azonenberg, ambient temperature in a furnace to melt iron is fairly high though...19:47
azonenberg_workbart416: i'm not talking thati19:48
azonenberg_worki'm talking like i said 1000C ish19:48
azonenberg_workgtg. class is out - back in a few19:48
azonenberg_workbart416: http://www.newtex.com/extremeprotective/protective_suits/fire_entry_suits/20:01
azonenberg_work3000 series is rated to 1650C20:02
azonenberg_work / 3000F20:02
azonenberg_workfor short duration20:02
azonenberg_workradiant heat20:02
azonenberg_workand ambient temperature of up to 1500F / 815C20:03
bart416What's short duration?20:03
berndjcripes! 1650C!20:13
berndjradiant heat != ambient20:15
berndjit's a bit fuzzy what "radiant heat" is supposed to mean when they use the term20:16
bart416Not really20:20
bart416Black body temperature ;)20:21
berndjwell, how big is the radiator?20:27
berndji'm wearing nothing special, and my clothes can withstand 3000C radiant heat easy peasy!  just switch on a light bulb and see for yourself!20:27
bart416yeah, now try that without a vacuum and a few kg of molten metal ;)20:33
azonenberg_workbart416: in any case its rated to 1500F ambient20:48
azonenberg_workWhich is pretty signiicant20:48
bart416I just wish it'd be acceptable to wear scrubs in public :(21:06
azonenberg_worklol who says it isnt?21:10
bart416I used to wear them when I was on my way home and people look weird at you on the bus and train heh21:10
bart416We all agreed they were far more comfortable than our regular clothes that we wore when we arrived at work21:11
bart416But loads of people put on their regular clothes again lol21:11
bart416Even if they weren't contaminated21:11
bart416Simply to avoid weird faces21:11
Action: bart416 stopped caring after a while though21:16
bart416+ it's not as bad as my girlfriend at the time21:17
bart416She once wore a lab coat on the bus lol21:17
bart416cause she spilled something nasty over her tshirt21:17
azonenberg_workshouldnt you be spiling nasty stuff on the lab coat?21:25
azonenberg_workand not your street clothes?21:25
bart416azonenberg, insane korean girl...21:39
bart416I don't think she ever did anything normal21:40
bart416That includes liking me21:40
bart416If it wasn't for the fact that she moved I think I'd still be together with her at this point heh21:54
bart416It's a small wonder we never got arrested heh21:55
bart416azonenberg_work, I like blowing up things as much as the next guy...22:01
bart416But she...22:01
bart416In the US she'd probably be on every single terrorist watch list by now lol22:01
azonenbergHow do you know she isn't still? :p22:52
bart416Cause she lives in South Korea?22:55
azonenbergBut how do you know she isnt on their watchlists? :P22:55
bart416She's too cute for that22:56
azonenbergToo cute to be on watchlists? Lol22:56
azonenbergKnowing some of the cops here that'd put you higher on the list :p22:56
bart416But seriously, she was the best thing that ever happened to me; and her having to leave was the worst22:57
azonenbergYeah... i know what you mean22:58
azonenbergThe one person i met at school that i was starting to like transferred out like a month or two after we met :p22:59
azonenbergwe saw each other irl... twice? in total22:59
bart416Heh, I knew her since birth though22:59
bart416We grew up together lol22:59
azonenbergoh, that would make it worse23:00
bart416And always had a thing for each other23:00
bart416We were 5 years old and they already said "that's going to become a couple later on"23:00
bart416Two over achievers that know each other from young age = not the safest thing23:02
azonenbergoh boy23:02
--- Fri Sep 23 201100:00

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