#qi-hardware IRC log for Monday, 2012-10-22

xiangfu(find a more precise fab) yes. totally agree. for fast, I just find random one in taobao. then they send back the PCBs in 3 days.09:03
xiangfu(a U-shaped ground trace) yes. I also notice that after I sent out those gerber files.09:03
xiangfu(one silo cap ) I ignore all those caps in first try. :-)09:04
xiangfuthe first try has totally messed. but I learn quiet some on KiCAD, gerber files, making PCB etc.09:05
xiangfuthe bad news is I never success with oven.09:06
xiangfuI made a working board today with hot air.(2 times hot air)09:09
xiangfuafter burned 7 PCBs and 2 chips. :-)09:09
kyakxiangfu: hi! i guess qt4 still didn't build on buildhost?09:23
xiangfukyak, checking...09:23
xiangfukyak, great. the qt4 stuff compile fine now.09:24
xiangfucheckout here: http://fidelio.qi-hardware.com/~xiangfu/openwrt-xburst.full_system/bin/xburst/packages/09:24
xiangfukyak, sorry for late reply. :) we have 17 qt4 package now.09:25
xiangfukyak, I think I will update the images and packages, just starting a continue build09:27
kyakxiangfu: yeah, it makes sense to re-release the image, how do you think?09:45
xiangfuyes. agree.09:47
xiangfubuilding now. 09:47
wpwrakxiangfu: (working board) wow, that's great. congratulations !13:36
xiangfuwpwrak, I can load configure bits file to that board. get some result from the firmware. :)13:59
qi-bot[commit] Xiangfu: qi_lb60: add ks7010 support (release_2012-10-11) http://qi-hw.com/p/openwrt-xburst/3f6249414:02
qi-bot[commit] Xiangfu: qi_lb60: add ks7010 support (master) http://qi-hw.com/p/openwrt-xburst/c3be28114:02
wpwrakxiangfu: not a bad result at all. i thought it would take you a lot longer to get something that works. did you only use hot air or also heat from the bottom ?14:31
xiangfuwpwrak, I heat the pcb and chip in oven for ~3 minutes. then use hot air on top.14:34
xiangfuI set the hot air to ~350C.14:35
xiangfu~3 minutes hot air on top of chip. 14:35
xiangfuwpwrak, oven: no matter what high temperature I set, the TIN only get soft. it doesn't reflow at all, 14:38
xiangfuif I stick >220C for more then 2 mins. the PCB start burn. :)14:39
xiangfuTIN: I mean the tin ball of the chip.14:39
larscxiangfu: with flames and everything?14:44
xiangfularsc, the PCB starts to change color(black). and smoke come out.14:45
xiangfularsc, http://downloads.openmobilefree.net/tmp/IMG_1393.JPG <-- checkout.14:46
viricwhat is a 'tin ball'?14:50
larscxiangfu: nice toast ;)14:58
larscviric: the small dots on the back of the chip15:01
viricmh back is where text is, no?15:01
viricor that is front?15:01
larscI'd call it front15:02
viricah ok :)15:04
viricyou are not imaging chips as bugs then15:04
viricyou mean the balls on the belly of the chip ;)15:04
whitequarkxiangfu: uh oh15:05
whitequarkare you trying to use pb-free solder? :)15:05
xiangfuwhitequark, you mean the solder on the PCB?15:08
xiangfuviric, yes. what is the correct name of those 'tin ball'? :)15:12
wpwrakjust "balls"15:17
wpwrakand chips don't normally have "front" and "back" but "top" and "bottom"15:18
whitequarkxiangfu: both on pcb and on the chip15:18
wpwrakxiangfu: using the oven to pre-heat is an interesting variation15:18
viricI thought that 'tin' was a metal closer to iron15:20
xiangfuwhitequark, the chip is pb-free. the PCB I don't know. some random fab. 15:20
viricas in 'tin can'15:20
whitequarkpb-free solder seriously sucks if you don't have an oven with programmable profile15:20
viricBut then I looked at the dictionary for the english word of the solder soft metal, and I discovered it's tin :)15:20
whitequarkÍ'd say that you can preheat the PCB at 170, or maybe 180 deg almost continuously15:21
whitequarkif you go higher, it'll fry sooner or later15:21
viricwhitequark: there comes into play the openPID?15:21
whitequarkso, I preheat it to 180 and then apply the heat gun on top15:21
whitequarkset to 32015:21
whitequarkfor 20 seconds and no more15:21
whitequarkworks very good on LQFP, but might not work so good on BGA15:22
wpwrakviric: maybe you can recycle tin cans in a pinch. heat them on the stove until they melt, add lead to lower the melting point, stir well, voila, kitchen-made solder :)15:22
viricyou don't cook in that oven later, right?15:22
whitequarkviric: haha, indeed15:22
whitequarkheavy metals are quite poisonous15:22
viricgood :)15:22
whitequarkwell I don't have one yet15:22
whitequarkdidn't have much time lately.15:23
xiangfuwhitequark, thanks for share.15:23
whitequarkactually, I have yet to turn on my M1 for the first time :/15:23
xiangfuwhitequark, then I also have to use heat gun from now on. 15:23
whitequarkxiangfu: probably. it takes some practice, but after twenty fried pcbs/chips or so I was able to do it correctly each time15:24
wpwrakwhitequark: why even bother with the oven for LQFP ? they're trivial with a soldering iron15:24
whitequarkwpwrak: naw, I used the heat gun from the bottom for preheating and top for actual soldering15:25
whitequarkfor both desoldering and soldering15:25
xiangfuwhitequark, (it takes some practice). I already fired 7 pcbs and 2 chips. I still need 10 burn chips class. :-)15:25
whitequarkwpwrak: fine-pitch lqfps aren't easy15:25
wpwrakok, desoldering is a different story15:25
whitequark.5 mm ones for example15:25
whitequarkI find it way easier to do this:15:26
whitequark1. cover each pad with an appropriate amount of tin with the iron and lots of RMA flux15:26
whitequarkrelying on surface tension forces here15:26
whitequark2. more flux, place the chip correctly, apply heat gun and push it _very_ gently15:27
whitequark3. if the thingy doesn't work, probably due to not heating it enough, use _dry_ iron on every pin again.15:28
wpwraki wouldn't put a lot of tin on the pads. else you have to maintain heat for a long time to make sure all pins actually sink into the solder15:28
whitequarkwpwrak: you cannot actually place "a lot" of tin on pads15:28
wpwrakwell, in the Z direction :)15:28
whitequarkthere's an amount it will absorb, and it will try very hard to get this exact amount15:28
whitequarkyou obviously need to have soldering mask, and the pads should be quite small15:29
wpwraki keep my tin flat (microns). then lots of water soluble flux (less messy than RMA) and always a "wet" iron15:29
whitequarkwpwrak: with wet iron, I tend to get a lot of solder bridges15:29
wpwrakah, don't have solder mask in my diy boards. that would make things too easy :)15:30
whitequarkwhich are incredibly hard to remove without ruining the pcb15:30
wpwrakapply flux and "paint" over the pins, away from the chip. surface tension will take care of the bridges15:30
Action: xiangfu will read logs tomorrow. have to sleep.15:30
whitequarkas per solder mask, I find it comparable by cost to just purchase the pcbs at fab15:30
whitequarkwhen you include the cost of my time spent fixing everything which could be just avoided by having a mask, not drilling anything, not having to remake the PCBs, etc.15:31
wpwrakah yes, drilling is a pain15:31
Action: wpwrak <3 his cnc mill ;)15:31
whitequarkdrilling is a huge PITA, positioning can be hard, chemical processes are not health-friendly and not easy either15:32
whitequarkunless you're doing lots of simple boards and need really low cost and small turnaround time, I wouldn't really recommend the laser printer process15:32
wpwrakfor me it's the turnaround15:33
wpwrakand yes, i try to keep them small15:33
whitequarkyou could pay $30 for a moderately complex board and have it in 3 days here in Russia15:33
whitequarkwith a russian fab15:33
whitequarkmoderately complex = 2/4 layer, mask, drilling15:33
whitequarkunder 10x10cm15:34
whitequarkwell maybe $50. I mean, per batch of 10. 15:34
wpwrakso $50 for 10 boards or for each of that batch ?15:35
whitequarkfor 1015:35
wpwrakok, those are good prices15:35
whitequarkhm, let me make sure I'm saying the correct price15:36
whitequarkwell no, I was not entirely correct.15:37
whitequark2 layers, mask, silkscreen on both sides: $60 preparation, $12 per dm², 3 days.15:37
wpwrakso $180 for the batch. and you have to wait :) but yes, if you actually need ten boards, it's more convenient. i tend to make two only identical boards at a time.15:39
wpwrakthen the next generation learns from my mistakes :)15:40
whitequark+$10 delivery, or you could pick it up yourself15:41
whitequarkwell yeah, there's a chinese fab which lets you have 10 boards less than 10x10cm for $25 total15:42
whitequarkplus delivery15:42
whitequarkif you use anything except airmail, it'll have comparable ETA and will be at least thrice cheaper15:43
whitequarkthey have some other nice offers like 4 layer 5x5 for $65, or 10x10 for $10015:44
whitequarkwhich is very competitive to other fabs I've seen15:44
qi-bot[commit] Paul Cercueil: Hide the 'params' option from the user on the contextual menu (packages) http://qi-hw.com/p/gmenu2x/0fc6ac621:38
qi-bot[commit] Paul Cercueil: Use the '%f' token to insert the selected file on the params. (packages) http://qi-hw.com/p/gmenu2x/e7e21b421:38
qi-bot[commit] Paul Cercueil: Build file extensions filter from the MIME types present on the OPK (packages) http://qi-hw.com/p/gmenu2x/5f1cff621:38
pcercueiWayland 1.0 released23:48
--- Tue Oct 23 201200:00

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