Hi The key trick that is often missed while watching it done is the need to set it (tune it) to operate at the frequency you are looking for. In other words, if you are testing a 4 MHz crystal, you need to first tune the machine to 4 MHz. If you truly have a bag full of “mystery parts” that’s not an easy thing to do :) The same thing applies to a whole raft of very similar machines. The reasoning is the same in all cases: You take out the effective load impedance of the device by tuning it to “series” first. In reality any oscillator you can tune up this way can be used to get the motional capacitance. The second trick is the need to calibrate the resistance reading on the device. That may seem easy, but it’s not quite as simple as you might think. Various resistors have some odd characteristics even at 40 MHz. Carbon comp’s are truly weird. A good thin film resistor is the right thing to use. Good luck finding one on most benches…. Finally, the motional stuff is done by popping a “load cap” in series with the crystal. The net result is only as good as the accuracy of the setting on that cap. In most factories an inventory of “standard crystals” is stored in some dark and dusty cabinet. When the meter comes in, the calibration is done such that those crystals give the correct results. It may all be wrong (who knows …) but at least the factory is producing stuff this week that matches up with what they made last week. I’m sure I’ve forgotten at least ten other quirks about the device …. That’s why including a summary of how it was used would be a really neat thing. Bob > On Jun 25, 2016, at 9:33 PM, Tom Van Baak <tvb@LeapSecond.com> wrote: > >> Hi >> >> Might be a little more fun if it showed the proper way to use the 150B (or any similar device). >> >> Bob > > Hi Bob, > > Can you tell those of us with those cool Saunders 150B crystal impedance meters how to do it right? > > /tvb > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

		Attila Kinali

On Sat, 25 Jun 2016 18:33:28 -0700 "Tom Van Baak" <tvb@LeapSecond.com> wrote: > Don't forget about University of Western Australia's multi-decade gift > to the world -- whispering gallery Cryogenic Sapphire Oscillator (CSO >) -- which have Q near 1e9. Yes, but these are entirely a different kind of resonator sturcture. While quartz crystals are mechanical oscillators, ie a piece of material stretching, contracting, twisting defining the resonant frequency, the CSO are electromagnetic resonators, that trap a wave inside a structure, much like cavity or stripline resonators. The big Q in CSO comes from a much lower damping in the material at cryogenic temperature and the ease at which a signal can be coupled in without disturbing the resonator. Their biggest disadvantage is that they need quite an infrastrucutre for cooling and constant maintenance. The CSO's i've seen are all usualy just a couple cm in size (around the size of a fist), but the cooling system fills the better part of an 19" rack. Fun fact: quartz crystals also get an increase in Q with cryogenic temperatures, but not as high as CSO's. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way.

Bob Camp: >Every paper I have ever read on the intrinsic Q of quartz makes the claim that Q * F is a constant ( Q goes up as frequency goes down). Unless blank diameter gets in the way, this has been true for any >crystals I have ever used. Q does change as overtone changes, but that is not related to the Q of the material. A given blank design may (or may not) be limited by the Q of the quartz at any specific >frequency. That is a function of a lot of things. >The material’s properties set a maximum Q you can achieve no matter how good your blank design is and how big the blank. Done properly, the best 5 MHz resonator you can do *will* have 2X the Q of >the best 10 MHz resonator. Indeed there is an physical limitation for the Q of piezoelectric resonators, which is given by phonon interactions etc. For quartz this limit is given approximately by Q*f = 15E12. See attached graph (sorry, in German). The real crystal Q is determined by a couple of other factors like - damping caused by the suspension (which for circular plano-parallel thickness shear resonators like AT and SC is the larger, the larger the thickness to diameter ratio is. The impact of the suspension can be reduced e.g. by contouring the crystal (beveling, plano-convex or bi-convex shape) - damping by the surrounding gas (dominating in low-frequency tuning-fork type crystals, important for low- frequency AT-cut crystals, less important for high frequency crystals - damping effect due to stress and losses between crystal blank and electrodes - mode of vibration: fundamental is worse than overtones, partly because the electrode losses apply only to two outer interfaces of the vibration sublayers rule of thumb for ATs with f in Hz: fundamental mode: Q*f about 1E12, 3rd overtone Q*f about 2E12 ... 4E12, 5th and higher overtone 4E12 to 8E12. for SC-cut 3rd or 5th overtone with optimized design Q*f can go up to 13E12, e.g. Q of a good 10 MHz 3rd is about 1.1 mio to 1.3 mio, a good 100 MHz 5th has a q of 120 000 to 135 000 - in tuning fork crystals (which are all evacuated) Q*F is about 0.6E12 to 1.5E12 Rule of thumb means: these are typical averages , there are exceptions BTW: This does not apply to the sapphire DIELECTRIC resonators or other kinds of resonators like DRO etc.. Those are different animals. Have fun Bernd DK1AG

Hi So if we could just get that 180 mm blank line up and running, you could get some pretty good 1 MHz crystals. Of course that also involves minor issues like a 200+ mm diameter cold weld package and all the processing gear …. Bob > On Jun 26, 2016, at 6:40 AM, Bernd Neubig <BNeubig@t-online.de> wrote: > > Bob Camp: >> Every paper I have ever read on the intrinsic Q of quartz makes the claim that Q * F is a constant ( Q goes up as frequency goes down). Unless blank diameter gets in the way, this has been true for any >crystals I have ever used. Q does change as overtone changes, but that is not related to the Q of the material. A given blank design may (or may not) be limited by the Q of the quartz at any specific >frequency. That is a function of a lot of things. >> The material’s properties set a maximum Q you can achieve no matter how good your blank design is and how big the blank. Done properly, the best 5 MHz resonator you can do *will* have 2X the Q of >the best 10 MHz resonator. > > Indeed there is an physical limitation for the Q of piezoelectric resonators, which is given by phonon interactions etc. For quartz this limit is given approximately by Q*f = 15E12. See attached graph (sorry, in German). The real crystal Q is determined by a couple of other factors like > - damping caused by the suspension (which for circular plano-parallel thickness shear resonators like AT and SC is the larger, the larger the thickness to diameter ratio is. The impact of the suspension can be reduced e.g. by contouring the crystal (beveling, plano-convex or bi-convex shape) > - damping by the surrounding gas (dominating in low-frequency tuning-fork type crystals, important for low- frequency AT-cut crystals, less important for high frequency crystals > - damping effect due to stress and losses between crystal blank and electrodes > - mode of vibration: fundamental is worse than overtones, partly because the electrode losses apply only to two outer interfaces of the vibration sublayers > rule of thumb for ATs with f in Hz: fundamental mode: Q*f about 1E12, 3rd overtone Q*f about 2E12 ... 4E12, 5th and higher overtone 4E12 to 8E12. > for SC-cut 3rd or 5th overtone with optimized design Q*f can go up to 13E12, e.g. Q of a good 10 MHz 3rd is about 1.1 mio to 1.3 mio, a good 100 MHz 5th has a q of 120 000 to 135 000 > - in tuning fork crystals (which are all evacuated) Q*F is about 0.6E12 to 1.5E12 > Rule of thumb means: these are typical averages , there are exceptions > > BTW: This does not apply to the sapphire DIELECTRIC resonators or other kinds of resonators like DRO etc.. Those are different animals. > > Have fun > > Bernd > DK1AG > > > <Qtimesf.gif>_______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

                   Attila Kinali

I'm not a fan of tweezers either. I use a sticky toothpick. Post-it note glue. Tweezers tend to make parts fly off into space. As for parts moving around, that is what vision is for, to find the part that needs to be picked up. On Sat, Jun 25, 2016 at 7:52 AM, Bob Camp <kb8tq@n1k.org> wrote: > Hi > > Even on a “real design” desktop pick and place, vibration is an issue for > parts moving around. The same > is true of parts “squirming” on a pick head as it does it’s thing. Part’s > aren’t as flat as you might think they > are and you can only get just so much vacuum. > > Lots of grubby design details. > > ==== > > One thing that has not been covered so far is (at least to me) the best > way to do manual pick and place. > A lot of people try to do it with tweezers. I find that to be a massive > pain. A vacuum pickup with a foot > switch goes *much* faster for me. It also is a much better way to keep > your hands out of the solder paste. > You can get some nice long pickups. A setup is not very expensive, even > with an illuminated magnifier to help see > what you are doing. > > As an added bonus, some systems will let you reverse the pump and use it > to dispense solder paste. The > net result is that you have an effective way to both put down solder and > place the parts. I prefer stencils for the > solder side of things, but that is very much a mater of debate. > > Bob > > > > On Jun 25, 2016, at 9:16 AM, bownes <bownes@gmail.com> wrote: > > > > And try to tell transistor A from transistor B from diode C when they > are all upside down. > > > > A moving head design can be made to pick up parts off of reels on all > four sides. But it takes more table space. Which is money. > > > > As someone else said, you need Z rotation, which isn't as easy as it > sounds when using pneumatics to pick up the part. > > > > Moving table design sounds like a recipe for shaking the parts off the > solder pads. I've not had good luck with solder paste staying tacky for > long. In which case you are dispensing paste then sticking part. Not a deal > breaker but slow. > > > >> On Jun 25, 2016, at 04:12, Adrian Godwin <artgodwin@gmail.com> wrote: > >> > >> Many parts can't be recognised visually. Capacitors are the obvious > example. > >> > >> On Sat, Jun 25, 2016 at 6:11 AM, Chris Albertson < > albertson.chris@gmail.com> > >> wrote: > >> > >>> The ideal hobby use pick and place machine would be very different > >>> from a commercial machine. Lets say I want one board made. What I > >>> want to minimize is my time. With a conventional machine by FAR most > >>> of my time is spent setting the machine up. In fact setup is so slow > >>> that for smaller PCBs I could do it with tweezers in a fifth of the > >>> time needed to set up the machine. > >>> > >>> So a hobby machine must be designed such that you could get it going > >>> in nearly zero time. In the ideal case you drop the parts all mixed > >>> up, (but right side up) in a small tray. They are mixed and in random > >>> orientation. then you give the machine your PCB design file (not a > >>> special pick and place file) and then a vision system IDs the parts. > >>> Today vision is dirt cheap. > >>> > >>> But the 3D printer needs one more degree of freedom. It must be able > >>> to rotate the part (or the PCB) as it is unlikely the part on the tape > >>> or tray only needs translation to the PCB, likely ration is required > >>> in almost all cases. > >>> > >>> I think a hobby machine would only be successful if it could reduce > >>> the setup time to nearly zero and for that it would need a really good > >>> vision system that could hunt down randomly placed parts. It would > >>> have to work pretty much like you or I would do the job manually. But > >>> we have software like openCV and good "board cams" with M7 > >>> interchangeable lenses for $35. A vision system actually saves a ton > >>> of money because the machine need not be so precise as vision closes a > >>> feedback loop. > >>> > >>> Also how many hobbyists are going to have reels of parts? I might buy > >>> some parts by the dozen but most no more than about 4 or 6 at a time. > >>> I don't want a large machine. It should have a working surface, a > >>> white melamine table about 12 inches square and I place the PCB to be > >>> stuffed and all the parts on the same foot square table at any random > >>> location then press the "go" button. The camera scans the table. > >>> This kind of machine would be horrible for production work but a one > >>> foot cube machine that required zero setup is what most of us want. > >>> > >>> Going a little farther. I'd like this SAME machine to actually make > >>> the PCB too. A 3D printer could route the copper and drill holes and > >>> print the solder resist plastic too. > >>> > >>>> On Fri, Jun 24, 2016 at 8:56 PM, Attila Kinali <attila@kinali.ch> > wrote: > >>>> On Fri, 24 Jun 2016 13:59:58 -0500 > >>>> "Graham / KE9H" <ke9h.graham@gmail.com> wrote: > >>>> > >>>>> Lots of problems to be solved... > >>>> > >>>> Most of these problems are easy: > >>>> > >>>>> How do you take loose parts or cut tape or tape reels > >>>> > >>>> You don't. No loose parts with any kind of pick&place machine. > >>>> As for cut tape, these can be taped on an empty reel to make > >>>> them compatible. Everything has to be in a tray, reel or similar. > >>>> > >>>>> and get the right > >>>>> part out, and into the chuck, oriented in the right direction? > >>>> > >>>> Orientation is defined by the reel/tray the parts come in. > >>>> This is also documented in the datasheet, usually. > >>>> > >>>>> How many different kinds of parts, sizes, shapes, pin counts, IC > >>>>> footprints, can you handle at once? > >>>> > >>>> As many as there is space around the machine :-) > >>>> > >>>>> How do you know it is the correct part? > >>>> > >>>> You put it manually in the right feeder and double check that it > >>>> fits the programming. > >>>> > >>>>> How do you know where the "+" end, or "pin 1" is? > >>>> > >>>> This comes with the orientation of the part in the reel/tray. > >>>> > >>>>> How do you know that there actually is a part in the chuck? > >>>> > >>>> Your trays are guaranteed to be non-empty by manually loading them. > >>>> > >>>>> How do you know the part in the chuck is oriented the way you > expected > >>> it? > >>>> > >>>> The manufacturer guarantees that the reels/trays are loaded correctly. > >>>> > >>>>> How do you know where the footprint on the circuit board is located? > >>> (to a > >>>>> few thousandths.) > >>>> > >>>> This is provided by the pick&place file. Usually its 3-5 digits after > the > >>>> decimal point, when using mm. But as I wrote before, you don't have to > >>>> place part hyper exact. Being within 0.1-0.3 of the pitch of the part > >>>> is usually enough. Surface tension does the rest. > >>>> > >>>>> How do you know the part left the chuck and ended up where you > intended > >>> it > >>>>> to be? > >>>> > >>>> You dont :-) > >>>> > >>>> The way how this is checked is either a pre-solder and/or post-solder > >>> visual > >>>> inspection. This is either done manualy or using a camera system where > >>>> computer compares the PCB to the picture of a known-good PCB. > >>>> As this is ment for a small volume and hobbyist system, doing the > visual > >>>> inspection manualy is good enough and more than fast enough. > >>>> > >>>> Attila Kinali > >>>> -- > >>>> Malek's Law: > >>>> Any simple idea will be worded in the most complicated way. > >>>> _______________________________________________ > >>>> time-nuts mailing list -- time-nuts@febo.com > >>>> To unsubscribe, go to > >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>>> and follow the instructions there. > >>> > >>> > >>> > >>> -- > >>> > >>> Chris Albertson > >>> Redondo Beach, California > >>> _______________________________________________ > >>> time-nuts mailing list -- time-nuts@febo.com > >>> To unsubscribe, go to > >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>> and follow the instructions there. > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California

                      Attila Kinali

Yes, I found that machine. There is work on going to get openPNP software to work on the liteplacer. So that machine will soon have all the capabilities of every other machine using openPNP. What has changed recently is that vision is so cheap and easy. You can buy a ready to use USB connected hi-def camera for under $10 and some have interchangeable lenses with M7 threads and you buy quality M7 lenses with metal housings for about $20. OpenCV makes vision software not so hard to do as it was. But a cheap person like me says "I have a milling machine" so I don't need to buy yet another X,Y,Z positioning machine. I put that on the end of a long list of projects I'll never get to. On Sat, Jun 25, 2016 at 10:06 AM, John Swenson <johnswenson1@comcast.net> wrote: > There is a "hobbY" pick and placer called LitePlacer that meets a lot of > your criteria. > > http://www.liteplacer.com > > It works on cut strips, not reals, it will handle random placed parts on > the table top, but so far I don't think it automatically figures out what > they are. But you can put a bunch of one part in one area, another bunch of > parts in a different area etc. But for most parts you just leave them in > the cut strips taped to the table. > > The cameras read the holes in the tape and use that to figure out where > the parts are. The first one it grabs from a tape it takes it over to an > upwards facing camera to make sure it gets rotation correct and knows > exactly where the pins are. > > It even has the white melamine table. > > I haven't bought one yet, but I'm strongly considering it. > > John S. > > > On 6/24/2016 10:11 PM, Chris Albertson wrote: > >> The ideal hobby use pick and place machine would be very different >> from a commercial machine. Lets say I want one board made. What I >> want to minimize is my time. With a conventional machine by FAR most >> of my time is spent setting the machine up. In fact setup is so slow >> that for smaller PCBs I could do it with tweezers in a fifth of the >> time needed to set up the machine. >> >> So a hobby machine must be designed such that you could get it going >> in nearly zero time. In the ideal case you drop the parts all mixed >> up, (but right side up) in a small tray. They are mixed and in random >> orientation. then you give the machine your PCB design file (not a >> special pick and place file) and then a vision system IDs the parts. >> Today vision is dirt cheap. >> >> But the 3D printer needs one more degree of freedom. It must be able >> to rotate the part (or the PCB) as it is unlikely the part on the tape >> or tray only needs translation to the PCB, likely ration is required >> in almost all cases. >> >> I think a hobby machine would only be successful if it could reduce >> the setup time to nearly zero and for that it would need a really good >> vision system that could hunt down randomly placed parts. It would >> have to work pretty much like you or I would do the job manually. But >> we have software like openCV and good "board cams" with M7 >> interchangeable lenses for $35. A vision system actually saves a ton >> of money because the machine need not be so precise as vision closes a >> feedback loop. >> >> Also how many hobbyists are going to have reels of parts? I might buy >> some parts by the dozen but most no more than about 4 or 6 at a time. >> I don't want a large machine. It should have a working surface, a >> white melamine table about 12 inches square and I place the PCB to be >> stuffed and all the parts on the same foot square table at any random >> location then press the "go" button. The camera scans the table. >> This kind of machine would be horrible for production work but a one >> foot cube machine that required zero setup is what most of us want. >> >> Going a little farther. I'd like this SAME machine to actually make >> the PCB too. A 3D printer could route the copper and drill holes and >> print the solder resist plastic too. >> >> On Fri, Jun 24, 2016 at 8:56 PM, Attila Kinali <attila@kinali.ch> wrote: >> >>> On Fri, 24 Jun 2016 13:59:58 -0500 >>> "Graham / KE9H" <ke9h.graham@gmail.com> wrote: >>> >>> Lots of problems to be solved... >>>> >>> >>> Most of these problems are easy: >>> >>> How do you take loose parts or cut tape or tape reels >>>> >>> >>> You don't. No loose parts with any kind of pick&place machine. >>> As for cut tape, these can be taped on an empty reel to make >>> them compatible. Everything has to be in a tray, reel or similar. >>> >>> and get the right >>>> part out, and into the chuck, oriented in the right direction? >>>> >>> >>> Orientation is defined by the reel/tray the parts come in. >>> This is also documented in the datasheet, usually. >>> >>> How many different kinds of parts, sizes, shapes, pin counts, IC >>>> footprints, can you handle at once? >>>> >>> >>> As many as there is space around the machine :-) >>> >>> How do you know it is the correct part? >>>> >>> >>> You put it manually in the right feeder and double check that it >>> fits the programming. >>> >>> How do you know where the "+" end, or "pin 1" is? >>>> >>> >>> This comes with the orientation of the part in the reel/tray. >>> >>> How do you know that there actually is a part in the chuck? >>>> >>> >>> Your trays are guaranteed to be non-empty by manually loading them. >>> >>> How do you know the part in the chuck is oriented the way you expected >>>> it? >>>> >>> >>> The manufacturer guarantees that the reels/trays are loaded correctly. >>> >>> How do you know where the footprint on the circuit board is located? (to >>>> a >>>> few thousandths.) >>>> >>> >>> This is provided by the pick&place file. Usually its 3-5 digits after the >>> decimal point, when using mm. But as I wrote before, you don't have to >>> place part hyper exact. Being within 0.1-0.3 of the pitch of the part >>> is usually enough. Surface tension does the rest. >>> >>> How do you know the part left the chuck and ended up where you intended >>>> it >>>> to be? >>>> >>> >>> You dont :-) >>> >>> The way how this is checked is either a pre-solder and/or post-solder >>> visual >>> inspection. This is either done manualy or using a camera system where >>> computer compares the PCB to the picture of a known-good PCB. >>> As this is ment for a small volume and hobbyist system, doing the visual >>> inspection manualy is good enough and more than fast enough. >>> >>> Attila Kinali >>> -- >>> Malek's Law: >>> Any simple idea will be worded in the most complicated way. >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> >> >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California

I read through the thread so far and thought I’d throw out there some of how I do it. I’ve done a lot of manual pick-n-place in a very short career. :) I used to always use stencils for paste, but now most of the time I use a dispenser and place the paste by hand. The exceptions are some of my smaller boards with QFN packages. Those get pasted with stencils always, but there are only a few designs that do that, and all but a couple I get made in batches by SBA. I place most things with tweezers, and I’m pretty good at it by this point. I have a vacuum tool that I use for QFN and for SSOPs that are too large to fit entirely in the tweezers. I grab SOICs by a couple pins, but SSOPs are too fine for that technique. I tend to use too much paste rather than not enough, which sometimes means SSOP devices need to be reworked with braid to remove bridges. Just part of the process for me. My passives are 0805 (when I have a choice). I probably could do 0603, but it turns out that the footprints aren’t terribly different between those two sizes. I don’t design smaller than that because I simply have no need. I do surface mount now because it’s *faster* for me than through-hole, and because you have a far wider variety of devices available than limiting yourself to through-hole devices exclusively. The fact that it’s smaller is kind of a nice side benefit. My rule now is that I don’t buy “ordinary” resistors now other than as a full reel, 1/8W 1% 0805. Specialized parts, like current sense or high power resistors don’t count. I have reels of MMBT3904/6 and MMBT4401/3, as well as 1N4148 SOT323, and BAT54. For caps, I keep 22µF, 10µf, 2.2µF, 1µF, 0.1µF, 0.01µF, 0.001µF and a few selected pF values on reels. I’ve also got a lot of other parts on cut tape. When I need parts for SBA that are too expensive to stock reels, I buy DigiReels or MouseReels. It’s cheaper to get them to treat cut tape thusly than to pay SBA the premium for them to deal with cut tape. My workbench is a *mess*. Tidying up is just never a priority somehow. My current inventory management system is best described as restrained chaos. I have “project bags” where I store non-common cut-tape parts for each particular product. I have a laundry tub where most of my reels are held, and a “stack” of commonly used values on the bench. I have 5 other bags of cut-tape parts that are categorized as integrated circuits; discrete semiconductors and LDOs; caps, inductors and crystals; miscellaneous parts (like trimmers, battery clips, tactile switches, etc); and through-hole parts - mostly things like screw terminals.

> Indeed there is an physical limitation for the Q of piezoelectric > resonators, which is given by phonon interactions etc. For quartz this > limit is given approximately by Q*f = 15E12. See attached graph (sorry, in > German). NIce figure! Here's a similar one for MEMS resonators (mostly Si I think) in a paper by Ghaffari et al. from 2013: http://www.nature.com/articles/srep03244 >From the figure it looks like the MEMS resonator for on a line Q*f = 5e12 Anders

Hi This whole thing *is* a multi solution problem. There is no one right answer for everybody and everything. It is refreshing to get past the whole “the world ends when we run out of DIP packages” hysteria that often grips us when talking about *building* a Time Nut gizmo. A *lot* of the things that we would all like to play with start off with “something” and then tie it to an FPGA and/or an MCU. Both of those parts are rapidly becoming a fine pitch SMD sort of thing for newly designed parts. Moore’s law still makes sure that the new part is the cheap one to use. To try to wrap this up: 1) You can do manual placement with or without a stencil. The stencil process does not add a lot of cost. Results are quite acceptable *if* you have the patience and eyesight to do the job. 2) There are some really interesting short run outfits popping up that may change the economics of short run boards. It remains to be seen if they are viable in the long run. It only makes sense if they can make enough money doing it to stay in business. 3) Various forms of pick and place gear are getting into the range of “same price as XXXX” that you already have on your bench. Right now, they are a hassle to use. Will they make sense … who knows. Getting anything working is always a process of multiple trials. Nobody ever gets it right the first time. Anything that takes the “cycle time” from months and years to weeks and months is a good thing. We have spent a lot of time talking about GPSDO’s, super duper counters, ADEV boxes, and phase noise test sets. I believe I can count the number of projects actually moving forward on one hand. I hope the increased awareness of how many ways there are to “build stuff” will significantly increase the number of projects we all can share in. Bob > On Jun 27, 2016, at 12:19 AM, Nick Sayer via time-nuts <time-nuts@febo.com> wrote: > > I read through the thread so far and thought I’d throw out there some of how I do it. I’ve done a lot of manual pick-n-place in a very short career. :) > > I used to always use stencils for paste, but now most of the time I use a dispenser and place the paste by hand. The exceptions are some of my smaller boards with QFN packages. Those get pasted with stencils always, but there are only a few designs that do that, and all but a couple I get made in batches by SBA. > > I place most things with tweezers, and I’m pretty good at it by this point. I have a vacuum tool that I use for QFN and for SSOPs that are too large to fit entirely in the tweezers. I grab SOICs by a couple pins, but SSOPs are too fine for that technique. > > I tend to use too much paste rather than not enough, which sometimes means SSOP devices need to be reworked with braid to remove bridges. Just part of the process for me. > > My passives are 0805 (when I have a choice). I probably could do 0603, but it turns out that the footprints aren’t terribly different between those two sizes. I don’t design smaller than that because I simply have no need. I do surface mount now because it’s *faster* for me than through-hole, and because you have a far wider variety of devices available than limiting yourself to through-hole devices exclusively. The fact that it’s smaller is kind of a nice side benefit. > > My rule now is that I don’t buy “ordinary” resistors now other than as a full reel, 1/8W 1% 0805. Specialized parts, like current sense or high power resistors don’t count. I have reels of MMBT3904/6 and MMBT4401/3, as well as 1N4148 SOT323, and BAT54. For caps, I keep 22µF, 10µf, 2.2µF, 1µF, 0.1µF, 0.01µF, 0.001µF and a few selected pF values on reels. I’ve also got a lot of other parts on cut tape. When I need parts for SBA that are too expensive to stock reels, I buy DigiReels or MouseReels. It’s cheaper to get them to treat cut tape thusly than to pay SBA the premium for them to deal with cut tape. > > My workbench is a *mess*. Tidying up is just never a priority somehow. My current inventory management system is best described as restrained chaos. I have “project bags” where I store non-common cut-tape parts for each particular product. I have a laundry tub where most of my reels are held, and a “stack” of commonly used values on the bench. I have 5 other bags of cut-tape parts that are categorized as integrated circuits; discrete semiconductors and LDOs; caps, inductors and crystals; miscellaneous parts (like trimmers, battery clips, tactile switches, etc); and through-hole parts - mostly things like screw terminals. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

On 28 June 2016 at 00:58, Bob Camp <kb8tq@n1k.org> wrote: > I believe I can count the number of projects actually moving forward > on one hand. I hope the increased awareness of how many ways there are to “build stuff” will significantly increase the number > of projects we all can share in. If anyone wants prototype time-nuts projects assembled, I'm happy to do so. I'd much rather people did good time-nuts designs, than worried over the building aspect if that's not something they want to do. (Cambridge, UK, for logistical purposes. The offer extends everywhere. Try to keep it to 0402 and 0.5mm pitch limits, if possible, and it'd be an infill job done when the machines are idle.) Steve