How do you design these days?
in [Design]
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From: qrk on 31 Dec 2009 15:30 On Wed, 30 Dec 2009 20:01:39 -0600, "RogerN" <regor(a)midwest.net> wrote: > >When I was in school components fit on solderless breadboards and we made >circuits using breadboards, power supplies, meters and oscilloscopes. Many >of today's components don't appear to be breadboard friendly, so how is it >done today? > >Is circuit design software and simulation good enough to go straight to a PC >board? Or do you use surface mount to breadboard adapters? Do you still >use a soldering Iron to solder or paste solder and an oven? > >I'm wanting to tinker with some circuits but some chips I'm interested in >only comes in MSOP or other packages that look intimidating to attempt to >solder. > >Thanks! > >RogerN > These days, I'll Spice it then go to schematic and layout. If I'm lucky, the board is ready for production. If not, I can usually test out most of my circuitry on the bum board. If it's a tricky circuit, like a wierd switching power supply which requires good layout practices, I'll do a prototype circuit board and run it through one of the quicky circuit board places like http://www.pcbexpress.com/ . I'll usually put a few test circuits on the board and maybe a circuit for a personal project or piece of test equipment on the board too. For digital projects, my colleague will do a test run on Xilinx place and route to catch I/O pin definition issues before committing to layout. For high-speed digital layout, treat it like an RF analog board. If you understand Spice, it is a valuable tool. Bad part models can get you in trouble. Rohm's transistor models I used were/are minus the junction capacitances. I knew something was wrong when the response was flat out to 10MHz. Sometimes I'll dead bug MSOP and similar packages, but only for small circuits. I need to be hard up to do this. You may consider surfboards to convert surface mount to through-hole. Digikey carries these things. These days, I have a zoom stereo microscope ($500), hot air plate for warming the board to 150 deg C ($155 + $30 in modifications), and a hot air station for soldering ($185). All equipment is cheap Chinese stuff which works fine for repair and prototyping small parts. Our labs are equiped with Metcal soldering irons which is the place not to skimp. I don't use solder paste on leadless packages as it is too hard to dispense on small pads (e.g. 8-lead 1.6 x 1.6 mm packages). Easier to apply a bump of solder to the PCB pad and coat the underbelly of the part with flux, then hot air solder. -- Mark
From: qrk on 31 Dec 2009 15:46 On Thu, 31 Dec 2009 09:10:22 -0700, Don Lancaster <don(a)tinaja.com> wrote: >John Larkin wrote: >> On Thu, 31 Dec 2009 14:01:44 -0000, "markp" <map.nospam(a)f2s.com> >> wrote: >> >>> "RogerN" <regor(a)midwest.net> wrote in message >>> news:ROudnXLvg9-Tm6HWnZ2dnUVZ_oidnZ2d(a)earthlink.com... >>>> When I was in school components fit on solderless breadboards and we made >>>> circuits using breadboards, power supplies, meters and oscilloscopes. >>>> Many of today's components don't appear to be breadboard friendly, so how >>>> is it done today? >>>> >>>> Is circuit design software and simulation good enough to go straight to a >>>> PC board? Or do you use surface mount to breadboard adapters? Do you >>>> still use a soldering Iron to solder or paste solder and an oven? >>>> >>>> I'm wanting to tinker with some circuits but some chips I'm interested in >>>> only comes in MSOP or other packages that look intimidating to attempt to >>>> solder. >>>> >>>> Thanks! >>>> >>>> RogerN >>>> >>>> >>> I tend to design a PCB with CAD software then have prototype PCBs made. >>> There are several companies out there who do 'pooling', i.e. they amalgamate >>> many designs onto one PCB, that way you end up only paying a small fraction >>> of the tooling cost of the PCB. Some companies can handle 6 layer boards >>> with this process. Example in the UK is PCB Snap from Spirit Circuits >>> (www.spiritcircuits.com). >>> >>> This can be quite cost effectve for producing protptypes that are as close >>> to the final product as practicable. >> >> Why not go for the real thing, first time? If you get it right, you >> can sell it. >> >> John >> > >It is NEVER right the first time. Most of our first boards go in to production without cuts and jumpers. These are usually moderately complex boards.
From: Joerg on 31 Dec 2009 15:50 Phil Hobbs wrote: > On 12/30/2009 9:20 PM, Joerg wrote: >> RogerN wrote: >>> When I was in school components fit on solderless breadboards and we >>> made circuits using breadboards, power supplies, meters and >>> oscilloscopes. Many of today's components don't appear to be >>> breadboard friendly, so how is it done today? >>> >> >> I even used bare thumbtacks on plywood for solder posts back then. >> >> >>> Is circuit design software and simulation good enough to go straight >>> to a PC board? Or do you use surface mount to breadboard adapters? Do >>> you still use a soldering Iron to solder or paste solder and an oven? >>> >> >> In the professional world (product design) we go straight from >> simulation to schematic -> layout -> board fab -> assembly. No >> breadboards. >> >> >>> I'm wanting to tinker with some circuits but some chips I'm interested >>> in only comes in MSOP or other packages that look intimidating to >>> attempt to solder. >>> >> >> Well, for hobbyists or one-off designs there is help but not very cheap: >> >> http://www.proto-advantage.com/store/images/PRODUCTS/PA0027_0.JPG >> >> This is the variety they have but I don't know this shop, just meant as >> an example: >> >> http://www.proto-advantage.com/store/index.php?cPath=2200 >> > > _THE_ professional world? Joerg, Joerg, you've been holed up in that > mountain lair of yours for too long. ;) > Now, now, we do have a modern feed store in this here town whar we're gitten them alfalfa bales and all that, and they even use a computation machine :-) > Simulate the parts that simulators get right, do the rote stuff by rote, > but prototype the stuff you're not sure will work. It's amazing the > amount of stuff you can learn in a short time from a dead-bug prototype. > > If you're just talking about laying out boards for circuit prototypes, > then I agree--you might as well try a bit harder and get it right the > first time. But trying out weird stuff, especially in mixed-technology > systems, really needs prototypes. > Ok, I did build a breadboard for my first noise-critical fiber-optics front end but that was more because the client really wanted that done. I ended up not changing a thing on there and going straight to a multi-channel layout. Since it has digital delay controls with SPI and stuff it (almost) counts as mixed signal. > Besides, lots of my protos are actually small instruments that I build > in half a day and then use for years. An example is the sub-Poissonian > current source and LNA I built for my tunnel junction work--very > specific, worked great for years, took a day all told to design and > build. Good medicine. > One-off things I also often build on experimental board. I am not a great friend of the dead-bug style, preferring Vector board with a ground plane. That's harder to find these days so I stocked up. Many things go into those little Pomona boxes that end up riding on the back of a coax connector. All good medicine, but at least I can put a shiny aluminum lid on it so the clients don't see the wire ball inside my probes. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 31 Dec 2009 16:07 qrk wrote: [...] > These days, I have a zoom stereo microscope ($500), hot air plate for > warming the board to 150 deg C ($155 + $30 in modifications), and a > hot air station for soldering ($185). All equipment is cheap Chinese > stuff which works fine for repair and prototyping small parts. Our > labs are equiped with Metcal soldering irons which is the place not to > skimp. I don't use solder paste on leadless packages as it is too hard > to dispense on small pads (e.g. 8-lead 1.6 x 1.6 mm packages). Easier > to apply a bump of solder to the PCB pad and coat the underbelly of > the part with flux, then hot air solder. > How do you get the flux back outta there? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Tim Williams on 31 Dec 2009 16:11
I've recently gone from the solderless breadboard - protoboard - PCB cycle to breadboarding the bits I don't know and CADing everything else. Motivation: even for one-offs, it's easier to move components around in CAD space than desoldering and moving things in real life. Layout is a lot easier when you already know where everything goes, the error rate is lower, and it simply looks better. Two boards so far, fairly large as hobby boards go (~500 holes), one worked perfectly first time (a switching power supply similar to your average computer PSU). The other had a few errors I missed on schematic entry, and a few other errors due to negligence. Nothing big, some flying wires and cut traces fixed it. 99% was fine, so it was a worthwhile prototype. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms "RogerN" <regor(a)midwest.net> wrote in message news:ROudnXLvg9-Tm6HWnZ2dnUVZ_oidnZ2d(a)earthlink.com... > > When I was in school components fit on solderless breadboards and we made > circuits using breadboards, power supplies, meters and oscilloscopes. > Many of today's components don't appear to be breadboard friendly, so how > is it done today? > > Is circuit design software and simulation good enough to go straight to a > PC board? Or do you use surface mount to breadboard adapters? Do you > still use a soldering Iron to solder or paste solder and an oven? > > I'm wanting to tinker with some circuits but some chips I'm interested in > only comes in MSOP or other packages that look intimidating to attempt to > solder. > > Thanks! > > RogerN > > |