[sdiy] Latvian CEM Synth IC clones

[rsdio at audiobanshee.com]

On Mar 14, 2018, at 4:39 AM, Alexandre Souza <alexandre.tabajara at gmail.com> wrote:
> $300 for a stencil? O_O 
> www.pcbshopper.com 
> In www.jlcpcb.com I do stencils for $9
> O_O

There are countless cheap options in China, but I live in Seattle. Borders aren’t always easy. I prefer a place that I can walk to. If I were going to order stencils from China, then I might as well order the PCBs from there and get things assembled, too - but then I’d have to import them and I have had significant delays at unexpected times.


On 2018-03-14 10:50, mark verbos wrote:
> Sorry if this is a stupid question, but when does it start to be an
> issue that the parts are too small. I mean in terms of current
> capacity and such. I use 0603 resistors and they are only 100mW at
> some point it starts to be an issue for analog circuits, right? Not
> that I really want to use 01005 passives anyway, but my pick ’n' place
> is supposed to be able to. They look like salt and pepper.

Are you asking about chips like QFN and BGA, or passives? For the chips, they’re all the same size inside - at least the working parts are the same. Only the casings have been getting smaller, not the current capacity. I tend to use SOIC because they’re easier to probe. If temperature is a problem, then the packages that have thermal pads are actually better than DIP or other large packages.

For passives, the answer is simple. Just do the math and calculate the Wattage you need, then buy parts that can handle the wattage. Some brands can handle more wattage in the same size.

Resistors can be a significant source of noise in analog circuits, but that is due to Johnson noise, which varies with Resistance, temperature and material. If you operate too close to the Wattage limit, then that can cause temperature to be a problem. Easy enough to avoid.

It’s a little more difficult for capacitors, because operating close to the Voltage Rating can cause the capacitance to diverge greatly from the marked value. In those cases, you want to make sure that the Voltage Rating is far above what you’ll actually use in your circuit. I’m not sure, but I don’t think that the High Voltage Caps are necessarily that much larger.

Brian


On Mar 13, 2018, at 9:49 PM, rsdio at audiobanshee.com wrote:
> I’m spoiled. The local assembly shop will do a small run for me without the cost of a stencil. That saves me $300 each time for prototypes. They have all of the microscopes and tools to hand-paint the solder paste on a few boards. The results looks just as good as production. Seattle and the surrounding area have a lot of assembly options.
> 
> QFN is probably the smallest I’ve worked with, though. I stay away from BGA. It’s not like I’m designing cell phones or other mobile, hand-held devices.
> 
> Brian
> 
> 
> On Mar 13, 2018, at 4:54 AM, jarno.verhoeven at ziggo.nl wrote:
> Seeeeeedstudio does offer cheaper stencils now, keen on giving it a try (especially since I cannot handsolder BCM847bs anymore).
> 
> ------ Origineel bericht------
> Van: Mikko Helin
> 
> QFN soldering by using a hot plate?
> 
> On Tue, Mar 13, 2018 at 1:20 PM, chris <chris at chrismusic.de> wrote:
> Can QFN be hand-soldered without an oven?
> 
> Chris
> 
> On Tue, 13 Mar 2018 11:10:51 +0000 paula at synth.net wrote:
> Tom,
> 
>  For me it's a size thing. I mean consider, a VCO, VCF, VCA and ADSR in
> a 4mm squared package?? I mean you've got a synth voice in such a small
> space. Small space ! = lower cost and better thermal coupling if you have
> multiple voices.
> 
> Paula
> 
> On 2018-03-13 10:22, Tom Bugs wrote:
> Can you expand a bit on that Paula?
> I've never really considered them...
> Is it mainly a size thing or am I missing something
> interesting/important?
> 
> 
> On 13/03/2018 10:16, paula at synth.net wrote:
> QFNs are awesome.
> 
> On 2018-03-13 09:00, Roman Sowa wrote:
> I've read somewhere that they don't do SOIC for anything greater than
> 16 pins, but can't remember exact explanation. In general it was in a
> spirit of "SOIC sucks". In every Alfa QFN chip they say about center
> pad greatly improving thermal stability.
> 
> Roman
> 
> W dniu 2018-03-12 o 22:34, Jay Schwichtenberg pisze:
> Wonder why they didn't do the AS3320 as a SOIC. Maybe they didn't
> have 18 pin SOIC packages and had QFN packages.
> 
> Jay S.
> 
> *From:*Synth-diy [mailto:synth-diy-bounces at synth-diy.org] *On Behalf
> *Sent:* Monday, March 12, 2018 12:27 PM
> 
> Of interest
> 
> http://www.alfarzpp.lv/eng/sc/application.php