[sdiy] Latvian CEM Synth IC clones

Joe Grisso jgrisso at det3.net
Sat Mar 17 07:45:49 CET 2018


In addition to China, OSHPark also has a stencil option for prototyping,
they make it out of polymide instead of steel, and is really cheap. Last
stencil I had made was $25 with a credit card squegee.

On Wed, Mar 14, 2018 at 6:00 AM, <rsdio at audiobanshee.com> wrote:

>
> 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
>
>
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-- 
Joe Grisso
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