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In-Reply-To:	<1508231827.AA21909@ivan.Harhan.ORG>
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Date:	Sun, 23 Aug 2015 20:56:58 +0000
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Subject:	Re: [geda-user] Microphone footprint woes
From:	"Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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On Sun, Aug 23, 2015 at 6:27 PM, Spacefalcon the Outlaw
<falcon AT ivan DOT harhan DOT org> wrote:
> Richard Rasker (rasker AT linetec DOT nl) wrote:
>
>> Correct me if I'm wrong, but I don't think that this is an SMD part, and
>> that you're supposed to simply solder wires to the contacts.
>>
>> For SMD type microphones, search for "MEMS Microphone", e.g.
>> SPW2430HR5H-B from Knowles.
>
> Thank you for shining the light on my ignorance!  As I have just
> learned, the type of microphones I've been looking at are called
> electret condenser: they are the type that's been used in the
> old-fashioned cellphones of the early 2000s, they are what the GSM
> chipset I'm using has been designed to work with, and I don't feel
> like changing to MEMS - my motto in this project is Do Not Innovate.
>
> And I also just learned why ECMs are generally not made in SMT form
> factor: they can't withstand the heat of reflow soldering.  This part
> certainly explains why most cellphones I've examined have their
> microphone on wires or on a little strip of flex whose other end is
> hotbar-soldered to the main PCBA, and very few of these old phones
> have their microphone directly on the main PCBA.  As for the few
> phones that did the latter (Openmoko GTA02 and Pirelli DP-L10 do that,
> which is where I got my naive idea of doing the same), it looks like
> there were some very few electret condenser microphones made in SMT
> form, but they are now "obsolete" and unobtainium.

A lot of the MEMS microphones are a pain to prototype with because of
their footprints. That said they are massively better than electret
condenser.

> My solution: I'll put a two-pin header on my board instead of the
> microphone part, and make the actual microphone a post-board addition.
> The same as I already did with the loudspeaker.

Can I suggest that you add a couple extra pins for power and gnd so
that if you change your mind you can?

> Thanks again for the education,
> SF



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