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 Forum index » DIY Hardware and Software
mail order custom pcb's
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deknow



Joined: Sep 15, 2004
Posts: 1307
Location: Leominster, MA (USA)
G2 patch files: 15

PostPosted: Tue Jun 28, 2005 6:52 am    Post subject: mail order custom pcb's Reply with quote  Mark this post and the followings unread

hey all,
i'm working on a project where i need to use some chips designed for cell phones (read: surface mount only). the chips are 4x4x.8 (mm), and have 16 (non-protruding) pins (4 pins in about 2mm of space on each side).

i could not find any reasonable (size or price) sockets or protoboards that were specific to the package (thin qfn, 16pin, 4x4mm), although there may be something out there with the same pin pitch that would work. my needs required that the whole thing be small, and it seemed i needed to make my own board (so i can attach the wires and components to the chip).

i found that using expresspcb (an integrated pcb layout program, and manufacturing process), i could get (3) identical 3.8"x2.5" boards (with a max of 350 holes per board...this is their "miniboard service") delivered in less than a week for $58 (including shipping). this seemed like a much better idea than doing my own etching (especially since the leads are .65mm apart center to center!). i'll have about 150 of my little adaptor boards for less than $60 and no chemicals, no uv light, and getting it right is someone elses problem (who hopefully does this better than i could)....and i get through holes!

there is also "padtopad" which will actually populate the boards as well as manufacture them, and emachineshop, which is more like autocad, and allows one to design castings, extrusions, machined parts, stampings etc. in any quantity.

with the newer electronic components all being designed for smt (surface mount) and machine soldering, this kind of thing will be more and more necessary for any diy or experementation (imho). the emachineshop product means that you can "invent" without having your own machine shop!

you can almost always get free samples of any of the new chips (they hope you will order 50,000 units for your product), and the degree of integration is astounding (this particular chip is an electret mic preamp with balanced line in and out with variable gain and a built in bias source...all in a 4x4mm package!). i would have a really hard time building the same thing from discrete components at all (i have no formal electronics training), never mind fitting it into such a small space.

i've done some reading on hand soldering smt chips, and i'm fairly confident i can pull it off (i used to make high end piccolos, and have very good soldering technique with a torch or an iron), but i am a little nervous that it will be harder than i think.

...now i've got to try and train my circus fleas to hold a soldering iron...

deknow
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jksuperstar



Joined: Aug 20, 2004
Posts: 2483
Location: Denver
Audio files: 1
G2 patch files: 18

PostPosted: Tue Jun 28, 2005 8:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Having a good iron makes all the difference. Those plug-it in, and wait for it to heat up ones (that cost ~$5) are big trouble. That said, it's actually pretty easy. I use a pair of tweezers, pre-solder the pads on the board, then just hold the part down and touch the pins/pads. It's not as "clean" as a manufactured board, but I don't have an oven that goes to 700+ degrees to bake down the components, either.

Another manufacturer of boards that I've used is Advanced PCB...they had a sale once for $25 setup, and 10cents /sqr inch. I got 10 2"x3" boards for $60.

That said, expresspcb is also nice, especially since they tie into Digikey and other suppliers, so your BOM can be directly ordered once you finished your design.
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mosc
Site Admin


Joined: Jan 31, 2003
Posts: 17606
Location: Allentown, PA
Audio files: 124
G2 patch files: 60

PostPosted: Tue Jun 28, 2005 9:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Good luck with that surface mount devices. Let us know how it works out.

I'm moving this to the new DIY Synths forum. Very Happy

_________________
--Howard
my music and other stuff
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Afro88



Joined: Jun 20, 2004
Posts: 701
Location: Brisbane, Australia
Audio files: 12
G2 patch files: 79

PostPosted: Tue Jun 28, 2005 10:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sounds like an interesting project. What are you building? A mixer or something?
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deknow



Joined: Sep 15, 2004
Posts: 1307
Location: Leominster, MA (USA)
G2 patch files: 15

PostPosted: Wed Jun 29, 2005 6:21 am    Post subject: Reply with quote  Mark this post and the followings unread

hopefully, this will be the next generation of flute pickup. i'm using this chip:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3761
which is designed for cell phones and the like. the reason i need such a small preamp is so it can all fit neatly inside the instrument, and have balanced line level output. wireless is an obvious next step, and i'll probably use one of the commercial "guitar bug" wireless systems that is on the market.

deknow
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Afro88



Joined: Jun 20, 2004
Posts: 701
Location: Brisbane, Australia
Audio files: 12
G2 patch files: 79

PostPosted: Thu Jun 30, 2005 4:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sounds interesting. I'm guessing the only pickups available at the moment are too bulky with wires that get in the way. I'd love to hear some sounds, processed or otherwise, when you get it up and running Smile

I love seeing people going "well, you can't buy it, so I'm going to build it" - great stuff.
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dnny



Joined: Mar 12, 2005
Posts: 519
Location: Helsinki, Finland
Audio files: 8

PostPosted: Fri Jul 01, 2005 1:53 am    Post subject: Reply with quote  Mark this post and the followings unread

deknow wrote:
hopefully, this will be the next generation of flute pickup.


hmm.. pickup for flute - this brings to mind old story about Electric Symphony Orchestra , Daniel Ravenaugh, Buchla, young Howard and the great race to build the monster mixer and giant PA.

if you haven´t heard it you should read it

Grandpa Mosc, tell us a story?

daniel
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algorhythm



Joined: Feb 22, 2005
Posts: 46
Location: Shoreline, WA

PostPosted: Tue Jul 05, 2005 3:58 pm    Post subject: soldering surface mounts Reply with quote  Mark this post and the followings unread

For surface mounts, get the pc board tined and use flux for surface mount. I was leary of soldering a surface mount chip to a pc board but it turned out to be really easy. The biggest issue is keeping the pins aligned. On a clean tined board smear some surface mount flux on the pads, align the chip on the pads (double check) solder one corner lead to the pad, two second with a low watt iron should do it, check the alignment (double check) the solder the lead diagonal from the first, check the alignment, finish soldering the corners, check the alignment, finish the rest of the leads.

Kevin Ross has a nice info site on soldering surface mounts and sells the pc board flux, like he says the 2 ounce 2 dollar tin will probably last 20 years.
http://www.kevinro.com/newdocs/learningcenter/surface.htm

Thanks,
Jeff Sandys
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