Need help with SMD protoboard selection

[Lston]

I am looking for a SMD protoboard for this component.
http://download.cypress.com.edgesuit...=1228097355670 I'll be using the Recommended Power and Ground Circuitry listed on page 7, I won't need the buttons or wheel encoder. I'll be reading the chip using my Atmel EVK1100 evaluation board "66 MHz MCU with 512K bytes Flash".http://www.atmel.com/dyn/Products/to...p?tool_id=4114 Page 1 of the data sheet says it is a "8x8mm QFN package". Page 4 shows the package pinout and there are 42 pins. Page 17 in the upper right shows the bottom view and lists the pad width as 0.20mm but I can't find the lead pitch "distance between the pads" or the pad length. Page 19 says: "Land pad architecture and spacing are consistent with JEDEC MO-220 (52-lead QFN)." Would this board work? http://electroboards.com/proddetail....od=SSO64-05-EB

[Lston]

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[OrionBlade2003]

The red board you posted a picture of is basically the fancy schmantzy version of DIP, or dual inline pin. The chips are generally much longer than they are wide, and have two rows of pins, one on each long edge.

You've got a QFN, with the Q meaning Quad. If you look carefully, not all the pins are present on the device, but they fit into a 52 QFN package, since the pins all land on the edges of a square at the correct pin spacing.

Either dead bug the chip, since you'll likely only need power, ground, and a couple of wires for the SPI bus connection to an MCU, or...

Etch your own PC board by printing your schematic at 1:1 scale from eagle cam on a transparency and using photoresist. To expose the photoresist, you can either spend a ton of cash on a high quality UV light source, or set the thing out in the sun for a few minutes.

Or heck, zap something with an arc welder near-ish the board.

Final option is to simply buy one of these:

http://www.mouser.com/Search/Refine....97&Keyword=QFN

There you go!

Also, I found these:

pitch 52 QFN

But your biggest problem with those, is that since it's a quad package, you're going to wind up cutting through your traces when you mount the clip-on lens.

So your best bet is either dead-bug (just grind yourself a tiny soldering tip and go to town with the finest wire you can manage to see under a magnifier) or etch your own PCB. Etching your own is actually pretty darned simple, and if you make multiple copies of the PCB on one transparency, you can make like a dozen of the little buggers in one shot.

Check out www.mouser.com or www.jameco.com for PCB etching supplies. You'll want the photosensitized boards, and likely it'll be a negative photoresist, so the masked areas are what stay, and the unmasked areas break down and get rinsed off in the etch process.

I think.

It's 1:30 AM and if you have any questions, just hit me up via PM and we can figure it out after I've had a few cups of coffee in the morning.

I do this sort of stuff for a living as a D&P Consultant, but I typically have catalogs coming out my ears and PocketRef pages dogeared left and right after any given project.

What's the project in specific? Might be able to solve your problem with an easier to manage version of the sensor...

[Lston]

Thanks for your reply; the project is for a "Microscribe" like device. See my post "Mouse sensor" (3/4 the way down, and the last 4 posts on the next page) here: http://cnczone.com/forums/showthread...=4424&page=23.
Yes I had considered using a Schmart board but it would only be good for developing the code and too big to actually fit into the device. I'am trying to create a schematic in Eagle now but the pad shapes are holding me up and unfortunately the chip isn't in the eagle library and Cypress doesn't have any files either. I've joined the Eagle newsgroup; watched some good tutorial video's;http://tangentsoft.net/elec/movies/ searched the net and posted at other sites but so far no luck.

[OrionBlade2003]

The QFN package is industry standard. You should be able to get a QFN package from Zilog (www.zilog.com) for one of their 52QFN microcontrollers.

If you don't care about the function of the device (spice files) then just get the package and drop it in your schematic and go cut/print/etc.

There actually should be a QFN package part in Eagle, based on my documentation searches. It's been a while since I used Eagle, but just poke around and you should find something. Or look on www.digikey.com and see if you can find an equivalent part. You will NOT find a part with the PCB cutouts, so those will need to be edited in, but as far as your pad placement and size, they're industry standard, you just won't be using about a dozen of them, since they're N/C.

Hope that helps. Feel free to PM me if needed, and I can see if I can poke around with you on it. I'll have to DL Eagle soon anyhow, since I have to build a driver board for a similar sort of sensor, but this one is a MEMS device that I'm fabricating myself.

think 200 micron diameter mirrors, 10 microns thick from chromium plated copper.

ZOMG.

Later,
Rion

[OrionBlade2003]

I have a maxim newsletter with some 8 by 8 QFN parts in it. I'll see if they'll work and send you the part numbers.

As far as the 52 vs 42 pin count problem - just think of it like a lego brick. A lego brick can have 8 bumps on top, or you can snip off two of the bumps if you need a flat spot and they're not going to conenct to anything. it's still consistent with a 2 by 4 bump brick, but it's only got 6 bumps, so you use a schematic for a 52 QFN, but you only run traces/connections for 42 of those pins, and there's nothing to solder there anyhow, so just leave the pads there and don't sweat it when you're putting it together in real life.

I'll hit you with that part number when I get back home - gotta jet!

[OrionBlade2003]

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3512/t/al

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5620/t/al

Those components are pin-position compatible with your part's package, as far as I can tell.

What's your background in electronics?

Have you considered hand-drawing the etch resist with a sharpie?

I did this for a 48 pin TQFP chip which was ungodly tiny, but I wound up drawing a heavy line where the pads would land, then "erasing" the etch resist between the leads. I stuck the chip down with some sticky tack (the stuff you hang posters with) and went in between the pins with a stainless steel dental pick and scratched away the sharpie. Etched the board, and everything came out beautiful-ish. Good enough to hold solder, and the chip worked.

OR - tweak the mask in a drawing program that lets you output real dimensions. The pin pitch, btw, is either .65 or .8mm....


http://www.onsemi.com/PowerSolutions...s&rpn=NB4N121K

http://www.onsemi.com/PowerSolutions...g&rpn=NB4N121K

There's a clock IC that has the same pin count and size, 8 by 8 mm, with a simulation file and the IC package drawing.

This should be everything you need to either drop into your schematic, or simply transfer the dimensions from the drawing. If not, then I'd suggest going to a local college electrical engineering department and grabbing a random EE student with a parts box in his hands and seeing where you're going wrong. That's what we pay our taxes for, right? ;-)

I would seriously reccomend reflow soldering using a paste and a mask arrangement if possible, and toss the sucker in your toaster oven instead of trying to hand solder it. If you don't have alot of experience with these parts, then you WILL burn them up.

Best of luck,
Rion

[Lston]

I did an update then rechecked the eagle library and there are no 52 pin QFN's. The Maxim parts you listed only have IBIS files, no CAD files and the Zilog links for searching cad files are broken.

OR - tweak the mask in a drawing program that lets you output real dimensions.

I have Adobe Illustrator CS2 and Autodesk Maya 8.0 which can both export to DXF but Eagle can't import DXF. I did see a conversion utility someone posted on Eagle's site called EAGLE PCB Power Tools:ftp://ftp.cadsoft.de/eagle/userfiles...ls5_02beta.exe
If you or anyone else can find a 8x8mm 52 pin QFN in in eagle or DXF format I would really appreciate it.

[Lston]

You said in your post "The pin pitch, btw, is either .65 or .8mm...." Where do you see that?
I've attached a drawing I found which is much clear than the one in the data sheet.
Looking at the: BOTTOM VIEW, then down and to the right of the words: SEE DETAIL - C it shows the pitch as 0.50mm
I also see:
Chip dimensions: 8.300mm SQ, Radius 0.25 "Just below the words: "TOP VIEW"
Pad Width: 0.20mm "Below the words: BOTTOM VIEW, and at the fourth pad from the left of the chip."
Pad Length: 0.50mm "Just below the words: SEE DETAIL - A"
Two holes: 0.64mm DIA. "Detail B, Lower Left"
Hole locations: 5.57mm center to center.
Top hole: 2.25mm from center line of chip.
Bottom hole: 3.32mm from center line of chip.
Edge of chip to hole centers: 0.85mm
3.32mm is center line of chip to center of bottom hole
" 8.300mm / 2 = 4.17mm; 4.17mm - 3.32mm = 0.85mm"

This is where I'am at in Eagle. I guess I still need Detail A, which I think is a heat sink.? and the keep-outs
mentioned on page 19 of the data sheet. The way I read it there are two holes, DIA: 1mm x 2mm and 4 other
keep-out but I don't understand the measurements.

[OrionBlade2003]

TQFN standard dimensions are 8mm square, 52 pins, .65 or .88 mm pitch.

Got 'em off a pdf I had for some other chips.

I'll follow up later when I have a bit more free time to post.