SO8

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Mike6158
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SO8

Post by Mike6158 » Thu Nov 25, 2004 5:27 pm

This is probably a dumb question but I'm stuck and I'm hoping that someone here can help me out. I'm working on a little temperature switch. I want to use a PIC12C508 and a MAX6675 T/C to digital converter to build it with. The library didn't have a MAX6675 in it so I made one. The 6675 only comes in a SO8 case. I have no prior experience with surface mount technology so I'm at a loss for how to mount it. I don't want to try to make a 2-sided board. One sided boards are enough for me to tackle rigbt now. How do I mount the thing? More correct... how do I build a board in Eagle to allow me to make a template for etching my board????<p>Should I use some other temperature sensor?<p>PS- I chose the PIC12C508 for prototyping. Eventually I will move the project up to a 16F84 and do some things with servo outputs based on temperature and monitorng servo input from a radio transmitter. There is some method to the madness. Not much... Just some.
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

Mike6158
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Re: SO8

Post by Mike6158 » Thu Nov 25, 2004 5:47 pm

Good grief... I've been jacking with this problem for hours and on a whim I re-read the manual for Eagle. Just after I made my post I opened the manual up and the page that it opened to explained what I needed to do (mirror the SMD package).<p>This place is magic. No doubt about it :D
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

terri
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Re: SO8

Post by terri » Thu Nov 25, 2004 6:53 pm

It's called the PON effect. You can't find something and turn the place upside down looking for it and gnashing your teeth amd rubbing ashes on yourself and finally you break down and go out to buy a new one and you come back with a shiny new one and when you walk in the door you trip over the one you couldn't find.<p>That's the Perversity Of Nature.<p>Einstein was wrong. Nature IS perverse.
terri wd0edw

Mike6158
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Re: SO8

Post by Mike6158 » Fri Nov 26, 2004 6:53 am

:D I'll remember the PON effect...<p>BTW- anyone here have any advice on how to breadboard a SMD? It just occured to me that it's not going to plug in to my breadboard... I suppose that I could solder wires to it or make a little pcb with pins sticking out but that means I still have to solder it to the board. If that's the best that there is then so be it. I just thought someone here might have a better idea...
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

redrocker
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Re: SO8

Post by redrocker » Fri Nov 26, 2004 8:51 am

As an aside off your main topic, you made mention of making use of the PIC16F84 later on. Forget the '84. It is essentially obsolete. Microchip is trying to discourage its use in new designs by making it more expensive than newer lines of chips. If you need the I/O capabilities of an 18-pin chip, consider the 16F628 instead. It has a more advanced core than the '84 and costs about $2 less than the '84.<p>As to your prototyping dilemma, Jameco sells SMD-to-Thru Hole adapters for just this purpose. One brand is called Surfboards and another is made by Bellin Dynamic Systems, an advertiser in N&V. An adapter for an 8-pin SOIC costs $3.55 at Jameco.

Mike6158
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Re: SO8

Post by Mike6158 » Fri Nov 26, 2004 10:21 am

No kidding? The '84 is going out of "style"? Thanks for the heads up.<p>Jameco... they get a lot of my money. Why I didn't think of looking there I don't know. Thanks.<p>Edit:
Well... those will work... but I would still need to solder the SO8 to their board and then unsolder it and then resolder it to the "real" board once I am past the prototype stage... Or maybe not. Maybe I buy two and one is always for prototyping... Thanks.,<p>[ November 26, 2004: Message edited by: NE5U ]</p>
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

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philba
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Re: SO8

Post by philba » Tue Nov 30, 2004 10:58 pm

SOICs are pretty easy to use and the surfboards (I make my own) are easy to use. Dont waste time desoldering the soic unless you have a decent hot air iron.<p>Since I make my own boards, I try to avoid drilling as much as possible. Thus, I LOVE SMDs and design with them as much as possible. soldering SMDs is, IMO, an essential skill for modern electronics.<p>For prototyping, I have a number of TH PICs (and avrs) that I use for proof of concept on a solderless BB. <p>Finally, the 16F628A is a drop in replacement for the F84. it is cheaper by half, faster by 5X, more code space and has way more features. <p>Phil

Mike6158
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Re: SO8

Post by Mike6158 » Wed Dec 01, 2004 4:38 am

It's probably the fear of the unknown (SOIC) that bugs me so much. I make my own boards and admittedly I don't enjoy drilling those little holes. I don't think a board that is 100% SOIC, other than the parts being so small, would be so bad... It's mixing a SOIC into a design that uses DIP's that initially made a mess.
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

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philba
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Re: SO8

Post by philba » Wed Dec 01, 2004 9:38 am

mixing TH and SM parts - its really easy. Just put the SMDs on the "solder side". I just finished a vent louver controller using a PIC16F877A DIP. Lots of TH headers (ICSP, LCD, Serial, ...). But I used SMD transistors, resistors and caps. By my count, I saved about 30 holes.<p>Its pretty easy to mount SMDs - even the tiny SOT23 transistors. Just flux all the pads and tin a corner one with some solder. Then, with tweezers (or forceps), position the part where you want it and touch the lead at the tinned part with the iron. Once the solder flows, take the iron away and wait for the solder to solidify and you've tacked down the part. About 3 seconds from start to finish. Then put a little solder on the iron and touch it to each lead in turn, doing the tacked one last. You may need to replenish the solder bead on the iron several times. I can do an SO16 in about a minute. 1206 Rs and Cs go really fast - no leads to form or trim. <p>Once you get good at this (like during your first session), you will never want to go back to TH stuff.

Mike6158
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Re: SO8

Post by Mike6158 » Wed Dec 01, 2004 1:36 pm

:D Not drilling holes sounds really good. I guess that I better stop turning my nose up at SOIC's :D
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

Enzo
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Re: SO8

Post by Enzo » Wed Dec 01, 2004 3:14 pm

Call me old school, but I absolutely hate SM. I get cross-eyed even with my magnifying lens, if you lift a pad you are screwed, and making test probe connections is a pain. And I don't do enough volume to warrant the expense of hot air.

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philba
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Re: SO8

Post by philba » Wed Dec 01, 2004 5:04 pm

Each to his own but you are missing out. There are lots of devices being released only in surface mount. You don't need a hot air station. I use a smallish tip in my iron and it works just fine. <p>You can mix TH and SM. So put your test points just like you would normally. You can even get clips that go onto SOICs and such for testing. its also a great way to ICSP PICs and AVRs. I have yet to find anything negative about SMDs except for the really tiny stuff like tqfn and such.<p>And I haven't even talked about doing reflow - think of it as toaster oven soldering. That's my next project - a reflow oven.<p>Phil

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Re: SO8

Post by Enzo » Wed Dec 01, 2004 11:03 pm

It also depends on what you are doing. I am in maintenance and repair, I am not inventing things. So I only need whatever the OEM used. And those tiny flat guys with 100 legs are really tough to do by hand. Removing them is hard, installing them on a clean board is more a matter of patience. Likewise test points. I don't have the luxury of designing points into a project, and my OEMs don't bother except for points to monitor operation or setup. I find it hard to find pin 68 or something on those LSIs, and if I do, I have to make sure my tips are super sharp to keep them on the trace.<p>In the absence of fancier gear, I have to use a removal iron, which requires me to get a tip for each size and shape component. It is a swell piece of technology, the suction collects the chip once loose, but the cost adds up quickly when tips are $40-50 each.<p>In something like a Mackie mixer, they have gotten to the point of mounting tiny sm op amps under connectors. To even get at them I have to remove a couple XLR jacks and a few small components. And then I am still working in a small clearing.<p>I have been soldering for 50 years, so maybe I am just an old dog looking at new tricks. I am pretty good on through hole though. If you like them, more power to you. I know they are not going to go away.

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Dave Dixon
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Re: SO8

Post by Dave Dixon » Thu Dec 02, 2004 5:03 am

Hi all,
To remove SMD's with lots of legs, I found some stuff called Chip-Quick from Emulation Technologies. I think it may be available from DigiKey. It's an alloy with a super low melting point. Just a little dab will mix with the existing solder, and the joints stay liquid for quite some time. Just be sure to clean it off, as you don't want parts falling off on a hot day!!!
Just my 2¢
Dave

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philba
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Re: SO8

Post by philba » Thu Dec 02, 2004 9:48 pm

interesting product. kind of pricey, though. The complete kit is about 2/3s the price of the hot air machine that circuit specialists has (and that I've been thinking of getting :) )<p>Phil

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