Pin-spacings on surface mount PICAXE's? [Archive]

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Grogster

31-01-2006, 01:10

Hi.
:-)

Simple question:

Q) What is the pin spacing on the surface-mount versions of the PICAXE's?

I am assuming a standard 1.2mm spacing for these chips, but it kinda depends on what surface-mount package you guys decided on(or that MicroChip decided on).

G.

Stan. SWAN

31-01-2006, 01:34

These are known as SOIC (Small Outline IC) with pin spacing half the normal 1/10th inch ( 2.54mm, so expect 1/20th inch or 1.27mm.

All manner of adaptor boards abound =>www.isipkg.com/images/adp_soic_soic.jpg <A href='http://www.isipkg.com/images/adp_soic_soic.jpg ' Target=_Blank>External Web Link</a> being typical. Even DIY should be possible however- I'm intending this in a future SiChip article. Stan

andypro

31-01-2006, 02:04

DIY surface mount is alot easier to make boards for...no drilling! I hate drilling. Soldering..well..tha'ts another story. It's not that bad on the biggish stuff though. Hot air rework stations do wonders. I think people are more affraid of the words "surface mount" than need be. Maybe your article will clear that up stan!

--Andy P

Grogster

31-01-2006, 03:27

Well, 1.2mm surface-mount is really quite easy!
All you need is a good soldering iron, with a fine tip, and a steady hand!

I think most people tend to be frightened of SMD, due to the difficulty in holding the tiny bits in place, and the fact that they generally have to be soldered much faster then their full-size equivilents, or heat will damage the device.

I "Sweat-solder" all my SMD - tin the PCB pad, then tin the underside of each IC pin, place the IC in place, hold with a toothpick or similar, and simply heat each pin in turn. The solder melts, and hey presto...
:-)

This also stops you from applying too much solder, which is easy to do...

I have PCB design software, so I will probably start any new PICAXE designs with the SMD versions.

G.

ylp88

31-01-2006, 06:28

I've soldered an SMD chip with 4 leads down one side with a spacing of 0.0256 inches (0.65mm). Using a chisel tip worked well - you just solder the whole side of the chip in one go! Then after it has had time to cool a bit, you can rework the solder and pull excess away onto the tracks. Works a treat!

Normal SOIC chips are also possible, one pin at a time, with the side of a chisel tip - I've done it woth 4049's.

ylp88

evanh

31-01-2006, 07:40

I was mighty impressed with a 0.4 mm pitch QFP package the other day, I had thought they had stopped shrinking at 0.5 mm. It had almost the same gap between pins but the pins are much thinner at around 0.16 mm!

Evan

ylp88

31-01-2006, 10:05

A while ago, I aquired some parts from a friend out of interest of their packages (ie. absolutely no intention of usung them). The packages are as follows:

sle20a
<A href='http://www.national.com/packaging/folders/sle20a.html' Target=_Blank>External Web Link</a>

ujb160a
<A href='http://www.national.com/packaging/folders/ujb160a.html' Target=_Blank>External Web Link</a>

I have to say that they look a lot better in real life than the images show. The images make them look really big, but just look at the dimensions stated to "see" how big they really are!

The following one was a package of a device I sample ordered from National but accidently selected the wrong package. I ended up using it as a die type of thing, with really thin wires hooked up to the necessary pin and then these soldered onto the PCB. Luckily I actually only needed around 10-15 of the 28 pins. The unfortunate news: a couple of the wires make bad conenctions and I tried resoldering it, only to have the solder spead flux everywhere which made it a nightmare and in the end, the whole thing didn' work - I thnk I fried the poor little (literally) chip...

lqa28a
<A href='http://www.national.com/packaging/folders/lqa28a.html' Target=_Blank>External Web Link</a>

I can just see the PICAXE-28 series being produced in the LQA28A case! With two 0603 22K and 10K resistors nearby, of course! Now to find a 3-pin connector that will be suitably small to keep the PCB foortprint on a thumbnail...

ylp88 

Edited by - ylp88 on 1/31/2006 9:08:18 AM

andypro

31-01-2006, 14:39

YLP88 said:

I can just see the PICAXE-28 series being produced in the LQA28A case! With two 0603 22K and 10K resistors nearby, of course! Now to find a 3-pin connector that will be suitably small to keep the PCB foortprint on a thumbnail...

I says:

Your sick. A sick sick man. hehe.

Actually..This is where hot air rework staitons come in handy :). You can get a hot air/solder iron station that's decent and relatively cheap from sparkfun, and it makes a WORLD of difference on the little stuff. Using that, the proper tip, and some solder paste, you can literally sodler anyhitng you can make a board for. And the neato thing is that the chip aligns itself. It's like magic...;)

--Andy P

Edited by - andypro on 1/31/2006 1:39:55 PM

Stan. SWAN

31-01-2006, 23:06

Since the thread has become SMD I'll mention that many of those dirt cheap ( ~US$2 ) solar garden lamps now come with the discrete components replaced by SMD versions. Hence aside from all the goodies in these lamps (White LED, 2V 30mA PV, NiCd etc), you can also cheaply practise SMD skills with 2 transistors,& assorted R & C etc. See pix => www.picaxe.orcon.net.nz/smd.jpg <A href='http://www.picaxe.orcon.net.nz/smd.jpg' Target=_Blank>External Web Link</a> Stan