SMD for Picaxe size

WHITEKNUCKLES

New Member
From sideboard thread.

BrendonP,
Nail hold-down is just that. Holding the component down with tweezers or toothpick means that position control is from the shoulder, at worst, or from the wrist. With the fingertip on the board and the nail on the component there is much less chance of movement. Fast and instructive, if you feel warmth you have taken too long.

Using toner transfer, PCBs are easier and cheaper than ever, the only cost is the board and ferric chloride.
Searching the web, there are almost as many ways to solder SM as there are people, it is indeed a personal thing.

For SM, solder on the pad is almost essential.
I paint the freshly cleaned tracks with used solder-wick held in a small insulated crocodile clip as the brush.

With the whole surface fluxed, I flux the curved end of the 'brush', place it over the far end of the board, heat with the Iron and draw all towards me painting a narrow strip. More flux and another strip. Surprisingly little solder is needed but frequent fluxing is required and excess solder is easily removed in the same way using new solder-braid. Clean thoroughly.

That part is quite therapeutic and in SMALL numbers somewhat absorbing, "Gosh that was easy" and grab another. The board in the photos was timed at 8 seconds start to finish, naw, the painting.

Narrow gauge multicored solder is helpful and a percentage of silver is recommend to prevent leaching.

On the top right hand pad I place the tiniest amount of solder, flux the pads, place and hold the component, clean the iron, pick up the smallest possible amount of solder from the reel onto the pointed tip to aid thermal conduction and place the iron on the track touching the end of the component wiping up and away.

Brown jelly flux in a small tub with a small scrap of paper inserted vertically and lightly smeared with flux, the end of the solder is drawn up the paper then placed half way across the end of the opposite pin, touching both track and pin. The cleaned tip of the iron is placed on the track as close as possible to the pin without touching, the tiniest hesitation then slide the iron up to the solder, watch the melt (flash), slide up over the pin and away.

OK down to 0603 as yet.

So how to 0.5mm?

Dave
 

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BrendanP

Senior Member
Thanks whiteknuckles for the input.

I've been doing a bit of work with a GSM/GPRS module as I have a few projects on the go that require remote control and reporting. The module uses a molex smd connector, 70 pins .05mm pitch. The SIM card holder is .100 and is laughably easy after the molex .05mm connector.

At first I was going to get some SMD soldering equipment form Zephyrtronics in California. They sell equipment to NASA, Raytheon, Boeing etc. for re work and R&D small batches so I figured it was good stuff. I still intend to do so a bit further down the track.

I came accross sparkfuns tutorial on SMD soldering. I was going to use the toaster oven but sparkfun said that the top heat of the toaster oven damages or even melts the plastic in the sim card and connector they used on their GSM break out boards. They said a electric frypan did a better job than the purpose made smd soldering oven they had bought.

So my girlfriend went on a mission to a local store and came back with a $50 frypan. She got a largish pan so it can take large boards.

I bought lead free paste made by Multicore from a local supplier here in Australia for $18 a tube. It has an ounce in the tube. I bought two , one however is more than enough and will last many jobs. I keep it in the fridge.

I have a fluro desk lamp that has a magnifiying glass built into it. This is CRITICAL on the .05mm work! I also use a jewellers loupe. This is one of those things you see diamond dealers holding in their eye when looking at stones. It is helpfull when examining the smd work of bridges,dry joints etc.


Silicon Chip, a local electronics mag here in Australia ran an article a while back on a home made high mag CCD camera which I will build soon as it will be great for checking out work.

It uses a old 50mm SLR lense off ebay for 20$ and a bare board CCD camera. They used plumbing fittings to make the housing to hold the camera and lense. They also use different lenghts of PVC pipe to give different focal lenghts for different magnification. You can use it at VERY high magnification. You look at the image through a large TV screen and things are huge.Fine focus is done with the slr lense.

So, I apply a very small amount of paste to the pcb off to the side of where the connector is going to go. I then use the the tip of the metal tube/hypodermic on the end of the syringe of paste to take paste from the little match head sized pile Ive put on the pcb off to the side and then transfer it onto the pads. I will use a toothpick in future for this.

The key thing Ive found is that you need very little. Dont be concerned if the paste gets onto the mask between the pads. When you heat it up it runs onto the tinned surface of the pads like the silver metal of that 'liquid metal' Terminator in the movie. Thats the closest analogy I can come up with.

I wipe off the small bead off paste off to the side with a piece of damp paper towell.
If you stuff the job up, no problem just wipe all the paste off and start again.


After I have got the paste on the pads I then put the board into the cold fry pan. The connector isnt on the board at this stage. I found if you move the pcb with the connector on the connector tends to slide aorund which smears the paste and tends to cause the paste to get up inside the connector which then cause bridges which you cant see and can only diagnose with a multimeter as shorts.

Once the pcb is in the pan I put a nob of blu tack on the connector and then poke a small screw driver into the blu tack and use that to pick it up. I carefully lower the connector onto the pads, the idea is to align it correctly so it touches down exactyl where it should be so it doesnt smear the paste around too much as you try to align it. I then use another small screw driver, probe etc to hold the part in position on the pcb while I pull the other screwdrive out of the blu tack . You can leave the little lump of blu tack there until after youve reflowed the paste.

I then turn on the frypan and crank up the heat until I see the paste melt. The part will self align to a certain degree due to the molten solder paste. I haven't had to worry about heat damage to the part because the connector/SIM tray are innert.

To gauge/calibrate temp Id stand a merc thermometer from a lab supply in the pan with a bit of coat hanger bent to hold it up right with the bulb on the pans teflon surface.

The pan will heat up form a cold start and melt the paste in around a minute.


As soon as the paste is melted I turn off the pan at the wall and let the pan cool down. Dont touch the pan while the sodle is molten.

Once cool I check every track for shorts to the track next to it. If there are, and there usually is with .05mm spacings, I get very fine good quality solder wick (gootwick I use) and put it over the pins on the connector and apply the tip of the iron for a few seconds and let it wick up the excess solder. This will draw out even solder that is right up insdie the conenctor that you cant see with your eye. But you know its there becasue your meter says there a short.

The good news is if you stuff up the placement of the part put the pcb back in the pan and heat the board up again and pull the part off with a pair of long nose pliars when the solder melts again. While the pcb is still hot use a bit of wick to clean up the molten solder left behind. Let the pan/ pcb cool and repeat the procedure of applying paste and part. I did this about 6 times to one pcb until I got it right and it didnt seem to bother the board. I did use a new part each time however. The silk screen on the side facing the pan got a bit smeared but no tracks lifted or anything radical like that.

The soldered joint is mechanically very strong, I ripped off a soldered connector with a pair of long nose pliars to see how strong it was. It took a lot of energy to rip the thing off. Some of the legs stayed attached to their pads and ripped out of the connector rather than off the pcb.

I don't say the fry pan is the pro way to do things but when you're on a shoe string budget you do what you have to do to get the job done.
 

WHITEKNUCKLES

New Member
BrendanP
Apologies, downtime

I doubt if our efforts could be further apart in this technology, and more power to your arm.

Very interested in the 35mm lens system and would appreciate more information.
I have just put a 1.5" loupe inside a 2.5" loupe and the combination in front of a 2.2Meg camera as a webcam with the results in the photo.
On the screen the image is magnified to 5 times the original but would be a struggle to use in practice as the clearance under the lens is about 1.5"

I have been struggling to get sufficient binocular magnification since I started drilling PSBs. Loupes are great for examining finished work but a stereoscopic view wins for working. I have been using 'over-strength' reading glasses which give a working distance of about 6", I really fancy 'dental binoculars', magnification and working distance to order, £1100 in the UK.

You mention solder paste at 18$ an oz, here it is £18 for less. Great stuff for hand soldering but the shelf life is so short.

I normally use UV photoresist but have tried toner transfer and find double sided boards are not easy with the toner transfer method but if the second side can be simplified to straight sided areas I have had success with scratching. With the image on side one and a resist applied and dried on side two, ruled scratches are made in the resist to define the areas. I use the 90* corner on the back of a modelling blade, about 15 thousandths wide. The photo also shows bandsaw nicks for wire 'vias' which are offset for the rc 0.1" pins on the pads, don't like drilling.

Dave
 

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BrendanP

Senior Member
I will give you the publication details re. the article latter today after work. I'll dig it out from my shelf.
 

BrendanP

Senior Member
The article was published in the October 2001 edition of silicon chip magazine. Their web site has back issues of the mag for sale or copies of articles or give me a postal address and Ill send you the article in the UK. Mail takes about 5 days to the UK from here.

The article talks about using the camera to view blood samples. It mentions 3200 X magnification in one part as low magnification it is capable of. It says its usefull for looking at metal cracks in auto parts, examining leaf structure, water, blood. I cant see its highest magnification. I guerss yould just use a higher mag. SLR lense. Theres plenty on ebay.

The housing is made form 50 mm PVC plumbers pipe and a piece of MDF board for a base.

I'd say yould knock the job over in a easy days work or 3 or 4 evenings.
 

premelec

Senior Member
A very cheap and effective tool for clearing solder bridges on SMD and other fine pitch items is the flat common wooden tooth pick - you can clip it to a fine point or use it as is - once it gets a little bit charred and some flux on it the molten solder 'jumps' away from it.... bamboo slivers should work equally well...
 

WHITEKNUCKLES

New Member
BrendanP,
I have been unable to make headway on the site trying to locate that article. My reading is worse than my writing and my amanuensis is away just now. I will give it another try and if unsuccessful I will ask you to get a backnumber for me. I do appreciate your kind offer.

In the meantime I dismantled the camera and dispensing with the loupes, removing and extending the lens, slightly better magnification and quality are available. This would be usable but the clearance remains at about 1 1/2", which is not all that much short of stereomicroscope's 50mm.
Replacing the lens (8.7mm, F3.0) with a selection from 35mm cameras has peen partially effective but the behind the lens macro adapter has failed to produce an image so far. It must be 30? years since I did 'Images and Information' and spent too long today failing to find the course material.
http://www.brunelmicroscopes.co.uk/
Have stereomicroscopes and field microscopes, helpful people, but on reflection I doubt if I could remain stationary to use one.

I use +3 dioptre glasses for reading and have just got a pair of +8 dioptre to replace the +6 that I have been using. Working distance is now 4 3/4", the seeing is good but my old elbows complain. To combat this I searched Google for Dental Binoculars I found both 3X and 4X adaptors on Australian eBay plus one set spectacle mounted, they offer working distance around 14".

Does anyone have a simple relationship between magnification, dioptre and focal length for lenses?

premelec,
For a while I thought at SM Picaxe sizes this would not concern me unduly but many support chips are getting smaller, thank you.

Dave
 

BrendanP

Senior Member
Looks like I gave you a bum steer Dave, Silicon Chip only has articles archived back to early 2001. In any case, if you want a copy let me know and I can scan it and email it to you or post a copy to you. I think this thing is just what you need.

Premelec, thanks for the tip re. the toothpic.

I believe working with SMD fine pitch parts will become a standard skill for anyone who wants to be involved in amateur electronics. Most new parts being released seem to only be offered in SMD.
 

Michael 2727

Senior Member
I saw an ad on the TV the other day, just spotted it again after looking for days, it's for a kids toy called "Eye Cyclops" it is a small camera that plugs into the telly that has a 200 X magnification, uses 5 x AA batteries. I have taken macro pictures using a web cam and changing the lens focus to get 1/2", 12mm away from the object but it is fiddly and you need very good lighting and a steady hand. If this Eye Clops has any focus adjustment I may invest in one for checking PCBs and SMD components. Looks like it has built in LEDs
for illumination. Anybody got/seen one of these ?
 

skyv

New Member
l spotted an interesting item from jaycar in sept silicon chip.
It is a USB digital microscope camera with magnification up to 130x with 5x optical zoom.
Looks interesting.

skyv
 

andrew_qld

Senior Member
I saw the Jaycar 'scope as well- looks interesting. Most cheap CCD camera's and web cam's will work quite well up close- I was thinking of getting something for SMD work myself.

Spark Fun Electronics has a good SMD tutorial Here They make it look simple! I have found 0.05" componants are no problem to do by hand, but the finer ones can be a bit tricky.

With the high density stuff I cover everything using a flux pen (Jaycar has them) first and just use lots of solder wick and a sharp knife to seperate any spill overs onto adjacent tracks.

Sorry the pics are not very good.

Andrew
 

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BrendanP

Senior Member
Blu Tack, the SMD workers friend.

I have discovered that Blu tack is very handy for holding the SMD component in place prior to and whilst it is in the fypan being reflowed.

I have used a bead about the size of a pea on either end of the part. The blu tack has enough 'give ' in it to allow the part to moved around a little in order to get it aligned exactly over its pads. It will then stay in position while you place the pcb into the fry pan and not slide around on the paste as it is otherwise prone to do.

The blu tack doesnt seem bothered by the heat of the pan. It gets softer due to the heat but firms back up when the pcb cools down. When you remove the blu tack a little bit gets lefts behind. Use another lump of blu tack to pick up the bit left behind on the pcb or part.

I think blu tack could also be helpfull to hold parts in postion when using a iron to solder SMD parts as well.

'Blu tack' is a sort of putty that is usually used to hold posters etc. on walls. Its made by Bostik.
 

WHITEKNUCKLES

New Member
It has taken me this long to get Blutack. Works very well with the iron, there are situations where it has advantages over other methods, particularly when added solder is needed.
Thanks for the heads-up.

Dave
 

BrendanP

Senior Member
Great to hear it works for you Dave.

The blutack and frypan is a winning combo.

BTW, I picked up a Zephyrtronics hot air pencil on ebay in the US last week. It will cost about $320 AU all up airmailed to me here in Australia from the US.

Have a look at their gear Dave.
 

BrendanP

Senior Member
hair dryer as PCB pre-heater

Im waiting on my airpencil from the US.

I was going to get a pcb preheater as well but my Dad suggested a hairdryer will do the job fine. It puts a stream of warm air underneath the pcb to reduce thermal stress in the pcb and provide rapid heat up when you start soldering smd parts with the pencil on the top side.

Zephytronics make a rack to hold the pcb horizontal so there will be space to run a piece of pvc tube underneath with a 90 degree elbow on the end to direct the air stream upwards directyl underneath were the smd part. is located that you are soldering.
 

WHITEKNUCKLES

New Member
Spent some time on the Zephyrtronics site and am much impressed. You have a real bargain price there.

I like your dad's idea with the hair dryer, I still have the Creda Grenadier firelighter ( coal fire, low airspeed, high heat ) that I used many years ago to salvage chips from through hole boards in much the same way. Stubborn devils they were too.

Still finding lots to do with the 08M and I do like the 08 Development Boards, being single sided they are easy to change or dismantle. The amount that can be placed on these boards is surprising. I have taken to using a hybrid SM and TH construction with the SM components mainly on the underside. By placing 0603 components on a tangent to the pads they fit in nicely and leave the holes available for the TH bits.

Dave
 

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BrendanP

Senior Member
When the pencil gets here I'll let you know what I think.

We've just a bought a house on a half acre block. I was looking at a 7 meter by 10 meter shed with three bays with roller doors to put in the back yard as a workshop. Now that will give me some bench space!
 

WHITEKNUCKLES

New Member
If that shed were mine I'd be forced to take the bench from the living room and the lathe from the bedroom, naw, best off as I am.

Just been hacking an 08 development board, cut across just above the 5 download socket holes to get it to slide vertically into a small case **(Rapidonline 30-0600, Boss) See note**, changed the pin0 select holes to 78L05 regulator, replaced the download with two stub wires and a vertical 22K. 3 cuts for the 78L05 and one on the +V line downstream from the 100uF, couple of bare links plus one insulated from the regulator to +5V. All picaxe functions, an LED sharing pin0 with prog out.

I use one method for PCBs and another for Veroboard, both using the same modified modelling knife. Using a bench stone I grind the point to a chisel edge varying from 20 to 30 thou wide (0.5 to 0.7?mm) depending on which edge I ground last. This is wide enough to cut most Picaxe tracks with a single push without much force, allowing good control of depth, another push from the other side guessing a 20 thou gap. Given the choice I push away from the pad at about 50deg. downward towards the track first, this will lift the cut end, the reverse cut removing the section.

Would anyone care to comment on how they Hack?

Can't get the hang of these photos at all. Changing a resistor TH pad to SM

Dave

**Note. Wrong box, the 30-0600 box arrived today as a replacement and although identical in appearance it is smaller than the one I used. The next 'Rapid' size is much bigger. The 08 Proto Board was cut to a template which measures 50mm tapering to 49mm to match the box. www.boss-enclosures.co.uk shows 4003 at 85x56x35mm this is the one I used.
Profound apologies.
Dave
 

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WHITEKNUCKLES

New Member
Just got some 0402 resistors at £0.13 per 100 (Rapid) and had to try my hand.

Photo shows the hack of the download section of the board in previous photo with the TH pad modified and a 0402 22k resistor placed there, above is a 0805 10k and a 0603 0.1uF.
Did another 0402, 0805, 0805, for practice, these boards are shown populated at http://www.picaxeforum.co.uk/showthread.php?t=7784 thread.

Using surface mount is not difficult for anyone with soldering experience and I would encourage all to give it a go.
These boards are now surplus and if anyone would care to finish one, or indeed would like a bare board to build, I would be happy to send one FOC.

Dave
 

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WHITEKNUCKLES

New Member
Care is suggested when hacking Vero type board, my feeling is that the glue that holds the tracks is not as strong as that on production PCBs, the base is not laminated between glass layers as are the other clad boards and the large holes cause weakness. Isolating tracks by drilling out a hole is fast and easy under an IC but tends to spread the circuit otherwise and I prefer to cut the track between holes.

The angle between the two cutting edges on the modified blade shown above is very much stronger than the original point and is quite capable of carving thin copper.

Holding the blade vertically on the far side of the track,hopefully 5 thou this side of centred between holes I draw the blade across the track a couple of times with medium pressure. I place the blade over the edge and an estimated 10 thou beyond the score mark, tilting the blade 20 deg away from the score I draw towards myself, shearing the track and hinging it up at the score. This allows components legs in adjacent holes with a SM resistor or capacitor between. Timed at a leisurely 20 seconds per break or 14 sec if pushed.

To clean small areas of stripboard I hold a curved blade at a trailing angle, swiping it down the tracks, progressing across the width, leaving shining metal. For SM I 'paint' the tracks with solder wick as described earlier and clean between tracks and cut ends with an old blade that has had most of the cutting V ground away for the entire length. The older, flat brass Swan Morton craft tool takes some beating, and it does.

The photo shows stripboard scraped and tinned with a 0402 between cut ends with a component lead in each hole and a 0603 between the tracks.

Dave
 

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Mycroft2152

Senior Member
The PICAXE Forum has members from all over the world, even though Rev-Ed is based in England. It is interesting at times, and as people forget, that there are "cultural" and location differences. This includes vendors, components, spelling and language.

The strip boards are one such item. I first saw them in the European electroncs magazines. They are an interesting technique for hand soldering but not readily available outside of Europe.

Before you guys from 'down under' start correcting me that you are not part of Europe, (I do know my geography) I'll just add that due to the British postal system, you are just a suburb of London. :)

Just my 2 cents (pence, lira, drachma, etc,) worth.

Myc
 
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demonicpicaxeguy

Senior Member
Before you guys from 'down under' start correcting me that you are not part of Europe, (I do know my geography) I'll just add that due to the British postal system, you are just a suburb of London. :)


Myc

i'd like to see what they would do if we went independant down here and "disconected" from the queen
 

hippy

Senior Member
The strip boards are one such item. I first saw them in the European electroncs magazines. They are an interesting technique for hand soldering but not readily available outside of Europe.
I'm quite surprised to hear that because they are (were) mainly known under their trade name of veroboard in the UK and I only started calling them stripboard because that was what they were known as in the US.

Looking at Radio Shack's online site they seem to be even worse than Maplins these days for UK electronic hobbyists so maybe stripboard is now an unknown quantity.

i'd like to see what they would do if we went independant down here and "disconected" from the queen
Shrug our collective shoulders I'd imagine, although the rightwing press will no doubt have a field day with it. I doubt you'd notice any difference, except in one respect ... What a recent PM did do was wake everyone up to what having a President would be like. It didn't do much to boost support for HMQ directly but it certainly did a lot to boost support against having a Presidency.
 
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