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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 28th Nov 2017, 1:28 pm   #1
paulsherwin
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Default SMDs and stripboard

I recently bought some MCP73831 charge controller chips. I knew these were SMD components but on arrival they are absolutely tiny. This is the first time I've tried to build something with SMDs. I don't have any specialist facilities or equipment, just a couple of 'helping hands' and a magnifier.

I want to use them on bog standard Veroboard, but the connections are much too close together to solder them to the copper tracks. I think I can solder solid core wires to the connections if I'm very careful, but does anybody have any better suggestions?
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Old 28th Nov 2017, 1:34 pm   #2
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Default Re: SMDs and stripboard

Quote:
Originally Posted by paulsherwin View Post
think I can solder solid core wires to the connections if I'm very careful, but does anybody have any better suggestions?
Hey Paul,

If you can give me a day or so, I have some pads that are designed for 'Manhattan style' construction. I use them a lot now.
Is it 8 DIL or 14 or 16?

Let me know and I can pop one in the post for you. They are great to use. A drop of superglue and you're away.

You might have to go fully SMD tactics and mount all the components on the track side, would that be a problem?
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Old 28th Nov 2017, 1:48 pm   #3
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Default Re: SMDs and stripboard

It's SOT23-5. I've attached the datasheet.

The initial requirement is to build a small charger for a li-ion cell, but I'd like to explore the subject more widely. More and more components are starting to become available only in SMD form.
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Old 28th Nov 2017, 1:49 pm   #4
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Default Re: SMDs and stripboard

By the look of this IC it comes in an 8 or 5 lead configuration.

The thing I do with these small IC's with fine pitch pins is to buy an adapter that converts them to DIL, then you can put it on your veroboard and with a socket to, without problems. These pre-made adapters are on ebay. To solder fine pitch surface mount IC's like this to their pads can be done with an ordinary sized iron, just flood solder all the pins and use solder wick on it after that which clears the solder between the pins but leaves enough for a good connection from the pin to the pcb pad.

I think one of these would work if it was a sot23-5 IC:

https://www.ebay.co.uk/itm/Surface-m...qJK2_ZonJ756mw

Also found this for a DFN12, but it would work for an 8 pin one I think:

https://www.ebay.co.uk/itm/Surface-m...zWGhyBeRZN4SNQ

Last edited by Argus25; 28th Nov 2017 at 2:00 pm.
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Old 28th Nov 2017, 1:58 pm   #5
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Default Re: SMDs and stripboard

I should explain that I deliberately ordered the SMD version of these chips as an experiment - they cost next to nothing so it's hardly the end of the world if I trash them.

I'm not on the scrounge for specialist adaptor boards or such like, just looking for general advice from people who've done this before.
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Old 28th Nov 2017, 2:44 pm   #6
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Default Re: SMDs and stripboard

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Originally Posted by paulsherwin View Post
It's SOT23-5. I've attached the datasheet.
Ahah, I may have the pad for that, Paul. (Although I now see that's not what your after?)

Have you also considered using an wire whose insulation breaks down under normal soldering heat? There are some fine ones suitable for the application you describe, certainly for logic circuits, if not power. I have done this with SOICxxx devices in the recent past.
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Old 28th Nov 2017, 3:56 pm   #7
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Default Re: SMDs and stripboard

If you don't want to spend money on adapter PCB which can be more expensive than the chips themselves you can stick the chip to your stripboard on it's back with double sided tape. You can then solder individual strands of wire to the legs and fan them out to the more useful 0.1" spacing. It's sometimes easier if you bend every other leg up or down as well. It depends how big your iron tip is and how steady your hands are. This technique works with quad sided packages as well, and if you're really careful with those ones without legs at all.

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Old 28th Nov 2017, 4:00 pm   #8
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Default Re: SMDs and stripboard

Good tip Ging.

It does look as if adapter boards are the way to go though. Is there any reason why I shouldn't just buy 10 generic boards from China for 99p? This is just for hobby jobs and doesn't need to be super reliable.
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Old 28th Nov 2017, 4:41 pm   #9
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Default Re: SMDs and stripboard

Having said that I do keep a stock of adapters - mostly Roth elektronik from RS et al.

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Old 28th Nov 2017, 4:49 pm   #10
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Default Re: SMDs and stripboard

If you do buy those adaptor boards, you may find that when fitting the IC, it's easiest to flood the pins with solder, then use a desoldering braid to mop up the excess and remove the inter-pin shorts.
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Old 28th Nov 2017, 5:15 pm   #11
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Default Re: SMDs and stripboard

Adaptor boards are the answer.

[Hint: use a tiny blob of superglue to attach the SMD to the board, *then* solder its pads down]
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Old 28th Nov 2017, 5:23 pm   #12
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Default Re: SMDs and stripboard

SMT is rather daunting at first look,you will soon get used to it, and love it as there are no holes to drill in home made PCBs. The way to "wire up" such a wide spaced chip (wide by SMT standards) is to stick the chip down and using heavily tinned thin wire (a core from stranded is ideal) with flux just dab it down with a soldering iron. It is all a matter of practice, at nearly 60 have no qualms making PCBs with 0.5mm pitch (0.25mm pads!) at home and soldering chips down, or using 0402 components (with tracks down the middle). Proper leaded solder does help a lot.

When it comes down to a quick "knock up" those adaptor boards are great.
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Old 28th Nov 2017, 7:15 pm   #13
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Default Re: SMDs and stripboard

A 'breakout board' with solder pads for the SMD chip which converts it to an 8-pin DIL header (and a range of other styles) takes a lot of hassle out of it, and maximises the chance of success, at only 72p each inc VAT from a UK supplier:

http://www.hobbytronics.co.uk/soic-dip-breakout-8-ht

Having grown up in an era when a B7G valve-holder was considered 'miniaturisation' as compared to Octal, SMDs do pose something of a challenge, but we know from some forum members that it's a challenge that they relish and rise to. About 18 months ago a chum who was doing some SMD work found it difficult to anchor the devices whilst holding an iron in one hand and the solder in the other, so I made him a little spring-loaded 'hold-down jig' based on an idea I saw in 'SPRAT' some years ago. (Hadn't considered superglue, which makes sense).

If ever I were to go down the SMD route, I think it would be solder paste and a hot air gun.

Best of luck in your endeavours Paul, and every success.
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Old 28th Nov 2017, 7:54 pm   #14
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Default Re: SMDs and stripboard

If you'd like a bit of fine gauge solderable enamelled wire to play with (used by me for just such a problem with an integrated fly speck, I'll pop some in the post.

A 10A scalpel to hold the b*****s down while you solder the first pin to a pretinned pad PCB is useful, the remaining pins can then be flooded and wicked as described or individually soldered if not too fine a pitch.
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Old 28th Nov 2017, 8:51 pm   #15
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Default Re: SMDs and stripboard

RS sell 1.27mm pitch matrix board from Roth electronics which are correct pitch for SOIC and SOT23 packages as well as 0805 sized parts. . I’ve done a lot of prototyping with that recently. Tools are weller TCP iron with 1.6mm chisel, xacto scalpel, flux pen, some expensive tweezers which are non magnetic.

You can see one of my slightly criminal early attempts here:

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Have used kynar and snipped resistor leads for wiring.

Works nicely even if it looks like crap. Best things are it is cheap and doesn’t take as much space!

I’ve ordered PCBs recently as it’s not worth spending the time prototyping when simulation and confidence are available. kicad on the EDA front and oshpark boards are good.

I’d tou don’t fancy that or waiting for China, bitsbox sell adapters individually: https://www.bitsbox.co.uk/index.php?...&cPath=255_313
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Old 28th Nov 2017, 9:30 pm   #16
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Default Re: SMDs and stripboard

Places such as HobbyCraft sell plastic tweezers. (non-magnetic). I found a roll of old lead 0.7mm solder on a car boot/market site. As for solder wick. It was common practice at MSDS for the reworkers ( fancy title for the holders of soldering gear) to strip the outer from mini-coax and use this with flux to remove solder. I've just had a look at Maplin, who sell something similar at 99p/metre. I used to use this when I worked at MSDS ( for home jobs with success), but I've also tried normal coax with little/no success.
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Old 28th Nov 2017, 9:59 pm   #17
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Default Re: SMDs and stripboard

Thanks for all suggestions. I'll do some experiments before seriously trying to build anything. As I said, the chips only cost pennies so I don't mind losing a few.

Has anybody tried attaching a bit of ring main copper wire to a standard iron to create a miniature tip?
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Old 28th Nov 2017, 10:28 pm   #18
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Default Re: SMDs and stripboard

I have actually tried that with the soldering iron years ago. It is terribly difficult to get it to stay on it and it doesn't have enough thermal mass to heat the joint very well. MacGuyer could build a mainframe with it to defeat a bad guy but I couldn't

WRT solder, RS sell multicore 0.8mm leaded but it's not cheap!

Chemtronics Soder-Wick is worth spending on over doing your own braid - the stuff is about 3.50 a roll from RS but is far superior to all other brands and methods I've tried.
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Old 28th Nov 2017, 10:36 pm   #19
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Default Re: SMDs and stripboard

The problem I've found with proper solder wick is that it tends to go off within a month or two of opening, presumably as it oxidises. I'll experiment a bit with coax braid.

I do have some very thin leaded solder which should be suitable.
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Old 28th Nov 2017, 10:36 pm   #20
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Default Re: SMDs and stripboard

25 years ago, I started working on CD players, most of which had the 48 to 80 lead ICs. I made a small "walking stick" from a thin beading needle, using the "handle" to lift legs after using solder braid. fitting new ones sounds similar to ideas for these micro things. I used to solder two opposite corner legs, then flood each side with loads of solder. Then, with my big Weller gun, and its real COPPER bits, I held each side vertically downwards, and simply wiped the excess solder off with the Weller gun. No need for solder wick when fixing, with its attendant risk of leaving no joint underneath but out of sight.
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