Author Topic: So surface mount it is  (Read 12863 times)

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Online paulcaTopic starter

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So surface mount it is
« on: February 05, 2018, 11:45:34 am »
Found my first need for surface mount stuff.

I am building a binary clock and was planning on using 3x74HC595s to control the 16 or 17 LEDs (depending on whether I want 12 hour or 24 hour clock).

Then while watching the Back to the future Time circuits video from Dave I spotted the TLC59282.  A serial-to-parallel constant-current 16 channel LED driver.  It cuts my component count by about 18 parts.  No need for the 16 resistors or any of the 595s.  I can drive a 12 hour binary clock straight off it.

Downside is... it's only available in SMD.

So I bought 2 chips, expecting to kill at least one and 5 adapter boards.

Deep breath, I wonder how this goes on my first attempt to solder SMD.  Although I did order two of those SMD practice boards, so maybe I should start there.
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Offline daqq

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Re: So surface mount it is
« Reply #1 on: February 05, 2018, 12:10:48 pm »
Quote
Deep breath, I wonder how this goes on my first attempt to solder SMD.
Good luck!

But don't be afraid of it, it's pretty simple after some practice. Soldering SMDs is unavoidable these days, you might as well start now.
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Offline max_torque

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Re: So surface mount it is
« Reply #2 on: February 05, 2018, 01:01:22 pm »
i've always found soldering SMD to be easier and faster!

The only downside is that you can't just stick the parts into a solderless breadboard, but buy some of those "DIP adapter" boards (small pcbs with 0.1" headers down each side, and a footprint for a SOIC or whatever in the middle) and even that becomes easy  :-+

 
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Online paulcaTopic starter

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Re: So surface mount it is
« Reply #3 on: February 05, 2018, 01:25:06 pm »
Quote
Deep breath, I wonder how this goes on my first attempt to solder SMD.
Good luck!

But don't be afraid of it, it's pretty simple after some practice. Soldering SMDs is unavoidable these days, you might as well start now.

So tack and drag.  The tacking I get, I'm less convinced the dragging is as easy as people like Dave make it look. 

Also without a microscope it will be tricky to verify/inspect the joints.
« Last Edit: February 05, 2018, 01:59:45 pm by paulca »
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Offline Photon939

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Re: So surface mount it is
« Reply #4 on: February 05, 2018, 01:47:37 pm »
Make sure you use lots of external flux, it helps a ton on preventing solder bridges when you're hand soldering SMD
 

Offline phil from seattle

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Re: So surface mount it is
« Reply #5 on: February 05, 2018, 03:41:34 pm »
SMD is pretty much unavoidable these days. The good news is it's not that hard to hand solder a lot of SMDs.  Avoid small pitch stuff but 1206s, 805s, SOICs, TSSOPs and so on are quite easy by hand if you have a reasonably good, fine tipped soldering iron. I think they are a lot easier and faster than through hole components. You might want to get some sort of magnifying visor or similar, depending on how good your eyesight is. A stereo microscope is great but not absolutely necessary.

If you want to take it to the next level, learn about reflow. It's pretty amazing to watch your components line up by themselves when they hit the right temperature.
 

Offline tooki

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Re: So surface mount it is
« Reply #6 on: February 05, 2018, 04:08:27 pm »
Quote
Deep breath, I wonder how this goes on my first attempt to solder SMD.
Good luck!

But don't be afraid of it, it's pretty simple after some practice. Soldering SMDs is unavoidable these days, you might as well start now.

So tack and drag.  The tacking I get, I'm less convinced the dragging is as easy as people like Dave make it look. 

Also without a microscope it will be tricky to verify/inspect the joints.
With decent flux and the right tip, drag soldering really does work that easily. It’s incredibly satisfying!!
 

Online paulcaTopic starter

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Re: So surface mount it is
« Reply #7 on: February 05, 2018, 04:29:17 pm »
I actually bought a flux pen recently, not used it much in anger yet.

I seen Dave was using only 260*C on the iron, is that right?  Sounds a bit low.
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Offline JacquesBBB

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Re: So surface mount it is
« Reply #8 on: February 05, 2018, 05:33:26 pm »
Look to the video of these guy.
The are the best I  could find on the web.



One could not say enough that the flux is essential.

Another very nice ingredient when you go to very small pitch ( 0.5 mm) is the binocular. But this is more expensive than the flux.
 

Offline tautech

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Re: So surface mount it is
« Reply #9 on: February 05, 2018, 06:34:53 pm »
Quote
Deep breath, I wonder how this goes on my first attempt to solder SMD.
Good luck!

But don't be afraid of it, it's pretty simple after some practice. Soldering SMDs is unavoidable these days, you might as well start now.

So tack and drag.  The tacking I get, I'm less convinced the dragging is as easy as people like Dave make it look. 

Also without a microscope it will be tricky to verify/inspect the joints.
Any of the magnifying headsets is all you need. I'm in my late 50's and I wear them all the time for any soldering.

To confirm others recommendations: flux, flux, flux !
I too have only recently got a flux pen and it sure helps and saves time not having to go over joints again.  :rant:
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Online paulcaTopic starter

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Re: So surface mount it is
« Reply #10 on: February 05, 2018, 07:04:36 pm »
So I use a manicure/nail light for soldering, but it's only 4x.

If I set my phone on the lens, it's fairly stable and I can get to this with a little digital zoom.


In fairness without the phone my eye sees things like that, just the way the lenses interact the phone doesn't get the full effect of the nail light lens.  If I moved the phone away from the lens it might, but then I'd have to hold it.
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Offline Electroplated

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Re: So surface mount it is
« Reply #11 on: February 05, 2018, 07:13:58 pm »
Not related to your project as such but.......

I remember years ago having to face soldering SMD for the first time, it filled me with dread thinking about damaging parts and pcb's so what I did was dig out a few SMD boards from my junk pile, removed a few assorted chips and practiced re-soldering them back.

Plenty of flux and solder wick at hand and just practice, this way your not wasting valuable parts while you gain experience.

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50 years working with electronics and I still wonder how small parts can have all that smoke inside !
 

Online paulcaTopic starter

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Re: So surface mount it is
« Reply #12 on: February 05, 2018, 07:59:05 pm »
I do have an old computer motherboard.  It's never going to work again because it wouldn't give me my heatsink I wanted so I asked the pliers to provide persuasion.    :D
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Offline Electroplated

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Re: So surface mount it is
« Reply #13 on: February 05, 2018, 10:07:44 pm »
I do have an old computer motherboard.  It's never going to work again because it wouldn't give me my heatsink I wanted so I asked the pliers to provide persuasion.    :D

A motherboard will do, so long as your aware that using a heatgun to remove chips for 'training' often melts anything plastic in the area, fumes can be bad enough but hot plastic on the skin is even worse !

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50 years working with electronics and I still wonder how small parts can have all that smoke inside !
 

Offline janoc

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Re: So surface mount it is
« Reply #14 on: February 05, 2018, 10:55:25 pm »
I do have an old computer motherboard.  It's never going to work again because it wouldn't give me my heatsink I wanted so I asked the pliers to provide persuasion.    :D

A motherboard will do, so long as your aware that using a heatgun to remove chips for 'training' often melts anything plastic in the area, fumes can be bad enough but hot plastic on the skin is even worse !

--

Uff, beware - the plastic is the least of your problems!

The components on these are often glued down and the fumes from the glue when heated up can be horrible. I had one laptop board which was producing something comparable to hydrochloric acid fumes when desoldering parts - extremely unpleasant stuff, I was wheezing for a good while afterwards. You do want to have some sort of ventilation/fume extractor when doing this. Normal flux fumes are Chanel No 5 compared to it.

And avoid heating any electrolytic caps - they love to go KABOOM when cooked with the heat gun.

« Last Edit: February 05, 2018, 10:57:58 pm by janoc »
 

Offline phil from seattle

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Re: So surface mount it is
« Reply #15 on: February 05, 2018, 11:21:54 pm »
I think it took 2 or 3 chips to get a decent feel for soldering SMDs.  But even my first was successful so don't be afraid. Maybe do a SOIC breakout board first.
 

Offline janoc

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Re: So surface mount it is
« Reply #16 on: February 06, 2018, 08:03:45 pm »
I think it took 2 or 3 chips to get a decent feel for soldering SMDs.  But even my first was successful so don't be afraid. Maybe do a SOIC breakout board first.

Yeah, or one of those toy SMD soldering kits - I think Velleman sells some. You will soon discover that if it has "legs" or accessible pins you will be able to solder it no problem, even very small pin pitches.

Now QFNs, CSPs and BGAs are a different story. QFNs are still mostly doable with a bit of care by hot air, the last two are really hard to do reliably without solder paste and some way of doing reflow.
 

Offline phil from seattle

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Re: So surface mount it is
« Reply #17 on: February 06, 2018, 08:08:35 pm »
Yeah. LGAs as well.  I use a toaster oven and monitor the temperature. Works pretty well. QFNs, LGAs.  I've heard of people doing BGAs in a toaster oven.  I've never gotten reliable results from hot air.
 

Offline schmitt trigger

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Re: So surface mount it is
« Reply #18 on: February 06, 2018, 08:19:13 pm »
Fortunately, Youtube literally has dozens and dozens of SMD tutorials.
Spend a lazy afternoon watching some of them, and you will avoid many rookie mistakes.
 

Online Simon

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Re: So surface mount it is
« Reply #19 on: February 06, 2018, 08:21:03 pm »
I could never get small SMD stuff done with an iron but SOIC is ok, stencils make life a breeze and actual paste is a good first step, if your board has a solder mask and you don't overdo the solder it will look after itself under hot air/infrared oven. Stencils from chinese PCB makers are very cheap so if your having boards made then just tick the box for unframed stencils.
 

Online paulcaTopic starter

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Re: So surface mount it is
« Reply #20 on: February 06, 2018, 08:55:03 pm »
Well, I did get one of the cheapo kits today.

Brace yourself, it's ugly.

I can see it's doable.  The chips I have had delivered are SSOP-24 and a little more forbidding looking.

Also, since you mention QFN and VQFN, when I am looking for DC/DC converters that supply both a boosted +12V and -12V for my audio project they all seem so be absolutely tiny little MSOP or VQFN chips :(  I suppose MSOP is probably achievable?  What do you think?

Oh... I do have a bottle of Isopropanol in the post and a small brush to clean things up.

Question... how do you stop the little "nipples" of solder plucking up when you remove the iron?

... and yes, the kits comes with a SOP-16 chip with 16 legs and... a SOP-16 area with 14 pads.  WTF?



« Last Edit: February 06, 2018, 08:58:17 pm by paulca »
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Online Simon

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Re: So surface mount it is
« Reply #21 on: February 06, 2018, 09:09:36 pm »
If it's you first hand soldering it's good, like I say nothing more gleeful than watching components right themselves! under hot air or in the oven.
 

Online paulcaTopic starter

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Re: So surface mount it is
« Reply #22 on: February 06, 2018, 09:18:12 pm »
Never trust the flux in solder wire. Always add more. No need to go to the other extreme like Louis Rossmann does, but you do need to add some flux.

I was using a flux pen.  I found it made things easier.  I also found it was better to apply a little after the chip is in place so the pins are coated too.  The side of the chip I did this went easier than the side I didn't.  The first with only flux on the pads the pins all joined together, luckily they unjoined with a few delicate pokes of the iron.

I think I will keep hunting for a DC/DC dual supply creator in a more sensible package.  I could end up with a boost and a second inverting boost though to avoid micro sized packages.

VQFN is the package the 16u2 on the Arduino UNO board isn't it?  Not a hope in hell of soldering one of them with an iron! :(
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Offline phil from seattle

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Re: So surface mount it is
« Reply #23 on: February 06, 2018, 09:20:50 pm »
Paul, you are doing fine. Just because they aren't perfectly aligned doesn't mean they won't work. And MELFs are a royal PITA anyway.  Anything with a lead sticking out is hand solderable.

MSOP is harder to solder with small pad design. With larger pads, it can be easier, but I only do absolutely small designs, so I can't say much about it.
QFN should be easy if you have some solder paste and a hot air gun or hot plate (or if your mom doesn't care if you cook your board with her dinner in the same oven).
Or go to a thrift shop and buy a second hand toaster oven. I see them all the time for $10-20 USD.  I highly recommend reflow for QFNs.
 

Online paulcaTopic starter

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Re: So surface mount it is
« Reply #24 on: February 06, 2018, 09:39:06 pm »
Do you think the guy who made those diodes round has a little giggle to himself every night?

EDIT:  I googled MELF.  Mostly End up Lying on the Floor
« Last Edit: February 06, 2018, 09:40:56 pm by paulca »
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