soldering SMD devices
davejames
Posts: 4,045
Hi All,
The older I become, the more I realize how much I don't know - so I thought I'd ask the Forum...
I've a project that uses the SSOP BS2 interpreter chip. The project was verified using a BS2 module and now it's time to drop in the smaller parts. Problem is that I do not have the tools to solder SSOP devices (after a miserable attempt with my usual), and that's the question being posed.
What do I use? I was thinking about a solder paste syringe to apply the solder and then a hot air gun to melt the solder. I do not want to go the oven route, thank you - unless there is overwhelming reason to do so.
Having the BS2/SSOP becoming too hot is always a concern; definitely a concern.
So, please, share with me some wisdom!
Regards,
DJ
The older I become, the more I realize how much I don't know - so I thought I'd ask the Forum...
I've a project that uses the SSOP BS2 interpreter chip. The project was verified using a BS2 module and now it's time to drop in the smaller parts. Problem is that I do not have the tools to solder SSOP devices (after a miserable attempt with my usual), and that's the question being posed.
What do I use? I was thinking about a solder paste syringe to apply the solder and then a hot air gun to melt the solder. I do not want to go the oven route, thank you - unless there is overwhelming reason to do so.
Having the BS2/SSOP becoming too hot is always a concern; definitely a concern.
So, please, share with me some wisdom!
Regards,
DJ
Comments
What I've done historically for SMD with legs is I've always just blobbed the solder all the way round. Then wipe the excess off with the iron tip. NOTE: It's important to use low temperature. The low temperature prevents flux from being burnt off so that the solder will bead and naturally stick only to the pins and pads as the excess solder is wiped away.
Finally, if it's a finished product, I use a solvent to remove the remaining flux.
Once it is ready you can run the solder down over all the pins with a warm iron so as to preserve the flux, ending back over the tacked pins last. Now turn up the heat and holding the board almost vertical you can run that hot chisel tip down along the pins dwelling long enough for the solder to flow and follow the tip downwards where you deftly lift it away on the last pin and flick that excess somewhere safe. This is how I do it manually especially back in the early 90s when I used 80 pin qfp packs and didn't have anything better. The finish is clean and pro looking. Cleaning up the flux residue is optional.
You can hold down the part with rubber cement and then once you get 2 corners down you are home free.
If you pre-tin the first corner it will suck the chip in place when heated, so just be sure that the pins are aligned before you tack the other corner.
Dave
That one got me a lot. Get a small bucket with sand in it.
Mike
Dave
I use ZephPaste for the solder material and hot air pencil for melting it. I have mentioned the re-purposed RadioShack desoldering tool/aquarium pump hack that has worked well for me, but there are some cheap air tools if you google or ebay them. Be careful with the cheapies, sometimes the air flow is too high blowing the parts out of place or the tip size heats a larger area than you want. I set the heat fairly high with a low air flow and use a piece of solder to determine if the temp is right using a real cheap bottom fedder unit at work. Even if you only use the paste on the first pad or two to anchor the part (easier to place the part), you can then go with Peter's method of chisel tip iron.
@davejames, time is also a factor. Only leave the iron on the pin and/or drag it fast enough to get the joint, but minimize the time for heat to build up in the part. You could get away with a regular size iron with the right tip if you watch your heat time.
A "hot air pencil" - time to go searching!
Thanks,
Dave
-Phil
Aside from being exceedingly rare, the iNTELLEGENT pencil tends to run a bit cooler and gives much more controled result as compared to the somewhat reduced quality of the hotter "tools".
Jim
Thanks much for various inputs. Decided to go the "paste & hot air pencil" route. The items have been ordered and I'll post about the effort after they arrive.
Regards,
DJ
Yup. But Peter, if you saw the way I tend to "assemble" things, you'd understand why its really ALL "rework"!
Edited to add: I'm also toaster oven shopping for the assembly process. Heck, even if it doesn't work for SMD PCB's, I figure the worst thing that can happen is I can stop paying Domino's for pizza delivery.
So, back to the pencil. For me it is a non-contact soldering iron that works very well with SMD parts. Now, mostly carriers from TI, ADAFRUIT and others that supply these to enable use of SMD parts in a breadboard project or maybe a wire-wrapped board. For me anyway. But even then it could be used just like the soldering iron of old to do a project with SMD parts on a PCB. Does not justify the price of a "real" pencil, so the solder tool/fish tank pump hack. Oh, just scored a used Zephtronics ZT-2 for $129.00 used on ebay. Pure luck. One was left for far less, but listed as broke, parts use only.
Regarding the oven, can double sided be done with it?
Remember that a big part will need a lot of heat but those tiny parts don't need much.
I went with this unit: https://www.amazon.com/Station-Soldering-Digital-Temperature-Display/dp/B07RKMGPTX/ref=asc_df_B07RKMGPTX/?tag=hyprod-20&linkCode=df0&hvadid=343325588840&hvpos=1o4&hvnetw=g&hvrand=13410106246566697734&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033770&hvtargid=pla-838293407967&psc=1&tag=&ref=&adgrpid=71789152231&hvpone=&hvptwo=&hvadid=343325588840&hvpos=1o4&hvnetw=g&hvrand=13410106246566697734&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033770&hvtargid=pla-838293407967
DJ
My project has one (1) 28-pin SSOP located in a corner of the PC board. Not much else is close by. The rest of the components are standard (read "old technology"), through-hole type. The SSOP will be mounted prior to any other component.
In other words, this is not a large number SMD assembly. And, if the pencil can un-solder (AKA "rework"), it can certainly melt solder for mounting purposes.
Regards,
DJ
I can certainly tell you that a chisel tip iron is way easier than the route you are planning for an SSOP package. I'm not trying to talk you out of it but you did ask the forum and I just would never do it that way and considering also that you haven't even tried it the simple way with stuff you already have. I can do a quick video if you like to show how easy and fast it is with regular solder and iron. Real easy.
That's fine and I'm glad for you.
Wow...really? How do you know what I've tried? Understand that I have exactly 24 BS2 SSOP devices left of which I will not risk damaging. The hot air pencil with its "no touchy the pins" aspect seemed safer.
Please do. Maybe that could have been offered earlier and my decision would have been different.
Regards,
DJ
That unit is a nicer version of the one at work that gets used for repairs and occasionally salvaging an interesting or expensive part. The heat on it takes a bit to come up so one trick is to put a piece of solder wire in the airflow and when it melts, the output is hot enough. It lacks any type of temp indication, true bottom feeder product; was lucky to even get that approved.
Just a thought to preserve your stock of "the Part"; you could always salvage some smd parts from a dead board and reflow them back where they came from to get a feel for the device and process. If you don't like how it came out, heat all the pins and tap the part off, clean the pads and try again. There is a good video of the whole process on the Zephtronics web page.https://youtu.be/f_yFDpSTfao No matter the air source, the process is about the same. The air bath preheat for the board would be nice but not needed, Certainly not at their price. NASA, yes, hobby level, 7734 no.
Good luck, let us know how it turns out.
FF
*added video link. ignore the propaganda
Rather than tilt the board and draw away the solder which works better on larger pitch parts like the Propeller in QFP, I just blobbed up the pins and then pressed a length of desoldering braid onto one row of pins and laid the iron tip along the length of it to heat the whole mess up in one go, nice and clean. Here are the final shots in the meantime and the video will be added to this album as well.
Great idea, however, I have no "dead boards" with which to play. And being located in the northern realm of Idaho, that type of stuff is not easily found.
Thanks for the link. I'll have to check it super early in the morning when In the "bonus zone" of HughesNet satellite Interweb.
LOL!
Roger that and thanks.
Dave
DJ
Next time you are in town stop by a PC repair place. My local guy had a box full of dead motherboards. I traded a box of donuts for the whole thing, and he was convinced he got the best of the bargain. I sliced a couple up into test coupons (an old tile saw worked great) and will eventually depopulate these before using them to test a toaster oven-based reflow machine.