• AVR Freaks

Hot!Soldering 100 pin PICS

Author
fsonnichsen
Super Member
  • Total Posts : 315
  • Reward points : 0
  • Joined: 2009/08/13 11:00:11
  • Location: 0
  • Status: offline
2020/08/21 05:31:12 (permalink)
4 (1)

Soldering 100 pin PICS

Can anyone versed in the art tell me how they are soldering 100pin PIC 24s?  Luckily(or not) up until now this has eluded me with either access to a commercial fabricator or using a PIM. But I am now saddled with several PIC24 100 pin boards and need to solder them. Reminder these have pitch 0.5mm.
   What doesn't work for me at least is an iron. I have done it, the results were sloppy, and it took a long time. I checked with a few professionals at an old workplace and even they find the 100pin at this pitch daunting when soldering with an iron--and they do have a failure rate whether using the "strip" method or pin-by-pin.
  Here I use either a "one off" reflow oven or a reflow nozzle depending upon what I am doing. I never had a trouble with SOIC, most other TSSOP or 402 caps. I use both leaded and unleaded and my boards are masked. Some particulars:
> When I used a needle I lay a "strip" of solder (~30 micron ball) using a 18-20 gauge needle. Laying individually doesn't work well at this pitch and the "strip" is standard. I use it for other low pitch devices.
> I have used stencils here with a similar paste. As is always the case the layout is very thin as is desired.
 
What happens:
> I always get bridges. Several per chip
> What is worse the pins are short and stand out--so the bridges go underneath and not just on the surface
> I am not averse to touchup with the microscope and braid but it does not seem to access the underside of the pins and I still have bridges.
 
Only other thing I can think of, is that I tend to "mush" the chip around a bit while seating it--I am seating by hand with a vaccum or regular tweezer. Not much to say here-some people are more steady than me for sure--but I just don't have this problem with 6pin chips for example.
 
Long winded but I really am frustrated with this problem and would like to hear from others.
 
Cheers
Frtiz
 
#1

16 Replies Related Threads

    NorthGuy
    Super Member
    • Total Posts : 6407
    • Reward points : 0
    • Joined: 2014/02/23 14:23:23
    • Location: Northern Canada
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/21 06:14:36 (permalink)
    4 (3)
    There are two kind of 100-pin packages - 0.5mm pitch (PF) and 0.4mm pitch (PT). Removing bridges from 0.5mm parts is much easier than from 0.4mm parts. IMHO, no matter how hard you try, you'll get a bridge now and then.
     
    I solder them pin-by-pin (no drag), actually in groups of pins. I use lots of tacky flux. I take relatively big chisel iron (so that it is as wide as few pins). I position the part. I tackle the pins keeping the iron at a relatively low angle and perpendicular to the side of the chip. I only try to touch the tips of the pins and wait until the solder gets sucked in. I try not to touch any part of the pin which are not on the pad  - in this case a bridge is almost guaranteed.
     
    If I get a tough bridge, I add flux, then I add a little bit more solder to the place (so that it is visible on the outside) then I suck everything out with a solder wick.
     
    That said, I have a socket for PT parts - much easier than soldering.
    #2
    GoEk
    Senior Member
    • Total Posts : 126
    • Reward points : 0
    • Joined: 2012/09/27 00:32:28
    • Location: Sweden
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/21 07:59:47 (permalink)
    4 (1)
    Pin-by-pin with a stereo microscope and a good solder tip but it requires experience. Have never tried drag soldering.
    #3
    acharnley
    Super Member
    • Total Posts : 629
    • Reward points : 0
    • Joined: 2016/05/01 06:51:28
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/21 08:35:05 (permalink)
    4 (2)
    You need a reflow station, a good iron and lots of flux. I use a Gordak 863 - superb bit of kit which costs peanuts.

    Drag soldering is the way to go. Get the chip on as best you can with solder paste first using the heat gun then add flux around the sides. Take the gun heat down to about 180c over the top of the chip and then drag the iron along to correct any bridges or missing joints. The heat gun at 180c makes all the difference.

    QFN chips are actually easier most the time as the solder won't bridge between the legs. I just did 40pin and 28pin UQFN 0.4mm chips this morning with this kit, no problem.
    #4
    MBedder
    Circuit breaker
    • Total Posts : 6926
    • Reward points : 0
    • Joined: 2008/05/30 11:24:01
    • Location: Zelenograd, Russia
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/21 14:21:12 (permalink)
    5 (3)
    Normally drag soldering the 0.4..0.5 mm pitch (T)QFP100 takes 1-2 minutes "turnkey". Watch this "how to" video (and bunch of similar ones) - https://www.youtube.com/watch?v=6PB0u8irn-4
    #5
    nigelwright7557
    Super Member
    • Total Posts : 471
    • Reward points : 0
    • Joined: 2006/11/06 08:15:51
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/21 22:09:46 (permalink)
    5 (1)
    i put flux paste over all the pads.
    i then tack down 2 sides of micro.
    i then put flux paste on all pins.
    i add some soler to iron tip.
    i then drag iron along pins ensuring pads and pins all get heated.
    a dab with soldering iron usually gets rid of any bridges.
    if not add more flux paste and try again.
     
    alternatively get jlcpcb to mount them for you.
     
    #6
    teenix
    Junior Member
    • Total Posts : 72
    • Reward points : 0
    • Joined: 2017/12/21 13:47:21
    • Location: Australia, Melbourne
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/23 03:32:27 (permalink)
    5 (2)
    There are 2 types of chisel tips, one that looks like a chisel and another that has a concave "well" that can hold a reservoir of solder. This is the one to use, probably a 2-3mm size. I have successfully hand soldered 18F66K40's which also have 0.5mm pin spacing.
     
    Solder any two corner PCB pads on the same side of the chip (ie top right, bottom right) 'without' the chip in place so that there is a small mound of solder on the pads.
     
    Position the chip and hold in place with tweezers.
     
    Place a small tip soldering iron on the soldered pad close to but not quite on the IC pin. The solder will melt, the chip pin will sink into the molten pool of solder, remove the iron quickly.
     
    The chip can now be manoeuvred slightly to align the pins properly if need be. Solder the other corner pad the same.
     
    Place some flux paste on the pins along one side of the chip that does 'not' have the corners soldered. Using the concave chisel tip place some solder into the well to fill it up - not over full, as not much solder is actually required to solder the pins. Place the soldering tip onto the pins so that the tip overlaps the pins and pcb pads and drag the iron along the side of the chip - not too fast, not too slow - some practice may be required, and you don't want to overheat the chip.
     
    Repeat the process with the other 3 sides.
     
    If you bridge the pins, make sure there is not too much solder in the tip well and place it straight onto the spot and drag it away from the chip at right angles. There is a good chance the excess solder will follow the tip.
     
    I wouldn't overuse the flux paste, even though some video clips say the more the better. A lot of excess can go under the chip and you cannot remove it, although some flux pastes are ok to leave as residue.
     
    Double check you work and re-flux, re-solder if required. A magnifier and strong light behind the PCB gives a good contrast between the pins and PCB pattern to see shorts.
     
    Check out U-Tube, there are many videos on the subject, also there was one using a halogen lamp.
     
    cheers
     
    Tony
    #7
    fsonnichsen
    Super Member
    • Total Posts : 315
    • Reward points : 0
    • Joined: 2009/08/13 11:00:11
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/23 06:12:32 (permalink)
    4 (1)
    A lot of excellent information here I and I really appreciate it.
       I think the consensus here is drag soldering and no oven. I found a 45 def "hoof" (Hakko T15-BCF2) in my tips here and used this to wick off the bridges left by the oven. It worked very well---So I guess part of my problem is I was trying to use a tiny conical tip and it just doesn't work for this pitch. (conicals worked fine for me in the past)
         So --I used the same tip to solder on another 100pin chip and it worked--Apparently as was mentioned here a lot of magic is in the tip. Tony- Interesting about the hollow tips (I knew there must be a reason for this). I bought an assortment 1 and 2mm hoof tips for the future.
       By the way I use a flux pen that is "liquid"--have never used (or needed) the paste but would be interesting to try.
        Andrew- Regarding the reflow station-I has used these but largely to even up the heat on my board. At present I am soldering just fine without it and use the oven for the delicate stuff. Just curious-are you preheating to ease the solder flow? I could see the value in this but I usually have to use a scope now and of course can't fit the reflow in there!
     
         So I think you guys solved my problem-largely by doing to strip (drag) soldering and - very important-using the beveled tip.
     
    I still like the idea of an oven as it has been so easy for everything else--and I get reliable results. Mine cost less than a board (T-962). I won't give up on it in my spare time (need to find something cheaper that a PIC24 for testing!) I would expect that the worst problem is "setting" and "mushing" the chip as I mention-maybe layout would help.
        Meanwhile I will drag solder with the 'hoof'-
     
    Cheers and thanks again
    Fritz 
     
    #8
    nigelwright7557
    Super Member
    • Total Posts : 471
    • Reward points : 0
    • Joined: 2006/11/06 08:15:51
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/23 08:16:59 (permalink)
    0
    you dont need a tip with a well in it.
    putting some solder on a normal tip works just as well.
    the trick is plenty of flux paste and making sure you heat both pad and pin to  make solder adhere to both.
    #9
    rfmerrill
    New Member
    • Total Posts : 3
    • Reward points : 0
    • Joined: 2020/08/16 21:54:02
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/23 11:15:15 (permalink)
    0
    Regular flat chisels are not ideal for drag soldering. I personally either use an angled 'knife' style tip or a bent conical. The 'hoof' shaped tips with or without the concave well are ideal, I just haven't had one handy in the right size.

    The key to soldering fine pitch QFP or SOIC type components is: LOTS of flux, VERY LITTLE solder. It's easy to use WAY too much solder. You also want to apply the iron only to the very tip of the leads if you can.
    #10
    teenix
    Junior Member
    • Total Posts : 72
    • Reward points : 0
    • Joined: 2017/12/21 13:47:21
    • Location: Australia, Melbourne
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/23 22:59:56 (permalink)
    0
     
    > By the way I use a flux pen that is "liquid"--have never used (or needed)
    > the paste but would be interesting to try.
     
    My apologies, my old brain was thinking the gel flux, but I wrote paste.
     
    cheers
     
    Tony
    #11
    acharnley
    Super Member
    • Total Posts : 629
    • Reward points : 0
    • Joined: 2016/05/01 06:51:28
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/08/24 00:06:41 (permalink)
    4 (1)
    fsonnichsen
    A lot of excellent information here I and I really appreciate it.
     I think the consensus here is drag soldering and no oven. I found a 45 def "hoof" (Hakko T15-BCF2) in my tips here and used this to wick off the bridges left by the oven. It worked very well---So I guess part of my problem is I was trying to use a tiny conical tip and it just doesn't work for this pitch. (conicals worked fine for me in the past)
       So --I used the same tip to solder on another 100pin chip and it worked--Apparently as was mentioned here a lot of magic is in the tip. Tony- Interesting about the hollow tips (I knew there must be a reason for this). I bought an assortment 1 and 2mm hoof tips for the future.
     By the way I use a flux pen that is "liquid"--have never used (or needed) the paste but would be interesting to try.
      Andrew- Regarding the reflow station-I has used these but largely to even up the heat on my board. At present I am soldering just fine without it and use the oven for the delicate stuff. Just curious-are you preheating to ease the solder flow? I could see the value in this but I usually have to use a scope now and of course can't fit the reflow in there!
     
         So I think you guys solved my problem-largely by doing to strip (drag) soldering and - very important-using the beveled tip.
     
    I still like the idea of an oven as it has been so easy for everything else--and I get reliable results. Mine cost less than a board (T-962). I won't give up on it in my spare time (need to find something cheaper that a PIC24 for testing!) I would expect that the worst problem is "setting" and "mushing" the chip as I mention-maybe layout would help.
        Meanwhile I will drag solder with the 'hoof'-
     
    Cheers and thanks again
    Fritz 
     



    If you don't keep the board heat up the heat at the pins via the soldering iron will differ too much, i.e some pins sink heat better than others especially GND pins. The air-gun over the top prevents heat spots and also keeps the flux flowing. It is at least half the effort doing it this way.
    #12
    fsonnichsen
    Super Member
    • Total Posts : 315
    • Reward points : 0
    • Joined: 2009/08/13 11:00:11
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/10/12 05:18:12 (permalink)
    4 (1)
    This post is a bit old but here is an addendum with some resolution
        I finally am getting good results soldering 100pin PICs.  I am using an oven as I have a lot of work to do and find this to be fastest. The T-962 for about $300 (less than the cost of a populated board) worked very well for me without modification.  Here is what helped:
     
    1) I made sure that the stencil is very secure--I paid a lot of attention to this and built a simple $7 clamp to help out. While I like electrical tape because it is simple, for the high density stuff I find this jig very useful. I am attaching photos of the jig and its clamping the stencil. I use 3 clamps as you may need to lift one to get underneath for complex chips. I chose 2 spacings for most of the stencils I used. I use metal stencils-I found that simple plywood had just the right friction to hold the stencil.

    2) After laying down the initial paste I make a "clearing run" with the pasting card, applying a fair amount of pressure. This insures a pretty thin layer. Just like hand soldering I found it was easy to use too much solder when learning. I check the solder with the microscope before laying chips.

    3) I did pretty well with the above methods but got even better results re-drawing my footprint. My original was from the PIC datasheet. It had very long traces, these running well underneath the legs. Using KiCAD I shortened them around the inner perimeter leaving little space for the solder to creep. Photo attached.
     
    Only other thing is it is important to place the chip very near where it belongs first time. Small (0.25mm) adjustments under the scope are OK after that--but if you lay it down "way off" to start you will "mush around" the paste, deplete it and cause trouble. I am working on a simple jig to hold and drop the PIC above the board with my vacuum pen.

    There is a Moores law for transistors but none for joints. Probably there are at least 6 joints for every IC. With all the thousands of volumes out there on ICs I could find none with detailed information on soldering techniques. Luckily there are forums like these. You guys are always great!

    Thanks all
    Fritz

    Attached Image(s)

    #13
    fsonnichsen
    Super Member
    • Total Posts : 315
    • Reward points : 0
    • Joined: 2009/08/13 11:00:11
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/10/12 05:18:13 (permalink)
    1 (1)
    e
    post edited by fsonnichsen - 2020/10/12 05:19:25
    #14
    Murton Pike Systems
    Senior Member
    • Total Posts : 77
    • Reward points : 0
    • Joined: 2020/09/10 02:13:01
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/10/12 07:48:58 (permalink)
    4 (1)
    I recently ran out of solder so bought in some cheap Chinese stuff.
    I tried to solder a 100 pin atsame70n19.
    What a complete disaster, the solder hardly melted and blobbed everywhere.
    The melting point of the solder was clearly far too high.
    I couldnt even remove the PIC with hot air, it wouldnt melt the solder !
     
    So found some old Maplin solder that is lead/tin and that made a much better job.
    I drag soldered each side.
    I had a few bridges so used copper braid to remove them.
    Some of the joints didnt look too good so I removed all solder from iron and touched up all the pins again melting the solder on them to the pin and pad. 
    I checked for shorts between power and ground and VDDCORE and ground and no shorts so powered it up and it worked first time.
     
     
     
    #15
    fsonnichsen
    Super Member
    • Total Posts : 315
    • Reward points : 0
    • Joined: 2009/08/13 11:00:11
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/10/12 08:46:35 (permalink)
    0
    Nigel- I share your grief with the solder. I am really suspicious of buying brand-x items, especially chemical and metallurgical ones where you can't tell the content by "looking". I usually go to Kester and Chipquick for my solders/paste/flux. I am lucky in that I usually have a very small amount of research grant money on hand for such things. 
       Drag soldering per the people on this post worked very well for me now that I learned to use the "hoof". Since I oven everything else however I am now happy I can do this for the complete boards. I usually write some quick check-software to run with the board is done. I do still get occasional bridges but they are now small and few and don't go behind the chip. I find that putting a good dose of flux on my braid and then running the hoof type iron over the pads--but NOT the pins--cleans up pretty well.
      I have some chipquick lead free on hand and will try that on some less finicky boards soon. Over 46 years in science and chemistry  I am probably full of every chemical and radiator imaginable but I am trying to keep honest with the authorities and it makes good sense to avoid lead.  Luckily my little oven has a good compliment of heat curves including the higher ones for lead free. (I will continue to drink cheap beer however!)
     
    Thanks
    Fritz
    #16
    Murton Pike Systems
    Senior Member
    • Total Posts : 77
    • Reward points : 0
    • Joined: 2020/09/10 02:13:01
    • Location: 0
    • Status: offline
    Re: Soldering 100 pin PICS 2020/10/12 11:37:03 (permalink)
    4 (2)
    I find plenty of flux paste helps things flow better.
    The solder tends to blob between pins less.
     
    #17
    Jump to:
    © 2020 APG vNext Commercial Version 4.5