ACL Strobe success at 90% so far....

Discussion in 'Strobes - LED or Others' started by CaptKirk, Jul 27, 2012.

  1. CaptKirk

    CaptKirk New Elf

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    So I did a test run of 10 last night to work out the process and not ruin a whole panel. Glad I did.

    You should use something like this to see:
    http://dx.com/p/light-head-magnifying-glasses-with-4-pieces-different-multiple-lens-2-aaa-52687?item=70

    Small tip tweazers worked really well to position parts. A chip vacuum pen might be better:
    http://dx.com/p/ic-chip-vacuum-sucker-pen-set-for-electronics-diy-4-piece-set-15080?item=1 if the tip is small enough. The tweazers are handy for flipping over parts that inconvieniently depackage upside down. I like the resistors all number side up, and the chips HAVE to be right side up. A small plate (like a tea cup saucer) can hold parts and not let them get away- use something, not the table, parts can get blown or swept off the table too easily!!

    TIP: for part positioning: the constant current chip in this batch has a white line toward one edge and that IS pin 1. The PICs have a white dot near pin 1. Resistors go either way- dont mix them up!!

    Also a dental pick will be handy, like:
    http://dx.com/p/stainless-steel-acne-blackhead-removal-needle-19881
    or
    http://www.widgetsupply.com/product/XTC3-DD3105C.html?gclid=CJSu1PWauLECFQ5ThwodEC8AwQ
    to fine tune part placement or cleanup paste.

    Tip: resistors get a dot or blob of paste - not more! chips get a line of paste like squeezing toothpaste out across the pins on the outer edges of the pads only much MUCH smaller. You would think that would short, but on reflow the solder gets sucked to the chip pads and pins like magic.

    Decided to griddle reflow the top of the board because it had more parts. That went well especially because the griddle I used also can grill (ala Foreman Grill but with flat plates) thus it folds! That worked sweet.

    The dental pick or tweazers can help nudge reluctant parts into place once the paste is flowing.

    Only had a couple of shorts (easy to see and correct) with my small Weller solder tip and a solder sucker which only sucked the excess solder if the soldering iron was left heating. It left a perfect solder joint.

    Now rethinking doing the top first because of the PIC pin pitch. The PIC is a PITA to hand solder especially if you decide to use a toothpick to apply the paste instead of an applier syringe. I have one but I cleaned it BEFORE I decided to do the back parts and I didn't want to clean it again (BIG MISTAKE - USE THE SYRINGE!!!). Wow what a mess. Had trouble getting the PIC to position properly with hand soldering. Managed on 8, got the ninth connected by the Grace of God (it sure ended up in a funny position shoved all the way to one side of the pads), and the tenth was an utter failure. The PIC initially soldered on one side off by one pad but the other side was lined up (picture it at an angle across the footprint). Well I figured on just heating and sliding but in the process I broke off a PIC pin and pulled up the pad because I just could not get the off kilter pins hot enough at the same time so I forced it and snap. Ah well that is all part of the fun. Maybe if I could have found my heatgun... <sigh>

    The programming went well. I wished I had looked on THIS forum first for a bigger variety of pre-built firmware but found the bottom three files found here on the author's site (THANK YOU for posting!!). Found I needed to apply pressure to the board to get the temporary programming header to make connection but that is easy. If the PIC was recognized, it programmed and worked. Dang these are BRIGHT.

    I now have nine working strobes and one lost cause. Hopefully my success rate increases with a full panel.

    What I recommend:

    -Use a head magnifier which ends up being more convienent than a magnifying light. I have this one:
    http://dx.com/p/light-head-magnifying-glasses-with-4-pieces-different-multiple-lens-2-aaa-52687?item=70 and it is nice because you can change the magnification. It is nice quality at a good price.

    -A Solder Paste syringe is essential to prevent a mess.

    -Use a solder sucker (to correct messes) like:
    http://dx.com/p/electronics-diy-disordering-pump-82431?item=3

    -Use tweazers and/or a chip vac pen to place parts

    -Dental pick to do fine tune and paste cleanup, but a toothpick can work also but I like the feel of steel in my hands when working ;-)

    -Griddle reflow works nice.

    -A soldering iron designed for surface mount like work is necessary. I have a Weller EC1302a with a tiny tip hooked to a EC2002 digital control unit I got out of the garbage at work because it needed a $9 ferrule. I found the right Weller tips on closeout at Frys Electronics around the same time for $.10 each (Yes I bought them out but they only had 4 available dang it.) The tiniest tip on my trust Hakko is gigantic compared to the tips on this iron- it is amazing the difference. You NEED the right tip/iron to do this!!

    That is all I can think of- thanks for reading.
     
  2. DougieB

    DougieB Full Time Elf

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    Thanks for the tips CK, was about to start my strobes this coming weekend. Need to look at my soldering tip, looks gigantic when I did a dummy run last night.
     
  3. DanoNJ

    DanoNJ Full Time Elf

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    The tweezers are a great tool to use on these. I ended up hand soldering all mine. What I found, for those of you wanting to hand solder, is place a small amount of solder on one pad first. Hit that with the iron and it will lock the chip in place for the other legs.
    Glad to see more people building this year!!!
     
  4. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    Some very good tips there. Its basically how i do mine. I use a tooth pick to actually apply the paste as i find this is the best way not to use too much as i learnt very quickly its the amount of paste that is applied that creates many of the shorts. I also used a hot airgun to flow the paste.

    But i was the same, the first batch i lost a couple from the learning experience, but the fact that im only really loosing a couple of dollars if i fail, then the loss is not much. I found these to be great to learn SMD soldering with, by the time you finish building these you will be more than confident to take on other SMD projects as its not really hard at all.
     
  5. DougieB

    DougieB Full Time Elf

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    Eddy
    do you have any sort of nozzle on your hot air gun and is there a risk of melting plastic components like 5050LEDs.
    Tips on how you do it would be much appreciated
     
  6. OP
    OP
    CaptKirk

    CaptKirk New Elf

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    So last night was a full panel run. Following my own advice was successful for side one (the NUB side) using the griddle method. Turned out relatively clean and with little stress. Just had one set of resistors that did not initially end up in place but bumping them about (and knocking the NUB clean off the board at one point) was about the only excitement. Cleanup was easy and taking care of a few bridges was simple. Side two as we go forward....
     
  7. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    My hot air gun comes with a selection of nozzles, i tend to use the medium sized nozzle. I will preheat the panel and parts first for 60 to 120 seconds before moving in closer to make the paste run. I have the hot air set at 360 degrees with an airflow of about 50% so the air is not strong enough to blow the parts off the panel.

    There are some great tutorials on SMD soldering on youtube, and its just really the way i learnt
    I must say though i have never soldered 5050 LEDs before so I cant comment on melting the 5050 LEDs. My thoughts would be that they should be OK
     
  8. DougieB

    DougieB Full Time Elf

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    Thanks Eddy
    will have a play with the hot air gun this weekend. My soldering iron tip is still 2 weeks away, out of stock in Oz apparently
     
  9. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    which way are you soldering these, with a hot air gun or with a fine soldering tip.
     
  10. DougieB

    DougieB Full Time Elf

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    Was going to use a fine soldering tip, but had to order one. Now I think I will give the hot air method a try
     
  11. OP
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    CaptKirk

    CaptKirk New Elf

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    I'm still at a 90% success rate after finalizing another row of ten. Had a LOT of rework on this batch so I need to work on my hand solder skills. With twenty complete, I have two dead where the pic will not erase, program or run... Ah well....
     
  12. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    I really wonder how people hand solder these, i couldnt imagine hand soldering these strobes, seems like a hard way to do it which doesnt give any consistancy.
    Ive used a hot air gun and have achieved 100% success from previous strobes i have built except for the first batch where i applied too much solder paste but i learnt quickly about applying the right amount of paste.

    I reakon you guys doing it by hand should have been micro surgeons, because you would have to have a very steady hand to hand solder these very small components
     
  13. OP
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    CaptKirk

    CaptKirk New Elf

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    The trick with hand soldering is moderation with the paste. I had been using WAAAAY too much before. A nice tiny tip on a SMD rework soldering iron helps also. I do have my heat embosser ordered and on the way. I hope that will make things work easier in the future.

    Did another batch of 10 hand solder last night and got all of them working! That brings my average suscess rate up a bit. Interestingly, the one that didn't work right away turned out to be a DEAD LED. I was not expecting that, but everything was working except the flashy part so I checked it and no light (in either polarity- I know about THAT issue).

    Is anyone else seeing fall-outs with the LEDs??
     
  14. OP
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    CaptKirk

    CaptKirk New Elf

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    Well the hot air embosser sure helped out on the failed units. I was able to unsolder one with the hot air and resolder on to new board and had it work (I also did the board where I killed the PIC but I am waiting for some samples of the part to replace it). I also used the embosser to "reflow" one strobe that I could not program the PIC and it worked after that (obviously a solder short I could not see).


    So I am at a point where I only killed ONE PIC (ripped that leg off it), trashed two boards (including the one where I ripped off the PIC leg) and have one dead LED. The boards I built using the spare BOMs all seem to work also (I am testing with another 8MM dome LED I had in my collection but horribly over driving the current). That means out of 55 boards I built I only have 1 dead so I am up to 98.2% success rate!!


    Thank you Mr. Eddy for a great group buy! Now we just need to figure out how to stop the triple shipping penalty from down under to US (shipping charges to you, bulk shipping charges to your US agent AND shipping charges from your agent to us in the US)!! With that only the shippers win!! ;-)
     
  15. breast69au

    breast69au Full Time Elf

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    Eddy do you use the heat gun on the other side too???
     

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