How-To: Add 7135 chips to a Driver Board (Stacking)

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Ouchyfoot
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I’m always worry about heat transfering through the legs destroying the internals of the chip.
I get peaks sometimes too. I think it usually means I’ve got too much solder. When that starts happening, I keep dabbing at it with the iron to remove the excess, and wipe it off the tip. Flux could also help it to flow more evenly.

relic38
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Flux and a little more heat could help with the peaks. I set mine around 375C.
The bond wire are encapsulated in the package and are bonded to the pin internally. If the act of bending the lead loosens it in the pacage even a little, it could weaken the bond. The risk is probably low. I don’t bother si ce soldering straight leads has always worked for me.

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Nightbird95
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My 2 Convoy C8s and a 10-pack 7135 arrived today from FastTech and I took the plunge of trying to add 2 7135 chips to one of the C8’s drivers. Smile

I destroyed one chip (broke pin 1) but I managed to attach 2 chips to the driver (though it took very long to connect the pins since my soldering skills are very limited). The problem is that when I reassembled the flashlight, it won’t turn on.

I took the pill out again and tried connecting it to the positive (positive terminal of the 18650) and negative (body) of the flashlight and was further confused with the results. It does not turn on when I connect it normally but turns on when the positive of the driver is connected to the body and the ground of the pill to the positive of the 18650. I tried the pill of the other C8 and it functions normally. I also rechecked the wiring using the stock driver as reference and the connections seem the same.

What have I done wrong? Did the long exposure to soldering iron heat damage my driver? I’m contemplating on replacing the 2 pairs of 7135 chips I bonded to each other. I still have 7 chips left.

Help please? :bigsmile:

Nightbird95
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Here’s the picture of the Convoy C8 driver with 2 7135 chips added. I followed OL’s technique of using hemostats to hold the driver and the chips together.

Sorry for the crappy picture. I have a crappy camera. :8)

Nightbird95
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Found the problem! |(

I almost lost hope when I took a closer look at the MPCB. The black wire was connected to the ‘”+” of the MPCB and the red wire was connected to the “-”.

I don’t know if Convoy made a mistake or its technicians did that on purpose. Sad

I connected the black wire to the positive of the driver and the red to the negative and my light now works. The light output difference of the two Convoy C8s is not evident but the 10*7135 C8 gets hot a little faster than the stock (8*7135) C8.

light junkie
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  You make so easy Ill give a shot!:-)

Lj

bibihang
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I cannot stick the blob of solder on my soldering iron tip, probably my tip has been oxidized. How do you guys maintaining the soldering iron tip in healthy condition?

Helios-
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Sal ammoniac (ammonium chloride). Your tip will be shinny as new.


Counterfeit 18650s, 2,<a href=“http://

bibihang
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Helios- wrote:
Sal ammoniac (ammonium chloride). Your tip will be shinny as new.

Oh really? I have browsed through few websites and couldnt find a good method, thanks for the suggestion. But I still don’t know where can I buy one.
DB Custom
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First off, I remove the spring to get it out of the way. This makes it much easier to access the pins on the inside. I also like to bend the pins in a 90 degree angle which lets them reach down and touch the top of the legs on the chip you’re stacking on. By applying a small blob of solder paste to each leg of the existing chip first, you can set the new chip on top and have the solder already in place.

Glue the chip on top with thermal adhesive and it won’t be moving around on you. Or find a way to otherwise hold it down while soldering. (I’ve mounted my hemostats in a counter-top mini vise and angle them so they are slightly lower than the chip when the driver is held in it’s mount. Then slide the driver under the stats and that little pressure is enough to hold the chip in place while performing the delicate solder operation)

The touch and drag method easily does the larger ground pin on the neg ring side, then all it takes is a touch of the iron to the tiny legs and each leg is soldered, neatly and with little danger of overflow compromising the integrity of the board.

Then a conical spring can be inverse mounted and you’re up and running!

My Hakko 888 station came with a brass scrub pad in a hole under the iron holder. Plunging the tip into this pad keeps solder wiped off and the tip ready for the next operation. So I’d expect a similar pad found almost anywhere (most likely an electronics store but also a grocery store) would clean a hot iron of excess build-up.

I’ve learned all this in the last couple of months since acquiring the Hakko 888 and my soldering has improved tremendously!

Thanks for the tips and directions guys, playing around with it gets you in your comfort zone and makes it…well…second nature! Smile

DB Custom
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I ran out of solder. So I squirted solder paste onto the counter-top and touched the iron to the paste to load a bit of solder. This actually worked very well, plenty of flux and a very small amount of solder allowed it to flow to the pins easily and neatly.

DBC_July 10, 2013_205524-2

The ground ring is sitting on top of a 1/2” thick copper heat-sink. Smile There’s 7 chips underneath the board, and 6 on top including the 2 I added. I cored out the aluminum pill in my HD2010 and replaced that center with 2 quarter inch thick copper rounds, taper press fit one from the top and the other from the bottom and reflowed together in the middle. The XM-L2 T6 this driver is powering is de-domed and hitting over 600 yds. Very pleased with my HD2010!

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I’ll have to try the solder braid trick. Might be a good way to reuse it and improve heat transfer for the top chip.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

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ohaya
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Need some HELP!

First time trying to stack a couple of 7135s.

I used Fujik glue (didn’t have any super glue) between the original 7135 and the new 7135. Maybe that was a mistake??

It seems like when I touch the iron to the ground tab, it melts the Fujik, because the top 7135 moves :(!

Does Fujik melt/liquify when it gets hot??? I don’t know if the Fujik just hadn’t cured enough, or if it melts.

Second mistake after re-reading the earlier posts was that I was using a really thin tip.

Sounds like I should use a fatter tip, maybe a chisel tip, at least for the ground tab??

This (stacking 7135s) has been something that I’ve been dreading for awhile, and now I know why :(!!

EDIT: BTW, the pics in the OP aren’t working.

Tom E
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No, please don't use any glue - no need. Just flux the pins, top and bottom, load the tip with solder, secure the top 7135 with a tweezer in one hand just small pressure to hold it down in place, then gentle, slow strokes upwards from the bottom pin until the solder starts building up. Always use a small wedge tip, never a pointy tip - holds more solder, gets more heat to where you need it. Here's 4.55A with 13 chips of 350's:

Double, triple, no prob! Here's another 2 more at 3.85A each:

ohaya
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Tom E wrote:

No, please don’t use any glue – no need. Just flux the pins, top and bottom, load the tip with solder, secure the top 7135 with a tweezer in one hand just small pressure to hold it down in place, then gentle, slow strokes upwards from the bottom pin until the solder starts building up. Always use a small wedge tip, never a pointy tip – holds more solder, gets more heat to where you need it. Here’s 4.55A with 13 chips of 350’s:

Double, triple, no prob! Here’s another 2 more at 3.85A each:

No problem? You guys must have nerves of steel, but I don’t think I’ll be trying this again any time soon!

I finally got one on ok, but I was only able to do that by bending the 3 pins on the 7135. There was no way I was going to be able to bridge the 3 pins. The PCB was very crowded (3.04A from IS), so I couldn’t even get the chisel tip to the pins.

I know that you all don’t recommend that (bending the pins), but I just had to.

How? I put the tiny 7135 in a vise, then “rolled” the end of a pair if needle nosed pliers over them.

I was then able to bridge the ground tab on that one (after several tries) using the chisel point tip, and solder the 3 pins using a small soldering tip.

Once I got that one, I was done :(…

Later,
Jim

bibihang
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I always skip the middle pin and just solder the ground tab behind, because I find it very difficult to solder the middle one as once I accidentally touch the other pins the solder would connect the middle pin with the others and mess everything up.

bdiddle
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I use CA to stick the chip on before soldering. The new one does not move that way Smile

Newb

ohaya
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bdiddle wrote:
I use CA to stick the chip on before soldering. The new one does not move that way Smile

What’s “CA”?

bdiddle
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Super glue. CyanoAcrylate.

Thin layer dries fast.

Newb

ohaya
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bdiddle wrote:
Super glue. CyanoAcrylate.

Thin layer dries fast.

Ahh. Ok, thanks.

ohaya
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ohaya wrote:
Tom E wrote:

No, please don’t use any glue – no need. Just flux the pins, top and bottom, load the tip with solder, secure the top 7135 with a tweezer in one hand just small pressure to hold it down in place, then gentle, slow strokes upwards from the bottom pin until the solder starts building up. Always use a small wedge tip, never a pointy tip – holds more solder, gets more heat to where you need it. Here’s 4.55A with 13 chips of 350’s:

Double, triple, no prob! Here’s another 2 more at 3.85A each:

No problem? You guys must have nerves of steel, but I don’t think I’ll be trying this again any time soon!

I finally got one on ok, but I was only able to do that by bending the 3 pins on the 7135. There was no way I was going to be able to bridge the 3 pins. The PCB was very crowded (3.04A from IS), so I couldn’t even get the chisel tip to the pins.

I know that you all don’t recommend that (bending the pins), but I just had to.

How? I put the tiny 7135 in a vise, then “rolled” the end of a pair if needle nosed pliers over them.

I was then able to bridge the ground tab on that one (after several tries) using the chisel point tip, and solder the 3 pins using a small soldering tip.

Once I got that one, I was done :(…

Later,
Jim

Tom E,

Which drivers are those in your pics?

Tom E
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Those are Nanjg's - best deal is FT for $3.05 each, in qty, cheaper. Some guys are against bending the pins, but I always do - did 100's of them. Don't use a vise though - I use a bent needle-nose and bend all 3 at once - go slowly though, and use my thumb to do the bend. Only time I've broke pins is when I hurried. They are all crowded - you need good vision, good light when doing this. I use drug store glasses (from DX maybe?), like 2.5x strength, but I need those for any close-up work anyway with how my contacts are.

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This was my first effort…

I used a drop of super glue to hold them and it worked a treat!

Tom E
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I'm going to do a couple of 14x7135's, 2 triples, so I'll take pics again. I got 18 Nanjg's floating around now and can easily go thru them all if I had time... At $2.68 qty 5, and the 7135's at 11 cents qty 100 (24 cents for 380's qty 10), it's really not much of an expense, so you don't have to worry so much about mistakes, but I've always been able to recover the board from bridging pins, or loosening a bottom 7135, etc.

ohaya
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With all of this, I was thinking (just thinking/some ideas) that it might be easier to:

- Bend 3 pins (already discussed)
- Use super-glue to hold the chips together
- Solder the 3 pins first

Assuming the 1st two above are done, the 3rd one (solder the 3 pins) is not difficult… it’s like “normal” soldering, albeit with sometimes cramped spaces. Then, once all 3 steps above, I’m thinking to put something between the unsoldered top and bottom chip tabs (not sure what yet, maybe small piece of small gauge wire, like wirewrap wire?) and then solder the tabs together, rather than just do the “glob of solder and drag and pray”.

Or, maybe “wire glue” (http://budgetlightforum.com/node/7691) would work for bridging the tabs?

Edit: Instead of super-glue, I was wondering if AA (2 part) would work? Does that melt under high-temp like the Fujik glue apparently does?

Ouchyfoot
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Don’t use Wire Glue. Those tabs are thermal pathways for heat transfer. I tried using a piece of wire, and copper braid. In the end, it was more of a hassle, and looked even sloppier. A nice fat soldering tip lifts the solder blob best.

ohaya
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Ouchyfoot wrote:
Don’t use Wire Glue. Those tabs are thermal pathways for heat transfer. I tried using a piece of wire, and copper braid. In the end, it was more of a hassle, and looked even sloppier. A nice fat soldering tip lifts the solder blob best.

I hope that I can explain this clearly… let me try: The thing that I had problem with was getting the soldering tip TO the tab on the bottom 7135. Some of the spaces were pretty tight, plus it seemed like it was really hard to angle the chisel tip to touch the tab on the bottom 7135.

I don’t know. Maybe I had the top 7135 “too far forward”, such that its tab was overhanging the tab from the bottom 7135?

Ouchyfoot
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Okay. You were talking about the three little legs(tabs) I thought you meant the large one on the back of the chip. I think it depends on the day. Some days everything goes great, and others, I ruin the whole damn driver. Keep trying different tips and temps til you find one that is best for lifting the solder from the bottom to the top. You can ignore the center foot since it does the same thing as the one in the back. You can snip it right off. I have stacked chips by placing a piece of pre-tinned small diameter wire against the bottom and top legs, touch your tip to it until it attaches, and snip off any excess at the top.

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A piece of awg12 solid(house wire) fits nicely between the large ground tabs and makes for a better thermal path for the upper chips.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

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