Impossible to solder SMD??

Ok I must have been crazy when I bought some SMD resistors from the Shoppe. I remember saying to myself..."go ahead you can solder these things"....."Oh yes I will be just like LitFuse"...."yep I can bump the current on this ARC all by myself"....."I mean how hard can it be". Man I must be crazy as I can hardly even see these little things much less solder them. Not sure how LitFuse did it to my modded board but can anyone tell me if this is even possible for a novice like myself? These resistors seem impossible to solder without blobbing solder all over this little thing. Gives me a new appreciation of LitFuse and his work and I can only imagine others work here who has even done smaller work. I wonder what I was thinking as I have a 15 dollar solder gun and some wire thin solder bought from WalMart...can this be done?

yes, it can be done. Though i am not sure if that solder gun might be too big for the purpose though. My suggestion for you would be the following:
1. get to ratshack or nearest electronic store and get one of those cheapy 25W soldering iron with a sharp pointy tip
2. somehow epoxy the resistor in place to the board. This will ensure that the resistor won't move around when you do your soldering. If you have tweezer, you might not need this step, but it is an idea
3. once you solder, don't put the solder on the soldering iron directly. Instead, put the tip on the resistor/board junction to heat it up for about half a sec then put the solder on the junction. the solder should melt and cover the junction with a nice blob of solder. Don't overdo with the solder. you don't want to solder to cover your resistor completely now, do you?
4. if you used too much solder, simply use solder wick to remove the excess.
5. don't forget 3 seconds rule. Basically, all the soldering steps should only take 3 seconds at most (excluding #1 of course)
well, that is it.

i am sure other can revise/correct me if i am wrong, but that is what i did so far and it has been working for me /ubbthreads/images/graemlins/grin.gif

Robocop- no, it's not impossible, but having the right tools for the job is crucial. You need to firmly clamp the work for starters. You'll need a fine tip iron, a pair of pointy tweezers, liquid flux, some solder wick, and some fine gauge solder ( I use .022 ). You'll also need to have good lighting so you can see what you're doing. As long as you have good eyesight and a steady hand, you should do OK.

Like anything else, there is no substitute for experience, so you can't really expect perfect results the first couple of times. The more you practice, the better your results will be.

If you don't have the tools, I would be happy to solder the boards for you at no charge- just send me a PM. /ubbthreads/images/graemlins/smile.gif

Peter

IIRC, the Arc boards accept 1206 size resistors. I'm not aware of Wayne selling 1206 resistors. I think he's only selling 0603 size resistors. Are you sure that you're using the right resistor. You may be making it harder on yourself than it needs to be.

When doing SMD, two irons can be handy, especially for removal.

For installation, some 0.010" solder comes in really handy to prevent your blobing problem.

[ QUOTE ]
Chop said:
IIRC, the Arc boards accept 1206 size resistors. I'm not aware of Wayne selling 1206 resistors. I think he's only selling 0603 size resistors. Are you sure that you're using the right resistor. You may be making it harder on yourself than it needs to be.

[/ QUOTE ]

Tony has a point- these resistors are smaller than they need to be. Unfortunately these are what The Shoppe stocks, and I have just continued to use them because of the ordering convenience.

Peter

I don't know, the resistors are bigger than they need to be, imho. Just use 0402, its a nice compromise, 0201 is too small for most folks to work with.

Wow, didn't know anyone still used the ancient monster sized 1206 packages much anymore.

Why... Why.. Ah jest set 'em all on da board an' blast 'em with the propane torch. Sodderz 'em right good.

I've discovered I need a good hands free magnifier of some kind and I have to stay from the rocket fuel coffee for a while before hand.

I agree with Uncle Fester - no caffeine prior to soldering SMD parts! And a liughted magnifier is a must, along with a soldering pencil with a 1/32" or preferably 1/64" tip.

I did it!!...finally after many hours I was able to complete these SMD resistors. I used a magnifying glass to carefully place the resistor between the spare pads and then cut a small piece of solder. I placed the small solder piece on the corner of the pad and lightly touched it and it worked. It is not that easy and took many attempts but it worked. I have no way of knowing the actual current to the Luxeon however I did test at the tail cap,before and after,while using the same battery. Before the addition of the resistor it showed 520 mAh and after it showed 1.13. I did 2 of my ARCs this way and swapped the factory Luxeons for SWOKs. I was also able to use the reflectors from the Shoppe so now both have bumped current,3 watt Luxeons and reflectors....man life is good. When compared to my LitFuse mod these SWOKs still are not as incredible as the TWOH however they do come close. I am taking pics now and will try to get some comparison shots up soon. Thanks to everyone for the help with this....Out of all of my LS ARCs I left the brightest factory one as is. I did add a reflector to it but was afraid to bump the current using the factory 1 watt luxeon. I am happy with the reflector and stock Luxeon and thought it would be nice to have one that would have a little better run time and not get so hot....All in all this was a lot of fun and I am happy with the results.

for those who are trying to do SMD. I have a small roll of 60/40 'Reliacor II' solder. Its diameter is .015 (it's REALLY thin. It is a few years old and has some surface corrosion but is still good. I am willing to 'give' some of this away. I will put a few feet in a standard emvelope and mail within US. All I would ask for is that postage, emvelope and travel to Post office (still unemployed), and friggin paypal charges. Lets say $1.
I AM NOT trying to sell this for profit or I would put it in B/S/T, I have done and still do SMD stuff, and thin solder makes it A LOT easier. PM me if anyone wants some.

ROBOCOP, congrats on swapping the resistors! SMD work with the right tools takes a light touch, doing it with regular tools takes a bit of insanity...
Jeff

Congratulations Noel, it's good to hear that you were successful! That 1.13A current sounds too high though, are you sure that's right? Make sure you use a fresh battery. I'm seeing around a 700mA draw for a mod that is biased at 611mA. I think you should be seeing a current draw about 100-150mA higher than what the board is set at.

Peter

Robocop,

Might want to practice on old spare pc boards lying around. Practice
removing componets using a wick and or solder sucker and soldering
back, a plastic vise grip (3rd hand) is must and a good soldering
iron as well

I'm using the isotip pro but find that the tips get worn out quickly
and at $4.00 each very expensive /ubbthreads/images/graemlins/frown.gif. Can someone please
recommend a good soldering station I believe it's time for me
to get a really good one that would last for years.

oops double posted sorry /ubbthreads/images/graemlins/frown.gif Robocop

I am using a cheap DMM that was bought at HarborFreight on sale. It works well enough for checking freshness of batteries but for other stuff I am not so sure. I am not even positive I have the dial set right to check mAh at the cap but I think it is correct. My QIII with a TWOK showed to have dead on 800 mAh at the tail cap. Out of all 3 of my modded Arcs my TWOH mod shows between 900 and 910 mAh with my other two SWOKs showing a little bit higher. These numbers were given using the same battery that tested at 3.04 volts. The two SWOKs were modded by myself and I could have possibly not got my soldering as clean as my TWOH that was modded by you Peter. It is possible that something is not working correct due to my poor soldering skills on these small SMD resistors however they all work very brightly. The brightness is similiar in all of them however the TWOH still has a small edge in tint and output...this is probably my imagination as the TWOH is my favorite. I may be also not having a good connection with my probes but for now I am kind of excited about my newly created mods. Let me tell you where I have the probes and dials set and maybe someone can tell me if the DMM is set correct. The red (positive) probe is plugged into the 10ADC plug with the black probe plugged into the COM plug. I set the dial to the .20 setting in the DCA section. The DMM I am using is made by Cen-Tech and is the yellow one sold by Harbor Freight. I have long since lost my instructions however I think these were the settings I read from the instructions. I only use this to check for voltage of batteries and current at the tail cap of various lights so my experience is limited here. Lets just say a SWOK modded ARC board is pulling 1.13 amps at the tail cap with a fresh battery. If so would it be a good guess that the actual luxeon is getting at least 750 mAh? I keep thinking that there is some form of chart to use or rule of thumb like saying if a light has x amount of current at the tail cap it will lose x amount of current before it gets to the luxeon. I kind of see now that this is not true between identical circuit boards however is a result of the VF of the luxeon itself. So basically is it true that if we have 2 identical boards with different VF luxeons they will draw completely different numbers at the tail cap. I am asking if there is a rule of thumb I can rely on to kind of "guess" what the Luxeon is getting. Above Peter stated I will usually see 100 to 150 mAh more at the cap than the luxeon is getting. Does this apply to almost all circuit boards or just these ARC boards? I am curious now as I am going to check some other lights I have and only have the tail cap method to use. I am wondering about how much to subtract to have a rough guess as to what is being lost before the current reaches the LED.

Also thanks for the tip cgpeanut. I must say that I am just barely able to solder items on a board and even that is shaky at best. I do not even know what those other items you have mentioned are..haha Solder sucker sounds kind of like some form of fish to me. Honestly I never have used a wick or any of the other items you mentioned. Are these vital to good soldering and if so can you tell me what they do? I kind of understand about the 3rd hand thing and that would have been very helpful in this mod for me. I used some surgical clamp type pliers to hold the board still. I am actually wondering about the sucker thing,the wick and the soldering back???...thanks again

A solder sucker is this



Just kidding /ubbthreads/images/graemlins/grin.gif

Actually it's a pump. You prime it an aim at the solder you want to
remove melt the solder with your soldering iron then pull the trigger
and if you aimed it right the melded solder gets sucked in.

A wick on the other hand os a copper braided wire that you use to
remove solder from components for repair. I use it to remove the stock lux on the arc pcb.

Radio shack has these items for sale, combined they should be around
10 bucks you can't do without these when doing mods on arc pcbs.

Asks the cute lady who works there to show you where they are. /ubbthreads/images/graemlins/smile.gif