Electronics > Beginners
SMD soldering for a 3030 led.
6PTsocket:
I just removed/ butchered a bad led off a pc board. This is my first experience with a device that is soldered on the back as opposed to the edge. I assume it is to get the best heat sinking to the copper on the pc board. The board has some high temp coating in both sides of the board with vent? holes around the led on both sides of the board. The only damage my soldering pencil heat did was discolor it. What is the best way to install the new led, hot air from the front, the back? Hopefully I can put the soldering iron next to the led and conduct enough heat under it to the pre tinned pads. See attached photos of front and back. The entire light fixture is around 60 bucks and I am sure going to try replacing the led first. The fixture worked at room temp and quit when it got cold in my freezer so it was probably a bad solder joint to begin with but I blew the led "testing" it. My bad.
I posted a question earlier about how to calculate the correct size led. I measured open circuit at 14.86 volts. I soldered in a 169.5 ( measured) resistor in for the led and measured 11.81 across it. That makes the series resistor 43.77 ohms. Assuming the 3030 drops 3 volts. That works out to 270ma or a 1watt led. I did, at one point, have the old led led pretty bright with a little under 3 volts so I am pretty sure it is not a 6 volt double led. Thanks.
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t1d:
YouTube has videos on soldering techniques, for this very type LED project. So, maybe check there.
I learned tons, about soldering, on YT. NASA even has soldering tuts, on there! It is easy to spot the folks that don't know what they are doing. Just move on, to the next one.
Plus, there are a lot of DIY work-around solutions, for tough problems, with limited specialty tools. Heat gun, hot plate, clothes iron, homemade reflow oven...
See "Mr. Carlson's Lab," for how to easily make a special tip, for the pistol-style soldering irons, that dumps a lot of heat, to a flat surface, in a hurry.
I made my own DIY reflow oven. It works, well enough.
See if there is a MakerSpace club, in your area. They often have great equipment, for the members to use. And, expertise, too.
Isopropyl alcohol and a static-free brush (An old toothbrush would be okay, here, because the component has been removed.) will help with cleaning the board. You can get it at most any pharmacy. Get the highest percentage of alcohol, that they have... 99%, but not all stores have it.
Do you have flux and solder paste (not solder wire?) If not, read up on those, too.
Please remember to post your solutions, to help the next guy... I would like to know what you do, myself.
6PTsocket:
--- Quote from: t1d on November 09, 2018, 10:41:28 pm ---YouTube has videos on soldering techniques, for this very type LED project. So, maybe check there.
I learned tons, about soldering, on YT. NASA even has soldering tuts, on there! It is easy to spot the folks that don't know what they are doing. Just move on, to the next one.
Plus, there are a lot of DIY work-around solutions, for tough problems, with limited specialty tools. Heat gun, hot plate, clothes iron, homemade reflow oven...
See "Mr. Carlson's Lab," for how to easily make a special tip, for the pistol-style soldering irons, that dumps a lot of heat, to a flat surface, in a hurry.
I made my own DIY reflow oven. It works, well enough.
See if there is a MakerSpace club, in your area. They often have great equipment, for the members to use. And, expertise, too.
Isopropyl alcohol and a static-free brush (An old toothbrush would be okay, here, because the component has been removed.) will help with cleaning the board. You can get it at most any pharmacy. Get the highest percentage of alcohol, that they have... 99%, but not all stores have it.
Do you have flux and solder paste (not solder wire?) If not, read up on those, too.
Please remember to post your solutions, to help the next guy... I would like to know what you do, myself.
--- End quote ---
Thanks for all the suggestions. I have a plastic welder that is basically a soldering iron. One of the tips is a flat pad that might do the trick. I'll have to check with the IR gun or thermocouple bead tip that came with my dmm to see if it gets hot enough. I think my old Weller gun has a spreader tip, too. I guess it is best to use a lot of heat and get out quick.
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Brumby:
--- Quote from: 6PTsocket on November 10, 2018, 01:33:14 am ---I guess it is best to use a lot of heat and get out quick.
--- End quote ---
Just be careful about "a lot of heat" - you can go too far (as I'm sure you know). The "get out quick" part is the right thinking, but make sure you don't get out too quick. An extra half second for the solder to flow properly on your first attempt is far less risky than having to go back and heat the whole joint for a second (or third, or fourth) time.
This type of board is made as a heatsink and it will draw heat away quite effectively, so my advice would be to preheat the board with a hot air gun (if you have one) so the soldering iron doesn't have to do all the work (which will likely take longer). This also minimises the time the LED spends at elevated temperatures.
t1d:
--- Quote from: Brumby on November 10, 2018, 03:31:18 am ---An extra half second for the solder to flow properly on your first attempt is far less risky than having to go back and heat the whole joint for a second (or third, or fourth) time.
--- End quote ---
Excellent point. And, with solder that is not completely liquid and just a little too much lifting force, you can pull the copper pads off.
--- Quote from: Brumby on November 10, 2018, 03:31:18 am ---This type of board is made as a heatsink and it will draw heat away quite effectively, so my advice would be to preheat the board with a hot air gun (if you have one) so the soldering iron doesn't have to do all the work (which will likely take longer). This also minimises the time the LED spends at elevated temperatures.
--- End quote ---
Great suggestion.
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