Different LED brightness?

[suchamoneypit]

So im in the process of switching out the LEDs in my car's dash ( @AdamIsaacLang helped me pick the correct ones, they work great) . Its been a very interesting project. This is what it looks light currently: 

black line was a mistake in paint im tired and dont feel like re-uploading.

 

So I have several questions. First off,  the LEDs for the PCB all worked, but after installation, it appears the LEDs for the temps in the right dial stopped working, and the needle for the RPMs might even be stuck, I will have to take a look at that.  It took me 5 tests to get the center LEDs to all work (they were a problem but all others were fine), and even now there is a slight red film left over (wasn't sure if I could accidentally sand through some stuff that would be visible on the other side, visible in this picture, to be brought up in another post (maybe even a different forum as this is pretty specific). The plastic near the right dials is also littered with imperfections, looks possibly heat related, this was there before though. Will have to buy a new plastic shield or something.

 

-My main question is in my RPMs, the LEDs for the 4, 3, and 2 are noticeably dimmer than the others, though the picture doesn't make this obvious. Could this be due to poor connection (its very possible, it was the first ones I did)? Should I re-solder or apply more solder?

[Hackentosher]

9 minutes ago, suchamoneypit said:

my RPMs, the LEDs for the 4, 3, and 2 are noticeably dimmer than the others, though the picture doesn't make this obvious. Could this be due to poor connection (its very possible, it was the first ones I did)? Should I re-solder or apply more solder?

My instincts tell me that if there was a bad solder joint, the led would either work or not work, not just be dimmer. I'd still look at the pcb and check. Maybe some of the LEDs are soldered backwards and are not turning on, making the display appear dimmer?

 

From the picture, it looks likes 2-4 aren't on. Check the joints for those. 

 

More solder won't help you. When it comes to soldering, quality over quantity rules. 

[suchamoneypit]

6 minutes ago, Hackentosher said:

My instincts tell me that if there was a bad solder joint, the led would either work or not work, not just be dimmer. I'd still look at the pcb and check. Maybe some of the LEDs are soldered backwards and are not turning on, making the display appear dimmer?

 

From the picture, it looks likes 2-4 aren't on. Check the joints for those. 

 

More solder won't help you. When it comes to soldering, quality over quantity rules. 

Yeah as I found out they are all on a circuit, so for example, if the LED for 4 in the RPMs was not working or soldering incorrectly, 5-8 would not work. Also, each of these numbers LED is fastened to a plastic face where each LED has its own plastic "chamber", so if 4 was not working, light from the LED for 2 and 3 would not illuminate 4 at all. So I'm guessing the core problem here is a poor joint. 

 

What do you consider a poor joint? Any examples of a good one vs a bad one? Any suggestions/examples on the best method of soldering something like this (its an extremely small LED).

 

When I bring up the more solder issue, Its more of the problem of I did it so poorly in the first place the solder isn't making full contact with the LED, so remelting and adding a little more would allow full contact.

[Huntsman]

You could try using some flux to alleviate the problem. It could be due to the surface having some contaminants during soldering and that could cause the joint to be faulty.

 

Good joints are well... good. Assuming you are using leaded solder, it should be shinny and smooth. There will be no gap whatsoever from the PCB pads to the components with minimal resistance.

 

Bad joints are a very wide range problem. It could be brittle and porous solder from temperature issues, it could be gap between solder and contacts due to contaminants etc. Most problems can be fixed with flux and "re-melting" the solder to make them  "flow" better.

[suchamoneypit]

11 hours ago, Huntsman said:

You could try using some flux to alleviate the problem. It could be due to the surface having some contaminants during soldering and that could cause the joint to be faulty.

 

Good joints are well... good. Assuming you are using leaded solder, it should be shinny and smooth. There will be no gap whatsoever from the PCB pads to the components with minimal resistance.

 

Bad joints are a very wide range problem. It could be brittle and porous solder from temperature issues, it could be gap between solder and contacts due to contaminants etc. Most problems can be fixed with flux and "re-melting" the solder to make them  "flow" better.

What type of flux would you recommend trying? The solder I removed from the PCB melted around 700-750 F, while the solder the new LEDs are on with melted around 450 F.

[Hackentosher]

1 hour ago, suchamoneypit said:

What type of flux would you recommend trying? The solder I removed from the PCB melted around 700-750 F, while the solder the new LEDs are on with melted around 450 F.

Erm... What's that in Celsius? I try not to go over 350c, any higher and the Flux in your solder burns up instantly. 

[suchamoneypit]

4 hours ago, Hackentosher said:

Erm... What's that in Celsius? I try not to go over 350c, any higher and the Flux in your solder burns up instantly. 

 

17 hours ago, Huntsman said:

You could try using some flux to alleviate the problem. It could be due to the surface having some contaminants during soldering and that could cause the joint to be faulty.

 

Good joints are well... good. Assuming you are using leaded solder, it should be shinny and smooth. There will be no gap whatsoever from the PCB pads to the components with minimal resistance.

 

Bad joints are a very wide range problem. It could be brittle and porous solder from temperature issues, it could be gap between solder and contacts due to contaminants etc. Most problems can be fixed with flux and "re-melting" the solder to make them  "flow" better.

 

5 hours of labor, 20 tests, and a lot of soldering and sanding later, Its redone. I had many issues. Definetly bad joints. Re-soldering the LEDs are on the right carefully got them working (took 3 tries). Re-soldering the dim LEDs made them bright, but then a bad joint on the "6" for the RPM dial caused a 10-15% chance of either a hard-to-notice flicker, or a 10-20 second delay in those LEDs lighting up. Re-soldered all LEDs after "5" for RPMs, and all LEDs are working and bright.

As the last picture, the places where the light leaks through is far more noticeable in this picture, in the real world is hardly noticeable, especially when your actually driving, I talk about it in the next paragraph

 

I did around an around of tedious sanding on the red film, making the cover the LEDs shine through significantly more clear (it went from very noticeable red tint to none at all!), and it looks a million times better. The only thing that needs a change is due to sanding some black areas let some light leak through. I will draw up a template with a perfect curve matching the stock curves where light is supposed to leak and will disassemble and touch up these places at a later date to make it perfect.

 

I'll make a project post eventually, I took pictures throughout the process. As a first time soldering experience (working with components on a PCB in general), and my second time taking apart my car, it was fantastically fun. It took me 45 minutes to tear down the entire dashboard to get to my speedometer the first time, after all this troubleshooting, no exaggeration, it takes me 2-3 minutes now that I'm not so damn nervous doing it, so changes in the future are a quick project. I attempted a aux mod myself a few weeks ago, with that experience and this, I can take apart the entire front interior of my car now, with me having no experience in that before.

 

I am extremely pleased with the results and very glad I went ahead into the unknown and did it.

[Huntsman]

Great job on the mods, it definitely looks sharp. Might attempt this on my car one day but I'll have to clear my list of pending projects first lol!

 

Back on the subject of solder types, generally you would want 60/40 solder. Which meant it consist of 60% tin and 40% lead. This is the most common type of solder. I prefer 63/37 for the eutectic characteristic but this is just a preference thing, does not really impact solder quality.

 

There's also lead-less solder which the industry is trying really hard to push with the RoHS standards. These are generally a pain in the behind as they're hard to melt, doesn't "flow" properly and they have a dull finish. So dull that you can't really discern if it is a cold joint or a proper one. Also they need some serious quality soldering station to work with. Avoid these if you could get away with it.

 

For all solders you would want to get a rosin cored or flux cored, preferably rosin. Rosin are less acidic and won't corrode your PCB pads after some time. It is very recommended to clean off your PCB of those rosin/flux stains after soldering. It's rare but it does eventually cause problem with the circuits. Just use some cotton buds and IPA to clean them off.

[Hackentosher]

9 minutes ago, Huntsman said:

Snip

8/8 answer. However, I prefer a spare tooth brush for cleaning, it won't get torn apart by surface components when you scrub the hell out of the burnt Flux. 

[suchamoneypit]

14 minutes ago, Huntsman said:

Great job on the mods, it definitely looks sharp. Might attempt this on my car one day but I'll have to clear my list of pending projects first lol!

 

Back on the subject of solder types, generally you would want 60/40 solder. Which meant it consist of 60% tin and 40% lead. This is the most common type of solder. I prefer 63/37 for the eutectic characteristic but this is just a preference thing, does not really impact solder quality.

 

There's also lead-less solder which the industry is trying really hard to push with the RoHS standards. These are generally a pain in the behind as they're hard to melt, doesn't "flow" properly and they have a dull finish. So dull that you can't really discern if it is a cold joint or a proper one. Also they need some serious quality soldering station to work with. Avoid these if you could get away with it.

 

For all solders you would want to get a rosin cored or flux cored, preferably rosin. Rosin are less acidic and won't corrode your PCB pads after some time. It is very recommended to clean off your PCB of those rosin/flux stains after soldering. It's rare but it does eventually cause problem with the circuits. Just use some cotton buds and IPA to clean them off.

 

5 minutes ago, Hackentosher said:

8/8 answer. However, I prefer a spare tooth brush for cleaning, it won't get torn apart by surface components when you scrub the hell out of the burnt Flux. 

do you clean off the flux with just a plain toothbrush? nothing else? is the residue a sort of powder that comes off that easy?

[Hackentosher]

7 minutes ago, suchamoneypit said:

 

do you clean off the flux with just a plain toothbrush? nothing else? is the residue a sort of powder that comes off that easy?

It's mostly the alcohol that does the cleaning, but if you have a bunch of burnt Flux, you will need a lot of elbow grease and a bit of time with your tooth brush. 

[suchamoneypit]

I edited a quick picture showing the two major steps on the mod, with a pic of what it looked like before.