Cold solder joints? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 10 Old 07-05-2019, 08:13 PM - Thread Starter
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Cold solder joints?

So I’m soldering up the one crossover that I have to for my HT-10s and it looks like I can’t get away from what looks like cold solder joints. I don’t want to keep holding the iron on the pads too long to avoid ruining the board. Thoughts? My iron goes to 900. I know I’m rusty at this but sheesh. Lol







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post #2 of 10 Old 07-05-2019, 08:35 PM
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What type of solder are you using? I've found lead free stuff can look dull like that when it cools.
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post #3 of 10 Old 07-05-2019, 08:51 PM - Thread Starter
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Quote:
Originally Posted by mtg90 View Post
What type of solder are you using? I've found lead free stuff can look dull like that when it cools.


Honestly I don’t know for certain if it is or isn’t. It was in a tube in a kit I just bought. My guess would probably be lead free. The connections seemed tight. I’ve read a bad/cold joint usually can crack and be wiggled but I couldn’t get it to do anything. I know that may not be the be all end all test.

Anything else I could do to test it for issues before mounting it all?


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post #4 of 10 Old 07-05-2019, 09:13 PM
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Quote:
Originally Posted by imrf View Post
So I’m soldering up the one crossover that I have to for my HT-10s and it looks like I can’t get away from what looks like cold solder joints. I don’t want to keep holding the iron on the pads too long to avoid ruining the board. Thoughts? My iron goes to 900. I know I’m rusty at this but sheesh. Lol




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Going back to my working days it was thought that you could visually inspect for cold solder joints. Having military customers we didn't want to make mistakes. Since this was 30 or so years ago things may have changed, in any case, sometime along the way a study was done by some respected people and they determined you couldn't identify a cold solder joint by visual inspection. Joints that were in fact bad could look all nice and shiny and visa versa... FWIW

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post #5 of 10 Old 07-05-2019, 11:35 PM
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Quote:
Originally Posted by imrf View Post
...Thoughts? My iron goes to 900...

You never usually have to set the soldering iron higher than 650°F to get a good solder joint, unless the only tip you have is too small for the joint.
A setting of 600°F should be hot enough for most connections.
Setting it to 900°F will just burn off the flux too fast and actually help create a cold solder joint.


Most lead-free solders solidify to a matte (non-shiny) finish, so you can't use that criteria to judge a solder joint as being cold or not.
Did the solder want to wet up the wire as you soldered it (good solder joint), or dimple down and not want to wet the wire at all? (cold solder joint)
Note: I've assumed the PCB pads and wire were clean and free of grease/oils before you soldered them, because they have to be clean before a good joint can be made.


If the parts were clean and the solder wetted both parts readily you can assume they're good joints, but good joints can still fail later if the solder is also being used to physically hold heavy components in place.
Make sure all bulky parts are secured with black zip ties or glue before soldering them to the crossover PCB, however, small resistors won't physically stress the solder joints so they don't need to be secured.
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post #6 of 10 Old 07-06-2019, 04:26 AM
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Add a bit of solder to the tip first, to ensure a good solder bridge. Depending on the tip size, it will determine your feed rate of the solder. Most joints look like they don't have enough solder. Clean the tip regularly. Make sure the tip touches the pad as well as the wire lead at the same time, so they both heat up, ensuring heat spread. The pad size and wire lead will determine how to withdraw the solder iron tip, you need to try and see what works best. Ideally you should cut the lead to the correct length then solder, that way you can pull the iron tip up the lead when with drawing it. This will ensure a nice conical shape as it cools.

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post #7 of 10 Old 07-06-2019, 12:16 PM
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Looks like a job well done to me.

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post #8 of 10 Old 07-06-2019, 12:34 PM
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Quote:
Originally Posted by mtg90 View Post
What type of solder are you using? I've found lead free stuff can look dull like that when it cools.
ditto; can't stand the new lead free stuff and try to avoid it if I can LEAD FREE SUCKS



Not sure if the pics or what but make sure some of those legs don't have a C or hole around them; could be the camera lighting but just make sure they are flowed in. Other than that looks good to me man.

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post #9 of 10 Old 07-06-2019, 07:02 PM
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Quote:
Originally Posted by mtg90 View Post
What type of solder are you using? I've found lead free stuff can look dull like that when it cools.
Quote:
Originally Posted by autox320 View Post
ditto; can't stand the new lead free stuff and try to avoid it if I can LEAD FREE SUCKS

I agree, I still have about a half spool of the old leaded stuff

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post #10 of 10 Old 07-06-2019, 07:16 PM - Thread Starter
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Thanks guys. To the one who asked, it’s the camera angle, no holes in the soldered components.

I hooked it up and did a dry run and it sounded ok to me, even cranked up. I’m going to run with it. Probably just the solder that came with the kit.

On a side note, the midbass on these it’s quite amazing!


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