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Used the wrong solder 10 years ago — Parallax Forums

Used the wrong solder 10 years ago

xanaduxanadu Posts: 3,347
edited 2013-07-09 06:00 in General Discussion
Plumbing solder. The circuit is two LM3915s, and it all still works if you hold it just right.

This board was soldered in 2003, picture taken today.

IMG_1911.jpg
IMG_1911.jpg
1024 x 768 - 74K

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2013-07-02 12:18
    Plumbing solder was often the same alloy mix as electrical solder... it was the flux that was considered a no-no.

    The acid flux corrodes heavily around electricity; the rosin flux is preferred. But these days, I think all the copper pipes are silver soldered to avoid lead... rather silly as tin alone would do nicely.
  • LeonLeon Posts: 7,620
    edited 2013-07-02 12:20
    If you used plumbing flux I'd scrap it and build another one using electronic solder and flux.
  • User NameUser Name Posts: 1,451
    edited 2013-07-02 12:22
    Clearly the flux was more of a problem than the specific alloy. Turns out that if you can remove all traces of acid-core flux (such as with hot soapy water, a toothbrush, and some elbow grease, followed by thorough rinsing) your board would be in great shape after 10 years.
  • User NameUser Name Posts: 1,451
    edited 2013-07-02 12:25
    Loopy Byteloose wrote: »
    ... rather silly as tin alone would do nicely.

    Not so. Pure tin, as a solder, has several problems, most of which are avoided with the addition of small quantities of alloying metals.
  • xanaduxanadu Posts: 3,347
    edited 2013-07-02 12:34
    I think the plumbing solder has some kind of flux core that did it in. I'm pretty sure I've never owned plumbing flux, but it was 10 years ago.
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2013-07-03 04:56
    Run the board through an automatic dish washer with detergent a few times.
    This should get the acid and grease off the board.
    Duane J
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2013-07-03 06:54
    One could neutralized with baking soda... but if not dissolved it can be abrasive.
  • ajwardajward Posts: 1,130
    edited 2013-07-03 06:56
    xanadu wrote: »
    I think the plumbing solder has some kind of flux core that did it in. I'm pretty sure I've never owned plumbing flux, but it was 10 years ago.

    Plumbing and automotive solders can contain an acid flux core, commonly Muriatic/Hydrochloric Acid. This reacts with Copper to form Copper Chloride, a light brown compound that absorbs moisture turning a blue-green color.

    Ten years! I seldom remember the drive to work in the morning. :-)

    @
  • RDL2004RDL2004 Posts: 2,554
    edited 2013-07-03 07:12
    I've cleaned lots of electronic stuff in the dishwasher. It works great. As soon as the last cycle stops, pull the board out and give it one last rinse with distilled water. Let it dry for about a week before powering it up. I usually give it a final bake in the oven just to be sure - an hour or two at the lowest temperature, usually around 150-175F.
  • AleAle Posts: 2,363
    edited 2013-07-04 11:15
    ajward wrote:
    Plumbing and automotive solders can contain an acid flux core, commonly Muriatic/Hydrochloric Acid. This reacts with Copper to form Copper Chloride, a light brown compound that absorbs moisture turning a blue-green color.

    Hydrochloric acid does not react with copper. It reacts with iron, zink, but not with copper. Actually only the protons react with iron or zink, but they are unable to oxidize copper, look for the reduction potential of H+ -> 1/2 H2 and Co(0) -> Co+ or Co++ and you will see that it lays at the "wrong" side of the table :), together with silver and gold.
    You may got confused because the so-called "acid" for etching boards reacts of course with copper, but that is Fe3+ :)
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2013-07-05 01:44
    50 years ago when one was building with their Weller Solder gun, sales people often got the acid core and the rosin core solder confused... many projects at that time ended up with the wrong solder.

    I am not sure what is meant by 'automotive solder'. If it is electrical connections it is one flux, if it is not electrical it is the other.

    And, I've no idea if the acid core is hydrochloric acid or some other acid flux.
  • LeonLeon Posts: 7,620
    edited 2013-07-05 02:16
    Hydrochloric acid is a liquid. It can't be that.
  • Martin_HMartin_H Posts: 4,051
    edited 2013-07-05 02:49
    Ale wrote: »
    Hydrochloric acid does not react with copper. It reacts with iron, zink, but not with copper. Actually only the protons react with iron or zink, but they are unable to oxidize copper, look for the reduction potential of H+ -> 1/2 H2 and Co(0) -> Co+ or Co++ and you will see that it lays at the "wrong" side of the table :), together with silver and gold.
    You may got confused because the so-called "acid" for etching boards reacts of course with copper, but that is Fe3+ :)

    I've seen a few YouTube videos where people make their own etchant by mixing hydrochloric acid and hydrogen peroxide. It turns a brilliant green as it works on the board. So how does that work?
  • AleAle Posts: 2,363
    edited 2013-07-05 07:48
    Hydrochloric acid is a gas, it is conveniently dissolved in water for easier handling.
    @Martin_H: Look what reaction hydrogen peroxyde in acidic media has :), that "per-oxyde" is not as innocent as it looks ;-)
  • LeonLeon Posts: 7,620
    edited 2013-07-05 14:02
    The gas is hydrogen chloride. Hydrochloric acid is hydrogen chloride dissolved in water.
  • garyggaryg Posts: 420
    edited 2013-07-05 20:04
    This is a very interesting discussion.
    I've been using Oatey #5 Soldering Paste forever.
    It's very difficult to clean off.
    I have not found it's solvent.

    When doing solder connections on my small electronics projects
    I always use 60/40 Rosin Core solder after dipping it in my Oatey#5 paste.
    When doing this, my joints do not fail and the solder actually sticks to whatever I'm soldering.
    My projects are pretty short lived, but I do have some that are 30 years old and still working.

    I maybe missed someone saying what soldering paste etc they are using.

    Thanks

    I think this fits into this discussion.
  • frank freedmanfrank freedman Posts: 1,983
    edited 2013-07-05 22:06
    RDL2004 wrote: »
    I've cleaned lots of electronic stuff in the dishwasher. It works great. As soon as the last cycle stops, pull the board out and give it one last rinse with distilled water. Let it dry for about a week before powering it up. I usually give it a final bake in the oven just to be sure - an hour or two at the lowest temperature, usually around 150-175F.

    If you look at some of the older Tektronix pages and materials, they used to actually power wash their scopes when they came in for service. Then bake then test, etc....
  • ajwardajward Posts: 1,130
    edited 2013-07-05 23:00
    Ale wrote: »
    Hydrochloric acid does not react with copper. It reacts with iron, zink, but not with copper. Actually only the protons react with iron or zink, but they are unable to oxidize copper, look for the reduction potential of H+ -> 1/2 H2 and Co(0) -> Co+ or Co++ and you will see that it lays at the "wrong" side of the table :), together with silver and gold.
    You may got confused because the so-called "acid" for etching boards reacts of course with copper, but that is Fe3+ :)

    Ack! You're right, I stand corrected. ;-)
  • xanaduxanadu Posts: 3,347
    edited 2013-07-08 23:43
    Thanks for the great information guys and gals, much appreciated. I intend to allow this circuit to continue to decompose until it no longer works. I have a few more like it from the only other place I knew of Digikey. This is the last of the end of the LM3915 which is what got me hooked on electronics way back in the day. Some people collect, some people dissect, and some people decompose innocent protoboards.
  • Mark_TMark_T Posts: 1,981
    edited 2013-07-09 05:32
    Martin_H wrote: »
    I've seen a few YouTube videos where people make their own etchant by mixing hydrochloric acid and hydrogen peroxide. It turns a brilliant green as it works on the board. So how does that work?

    According to my book on inorganic chemistry the coinage metals (copper/silver/gold) in general resist non-oxidizing acids (such as HCl),
    but mixing in an oxidizer changes that.

    For instance conc. nitric acid doesn't dissolve gold until you add some conc sulfuric acid (the archetypal oxidizing acid). Copper reacts with carbonic
    acid (dissolved CO2) only when oxygen is present I believe (this is what turns copper roofing green). This is the same sort of reaction
    that acid flux residue enables I suspect.
  • Martin_HMartin_H Posts: 4,051
    edited 2013-07-09 06:00
    Mark_T wrote: »
    According to my book on inorganic chemistry the coinage metals (copper/silver/gold) in general resist non-oxidizing acids (such as HCl),
    but mixing in an oxidizer changes that.

    Thanks for the explanation.
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