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Vapourizing Tracking on top side of 48k Speccy Boards.

harriusherbartioharriusherbartio
in Hardware
I think I used a hot soldering iron and it caused the tracks to disappear on the top side of two Spectrum 48k boards I was renewing the capacitors on.

Has anyone else had this problem? Is it a known problem or am I imagining it!!

Comments

  • harriusherbartioharriusherbartio
    Or is it caused by leakage from capacitors (unlikely as one of the Speccies was working OK prior to me starting work)
  • Ast_A_MooreAst_A_Moore
    You can’t really vaporize copper traces with a soldering iron. You could, however, simply delaminate (parts of) them from the board—and the vias—by overheating the leads of components (easy to do on old, low-quality PCBs), and then those parts got stuck to the tip of the iron and thrown away as you cleaned the tip.
    Every man should plant a tree, build a house, and write a ZX Spectrum game.

    Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
    and zasm Z80 Assembler syntax highlighter.
    Member of the team that discovered, analyzed, and detailed the floating bus behavior on the ZX Spectrum +2A/+3.

    A few Spectrum game fixes.
  • harriusherbartioharriusherbartio
    edited April 2017
    Reply to Ast_A_Moore

    Yes that is what I thought , it does not make sense after all I have been working on the other side of the PCB which should remain cool . So on the face of it it does not make sense

    Possible explanations

    1) I have got it wrong , something else is happening or the boards are slightly different etc (the General Ignorance explanation)

    2) Oxidization setting it up for vapourization later when slight heat applied

    3) Lack of protection on the top side

    4) Leaking capacitors

    5) A combination of all the above : the hybrid explanation .

    It would be good if I could find some before and after pics.This explanation will be a work in progress as I think "something is up" (even if it is just me trying to overcome General Igorance!)

    Symptoms.

    A grey powder where the vias were . This is easily rubbed away and does not conduct It appears to follow the old tracks though

    I think I have got a possible reason . My unorthodox using of a needle to clear solder holes . Maybe this transmitted an unusually high level of heat on the upper side and reduced up to half inch of tracking to a grey powder whilst leaving the underside totally unaffected
    Post edited by harriusherbartio on
  • harriusherbartioharriusherbartio
    Well I have got my first "before" pic

    https://photos.google.com/share/AF1QipPiz92qti_Qo-D2EVUX8N-nVZOBdeaK2drl9-EeZyW3XcGb_kO2LLQVsw9D867BhQ?key=czN1QXAtbnA3amotUU4wWXlVR1U4VUFSSkYyd3V3
  • harriusherbartioharriusherbartio
    Re above

    The cap has been upended . The hole to the right of c65 shows the tracking still intact from the empty hole . The "after" pic has not yet been taken
  • harriusherbartioharriusherbartio
    Eyesight problem! (yes I had not thought of that explanation)

    Subsequent examination under the microscope shows the tracking still there but in greyer less shiny form than other parts of the board and the comparison board .Conductivity is still there

    I was probably panicking as it was not working (panicking is not good!)
  • harriusherbartioharriusherbartio
    edited April 2017
    The After pics

    The second pic is from a comparison board . Under the scope they look similar but to the naked eye...

    Me trying to find the wrong explanation for why it was not working

    https://photos.google.com/share/AF1QipMdZ3sVyK6DRlrjTR6NFlJXhFu3iY9ZqMQPK_VhtpogMFXU_3zCUK1vAmLqVcWQhw?key=NkxyT0lyeFo1UH
    doNldUUm9zOXZBSlBRWkFtdjJ3

    The bad repair on the hole is not the cause . By then I had redone it a few times!
    Post edited by harriusherbartio on
  • Ast_A_MooreAst_A_Moore
    harriusherbartio wrote: »
    My unorthodox using of a needle to clear solder holes.

    Here’s a method for clearing vias I learned from an old and very experienced engineer a few decades ago. Sharpen a match (or just use a toothpick), dip it in a molten rosin, and let is soak for a few seconds. Then heat up the via until the solder melts, and use the toothpick to poke a hole through.

    Of course, a solder sucker works better, but it might delaminate the traces, in which case, use desoldering braid. Oh, and don’t forget to reflow any joint with fresh solder prior to desoldering.
    Every man should plant a tree, build a house, and write a ZX Spectrum game.

    Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
    and zasm Z80 Assembler syntax highlighter.
    Member of the team that discovered, analyzed, and detailed the floating bus behavior on the ZX Spectrum +2A/+3.

    A few Spectrum game fixes.
  • harriusherbartioharriusherbartio
    Reply to Ast_A_Moore

    Thanks for the tips Yes lifting pads has been a problem .For me its " Back to the drawing board......"

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