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Electronics - Tapping and repairing PCB traces.

Discussion in 'Amateur Radio News' started by KB7TBT, Aug 10, 2019.

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  1. KB7TBT

    KB7TBT Ham Member QRZ Page

    Electronics - Tapping and repairing PCB traces.

  2. W1YW

    W1YW Ham Member QRZ Page

    PLEASE --DO NOT-- blow dust made from FR4!!!!

    The 'green PCB' stuff is of FR4 composition.

    Inhaling FR4 dust exposes your lungs to many dangerous compounds: fiberglass; resins, etc. Go look up the typical composition of 'fire retardant 4'. Having the microparticles around like dander is an invitation to irritation at best, cancer at worst!

    Solder mask is also a sealant for FR4. It was not meant to be scrapped off.

    IF you MUST remove the coatings to get at the copper, then use a moist paper towel to remove the dust. Also, if the board is multi layer, well, good luck! The substrate is part of the circuit as an embedded (in) dielectric. Insulating to DC is loading to RF.

    "The production and handling of fiberglass can produce fibrous glass dust that is considered by the National Toxicology Program to be “reasonably anticipated as a human carcinogen” if it is inadvertently inhaled, although it has not been directly linked with mesothelioma..."

    Chip W1YW
    Last edited: Aug 17, 2019
    WA7PRC and N0TZU like this.
  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Usually soldering to a trace is a last resort. Much easier to run another wire between the closest pins or parts and route over the trace. Unless of course there is an overiding factor like too much cross talk, or inductance if the trace is actually half of a controlled impedance transmission line.
    WA7PRC, AE8W and W1YW like this.
  4. W1YW

    W1YW Ham Member QRZ Page

    Mask and safety glasses.

  5. KG6DQL

    KG6DQL Ham Member QRZ Page

    would be way better and cleaner if you use soldering paste this way you don't get spikes on the solder, simply use alcohol to clean the paste after you're done
    W1YW likes this.
  6. W1YW

    W1YW Ham Member QRZ Page

    Soldering paste yields an even flow of heat, but residual flux can enhance growth of dendritic shorts, that destroy PCB's. Tough to get it all off.

    For those who are interested, the 'PCB shorting' problem has a design-based solution. To wit:
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    It helps to have some to drink also. :)

    I use Everclear multi purpose alcohol.
  8. KG6DQL

    KG6DQL Ham Member QRZ Page

    LOL, share the love my friend :)
    fyi i used to work at a pcb manufacturing company, i should know what's best, i'll say it again, use alcohol to clean the residue
    and no it does not cause any shorts, solder paste is not conductive people, pun totally intended ;)
  9. W1YW

    W1YW Ham Member QRZ Page

    Please read carefully:

    No one said solder flux was CONDUCTIVE.

    It DOES enhance dendritic growth. Solder flux , if not properly removed, will PROPAGATE DENDRITES and these SHORT OUT TRACES.

    The dendrites are CONDUCTIVE. The solder paste IS NOT. OK?

    If you WORKED at a PCB company--as opposed to SOLVED the problems of such companies--then why don't you know that?

    Chip W1YW
  10. WR2E

    WR2E Ham Member QRZ Page

    Iron too big, solder too big, shaky hands...

    W1YW likes this.

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