SMD soldering (lack of solder)

Discussion in 'General Electronics Chat' started by Dritech, Aug 21, 2016.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    Hi all,

    When soldering SMD components, it is a bad practice to leave the pads visible (as shown in the photo below)?

    Also, is it normal for high temperature solder not to be shiny (as shown in the photo below)?
    upload_2016-8-21_15-25-55.png upload_2016-8-21_15-26-23.png upload_2016-8-21_15-27-2.png
    Are these solder joints any good, or will they cause intermittent problems?

    Thanks in advance.
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Unless the pad-plus-solder is being relied on as a heatsink I see no problem with the pad not being totally covered in solder.
    Lead-free solder joints may be dull. Don't know about high-temp solder joints.
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Hi temp solder is ugly looking, never bright smooth joints like the time tested 60/40 tin lead solder makes.
    KeepItSimpleStupid likes this.
  4. dl324

    Distinguished Member

    Mar 30, 2015
    Most of them look like they have too much solder.

    If oxidation is limited to the surface, it won't be a big problem.
  5. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    Thanks for the replies. The first and last photos look ok, although the finish is not shiny. But is the solder joint shown in the second photo normal? its eggshell surface does not give me the impression of a good solder joint.
  6. ScottWang


    Aug 23, 2012
  7. ian field

    Distinguished Member

    Oct 27, 2012
    One school of thought suggests if the components are too well soldered, thermal expansion can cause fractures - the opposite view is that the fractures will happen in the solder if the fillets are a bit thin.

    Moderation is the name of the game, like anything; there's always compromises.

    Some of the solder in the image looks a bit thin, but I'd examine closely with light an magnifier, and only fix the ones that are broken.

    The definition of "broken" is any evidence of hairline fracture.

    Lead free solder usually looks like dry joints anyway - so that isn't necessarily a criteria.
  8. SLK001

    Active Member

    Nov 29, 2011
    The joints in the second photo look slighly cold. Make sure that you use adequate flux when creating the joints.

    Why are you using high temp solder?

    Is that a gold finish on your pads? If so, what is its thickness?
  9. Veracohr

    Well-Known Member

    Jan 3, 2011
    The SMD would be considered "insufficient wetting" by the IPC A-610 standard.