What is this small unconnected solder blob on this PCB?

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There's a small solder blob in the middle of this one-sided PCB (a switch-mode power supply), surrounded by unmasked board. The blob is 1.5mm in diameter, and the non-masked area is 4mm in diameter. There's nothing on the other side of the board, and there is no hole.



PCB with blob



What's the purpose of this blob? My guess is some kind of manufacturing artifact, but I'm not sure exactly.






pcb reverse-engineering manufacturing







share|improve this question























  • Possibly a marker put in as a drill guide before drilling and slot cutting begins. Often many boards are on a sheet with a stack of 5 or more sheets. There needs to be an absolute ref marker for drilling to be precise. That's my guess.
    – Sparky256
    4 hours ago










  • @Sparky256 I don't believe this is the case--it's just a blob of solder on the bottom of the board, it doesn't pass all the way through.
    – user60561
    3 hours ago










  • Then read Dave Tweeds more accurate answer. It is a ref maker for the ABS position of parts, one of several that can be on a board. This board has one as it is for through-hole parts, so great accuracy is not needed.
    – Sparky256
    3 hours ago










  • @Sparky256 and I did accept that answer :). I appreciate how helpful you and everyone else are here, even though it's clear that I know nothing about the subject.
    – user60561
    3 hours ago














up vote
1
down vote

favorite












There's a small solder blob in the middle of this one-sided PCB (a switch-mode power supply), surrounded by unmasked board. The blob is 1.5mm in diameter, and the non-masked area is 4mm in diameter. There's nothing on the other side of the board, and there is no hole.



PCB with blob



What's the purpose of this blob? My guess is some kind of manufacturing artifact, but I'm not sure exactly.






pcb reverse-engineering manufacturing







share|improve this question























  • Possibly a marker put in as a drill guide before drilling and slot cutting begins. Often many boards are on a sheet with a stack of 5 or more sheets. There needs to be an absolute ref marker for drilling to be precise. That's my guess.
    – Sparky256
    4 hours ago










  • @Sparky256 I don't believe this is the case--it's just a blob of solder on the bottom of the board, it doesn't pass all the way through.
    – user60561
    3 hours ago










  • Then read Dave Tweeds more accurate answer. It is a ref maker for the ABS position of parts, one of several that can be on a board. This board has one as it is for through-hole parts, so great accuracy is not needed.
    – Sparky256
    3 hours ago










  • @Sparky256 and I did accept that answer :). I appreciate how helpful you and everyone else are here, even though it's clear that I know nothing about the subject.
    – user60561
    3 hours ago












up vote
1
down vote

favorite









up vote
1
down vote

favorite











There's a small solder blob in the middle of this one-sided PCB (a switch-mode power supply), surrounded by unmasked board. The blob is 1.5mm in diameter, and the non-masked area is 4mm in diameter. There's nothing on the other side of the board, and there is no hole.



PCB with blob



What's the purpose of this blob? My guess is some kind of manufacturing artifact, but I'm not sure exactly.






pcb reverse-engineering manufacturing







share|improve this question















There's a small solder blob in the middle of this one-sided PCB (a switch-mode power supply), surrounded by unmasked board. The blob is 1.5mm in diameter, and the non-masked area is 4mm in diameter. There's nothing on the other side of the board, and there is no hole.



PCB with blob



What's the purpose of this blob? My guess is some kind of manufacturing artifact, but I'm not sure exactly.






pcb reverse-engineering manufacturing




pcb reverse-engineering manufacturing






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 3 hours ago

























asked 4 hours ago









user60561

1826




1826











  • Possibly a marker put in as a drill guide before drilling and slot cutting begins. Often many boards are on a sheet with a stack of 5 or more sheets. There needs to be an absolute ref marker for drilling to be precise. That's my guess.
    – Sparky256
    4 hours ago










  • @Sparky256 I don't believe this is the case--it's just a blob of solder on the bottom of the board, it doesn't pass all the way through.
    – user60561
    3 hours ago










  • Then read Dave Tweeds more accurate answer. It is a ref maker for the ABS position of parts, one of several that can be on a board. This board has one as it is for through-hole parts, so great accuracy is not needed.
    – Sparky256
    3 hours ago










  • @Sparky256 and I did accept that answer :). I appreciate how helpful you and everyone else are here, even though it's clear that I know nothing about the subject.
    – user60561
    3 hours ago
















  • Possibly a marker put in as a drill guide before drilling and slot cutting begins. Often many boards are on a sheet with a stack of 5 or more sheets. There needs to be an absolute ref marker for drilling to be precise. That's my guess.
    – Sparky256
    4 hours ago










  • @Sparky256 I don't believe this is the case--it's just a blob of solder on the bottom of the board, it doesn't pass all the way through.
    – user60561
    3 hours ago










  • Then read Dave Tweeds more accurate answer. It is a ref maker for the ABS position of parts, one of several that can be on a board. This board has one as it is for through-hole parts, so great accuracy is not needed.
    – Sparky256
    3 hours ago










  • @Sparky256 and I did accept that answer :). I appreciate how helpful you and everyone else are here, even though it's clear that I know nothing about the subject.
    – user60561
    3 hours ago















Possibly a marker put in as a drill guide before drilling and slot cutting begins. Often many boards are on a sheet with a stack of 5 or more sheets. There needs to be an absolute ref marker for drilling to be precise. That's my guess.
– Sparky256
4 hours ago




Possibly a marker put in as a drill guide before drilling and slot cutting begins. Often many boards are on a sheet with a stack of 5 or more sheets. There needs to be an absolute ref marker for drilling to be precise. That's my guess.
– Sparky256
4 hours ago












@Sparky256 I don't believe this is the case--it's just a blob of solder on the bottom of the board, it doesn't pass all the way through.
– user60561
3 hours ago




@Sparky256 I don't believe this is the case--it's just a blob of solder on the bottom of the board, it doesn't pass all the way through.
– user60561
3 hours ago












Then read Dave Tweeds more accurate answer. It is a ref maker for the ABS position of parts, one of several that can be on a board. This board has one as it is for through-hole parts, so great accuracy is not needed.
– Sparky256
3 hours ago




Then read Dave Tweeds more accurate answer. It is a ref maker for the ABS position of parts, one of several that can be on a board. This board has one as it is for through-hole parts, so great accuracy is not needed.
– Sparky256
3 hours ago












@Sparky256 and I did accept that answer :). I appreciate how helpful you and everyone else are here, even though it's clear that I know nothing about the subject.
– user60561
3 hours ago




@Sparky256 and I did accept that answer :). I appreciate how helpful you and everyone else are here, even though it's clear that I know nothing about the subject.
– user60561
3 hours ago










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It's most likely a type of fiducial marker, used by a pick-and-place machine to correctly place the SMD parts on the copper side of the board.






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    1 Answer
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    active

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    1 Answer
    1






    active

    oldest

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    oldest

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    active

    oldest

    votes








    up vote
    9
    down vote



    accepted










    It's most likely a type of fiducial marker, used by a pick-and-place machine to correctly place the SMD parts on the copper side of the board.






    share|improve this answer
























      up vote
      9
      down vote



      accepted










      It's most likely a type of fiducial marker, used by a pick-and-place machine to correctly place the SMD parts on the copper side of the board.






      share|improve this answer






















        up vote
        9
        down vote



        accepted







        up vote
        9
        down vote



        accepted






        It's most likely a type of fiducial marker, used by a pick-and-place machine to correctly place the SMD parts on the copper side of the board.






        share|improve this answer












        It's most likely a type of fiducial marker, used by a pick-and-place machine to correctly place the SMD parts on the copper side of the board.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 4 hours ago









        Dave Tweed♦

        113k9136245




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