What are these small squares along track and what are they used for!?

Thread Starter

Younes Thabet

Joined Jan 9, 2019
24
What are these "what seems like small pads" coming from power connector and going along AC-line track!?
what are they used for!?
scan-2020-09-23.jpg
 

ci139

Joined Jul 11, 2016
1,696
i speculate it may be alternating impedance trace for some sort of RFI EMI block . . . but i cannot find anything such from www

the idea behind could be that the impedance change in transmission line creates a reflection . . . just perhaps = don't trust me on this particular one

. . . it also might be - say - ?? for the thermal balancing ??
 
Last edited:

Papabravo

Joined Feb 24, 2006
14,655
i speculate it may be alternating impedance trace for some sort of RFI EMI block . . . but i cannot find anything such from www

the idea behind could be that the impedance change in transmission line creates a reflection . . . just perhaps = don't trust me on this particular one

. . . it also might be - say - ?? for the thermal balancing ??
There are two possible explanation, which are not incompatible with each other.
  1. The solder mountains add significant mass to the thin copper trace
  2. There is a not insignificant increase in surface area
I tend to doubt the impedance discontinuity approach as the description "AC motherboard" implies power line frequencies rather than RF (aka Nervous DC).
 

Thread Starter

Younes Thabet

Joined Jan 9, 2019
24
i speculate it may be alternating impedance trace for some sort of RFI EMI block . . . but i cannot find anything such from www

the idea behind could be that the impedance change in transmission line creates a reflection . . . just perhaps = don't trust me on this particular one

. . . it also might be - say - ?? for the thermal balancing ??
I suspected the same but I wasn't sure about it ....I didn't even know what to type in the search bar lol.
 

Thread Starter

Younes Thabet

Joined Jan 9, 2019
24
There are two possible explanation, which are not incompatible with each other.
  1. The solder mountains add significant mass to the thin copper trace
  2. There is a not insignificant increase in surface area
I tend to doubt the impedance discontinuity approach as the description "AC motherboard" implies power line frequencies rather than RF (aka Nervous DC).
So these things are called solder mountains!?
What's the advantage of adding mass to track?is it to allow for more current!
I didn't get your second point
 

Papabravo

Joined Feb 24, 2006
14,655
So these things are called solder mountains!?
What's the advantage of adding mass to track?is it to allow for more current!
I didn't get your second point
I don't know if solder mountains is a universally accepted name - it's just what I call them.
More mass means that it takes longer to heat up and cool down. Think about a copper quarter and a cubic meter of copper. Clearly the cubic meter will take longer to heat up and cool down.
If you study the transmission of heat, there are three primary mechanisms of heat transfer.
  1. Radiation
  2. Conduction
  3. Convection
In this case conduction is a function of surface area. Imagine our cubic meter of copper completely surrounded by an adiabatic blanket except for a one square centimeter spot on the top surface, Now clearly the cubic meter of copper in the blanket will cool very very slowly. Take the blanket off and we now have at least five square meters of surface area for heat to be conducted away from the block. This assumes that the adiabatic blanket remains underneath the block of copper.
 

ronsimpson

Joined Oct 7, 2019
1,000
I used "solder mountains" in single sided PCB in power supplies. Years ago single sided was lower cost and thin copper is low cost. In the high current traces we removed the solder mask and built up solder. I know the solder is high resistance compared to Cu but the copper is very very thin and the solder mounds are very thick. Also the solder increases the surface area for heat. On the forum we argue if it works. Either way it is/was common practice on single sided boards.
 

Papabravo

Joined Feb 24, 2006
14,655
I used "solder mountains" in single sided PCB in power supplies. Years ago single sided was lower cost and thin copper is low cost. In the high current traces we removed the solder mask and built up solder. I know the solder is high resistance compared to Cu but the copper is very very thin and the solder mounds are very thick. Also the solder increases the surface area for heat. On the forum we argue if it works. Either way it is/was common practice on single sided boards.
Was calling them "solder mountains" just a lucky guess?
 

Ajith-N

Joined Sep 14, 2020
14
I'm guessing -- these solder bumps help you to solder a thick copper wire all along the track, to beef up current capacity of the track. But of course, no such wire has been soldered on -- yet ;)
 
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