Thru hole electrolytic capacitors in SMD boards

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Internauta

Member
Joined
Jan 22, 2015
Messages
11
Hello,
does anybody know why many boards with almost all the components surface mount
still do have thru hole electrolytic capacitors?
Is it due to the cost of SMD electrolytic, or thru hole parts in this case are more reliable?


 
 
Internauta said:
Hello,
does anybody know why many boards with almost all the components surface mount
still do have thru hole electrolytic capacitors?
Is it due to the cost of SMD electrolytic, or thru hole parts in this case are more reliable?

I have used smaller electrolytic caps that are available SMD while the robustness for high vibration applications is not as good. More massive larger electrolytic caps will benefit from thru hole.  While working at Peavey when we first started using SMD (decades ago), we mixed technology using SMD and  thru hole parts on the same PCBs. Back in the early days of SMD we didn't have the wide SMD component selection we do today. Caps have also gotten smaller, while i expect large reservoir caps to still be TH.

JR
 
SMD elco caps can be a real PITA to solder well by hand as well, as 90% of the pad is "under" the body of the cap.  You have to use a flux pen and judicious heating to make sure contact is done well.

In addition, may higher voltage caps wont be available in SMD flavors:  typically they'll max out at about 35V, which doesn't help for phantom filtering.  Often it's better to have all the SMD done by pick and place, and just the radial elcos done by hand towards the end of the process, rather than trying to series connect smaller elco's to get higher voltages.
 
Matador said:
SMD elco caps can be a real PITA to solder well by hand as well, as 90% of the pad is "under" the body of the cap.  You have to use a flux pen and judicious heating to make sure contact is done well.

In addition, may higher voltage caps wont be available in SMD flavors:  typically they'll max out at about 35V, which doesn't help for phantom filtering.  Often it's better to have all the SMD done by pick and place, and just the radial elcos done by hand towards the end of the process, rather than trying to series connect smaller elco's to get higher voltages.

Radial caps were machine inserted long before SMD came along, but onsey twosey may not justify running the boards over another work center, especially if building in a low labor region.

JR
 
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