High power board-to-board interconnect between two PCBs

Design and Layout
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1

Hello everyone,

I am working on a DC link capacitor bank design which is to be mounted inside an enclosure. The capbank assembly consists of two PCBs with capacitors soldered on them (8 x 1000 uF, arranged in a 4 x 2 grid), and the PCBs are mounted on two sides of a mounting plate. Both the boards have connectors for input and output power (they are shorted since this is capbank is in parallel to the DC source). The nominal operating voltage is 300 V and nominal current is 8 A, although, this current is not carried by the PCB copper - only by the input-output connectors. The PCB only carries the capacitor current during operation.

My design challenge is how to interconnect the two PCBs to combine the total capacitance (2 x 8 x 1000 uF) which these goals in mind:

  1. Minimum interconnect resistance: this is usually a given but especially important in this case because the capacitor bank is expected to respond quickly to transient current draw events at the load
  2. Enough spacing between V_p and V_n: The nominal voltage is 300 V, with maximum up to 350 V at full battery

These are the challenges/restrictions I have to work with:

  1. Small size: There is very little space on the PCBs. There is a 18 x 18 mm gap in the middle of the capacitors, and some space at the edge of the board
  2. Maintainability: The PCBs should be separable easily, which is why I can’t just solder solid connections between the two boards after assembly.

Until now, I have tried to use board-to-board connectors from Samtec, but the pins are too close to each other and I’m worried about arcing between them (anyway, I have conformal coated the PCBs)

Do you have any suggestions from your experience on how to do this? I’m looking for general solutions that can be applied to other similarly mounted assemblies, not just this specific case.

2

Hello,

  1. Generally the interconnect resistance for high voltage and high current should be less than 10m Ohms and for general purpose applications should be 100m Ohms.

  2. Spacing between V_p and V_n at 350 volt for external conductor uncoated PCB should be 72.5 mils.

So we have select a connector having contact resistance 10m Ohms, voltage rating 600 volts, current rating 15 ampere, terminal spacing 200mils.

MPN : 1-179276-2

Manufacturer : TE Connectivity AMP Connectors

datasheet : https://www.te.com/usa-en/product-1-179276-2.datasheet.pdf

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3

SAMTEC does have the mPOWER and POWER STIRP series that can meet the voltage and current requirements. One thing to keep in mind with these types of connectors, is the number of cycles (connect/disconnect) that the connectors are expected to experience.

If low cost is desired, Molex has the 0.156-inch series that are rated for 600V. The pins will likely need to be doubled-up (or more) to meet current and resistance requirements.

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