Clad AL substrate - high current interconnect

[legg]

Any bright ideas out there for high current connections to power
circuits, surface mounted on clad Al substrates?

At the moment, the only practical hardware seems to be SMD .050sq post
double-row male pins. There may be registration issues with these. The
Al substrate is not friendly to locating retainers.

RL

 

[John Larkin]

Any bright ideas out there for high current connections to power
circuits, surface mounted on clad Al substrates?

Got any links to the clad Al substrates? Is this the Bergquist stuff?
Is the Al always insulated from PCB traces?

I assume that, if it's a pc board bonded to an aluminum plate, you
must use all surface-mount connectors.

Is this stuff cost-effective? You could just bolt a PC board onto a
hunk of aluminum or a heat sink, but then you could provide clearance
holes for serious thru-hole connector pins, and use the mounting bolts
(with proper washers!) to connect to the substrate and use it as a
conductive layer.

At the moment, the only practical hardware seems to be SMD .050sq post
double-row male pins. There may be registration issues with these. The
Al substrate is not friendly to locating retainers.

I like to use 0.25" faston blades on pc boards for high currents, with
the female mate crimped onto harness wires. You can parallel these for
higher currents, with the wires acting as current-balancing ballasts.
But if you're limited to surface-mount, you'd have to be careful, use
a *lot* of copper on the board, so that the connect/disconnect forces
don't rip the tabs off the board.

How much current? How many circuits?

John

 

[Robert Adsett]

Any bright ideas out there for high current connections to power
circuits, surface mounted on clad Al substrates?

At the moment, the only practical hardware seems to be SMD .050sq post
double-row male pins. There may be registration issues with these. The
Al substrate is not friendly to locating retainers.

As John said, define high current. I've used several different methods.
For low current, I've use 0.50sq posts, these provided control signal
connections. For high current the easiest method was to simply sandwich
Cu bar between the AL clad substrate and another FR4 PCB. Another
method was custom clips shaped sort of like a U with a flat bottom and
the top of the U pinched together. This was soldered on the metal clad
and Cu 'legs' slid in. Similar to the clips used to hold EMI shield in
place on a PCB, just heftier.

Robert

 

[legg]

Got any links to the clad Al substrates? Is this the Bergquist stuff?
Is the Al always insulated from PCB traces?

I assume that, if it's a pc board bonded to an aluminum plate, you
must use all surface-mount connectors.

Is this stuff cost-effective? You could just bolt a PC board onto a
hunk of aluminum or a heat sink, but then you could provide clearance
holes for serious thru-hole connector pins, and use the mounting bolts
(with proper washers!) to connect to the substrate and use it as a
conductive layer.

The requirement for SMD connectors is driven by application of the
substrate.

I like to use 0.25" faston blades on pc boards for high currents, with
the female mate crimped onto harness wires. You can parallel these for
higher currents, with the wires acting as current-balancing ballasts.
But if you're limited to surface-mount, you'd have to be careful, use
a *lot* of copper on the board, so that the connect/disconnect forces
don't rip the tabs off the board.

How much current? How many circuits?

I'd considered using faston pins, as there are methods of adapting the
socket component for bottom entry.

SMD of the pin could be a bit hit and miss, particularly if it has to
have any length.

Current is in the region of 40A/connection and subdivisions of same.

Although cost isn't currently the issue - this having been resolved
before starting, so as not to waste the design effort - the processing
of a troublesome interface could be an added cost that wasn't
anticipated.

RL

 

[legg]

As John said, define high current. I've used several different methods.
For low current, I've use 0.50sq posts, these provided control signal
connections. For high current the easiest method was to simply sandwich
Cu bar between the AL clad substrate and another FR4 PCB. Another
method was custom clips shaped sort of like a U with a flat bottom and
the top of the U pinched together. This was soldered on the metal clad
and Cu 'legs' slid in. Similar to the clips used to hold EMI shield in
place on a PCB, just heftier.

How did you establish/maintain good contact/pressure in the sandwich?

RL

 

[Robert Adsett]

How did you establish/maintain good contact/pressure in the sandwich?

Bolts/nuts and belleville washers. Works quite well. Used it for
PCB/PCB sandwich as well.

BTW on the small posts we didn't have much in the way of registration
problems between boards, can't say as I'd want to fit together a large
number of pins though. We were using a 4x2 IIRC.

Robert