ruffrecords
Well-known member
The Eurocard rack mechanical standard has a 2.54mm (0.2 inch) gap between the front vertical edge of the PCB and the back face of the front panel. I have no idea why this is so and I question if it is necessary. It is a real pain when designing PCBs with controls that are on the PCB but are also attached to the front panel. You either use a standard footprint and accept that part of the silk screen will be off the board ( and have to tell the PCB fab house it is OK when the inevitably query it) or make special footprints just for this purpose.
Also, the PCB is attached to the front panel using a pair of special die castings that enforce this gap. The have a ridge that the PCB front edge mates against and the die casting is 2.5mm thick to enforce the spacing:
Also, the die castings are expensive and waste a lot of front panel space.
Some time ago Abbey suggested using these cheaper simpler tapped cubes instead of the die castings:
http://uk.farnell.com/ettinger/05-60-223/cube-standoff-threaded-m2-5-m3/dp/1466865
The interesting thing is if you fit one to a PCB is protrudes by 2.24mm so it very nearly meets the standard (it is 0.3 mm = 7.62 mil short) but of course it does not have the shoulder the die casting has so the PCB sort of flaps in the wind.
So it occurred to me all I would need do is make the PCB 2.24mm longer and the PCB front edge would be flush with the front panel. So I could use these cheaper fixings and not have to worry any more about PCB footprints. The question remains; why does the Eurorack standard have this 2.54mm gap in the first place? Have I missed something?
Cheers
Ian
Also, the PCB is attached to the front panel using a pair of special die castings that enforce this gap. The have a ridge that the PCB front edge mates against and the die casting is 2.5mm thick to enforce the spacing:
Also, the die castings are expensive and waste a lot of front panel space.
Some time ago Abbey suggested using these cheaper simpler tapped cubes instead of the die castings:
http://uk.farnell.com/ettinger/05-60-223/cube-standoff-threaded-m2-5-m3/dp/1466865
The interesting thing is if you fit one to a PCB is protrudes by 2.24mm so it very nearly meets the standard (it is 0.3 mm = 7.62 mil short) but of course it does not have the shoulder the die casting has so the PCB sort of flaps in the wind.
So it occurred to me all I would need do is make the PCB 2.24mm longer and the PCB front edge would be flush with the front panel. So I could use these cheaper fixings and not have to worry any more about PCB footprints. The question remains; why does the Eurorack standard have this 2.54mm gap in the first place? Have I missed something?
Cheers
Ian