Some PCBs, like the PCI card specification have gold fingers which start very narrow near the bottom edge, and gain their usual width much higher, where the actual contact is expected to be made.
What is the advantage of having the narrow part?
Why not make the pad fully wide all the way to bottom, like ISA cards, DDR, etc.? Or simply make the finger shorter, only in the area of contact? What is better in gradually increasing the width?
To connect ground pins first- All the pins have this shape. Resistance against peeling the pad off- The smaller trace seems much more susceptible to damage Insertion force- I expect the narrow part to be made of equally thick gold, which would require the same amount of force.
- Insertion force - Can it be that some number of the connector contacts (in motherboard) get pushed sideways in each stage as the card goes in, lessening the amount of force needed to insert the board?
Can't seem to find any evidence or description why this is designed this way. Some high frequency high pin count stuff (DDR modules) use rectangular pads.
Note: See page 196 of the linked PCI card specification document.