I have now some new project and there are various I/O going stright
out of a complex hybrid chip to external wiring which is a house
installation.

The previous circuits had either NOTHING as protection or large PTC
resistors in the lines and couple of zener diodes to ground on each
lead.

I need to do something of 'present day' kind, but it should still do
the job well. I though abt some transil /transorb etc diodes, however
it looks like that those suitable for protection of 5V logic lines
have leakage of abt 1mA!

And do I have to still add some serial PTC resistors in this case?

How is this handeld to day in general?