is a 24k, soft gold that is being sought when wirebondable gold is speicified. This is as opposed to hard gold which is "alloyed" with nickel or cobalt and commonly used in PCB manufacture for separable edge card contacts. The thickness requirement will vary with the type of bonding to be done. Aluminum wire wedge bonding normally requires ~ 0.1 to 0.25 microns ( 6-10 microinches) over nickel while gold thermosonic wire commonly requires 0.75 to 1.25 microns (30 to 50 microinches). Control of the bath is critical as impurities can cause problems. Also surface cleanliness is very important to achieving good joints. Beware of the fact that wirebond schedules may need to be adjusted for the different base materials used in PCB manfacture. Cheers, J. Fjelstad