ASTM B488 Technical Notes
Prior to requesting a quote, the purchaser needs to supply the following information to the supplier in the purchase order or other governing document:
1. The name, designation, and date of issue of this speciﬁcation.
2. Classiﬁcation: Type, Code, and thickness (or mass per unit area)
3. Presence and thickness of underplating, if required
4. Signiﬁcant surfaces must be speciﬁed
5. Requirement, if any, for performance testing such as porosity testing, solderability testing, ductility testing etc.
6. If the substrate is one that requires a nickel underplating
7. Whether or not stress relief has been or is to be done, whether embrittlement relief bake is to be done (steel parts only).
8. Sampling plan employed.
Coating Class is the coating thickness in micrometers. Ex: Class 0.25 has a coating thickness of 0.25um.
Type represents the percentage of the plating is pure gold:
Type I = 99.7% pure gold, Type II = 99% pure gold, and Type III = 99.9% pure gold
Type I—For general-purpose, high-reliability electrical contacts, and wire wrap connections
Type II, General-Purpose Wear Resistant Gold— Will not withstand high-temperature applications because the hardening agents in the gold coating will oxidize
Type III, Code A Gold—For semiconductor components, nuclear engineering, thermocompression bonding, thermosonic bonding, ultrasonic bonding, solderability, and high-temperature applications
Knoop Hardness Range ASTM Code MIL-DTL-45204 Grade
90HK maximum A A
91-129 HK B B
130-200 HK C C
>200 HK D D
Nickel Underplating—For thickness Classes except 5.0, a nickel underplating shall be applied before the gold coating when the product is made from copper or copper alloy.
Strikes—It is recommended to apply a gold strike to the underplate or substrate, except if the latter is silver or platinum, prior to applying the gold top coating.