Gold plating thickness required for connector

A. Hi, LI
You need minimum 40-50 µ" ( Approx. 2 µm) of Nickel for Barrier between copper and Gold.

A. The small grey/green/black spot on gold plated connector appears to be due to pore corrosion. It could be due to the porosity in the Au and/or the Ni coating.

The AMP INCORPORATED Technical Report on ¡°Golden Rules: Guidelines for the use of gold on connector contacts¡± suggests the following points. I hope it will be of use to you.

Gold coating is applied over a high-quality underlayer such as nickel. A nickel underlayer can act as a: (i) pore corrosion inhibitor; (ii) corrosion creep inhibitor; (iii) diffusion barrier; and (iv) mechanically supporting underlayer. However, the nickel underplating must be continuous and have sufficient thickness to perform the particular function for which it is intended. As a general rule, a minimum thickness of 1.3 microns (50 µ") of nickel should be used. The choice of a suitable gold coating thickness depends on the degree of durability and environmental protection required by the application. In general, a 0.8 micron (30 µ") coating of hard gold over a minimum of 1.3 microns (50 µ") of nickel gives a degree of durability considered adequate for most connector applications. Thin coatings of 0.03 - 0.1 microns (1 - 4 µ") of hard or soft gold over nickel underplate should be used only for applications in which the risk of fretting is minimal. Increasing the thickness of a gold coating tends to decrease the porosity which reduces the contacts' vulnerability to pore corrosion. In general, a 0.8 micron (30 µ") coating of hard gold over a minimum of 1.3 microns (50 µ") of nickel provides exceptional environmental protection. Contacts coated with a thin hard or soft gold coating on the order of 0.03 - 0.1 microns (1 - 4 µ") in thickness over a nickel underlayer can be used in benign environment applications.

Increase in the thickness of the nickel and gold coatings will reduce the porosity and help avoid the problems due to pore corrosion.

I believe that the migration of Cu observed in some connectors could be due to the lack of thickness of the Ni underlayer in those contacts.

The problems due to pore corrosion and diffusion of elements from base metal are not specific to bronze and it could occur on other types copper alloys also as they depend on the coating thickness of both Ni and Au.

A. The shelf life of the connectors depends on storage conditions.

The following specifications will be of some help to you.

ASTM B488: Electrodeposited gold coatings for engineering use

MIL-STD-1344: Test methods for electrical connectors
- Method 2016- Durability
- Method 1005.1- Temperature life
- Method 1002.2- Humidity
- Method 1001.1- Salt spray

ECA EIA 364-09: Durability test procedures for electrical connectors
ECA EIA 364-31: Humidity test procedure for electrical connectors
ECA EIA 364-26: Salt spray test procedure for electrical connectors
ECA EIA 364-17: Temperature life with or without electrical load procedure for electrical connectors

The copies of MIL Standards can be obtained from:
DODSSP Standardization Document Order Desk
700 Robbins Avenue, Building 4D
Philadelphia, PA 19111-5094
Web site: http://astimage.daps.dla.mil/online/  ^ ^{https://quicksearch.dla.mil/}

Electronic Industries Alliance (EIA) standards can be obtained from:
Electronic Industries Alliance (EIA)
2500 Wilson Boulevard
Arlington, VA 22201-3834
Website: http://www.eia.org/

ASTM specifications:
Website www.astm.org

A. Hi Bharathi. Assuming there is no wear, then you need a thickness sufficient to have no porosity or pinholes, and to not diffuse into the copper too quickly. This is probably best met by nickel plating followed by gold plating as described by TSN Sankara above.

Regards,

A. Hi Barathi
There is plenty of good advice and precedent for gold on electronic connector, etc., but you have a special application and will have to determine the best thickness for yourself. To prevent migration of the gold, 2 microns of nickel undercoat is reasonably standard.
I would expect the gold to be about 5 microns but, as Ted says, porosity is the main criterion. This is not always easy to achieve on a regular basis. Your quality control should include a porosity test ( dimethylglyoxime )

? Hi Narasimha. It's hard for me to suggest how thick the gold needs to be for functionality, when I don't understand why you even need it gold plated rather than nickel plated anyway :-)

I could be wrong, but I thought nickel was adequate for battery contacts, and the more so if sealed inside a watch. Can you explain or comment?

Regards,