INTA Technologies Corporation 2281 Calle de Luna, Santa Clara, CA 95054 || Tel: 408-748-9955 || Fax: 408-727-3027

 

 

Gold Plating

 

 

Table of Contents

 

 

 

What is gold plating?

Gold plating is a technique used to deposit a rugged coating of gold onto a substrate. The substrate can be a metal or a non-conductive material such as ceramic or plastic. The deposit is very rugged and it does not come off by means of scratching or applying a tape test. Plating thickness is generally in the range of .0001”

 

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Why use gold plating?

Gold is very expensive yet very useful. Rather than making a component out of solid gold, why not make the component out of a less expensive material and apply a gold coating. If a component is to be brazed, gold plating is often necessary to achieve adequate wetting depending on the type of wire bond or braze. Gold offers terrific corrosion resistance.

Gold properties:

Thermal conductivity: 300 (W/mK)

Density: 19.3 (gm/cc)

CTE: 14.3 (ppm/deg C)

 

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How much does gold plating cost?

Pricing depends on size and other issues including part geometry and any masking involved. Gold plating is fairly expensive, more expensive than nickel, copper or silver plating. Drawings and specs are needed before pricing can be discussed. Contact our sales office to talk about pricing: sales@intatech.com

 

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What is the difference between soft and hard gold?

Soft gold is popular in the semiconductor industry and is ideal for parts set for wire bonding. Soft gold produces a slightly less shiny appearance compared to hard gold. Hard gold contains some nickel and cobalt and is not ideal for wire bonding. Hard gold is suitable for applications calling for mechanical wear and/or shiny appearances. Soft gold is much more popular than hard gold among our customers. When in doubt, consult INTA Technologies Corp.

 

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How much thickness is needed?

Varies depending on application. Contact Blake Kneedler, Manufacturing Engineer 408-748-9955 x113 for details.

 

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Does INTA offer MIL-H-38534 plating?

Yes, INTA offers MIL-H-38534 Finish C and Finish X only. The specification relates to hybrid microcircuits and can be found at http://assist.daps.dla.mil/quicksearch/

 

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What is MIL-H-38534?

This is a detailed specification relating to hybrid microcircuits. The most recent revision is F, released in 2006. Another name for it is MIL-PRF-38534F or MIL-PRF-38534. See the previous answer for further details or contact INTA.

 

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Are there any types of MIL-H-38534 finishes INTA does not offer?

Yes, INTA does not offer Finish A or B. INTA offers Finish C and X only.

 

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What is the lead time for gold plating?

Typical lead time is five (5) business days. Expedite service is available in many cases for an additional charge. Expedite service can be as fast as same day although 2-3 days is more typical.

 

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Are there any alternatives to gold plating?

Yes, there are many options available although gold plating is unique. All the options must be weighed before considering surface finish. Sometimes a silver or nickel finish will suffice. For very high temperature applications, gold plating may not be the best option. Rhodium or platinum coatings may be able to endure high temperatures much better than gold coatings (1300 deg C, for instance). Contact INTA to discuss your application sales@intatech.com

 

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What is the smallest part INTA can gold plate?

.040” x .040” x .020”

1mm x 1mm x .5mm

These dimensions are approximate.

 

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What is the largest part INTA can gold plate?

Largest items are 12” in length and 6” in diameter (all dimensions approximate).

 

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Can INTA plate selective areas on a part?

Yes, this is routine for INTA, although more costly.

 

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How does INTA Technologies ensure quality?

INTA inspects and tests components at incoming and outgoing. If problems are noticed at incoming the customer is informed right away. Coating thickness is documented by use of an XRF machine. Customers may ask for certain areas to be checked for thickness with documentation. AQL sampling standards apply. Material is packed to ensure safe delivery. For further details please contact Quality Manager, George Baltazar 408-748-9955 x123 or gbaltazar@intatech.com INTA uses industry standard specifications and takes extra steps such as post-plate bake to check for problems. Tape test and scratch test are also common. If you would like more information about quality manufacturing practices we encourage you to read a classic book by Val Feigenbaum entitled, Total Quality Control. The Goal by Eliyahu Goldratt is another good quality management and production/manufacturing reference.

 

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What is a typical gold plating specification?

ASTM B 488 Electrodeposited Coatings of Gold for Engineering Use
AMS 2422 Gold Plating for Electronic Applications
MIL-G-45204 Gold Plating, Electrodeposited, Grade A or Grade C

 

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How much does gold cost?

The price fluctuates but is in the range of $1k/toz (USD).

 

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What is the melting point of Au?

Approximately 1064.18 oC.

 

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What is gold’s boiling point?

Gold boils if you call it silver. Just kidding! The boiling point is 2856 deg C.

 

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What is the density of Au?

19.32 g/cm3

 

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What is gold’s IUPAC group?

11

 

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What is the atomic number for gold?

Gold’s atomic number is 79.

 

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What is the atomic mass for gold?

196.967 amu

 

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What is Au’s electron configuration?

[Kr] 6s1 4f14 5d10

 

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What is an undercoat?

Base metal coat which is found below the top coat and above the substrate.

 

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Why use an undercoat?

Many reasons exist depending on the application. Here are some benefits:

 

Improved adhesion

Improved solderability

Improved corrosion resistance

Improved bondability

 

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What are common undercoats?

Nickel, silver, copper and other metals are commonly used.

 

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Gold plating on plastic?

INTA Technologies offers gold plating services on most materials, including most types of plastic and similar materials. Samples of gold plated parts are occasionally available upon request (restrictions apply).

 

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Is gold plating useful for wire bonding applications?

Yes, very useful for AuGe and similar wire bonding applications.

 

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What industries use gold plating?

Virtually all industries use gold plating. Gold plating is especially popular with energy (and alternative energy), medical, electronics, aerospace, defense, vacuum and other customers. Gold plating provides long-lasting protection in difficult environments.

 

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How does a gold plated item react to an X-Ray?

Gold absorbs about three times more x-rays than iodine. Gold plating is useful for biotechnology, medical, aerospace, satellite, defense, energy and other industries which use x-rays or equipment/components that are exposed to x-rays.

 

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Are gold plated items biocompatible?

Yes, gold plating is biocompatible in most cases. Contact INTA Technologies for further details. contact@intatech.com

 

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How can we test biocompatibility?

Many tests exist including salt spray, saline soak and others. A prolonged saline soak is very effective.

 

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How do I clean a gold plated part?

Contact Blake Kneedler @ 408-748-9955 to discuss your particular project. Cleaning processes vary according to condition, substrate material, gold thickness, etc.

 

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How do I handle gold plated parts when they arrive from INTA?

When parts are sent from INTA they are cleaned thoroughly and preserved by INTA. When the customer opens the package, they should wear nitrile gloves at all times and handle the parts in a clean room or clean environment. No cleaning is necessary because the parts will arrive clean.

 

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Can I do my own gold plating?

It is not recommended to attempt gold plating without training. INTA has a trained Chemist and several scientists on staff. Our combined experience is astounding and yet we continue to learn new things.

 

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Why do some jobs have longer lead times?

The following factors tend to produce longer lead times:

 

Selective plating

Complex items

Large items

 

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What about selective gold plating?

INTA offers selective gold plating on plastic, metal and certain other materials. Selective plating can be more expensive than full coverage. If plating is needed on the ID, a reasonable aspect ratio must be specified. A long, slender ID would be very expensive to plate.

 

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What is an ideal thickness of gold plating for wire bonding?

In general, gold plating with 50-200u” (1.25 – 5 microns) works well. Soft gold is generally preferred.

 

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How pure is the gold coating using a plating process?

Gold plating produces 24 K pure gold. For higher purity, soft gold is used (99.7-99.9% pure). Hard gold is less pure but still 99% pure gold.

 

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If I have a highly technical question regarding gold or gold alloy (such as AuSn) plating, who should I contact?

Dr. Francis Honey, Engineering Manager, fhoney@intatech.com, 408-748-9955

 

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How does gold plating compare to rhodium plating?

Rhodium is more expensive, harder, better for high temperature uses. Rhodium plating is best suited for small parts. Platinum is another option for high temperature applications. Here are the various melting points in Celsius:

 

Au

1064 deg

 

Pt

1768 deg

 

Rh

1964 deg

 

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Interesting and Informational Links

http://en.wikipedia.org/wiki/Gold_plating

Background information related to gold plating.

 

www.metalfinishing.com

Metal Finishing Magazine – interesting articles and research.

 

www.qualitydigest.com

Quality Digest Magazine

 

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Last revised: 19 JUL 2010