Occasionally, customers will come to us with concerns about the variance in gold color across an entire lot. In essence, they have a mindset of, “If it looks good, it is good,” and, “Anything that doesn’t look good, isn’t good.” In the retail space, specifically jewelry, they would have a very valid concern. Various types of gold are used in that industry including white gold, rose gold, green gold, etc. These are all alloys with metals including palladium, copper or silver. Let’s face it, with jewelry, looks matter!
Understanding on the Key Factors of Component Plating
However, when it comes to MIL-SPEC gold plating for electronic components, it’s a different story. The type of gold used for these parts, such as pins and connectors, is most often hardened with trace amounts of cobalt or nickel. Three key things matter when plating these components: hardness, purity, and thickness. Each of these attributes is normally specified by the end-user and is easily controlled by the electroplating process. While color and appearance may be expected to look like jewelry, that expectation is simply not specified. The end result is parts that do in fact meet spec, but may have some areas that are duller than others. These typically include the inner diameter or the valley of threaded areas.
What Causes Color Variation when Plating with Gold?
The variation is most likely caused by differences in electrical current density over the part itself or the tendency of parts to self-burnish as they are tumbling in a plating barrel. In a job shop, small lots of parts may need media added to make electrical contact. The media and the parts have different geometries and will attract electrical current differently. The MIL-SPECs do not allow for post-plate tumbling to correct this phenomenon.
So, in cases where looks do matter to the customer, what is an electroplater to do? It comes down to controlling brightness. The brightener used in a hard gold bath is either a nickel or cobalt hardener. Levels need to stay in range so that the purity of the gold is kept in spec. Correct amperage is also essential in achieving a bright and consistent deposit.
But it all starts with looking beyond the MIL-SPEC and knowing your customer’s expectations. They must then be clearly communicated to operators and inspectors in their work instructions.
The end result? Bright, consistent components – and happy customers.