Metals: Gold, Silver and Copper and their use in the Electronic’s Industry

Welcome back to TAXING TARIFFS! In this post we’ll be looking at metals: what they are, where they’re used, how they’re used, and of course, which tariffs apply. As always, Taxing Tariffs is brought to you by Micron Corporation, where “WE BUILD IT BETTER.”

In times of peace and times of war, in prosperous periods and those of abject poverty, there are always metals. Metals are used in industry to build useful articles and great structures. Metals feed the war machines in times of conflict. They are present throughout some societies in periods of flourishing trade and invention and are highly coveted and sought after in periods of socio-economic decline. And they are omnipresent throughout the ever-expanding world of electronics manufacturing.

Printed circuit board assemblies (PCBA) can be divided (though not inclusively) into three major part groups: PCB, electronic components, and solder. All three of these contain small yet significant amounts of metals, some of them precious. Other hardware items used on, in or with electronics such as shielding, frames, fasteners, heat sinks, and enclosures are also made of metal. Those are usually made of steel and aluminum. All of these items are used in electronics manufacturing.

We’ll focus on three metals: gold, silver, and copper. They are the three most conducting elements (not just metals) on earth. And that is why they are used in electronics. By weight, gold is rare in PCBAs and, perhaps not surprisingly, copper is the most prevalent metal (again by weight) used in this grouping of metals in electronics manufacturing. In fact, the three are listed in ascending order of prevalence in electronics manufacturing. Take a look around you and you will see the same ordering of prevalence in society as you see in electronics. Look around your home (and thank God you have one) then consider how much copper you see and then how much you don’t see. Okay, now how much if any silver. Gold? To sum up that situation by mangling and abusing an age-old adage; as in society, so in electronics. All right then, we’re interested in three metals, one of them used mostly in industry and two of them are considered precious.

Let’s begin then with copper, silver, and gold. Their relative use in the industry can be estimated by considering ratios of the weights of each metal used in terms of orders of magnitude. To simplify the statement of the ratios we’ll use the Latin abbreviations of the elements (pure metals are elements). Copper is Cuprum in Latin and is abbreviated Cu. Silver is Argentum in Latin, thus Ag. And Gold is Aurum or Au. Then the ratios are as follows. Normalize the use of silver by weight to be 1, that is to say, whatever the total use of silver is, in any unit of weight – we’re calling it 1. Then there is 1000 times more copper use by weight. Again with silver as 1, there is 0.01 gold used. To restate this succinctly we can use the Latin abbreviations. Cu/Ag/Au ~ 1000/1/0.01. Copper is by far and away the most used of this three-metal grouping. Five orders of magnitude more than gold. There’s a reason they call gold and silver precious and one is made aware of that by their sparse use in electronics.

Tariffs on these three metals make it apparent, perhaps in a perverse way, which two are precious (silver and gold) and which is a base metal mostly of industrial use (copper). Gold and silver are exempt from tariffs (or 0% if you like) and copper has a 50% tariff. Admittedly, some collectible coins, bullion coins and special bars made of gold and/or silver do have tariffs.

Gold is used in component terminations for surface mount devices such as chip resistors and Integrated Circuit (IC) leads. The other main application of gold in electronics is on the surface of PCB pads. Two surface finishing procedures use gold, these are Electroless Nickel Immersion Gold (ENIG) and Electrolytic Gold. In the electronics industry we call 1/1000th of an inch a “mil” and it is not to be confused with a millimeter. ENIG lays down a thin layer of gold some 5 mil thick. Electrolytic processes can lay down 15 to 50 mil of gold. It may cost a lot per gram but that’s not a lot of grams.

Silver is found mostly in solder joints. It appears in both lead-free solder pastes and on the surface of pads. During reflow the silver on the pads quickly diffuses into the solder joint. All the silver ends up in the solder joint. Immersion silver (ImAg) is the most common process by which silver is deposited onto the PCB pads. By far, most of the silver comes from the solder. Solders such as SAC305 contain 3% silver. SAC305 refers to the Latin abbreviations; S (for Stannum) being Tin, A being silver, and C for copper. The 305 indicates 3% silver and 0.5% copper with the rest made of tin. More than gold, yes, but still not a lot of silver.

Copper is used in quantities that are three orders of magnitude more than silver use in electronics. It is used primarily in the conducting planes of PCBs. Copper traces and planes are the guts – if you will – of the PCB. And there’s a lot of guts in a twelve-layer PCB. Electronic component leads are also often made of copper. Though most comes from the PCB itself. Copper, also known as Dr. Copper, is the super heavyweight of this group.

Do you have any comments about Gold, Silver, or Copper? Are you appreciative of the fact that gold and silver are not subject to tariffs? Let us know at INFO@MICRONCORP.COM and then we’ll see you next time on TAXING TARIFFS.