Conard's Photo Etching Blog

In the midst of the COVID crisis, thousands of companies and tens of thousands of people stepped up to join in a herculean industrial effort to ramp up production of desperately needed medical equipment and supplies.

Aluminum is a light and versatile metal. However, it has a couple of characteristics that give etching houses fits. It is highly reactive and will etch in both acids and bases. Common photoresist film is designed to repel acid, but to remove it you need to use a fairly high Ph caustic solution. And, oh darn, that etches aluminum, too. So, say bye-bye to dimensional tolerances. For many etchers, the headache isn't worth it. (And, shhh, don't tell anybody... but sometimes they come to us for aluminum.)

In my experience, professionals involved in designing, engineering, and sourcing precision metal components have a pretty good grasp of a variety of fabrication processes. Except for photo chemical machining (metal etching), to which the response is usually a blank look, shrugged shoulders and a negative head nod. You don't have to be one of those people any more.

When the heat is on, many look to photo etching to move it around or make something useful of it--like electricity.

 Photo Etching vs. "the Others"

Photochemical machining is the industry's preferred moniker for this metal fabrication process.  It is also readily called photo or chemical etching,  The process derived from the then-nascent printed circuit board industry in the 1950s. The fabrication steps are nearly identical.

More recognized processes such as metal stamping and punching utilize hardened steel tools to shape metal parts and have long histories in metal fabrication.  Plasma, laser and water jet cutting utilize directed energy to shape parts. And, wire EDM uses a wire electrode to burn away metal. In these cases the evolution of CNC (computer numerical control) in the 1970s allowed part geometries to be programmed directly into cutting machines.

The most "traditional" processes, stamping and punching, are sort of "brute force" processes, shearing metal using powerful presses.  Plasma, laser and EDM rely on intense energy, literally burning their way through metal.  Waterjet is sort of the "hot knife through butter" option, but you definitely wouldn't want to get in the way of a pressurized stream of water that can cut through an inch of steel!

Photo etching, in contrast, would be like running a sheet of metal through your dishwasher and then taking out a sheet of parts.

"Stress Free" Precision Metal Fabricating 

Photo etching is deemed a "non-conventional" method that fits alongside plasma, laser, waterjet and wire EDM for manufacturing many types of metal parts. 

The more well-known fabrication methods have their own sets of undesirable side effects.  Stamping and punching produce burrs from the shearing forces, and often cause "cold working" of the metal that may need to be alleviated by annealing. Plasma, laser and wire EDM impart significant heat into the work material.  Plasma operates at about 25000 deg F; laser and EDM typically between 2500 and 5000 deg F. In these cases, the side effects of the intense heat include what are called "heat-affected zones" or recast layers that need to be rectified by secondary processes.

Photo etching completely avoids all of these side effects. The maximum temperature metal is exposed to in etching is 165 deg F. In addition, etching is particularly capable with very thin materials (routinely down to .001")--which is beyond what is in the comfort zone for the other processes. Etching is also very capable with regard to both reflective and thermally conductive metals such as aluminum and copper, which can be problematic for lasers in particular.. 

Here's a quick run down of etching specs and tolerances.

For more detail:

The photo etching process is used for fabricating metal parts for many different industrial applications including sensors, shields, retainers, flat springs, strain gauges, filters, screens, grids, shims, gaskets and more. For electronics, etching is used to produce a host of metal components used in RF, microwave and wireless applications, as well as lids and leadframes for microelectronics packaging.  Photo etched direct bond copper is increasingly used in power electronic applications, particularly in wireless devices. It is also used to produce a host of electrical contacts, buss bars and other electrical interconnect devices.

Why Metal thickness Matters so much in Etching

We've seen it time and again. From never heard of it to can't manage without it. Photo etching becomes the go-to solution for precision metal parts fabricating once people understand its advantages. Among the key features are inexpensive, rapidly produced phototools ( 1 day), the ability to process metal foils as thin as .0005 inches (really!), and completely "stress free machining": no burrs and no mechanical or thermal effects.

Many design platforms now offer some basic cost estimating for the fabrication processes that are already programmed in. But NONE of them know anything about photochemical machining, so how can you be expected to know whether etching might be your best option.