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Conard's Photo Etching Blog

Why Choose Photo Etching for Producing Metal Parts

Posted by Kathleen Stillman on Aug 8, 2013 10:57:00 AM

The biggest problem with photo chemical etching is that it is unfamiliar to many designers and engineers. The second problem is that it has too many names: “PCM,” photo etching, chemical etching, acid etching, chemical machining, metal etching.  People don’t know what to ask for.

photo etched and gold plated leadframe

And just to add to the confusion, there are several other processes that sound similar, but aren’t the same.  Electrochemical etching is used for part-marking.  MetalPhoto is a photographic process for making nameplates that entails no etching at all. And, chemical milling is used to selectively alter three dimensional parts to change the surface or reduce the weight of the metal.

Photo etching is a metal fabricating technique that fits in a spectrum of processes that include metal stamping, CNC punching, laser and water-jet cutting  and wire EDM.  The end result of all of these processes is flat metal parts, that may be subsequently formed or finished by other methods. 

One of the chief advantages of photo chemical etching process is that photo etched parts do not acquire any thermal or mechanical stresses during fabrication.  The unwanted metal is dissolved by the etchant and rinsed away.

Stamping and punching are processes that require hard metal tooling to cut parts from sheets of metal which can cause cold working of the metal. Plasma, laser and water jet use narrow beams of focused energy.  In the case of the laser, the energy comes from colimated light, and the water jet uses a pressurized abrasive slurry, and plasma uses ionized gas.  Wire EDM uses a wire electrode to burn the parts out of metal.

Photo chemical machining is a relatively rare process.  There are only about 100 PCM shops in the country and barely a few hundred globally.  Compare that to several thousand metal stamping shops just in the US.  Photo etching is often a better solution to fabricating flat metal parts, but too few people are familiar with the process.  This video provides a 2-minute overview of the photo etching process: http://www.iplayerhd.com/player/ConardCorp

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Topics: photo chemical machining, photo chemical etching, chemical etching, etching stainless steel, photo etching problems, chemical machining problems, chemical machining, photo etching metal, etching with ferric chloride

What Engineers Need to Know about Photo Etching

Posted by Kathleen Stillman on Jul 8, 2013 2:28:00 PM

The hardest job we face is educating designers and engineers about the capabilities of the photo chemical etching process.  Conceptually, it's alien to people who picture stamping and punch presses and laser, water, and plasma cutters for creating metal parts. Each process has it's pluses and minuses, and in some aspects the capabilities have some overlap.

One of the first criteria to think about is quantities.  If the application is going to run in the millions, then stamping is the most efficient alternative.  But for quantities from dozens to 100,000, then photo etching may prove just as effective, and with a far lower tooling investment -- typically less than $300, no matter how complex the part.

Using photo etching, the test part shown below is no more difficult or costly to make than a simple washer.

CCSTAR crop

Another factor is the material thickness.  Most stamping and CNC punching tend to avoid working with very thin materials because of material handling.  Plasma and laser cutters are typically not very "thin" friendly due to the heat involved.  Water jets avoid the heat problem, but the pressure can be a problem of shredding very thin metals.  Although photo etching is practical for a wide variety of thicknesses, its greatest advantage is with the very thin materials, down to .0005", although the typical range is from .001" to .032".

Dimensional accuracy is also an important consideration. Fine blanking is the highest precision option in stamping and can achieve dimensional tolerances of as little as +/-1% of metal thickness, to a practical limit of about +/-.0003".  But the tooling can be very expensive. Photo etching typically runs about +/-15% of metal thickness, which still easily accommodates +/-.005" tolerances on materials up to .032" thick. Plasma cutters are reported to hold tolerances to +/-.015", and lasers +/-.005".

Alteration of metal characteristics can be problematic in stamping and punching, as cold working can occur at the shearing points.  Some alloys can be annealed afterwards, but many, like 300 series stainless steels, can not be.  Laser and plasma cutters impart intense heat and the metal adjacent to the kerf lines may be subject to embrittlement or other thermal distortions.  Photo etching, which runs about as hot as your dishwasher (about 130F), poses no threat of inducing thermal or mechanical distortions.

In photo etching, the metal thickness is the key determinant of feature sizes, minimum radius and dimensional tolerances.  Through holes or slots must be at least 110% of the metal thickness.  Minimum land area between through features should not be less than the metal thickness.  And, in general, minimum radius is approximately equal to metal thickness.

Another feature of chemical etching is the sidewall.  The etching process occurs from both sides of the sheet, and as the etch depth increases the side wall slopes away from the etch line at the rate of .00025" per .001" of depth.  This creates a slightly hexagonal cross section with a small feature we call the "feather" at the breakthrough point.

Simplifying complexity is perhaps one of photo etching's greatest advantages. The process is utterly indifferent to odd shapes, multitudes of holes or other less ordinary features.  Photo etching can produce part geometries that would be extremely difficult, if even possible, with stamping or punching.  Laser and plasma cutting are more flexible in this regard, however every feature and every hole must be addressed in a linear way, as if tracing with a pencil.

Photo chemical machining has been call "manufacturing's best kept secret."  We aim to change that! 

To that end, we have created several informative documents to help engineers and designers understand the

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Topics: photo chemical machining, photo chemical etching, chemical etching metal, etching stainless steel, photo etching problems, chemical machining problems, photo etching metal, etching with ferric chloride

How does Chemical Etching Work and What Can You Do with it?

Posted by Kathleen Stillman on Apr 15, 2013 2:03:00 PM

Chemical etching is a method of fabricating metal components that relies on an acidic solution to dissolve unwanted metal.  Stamping and punching utilize hardened steel tools to shape metal parts.  Plasma, laser and water jet cutting utilize directed energy to shape parts. And, wire EDM uses a wire electrode to burn away metal.

Photo etching is also known as chemical etching and photo chemical machining.  It evolved in the 1950s as an off-shoot of printed circuit board fabrication, and the production process is very similar.

The basics of the process include creating the photomask, which today is derived from CAD data and output on film from a laser photoplotter.  This is known as the phototool.  The metal to be etched is carefully cleaned and coated on both sides with a polymer film called photo resist.  When applied, the photoresist film is unexposed and this must be done in a yellow safe-light environment.

Inspection a phototool in the imaging process

The coated metal and the phototool come together in the imaging process where the black regions on the phototool prevent the exposure of the resist under intense UV light.  The unexposed resist is washed away in a developing solution, leaving bare metal in the areas to be etched.

In the etching process, the exposed photoresist is strong enough to withstand the effects of the ferric chloride etchant.  But the unprotected metal is dissolved right up to the edge of the resist.  The etchant is sprayed at both sides of the sheet until cut through is achieved.  After etching, the resist is washed away in a different solution.

 

 

So, just by thinking about the processes, you can easily see the differences.  Stamping and punching are sort of "brute force" processes, shearing the 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.

So, what can you do you with chemical etching? You can make very thin metal parts, as thin as .0005" (yes, five ten-thousandths).  You can make fairly thick parts: up to .040" in ferrous alloys, .065" in copper alloys, and .080" in aluminum.  You can make parts with funny shapes and lots of holes and it doesn't cost any extra. You can make some very little parts, as small as .020" diameter.  And, you can make some fairly big parts, up to 24" x 60".

Chemical etching 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 semiconductor 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. Decorative etching is widely used for giftware, jewelry, scale models, architectural, and ornamentation for apparel, eyeware and home furnishings.

What would you like to do today?

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Topics: photo chemical machining, photo chemical etching, chemical etching, chemical etching metal, etching stainless steel, chemical machining problems, chemical machining, photo etching metal, etching with ferric chloride

The Benefits and Drawbacks of Photo Etching with Ferric Chloride

Posted by Kathleen Stillman on Mar 14, 2013 10:03:00 AM

IMG 6838 resized 600Ferric chloride is the most widely used etchant for commercial chemical etching facilities.  It is comparatively inexpensive, safe to use, consistent in etching performance, and versatile in etchable alloys.  It is especially well-suited to etching the “white” metals, which include the iron- and nickel-based alloys, as well as zinc, manganese, indium and tin.

The primary iron-based alloys include stainless, carbon and silicon steels.  Kovar and Invar are iron-nickel alloys often used in etched electronics packaging applications.  Alloys whose major fraction is nickel include Alloy 42, Inconel, and Mu-metal.  Although ferric chloride will not directly each certain pure metals including cobalt, chromium and tungsten, these elements may be present up to certain fractions in iron or nickel alloys and they will be etched.

Using ferric chloride to chemically etch white metals produces a smooth side wall with a consistent and predictable etch rate.

Another benefit to using ferric chloride is that it can be regenerated in process.  Instruments within the etching process monitor the chemistry on a continuous basis.  At specific thresholds, the etchant is refreshed by injections of muriatic acid, chlorine and water.  In this way, the etchant bath life can be extended to several weeks.

Even after several weeks of etching white metals, ferric chloride continues to be useful.  It can be modified to be suitable for etching “red” metals.  Red metals are copper based, and include primary coppers, brass, bronze, Monel, nickel silver (a copper alloy that actually contains no silver at all), and some specialty alloys.  Again, the condition of the etchant is monitored automatically and refreshed as needed.  In this way, the life of the original etchant is extended for several more weeks.

After the ferric chloride has done its work etching white and red metals; it is reconfigured one more time to etch aluminum.  Aluminum is a very light metal, about one-third of the density of the red and white alloys.  It is also very reactive and wants to oxidize readily.  The modified etchant is suited to this task.

From an operational point of view, ferric chloride is fairly benign to work with.  Casual exposure does not cause injury and is readily remedied with water.  There are etching chemistries, both acid and alkaline, that will cause significant injuries on contact, and one –hydrofluoric acid, that can cause death.  Ferric chloride has none of those risks. 

However, ferric chloride doesn’t etch everything.  In particular, the “noble” metals: gold, silver, platinum, palladium, tantalum won’t etch in ferric chloride.  The so-called “high temp” metals: titanium, molybdenum, tungsten, cobalt, chromium, niobium also do not etch in ferric.

We have alternative etchants that are effective for silver and molybdenum.

These “non ferric” alloys can be etched with other solutions which are sometimes combinations of different acids like sulfuric, nitric, hydrochloric or phosphoric.  Or, when the etching facility is especially equipped for containment and safety, hydrofluoric etches just about everything.

Although regeneration and re-purposing of the ferric chloride etchant extends the life and usefulness of the etching solution, it does have a side effect.  The process actually increases the overall volume of the etching solution by several times.  After the etchant is consumed, the spent solution is neutralized.  The dissolved metals are precipitated out and sent for refining and recycling. The remaining liquid, which is basically water, is treated and can be recycled as well.

Because ferric chloride is so “user friendly,” it-unfortunately- is also concocted by the “DIY” and home etching fan

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Topics: photo chemical etching, chemical etching, chemical etching metal, etching stainless steel, photo etching problems, photo etching metal, etching with ferric chloride

What are the Problems of Cutting and Photo Etching Aluminum?

Posted by Kathleen Stillman on Mar 6, 2013 1:20:00 PM

Photo etched aluminum heat sinkOne of the lightest metals, aluminum, is one of the more challenging alloys to to process. This post will compare laser and plasma cutting with photo etching with regard to cutting aluminum.

The biggest problem with laser and plasma cutting is heat. Aluminum melts at about 1200 degrees F. The plasma stream is about 25,000 degrees.  By definition, laser cutting is a process of melting the material in its path, so the work piece will be subjected to high temperatures. The thermal impact of these processes can produce a recast or slag layer, known as the Heat Affected Zone (HAZ). This thermal exposure can alter the properties of the metal, which is generally undesirable. By comparison, the photo etching process rarely gets warmer than 150 degrees, about the same as your dishwasher.  

Dimensional accuracy is another area where there are meaningful differences between laser, plasma, and photo etching.

On plasma cutters, the beam width is determined by the nozzle size, with a ratio of 1.5 to 2X nozzle diameter to beam width.  It is possible to put a .001 nozzle on a plasma cutter to produce a .002 beam, but you can't push very much power through that aperture.  Dimensional accuracy of plasma cutters runs about +/-.015-.020".

On laser cutters, the beam width is determined primarily by the optics.  For metal cutting machines, typical beam widths of .006-.016". (Laser marking machines can have much smaller beams.) Laser cutters can achieve +/-.005" dimensional accuracy.  Two additional issues with laser cutting aluminum are optical reflectivity (aluminum is shiny) and thermal conductivity (the metal dissipates the heat the laser is trying to generate.)

In photo etching, dimensional tolerances are +/-15% of material thickness. For metals that are .032" or less in thickness, photo etching will easily produce tolerances that are tighter than +/-.005".

The etching challenge with aluminum is that is it a very active and reactive metal.  It oxidizes readily and actually becomes fuel for the etching reaction. Another problem is that aluminum will etch in both acids and bases.  The solution used to dissolve the acid-resistant photo resist is a base.  In the process design for etching aluminum, allowance has to be made for the slight but inevitable etching during the stripping process.

Photo etching has proven to be a versatile and cost effective method of fabricating thin-gauge metal parts in many alloys.  The vast majority of metals can be successfully photo etched using ferric-chloride etchants, which are among the easiest, safest and most economical to use. However, ferric chloride does not produce the best results on aluminum.

Etching aluminum is the foundation of Conard’s business.  In the early 1960’s, Dick Huttinger, a metallurgist for Pratt and Whitney, was trying to find a better way to finish the surfaces of forged aluminum propeller hubs.  At that time, CNC machining was neither sufficiently sophisticated nor cost effective for the task.  Huttinger believed that it could be done chemically and developed the methodology that we continue to use to this day.

Our General Manager, Art Long, has worked in this industry for more than 30 years and is well familiar with the challenges of etching aluminum. “The biggest problem is edge consistency, sometimes the edge would look smooth and other times it would appear very rough. It was difficult to control the quality of the etchant from one bath to the next and from one alloy to the next,” said Long.  “When I joined Conard in 2003, I noticed that the aluminum etching capabilities were head and shoulders above the previous companies I had worked for. The product had consistently smooth sidewalls and was precise in a wide range of different aluminum alloys and thickness.”

From the beginnin

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Topics: photo chemical machining, photo chemical etching, chemical etching metal, photo etching problems, chemical machining problems, chemical machining, laser cutting, etching with ferric chloride

Benefits of Working with an Outside Photo Etching Supplier

Posted by Kathleen Stillman on Feb 27, 2013 1:11:00 PM

automated photo etching equipmentTwenty-five or so years ago, the photo etching process was a lot more common in manufacturing, particularly for printed circuit boards. Back then, there were at least 100 companies, just in Connecticut, that etched circuit boards.  Today, there are barely a handful and only a few hundred in the country.  As pcb manufacturing migrated overseas, the knowledge base for photo etching declined.

When there was a population of people who had etching experience, there were companies that decided to do their own etching.  In those days, environmental requirements were less rigorous and the costs of waste management were much lower.  Over the intervening years, things have changed quite significantly with regard to photo chemical etching.

Today, environmental compliance costs, safety, and waste treatment and disposal are significant cost factors for etching. Interestingly, there are about the same number of commercial photo etching companies today as there were 25 plus years ago.

In addition to shouldering the costs of the regulatory and environmental burdens, photo etching equipment is not a long-lived asset.  Exposure to the etching solution, which is both heated and pressurized, takes its toll on the conveyors, bearings, and pumps.  We routinely replace equipment every four years. If you are etching only part time, or intermittently, your etching equipment is degrading in place.

There are eight reasons why you should be working with a commercial photo etching supplier rather than doing your chemical etching in house:

 

1. Utility Costs:  chemical etching equipment uses a ton of power to run compressors, pumps, conveyors and sprayers.  The etching process also uses a lot of water for regeneration, rinsing, developing and stripping.

2. Chemistry and supply costs:  Etchant, developer, stripper and photoresist are significant elements in the cost of goods.  And, if you are not etching on a continuous basis, those costs are not amortized efficiently.

3. Waste treatment and disposal:  Even with on-site waste treatment, what and how much can be put down the drain is tightly regulated. Other wastes must be processed by regulated facilities and everything has to be accounted for and documented in perpetuity.

4. Regulatory and compliance costs:  It's not enough to follow the rules.  You have to pay permit fees, audit fees, consulting fees, disposal fees and more, just for the fact of using photo etching as a manufacturing process.  And, don't forget the potential for fines if you have a problem.

5. Maintenance and repair costs: Photo etching equipment requires regularly scheduled M&R, just like an airplane.  After every so many hours of operation, there are parts that need to inspected, serviced or replaced.  Keeping an etching line running for 4 years isn't like keeping a refrigerator plugged in.

6. Capital Expenses:  After keeping an etching line running for four years, you still have to replace it.  Just write a check in the six-figure range.

7. Training and Safety: There are state- and federally-mandated safety training requirements  for which a certified instructor is required.  Every new employee must be trained to the requirements and every employee must complete retraining annually.

8. Determining your true cost of goods:  Do you really know what your etching costs are?  It's not just the cost of the metal.  What about the defective parts you make?  What about unabsorbed overhead related to start up and shut down?  What about production efficiency? Can you run that equipment as productively as a full time facility?

When you work with a commercial etching facility, all of these issues evapor

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Topics: photo chemical etching, chemical etching metal, photo etching problems, chemical machining problems, photo etching metal, etching with ferric chloride

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