Wet and Dry PCB Etching Solutions: Which Process is the Right Solution?
I have always been a very visually-oriented thinker. When I was much younger, I used to look up maps to video game levels online and put a sheet of tracing paper up against the screen to copy them down. The Zelda games specifically would always leave me with a notebook full of maps and, on the more challenging dungeons, color-coded warnings. If I sneezed once in my tracing process or the screen moved or I was called away mid-tracing, my map would be restarted.
One time, I spent hours in a dungeon only to realize that I’d done it all wrong because of a mistake in my process and had to backtrack to understand exactly where I messed up. Now, we don’t have to worry about etching mistakes so much with more intuitive dungeon-layout logic in games and, more generally, the availability of phone and computer screens.
It does make sense, though, that I’ve worked in positions that make me recognize the PCB etching process. When I was just getting started in design, I had very little idea about etching and how it worked. But as my experience grew, I was put into positions which required me to have more of a direct understanding of production and manufacturing processes. Having this knowledge will allow you to have a smoother transition to production.
Know the Process Options: What PCB Etching Solution is Available?
Etching your PCB is a mandatory step for any sort of PCB production. Whether it is a simple prototype or a full-blown manufacturing batch, your board’s connection paths will need to be precisely defined and laid out so that your components will be able to successfully communicate with one another.
There are various styles of PCB etching that can occur in order to achieve similar results. The style that you choose, however, could depend on many factors involved. Is this simply a one and done PCB? Is time a factor in your decision? What about environmental impacts to larger production runs? How tightly packed and complex is your design?
There are two main schools of application when it comes to PCB etching. The first and most widely understood method of etching is wet etching. This involves the use of chemicals for your etching solution. The board essentially bathes in which chemically removes a specified area of the original copper plate leaving behind your predefined copper paths (once cleaned).
The other, slightly newer method of etching is known as dry, or plasma etching. This process involves the use of a chamber filled with a positively charged gaseous solution that essentially eats away the unwanted copper material leaving behind a similar looking path to that created by the aforementioned wet method. Of course, knowing which is right depends on your application.
Applications of Wet Etching
If you perform a quick search of the term ‘PCB wet etching’, you’ll find a plethora of DIY videos and instructions on how to etch your own circuit board with simple, easy to attain items. The materials involved can range from simple household items such as the use of hydrogen peroxide, vinegar, and salt. Other, more robust applications involve the use of more ‘potent’ chemicals such as cupric chloride (copper chloride) or ferric chloride (iron chloride).
One advantage of using the wet method is that it is relatively simple to perform and is ideal for one-off DIY designs. If you are in a crunch for time and can’t wait for the fab house to get you a prototype board out, you will certainly be able to procure your own etched circuit board within a day or so. This method, of course, is rather messy and does require some knowledge of the chemicals and process involved as you will literally be soaking your circuit board for a short amount of time.
Using the household materials as listed above is obviously a cleaner set up, however, using the industry standard cupric chloride will involve some forethought on proper handling and disposal of the etching solution as it is terribly harmful to the environment (especially with all that dissolved copper floating around in it).
If you are in need of a higher quantity production, further considerations should be made accordingly. The amount of material alone in a production level wet etch will surpass that of the dry method, along with floor space required for bathing, proper training and education of your workers, as well as governmental permits required for disposal.
Applications of Dry Etching
On the other side of the coin, the dry etching method is a far more complex operation requiring a dedicated machine for its operation; however, the process is a slightly cleaner way of etching in my opinion. The amount of training that is required for operation is far less than any wet method making it a better solution for a more agile operation.
The use of positively charged gas, or plasma, that is used for the physical etching of the copper leaves no residue for any further cleaning stage making it more suitable for higher quantity production runs. The disposal of the residue will be released straight to the atmosphere which can be viewed in a negative context, but when comparing to the wet method, it appears that less waste will impact the environment as a whole.
Drawbacks to this method of etching are limited if you intend to reproduce a printed circuit board in multiple quantities, but if you are simply looking to develop a handful of one-off prototypes, the investment in these machines may outweigh the return.
Which Process Will Get You to The Treasure?
If you are in a time crunch with a need for a specific PCB layout, you can easily get away with a quick and dirty DIY wet etching operation. If you are in need of higher quantities of boards, or if you are to the point in your production where timing, accuracy, and environmental concerns arise in your decisions, then utilizing dry etching methods with the use of dedicated etching machines will likely be for you.
Take careful review of your manufacturers and ask for an overview of their process in all aspects like preparation, operation, and disposal; ensure their standards align with your needs and concerns before jumping in. To get you to a point where you can consider your manufacturing and production options for your designs though, you should be using PCB design software which can contend with your design demands, and prepare you for next steps.
A strong design software will allow you to move seamlessly between schematic, footprints, layout, and manufacturing outputs without painful transferring and translating processes. Through a unified design environment, you won’t need to rely on a horde of different softwares or tools to find the treasure at the end of the dungeon. With the idea of a smart, intuitive design approach in mind, Altium Designer® would be the right fit for any designer.
If you want to further discuss etching concerns or progressing your designs through all phases of the process, talk to an expert at Altium Designer today.