This may seem a wild idea to some but using a hybrid of machine etching and hand etching is the best way to ensure no errors in your expertly manufactured PCB design. PCB etching is how we cut the copper traces into shape for those who don’t know. When we cut the tracks, they have to be etched. Rayming PCB & Assembly have access to a photolithographic service wherein we etch the copper tracks using a laser. Though this method will ensure that there are no errors in the copper routing, it is not suitable for every design because of several reasons:
1) The etch solution is NOT compatible with hand-etched copper traces.
2) The etch solution can waste time and significantly reduce manufacturing costs if done wrong.
3) Each etch solution has different requirements that may or may not be compatible.
Factors you need to consider before starting an etching project
The first step is to ensure that the board design meets all the requirements that each etch solution requires. We can do this during the design stage itself. Why, if you can do it during design itself? There are four main reasons:
1) The requirements for each etch solution are the same and not different depending on the design.
2) Since it is a single set of requirements, you can apply all your resources to the board design stage without worrying about any etching issues affecting their work.
3) If there are any errors in the PCB design, you can correct them before submitting them for manufacturing, saving a lot of time and money.
4) It is impossible to predict precisely which parts of the design will require modification for each etch solution.
A better method to ensure that there are no errors in your design is to use a combination of both hand etching and machine etched copper traces on your board. We refer to this hybrid approach as “hybrid etching.”
Hybrid etching can help you solve many of the problems mentioned above that come from using machine etched copper traces – problems like compatibility, waste of time and money, etc.
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What is a PCB etching solution?
A PCB etching solution is a photolithographic (laser) etch medium that we can use to etch the copper traces on your PCB. There are three different types of etching solutions used currently in the industry:
1) Aqueous Phosphate ETCHING SOLUTION
– This is the most common type of etchant, which has been used for more than 20 years now. It works by dissolving phosphorous ions in water to give off a gaseous phosphoric acid.
We can use it with both machine and hand etching.
2) Polyamide ETCHING SOLUTION
For those concerned about the toxic effects of phosphoric acid, a Polyamide (PA) etching solution has become a popular choice because it is environmentally friendly. As a result, aqueous and Polyamide solutions have been helpful in many commercial applications.
3) The most recent addition is Thermal Conductive (TC) solution
It has gained popularity in the past two years because we can use it with machines and hand etching to obtain excellent results. In addition, the TC etching solution has a unique method of etching that uses heat to remove the copper from the board.
For those concerned about the toxic effects of TC etchant, there is a TC-non-toxic version that we can use for PCBs.
4. Ferric Chloride Etching solution
It is typically used for automotive applications. For all of these etch solutions, the best way to ensure that the etching comes out correctly is to test the etch solution on a sample board before starting your project so you don’t run into problems. We can do this by purchasing one of the many purpose-built copper printing boards available. Manufacturers design it to be etched with these solutions and produce a defect-free printed copper board without any problems.
5. Ammonium persulfate etching solution
It is helpful for etching Silicon/Polyimide (Kapton) coated PCBs.
To ensure that you get the best quality to etch results, it is essential to do a few simple things.
– Don’t etch at high speeds. There are no positives to this except for reducing time.
– Always be aware of the ‘Bath Temperature.’ This can vary from solution to solution, depending on its cooling method and other factors.
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How does a PCB etching solution work?
Before getting the etching action started, you must clean the copper of any dirt and contaminants. You must first separate your PCB from the primary masking tape used for masking in the manufacturing process. Then, using either a magnifying glass or a jeweler’s loupe so that you can see the copper better, clean each copper trace of any debris and contaminants, which can prevent an error-free etch. Finally, let each trace dry completely before proceeding with the etching.
The next step is to prepare your etching solution. We do this by mixing 1 part of the etching solution with 1 part of deionized water (DI water) through a ratio of 1:2. Bring it to a boil in a saucepan on your stove, then let it cool down until it reaches room temperature.
After mixing your etching solution, pour it into a suitable container that we can use for the etching process. Ideally, this container must be able to hold all your PCBs at once. Cover the container securely with a lid to prevent evaporation of the solution over time.
Now it is time to place your PCB(s) in the etching medium. We must place each copper trace on your board in this etching solution. It is a good idea to put one PCB at a time to ensure that there are no errors in your design by checking the etch results on the PCB itself. Then, remove it from its container and place it face down onto an etch-proof carrier (like cotton). When you place the first PCB carefully, let it sit for a few seconds so that any air pockets form inside it.
Which is the best etchant for PCB etching?
There are three different types of etchants for PCB etching. Unfortunately, they provide their benefits and problems, making it hard to choose the perfect one in each situation.
When you decide which etch is ideal for your project, the first step is to understand the various components of these etchants to choose the best one to meet your needs.
The main components that make up an etchant solution are:
- Conductivity: All the PCB etching solutions mentioned above have conductivity. Therefore they can helpto etch both PTH and LTH pads. This is especially ideal for those who prefer to use hand etching methods.
- Reliability: Every PCB etching solution has a different track record for reliability. This means that some solutions may etch your board faster than others or will produce better or worse results.
- Precision: In the past, manual PCB etching methods have been error-prone in the etching process itself. With the development of new laser machines and advanced software, laser machines have become more precise. They provide excellent results with more control allowing you to get only what you want on your board.
- Cost: Cost will be a significant consideration when choosing an etchant solution. PCBs themselves are enough to make some people want to cut costs in any way possible. But the cost can be an issue if you are using manual methods.Thus,get the most bang for your buck and choose an etchant solution that will save you money.
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Conclusion
When designing a PCB, it is essential to consider how you will eventually make it. Therefore, it is good to look into etching options and determine which type of etching method you will use before designing your PCB. This will make creating your board much easier and save you from a lot of lost time in the future.
The etch will determine how you etch the board and its time, so you will create enough time and money to spend on your project. Suppose a larger PCB or one with more complicated circuitry is involved. In that case, it’s also a good idea to look into the cost of an automated laser printer. They can provide much better reliability and precision in your board.
