Everything You Need to Know About Which Chemical Is Used for PCB Etching

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You must go through different steps to turn your PCB imagination project into reality. First, you make a design of the PCB online. After that, you get it printed on a copper plate. Before you jump onto the next step, you must take care of extra copper to get your desired pattern on the board.

You will have to do PCB etching. It will be a process of removing excess copper from the copper plate to turn it into a PCB. You might think that you can remove excess copper from a copper plate. Well, you will have to make a solution for that. Which chemical is used for PCB etching? This might be your next thought. Don’t worry, and we will discuss it in further detail.  

There are different techniques for PCB etching, but you have to be very careful while doing that. If you are not careful enough, you might end up causing damage to the PCB at the same starting stage of manufacturing your first PCB. The entire process of building a PCB depends on its patterns, and to get a desirable pattern, the etching of the PCB is important.

Etch layer in PCB: What it is?

PCB etching is one of the most important steps before it gets installed in any electronic device. Without PCB etching, no PCB gets installed in the electronic device it has been designed for. With the help of a chemical solution, this process completes. To achieve desired PCB pattern, it is essential to remove excess copper.

While you work on installing different electronic components on the PCB, it is obvious it gets messy on it. The tin is stripped, and the copper gets cleaned. Once PCB etching is done, the newly manufactured PCB is ready for the next phase.

Why do you have to do PCB etching?

Without PCB etching, you won’t be able to achieve your desired PCB pattern, as we have said above. Removing excessive copper traces from PCB helps you understand and have a clear view of your hard work on the PCB. You will get to know whether everything is perfect about the PCB or not.

Without achieving your desired PCB pattern, it won’t be ready to get installed in the electronic device. Therefore, PCB etching is an important step.

Ways to do PCB etching

There are two ways through which you can do PCB etching:

Wet etching

If you go for wet PCB etching, this technique consists of using a solution on PCB that helps in removing excessive copper traces. Now you might think about how you can use a solution on a circuit board. What if it causes any damage to the board? Well, it is one of the common methods used for PCB etching.

You have to take care of the following three factors if you are going to do wet PCB etching:

  • Etching solution concentration
  • Etching solution temperature
  • Stirring

The characteristic of wet PCB etching is isotropic, so increasing the etching temperature and adding stirring will speed up the etching process. We are just qualitatively mentioning this fact about wet etching. Now you might think, which chemical is used for PCB etching? We are going to discuss this in further detail:

Wafer etching

A variety of common substances are going to be used in manufacturing the solution for PCB etching. Silicon dioxide, silicon nitride, and aluminum are used for wet etching silicon. Polycrystalline silicon and Monocrystalline etchings are the hydrofluoric acids and nitric acid mixture for silicone dioxide oxidation on the silicon surface. It will form a silicon solvent removal.

Use diluted hydrofluoric acid and add fluoride as a buffering agent to control PCB etch rate. First, you need to heat silicon in a 180-degree phosphorus acid solution. For aluminum alloy, use nitric acid, acetic acid, phosphorus acid, and water.

The quantity of the following chemicals has to be:

  • Phosphorus acid = 80 %
  • Nitric acid = 5 %
  • Acetic acid and water = 10 %

You need to mix all these chemicals to make a solution that will help you to do wet PCB etching. Make sure to add all the chemicals carefully and pay attention to the number of chemicals you will add to make a solution.

PCB

Current famous PCB etching solvents

Currently used PCB etching solvents are cupric chloride, iron, sulfuric acid hydrogen peroxide. Alkaline ammonia, ammonium persulfate, and sulfuric acid – chromic acid etching solution. The chemicals used for preparing a PCB etching solution are copper chloride, alkaline etching, ferric chloride liquid, and acid/hydrogen peroxide.

Chloride copper is etched by chloride copper while adding hydrogen peroxide and water. You can prepare a solution of three ferric chlorides etched liquid by three ferric chlorides, hydrochloride, and water. For the composition of the alkaline etched liquid, you will need copper ammonia complex ion; sulfuric acid/hydrogen peroxide.

The three solutions we have mentioned are commonly used for PCB etching. PCB manufacturers, some uses 95% copper chloride (CuCl2), 20% using copper chloride (CuCl2), and 80% using ferric chloride (FeCl3). The manufacturers use the PCB etching solution that they find perfect for this process.

Pros of wet PCB etching

  • This process will have better surface uniformity.
  • It works for almost all sorts of glass, plastics, metals, etc
  • Cost-effective method
  • Wet PCB etching won’t cause any damage to the PCB

Cons of wet PCB etching

  • It is an isotropic etching
  • Pattern fidelity is not ideal

Dry etching

The main component of dry PCB etching is plasma. Regarding sub-micron sizes, PCBs dry etching is one of the most important methods. Using plasma helps in PCB etching because it reacts with the surface film and it will form volatile substances. You can also directly bombard the surface, and the dry etching characteristic is anisotropy.

Pros of dry etching

  • Better etching uniformity
  • Cost-effective method

Cons dry etching

  • It might cause damage
  • Expensive equipment is going to be required

Do you have to prepare new etching solution to work on PCB?

For PCB etching, you must prepare a new etching solution every time. If you are inexperienced and are trying to learn which chemical is used for PCB etching and how to use it, then you should keep in mind that it would be better to prepare a fresh solution for wet PCB etching.

You can keep using that solution until its etching performance gets affected. Never dump the etching solution in the drain after using it. It would help if you collected and put it in the hazardous waste collection point.

Guideline to do PCB etching

You know the two ways of PCB etching that we have discussed above. You know which chemical is used for PCB etching as well. Let’s get you through the PCB etching process step by step, so you don’t end up making any blunders and ruin your PCB:

  • First, you must design the board and the patterns you want on the PCB.
  • You have to be careful while cutting the copper plate that you would like to have to use for the printout.
  • Now print out the design on the copper plate.
  • Once you print the design on the copper plate, you need to iron the circuit from the paper. (place the plate on a wooden table, and the backside of the photo paper must be facing you)
  • It would be good to wear rubber gloves and place a newspaper on the floor, so the floor doesn’t get dirty from any etching solution.
  • You will need a plastic bowl to prepare the etching solution
  • Now dip the board in the solution slowly and very carefully, so the solution doesn’t get spilled all over the floor and on your clothes as well
  • Now the last step is cleaning and finishing. Take out your PCB from the solution carefully and use a clean cloth to dry the PCB
  • Don’t rub the cloth on the PCB as it might cause some damage to the PCB surface

Can you prepare a PCB etching solution at home?

You can prepare a PCB etching solution at home if you are a pro at this job. Do you know which chemical is used for PCB etching? Now you must know after reading all the information discussed above.

For preparing a PCB etching solution at home, you will need the chemical and a plastic box. Yes, take a plastic box and fill it with water. Now dissolve 2-3 teaspoons of ferric chloride. Once the solution is ready, dip the PCB in the solution for about 30 minutes.

The ferric chloride solution now reacts with unmasked copper, and it will remove unwanted copper from the PCB.

The final words:

You might have got the answer to which chemical is used for your PCB etching question. Well, we have mentioned and discussed two different methods for PCB etching. Wet PCB etching is more famous. It depends on which method you find easier to perform. Without PCB etching, your PCB is incomplete. Therefore, these steps hold quite important in designing and manufacturing PCBs.

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