PCB etching is clean and safe. Recipe with citric acid and hydrogen peroxide

From the editor:

The article was inspired by a short comment by comrade sergey_esp. We have studied the topic, tested it practically, expanded it, deepened it, added all the explanatory photos and even the recipe itself. In total, the article was brought to the Datagorian canons.

It is difficult to remove ferric chloride from a sink or a kitchen towel. It's hard to explain the acid hole in my pants to my wife. I recently switched to the cheapest and cleanest method of etching printed circuit boards. Thanks to the unknown chemist who first described this method on the Internet. Unfortunately, I don’t remember where or who he is.

Later, I saw similar recipes many times on different sites on the Internet, and decided to add this cheat sheet to Datagor, so that it is always at hand and in the appropriate section. This method of etching boards is great for both beginning radio amateurs and elders.

To chemicalize the etching solution we need safe and affordable potions

☂️ Please note that there is no water in the recipe! ⚖️ This amount of solution is enough to etch ≈100 cm² of copper foil with a standard thickness of 35 microns.

Cleaning copper, coins, antiques with a special metal cleaner

™ metal cleaner copes remarkably well with copper deposits and will carefully remove dull and thermal stains from unpolished copper surfaces using chemicals and a gentle abrasive .

To clean copper coins or other copper surfaces, apply a small amount of AMWAY HOME™ LOC™ to the surface to be cleaned and lightly rub the surface using a buffing motion using a sponge or cloth. After cleaning, rinse off the paste with warm water and wipe the product dry.

The product will shine with purity and newness.

Cleaning copper products is quite simple. It is necessary to test the chosen method in a small area in advance to ensure its safety and effectiveness.

↑ How to use the recipe?

All this must be mixed before use in glass or plastic containers. The amount of ingredients can be changed proportionally, and more citric acid can be used
.

Etching time about 20 minutes

at room temperature, depends on the area of ​​the board. Increasing the temperature does not lead to a significant increase in activity, so I believe that heating is not necessary. It is important to stir the etching solution to access fresh solution and wash away reaction products.

The solution according to this recipe does not corrode hands and clothes

and does not stain the sink. Initially, the solution is transparent, but as it is used, it acquires a “sea wave”, greenish-bluish color.

Photo in progress, sent to Datagor Beso

(Minsk): “Indeed, it poisons quickly, poisons cleanly, and, most importantly, poisons cheaper than with ferric chloride.”

To correct LUT imperfections, a permanent marker, paint marker or nail polish is suitable.
The solution is not stored; it is always better to etch in a freshly prepared mixture
.

My version of pickling in a bucket of some kind of food. The solution is used very economically.

They also offer an option on the Internet that involves replacing citric acid with 70% acetic acid. I believe that this can only be done as a last resort, because we end up with a stink and working in a more dangerous environment.

How to clean copper from oxide and dark deposits using vinegar?

One way to clean copper is to use vinegar.

Instructions:

• Apply a little vinegar to the dishes and leave for a few minutes. After this, wipe with an old toothbrush and rinse off the vinegar with water.
• The acid will corrode the copper oxide that has formed on the surface of the cookware.
• You can remove plaque from copper products using a mixture of vinegar, salt, and flour.
• Mix fine salt, flour in equal proportions and add a few tablespoons of vinegar
• It is necessary for it to turn out to be a slurry. Apply this paste to copper products
• Leave for a few minutes, then use the hard side of a sponge or brush to wipe the products with force.

IMPORTANT: We do not recommend using large salt crystals, as this may cause scratches on copper cookware.

• If these methods do not help you, we recommend using a more aggressive method.
• It is necessary to place the dishes in vinegar and add two tablespoons of salt to it. Heat the mixture to a boil and immerse the copper items in it. You can boil them in this solution for a few minutes
• After this, rinse with cool water and rub until shiny with a soft cloth.

IMPORTANT: Before carrying out all manipulations, we recommend conducting a test. To do this, you need to apply whatever cleanser you are going to use to inconspicuous places and try to rub. If the item does get clean, you can continue cleaning and apply the product to the entire surface of the item.

Cleaning copper spoons

Preparing solutions at home

So, after carefully weighing all the pros and cons, you should choose the optimal etching method and prepare a solution for the experiment. Once again, we draw your attention to compliance with safety precautions during a chemical experiment. Even if you have extensive experience in handling reagents, you should not neglect your own safety, as this can end very sadly. For example, under no circumstances add more reagents to the solution than recommended, because this can not only lead to health problems, but also completely destroy an expensive copper product. You will find more detailed information on how to make this or that solution at home in the following sections.

Etching boards with peroxide and citric acid

Mix all ingredients in proportions: hydrogen peroxide-100, citric acid-30, salt-5.

Unlike etching solutions such as ferric chloride or sodium persulfate, this solution does not stain. The cost of such a solution is very small compared to others. The entire etching process takes no more than 15 minutes.

To draw the tracks on the board, I use nail polish and ink from a ballpoint or gel pen. I mix in a ratio of approximately 50 to 50. I take the ball out of the rod by pushing it out from inside the head of the rod with a regular sewing needle. Then I fill the varnish solution and ink back into the refill with a syringe. When it comes into contact with the printed circuit board, it begins to gradually come out of the rod, drawing tracks. Don't forget to dry it thoroughly before putting it into the board etching solution.

Persulfate etching

Ammonium persulfate is a fairly well-known chemical reagent, which in appearance is very similar to ordinary table salt and can be used for etching copper. However, it is immediately worth mentioning that after such a procedure, a special coating will remain on the metal, which will have to be removed manually. Well, the list of advantages of weed in this way looks something like this:

• ammonium persulfate is absolutely harmless to clothing and interior items;
• For a full chemical reaction, one key element is enough;
• a fairly high rate of chemical reaction.

Although one important clarification should be made regarding the first point. The reagent is harmless only if it gets on clothing or an object in small quantities. In large volumes it is capable of burning through soft tissue and even flesh.

Uses of ferric chloride

Often when etching printed circuit boards at home, ferric chloride is used. To perform the etching procedure, it is recommended to use a plastic or glass container with water poured into it. It should be noted that the water temperature should vary between 50-70 degrees Celsius. Otherwise, if the water temperature is higher than these values, the pattern applied with toner or varnish will gradually melt and then move.

To etch a board in ferric chloride, you first need to make a special solution. You need to take ferric chloride and add it to the water in small portions, constantly stirring. It is worth noting that when making such a solution, it is recommended to use a respirator, since when ferric chloride gets into the water, a chemical reaction begins, which results in the formation of fumes harmful to human health.

As a result, after adding ferric chloride to the water, you should get a composition with a brown tint. It is worth noting that if the resulting mixture has a darkish greenish tint, then the chemical reaction process will take much longer.

To etch a printed circuit board, it must be placed in the resulting solution so that the printed conductors are at the bottom. When etching double-sided boards, it is recommended to lower the layer that contains the maximum, high level of density to the bottom of the container.

To fix the board in the solution, you can use small pieces of foam or a thread stretched longitudinally over the container. When etching a board that is in a solution, it is recommended to periodically shake it. The average duration of etching in a ferric chloride solution can range from 10 minutes to 1 hour.

It should be noted that the etching time in a fresh, just prepared solution can be about 3-30 minutes. This is due to the fact that the speed of chemical processes is affected by both the concentration of the solution made and the water temperature.

Preparation of copper sulfate solution

If you decide to start etching copper using copper sulfate, then for this you will need not only the active substance, but also ordinary table salt, as well as water and a container. All components must be mixed together in a 1:1 ratio until a common consistency is formed and the salt is completely dissolved in water. Copper must be placed in an open vessel for several hours until it acquires a characteristic shine.

Do not forget that copper sulfate vapor can be quite toxic to humans, therefore, when etching copper, safety rules should never be neglected. It is best to conduct experiments outdoors or in a well-ventilated area. It is also recommended that you use a respirator to prevent harmful fumes from entering your lungs as an additional precaution.

Preparation of a persulfate solution

First you need to find a suitable container. It should be made of glass and not be too deep (although the volume largely depends on the size of the copper product). Pour a small amount of powder into the vessel, then fill it with running water. As soon as it is possible to achieve a homogeneous consistency, place the copper product in the bowl and close it with a lid.

As mentioned earlier, etching copper with persulfates can leave a residue on the precious metal piece that needs to be cleaned off. The easiest way to do this is with hydrogen peroxide and hydrochloric acid, mixing them together in advance. For every 100 milliliters of liquid substance you will need to put two tablets of hydrochloric acid. After this, copper is added to the container and kept in the composition for several hours.