As one of the most essential steps of PCB manufacturing process, etching influences the PCB products a lot and if you are curious about the PCB etching details, please check the content below. This article offers insightful information regarding DIY PCB etching while touching on steps to follow, tools that you may need, and safety measures, among others.
What is PCB etching?
The PCB etching merely is defined as the selective removal of material from the surface of the Printed Circuit Board with the aid of the chemical action of an etching agent. Etching usually entails the removal of copper areas that are not needed on the completed Printed Circuit Board. The process of etching can be carried out by placing a cover that can shield the parts of the laminate and thereby excluding the copper layer. The PCB Etching is an easy and economical procedure that can be carried out at home or in the lab.
PCB etching Pen
The PCB Etching Pen is more like a water-proof pen enclosing permanent ink. The ink contained in the PBC etching pen has properties which can resist etching. The pen has a nylon tip that enables fast manufacturing of the printed circuit boards. An example is its use on Copper printed circuit board; Circuits can be drawn on plain copper laminate and then etched in Ferric Chloride or etchant solutions, this is allowed to dry for few minutes, then immerse the board in etching fluid until you confirm that the copper is dissolved. After the etching process, the ink can be evacuated with the aid of cleaning fluid or Printed Circuit Board Cleaner. After this processes have been successfully carried out, then the circuit board is ready to be drilled and assembled.
PCB etching acid
The PCB etching chemicals used industrially
Copper etching PCB
To get rid of undesired copper from copper clad substrates to form electronic circuits, two methods are discussed. They include;
Mechanical etching: in the mechanical etching, a special cutter and a machine tool are used to get rid of a narrow strip of copper from the boundary of each pad and trace. In doing this, the circuit elements are electrically separated from the rest of the foil.
Chemical etching: the chemical etching depends on the activities of a corrosive fluid to chemically disintegrate away undesired copper to clarify the desired circuit. In this process of chemical etching, etching is generally done by full immersion of the board in the chemical; an etching resist used to protect the desired copper from the etchant.
PCB Etching Kit
The PCB etching kit comprises of different tools (combining matching materials with chemicals) that can be utilized in fabricating the printed circuit board from the scratch to the completion. Now that you are familiar with the fundamental’s of PCB design, it is often difficult for starters to choose the suitable etching tools to fabricate their printed circuit board. The only difference that can be made with the tools is selecting the best out of various available ones in the market.
Although After merging the tools and chemicals, it might still not yield a perfect result, and this is because the chemicals might not be in a balanced ratio or the materials may not fit together perfectly. It is hard getting the small drill bits for making the PCB holes, and due to this reason, the PCB etching kit packages the required drill bits. Included in some starter’s PCB etching kit is a small dc driller motor that can be used in making the holes. The material’s quantity ratio must be carefully selected to avoid needless components. As time goes on, the skills to PCB fabrication can be perfected.
PCB Etching Solution
When we refer to the cheapest and readily available solution for PCB etching, then we are referring to ferric chloride. The ferric chloride is available in the form of a liquid, or in concentrated form, which must then be diluted. When this solution is used, immerse your PCB board into the liquid, wait for some little while and check to know how far it has gone.
Though heating the liquid can be of great help, it is not necessarily required. The ferric chloride is cheap, but it cannot be used over again, and also, it is not environmental friendly. Therefore after use, it is essential to dispose of it properly at a waste site.
Another solution is the Ammonium persulphate which is available for copper etching PBC, and it is often used in etching circuit boards. The Ammonium persulphate is a powdery substance that requires the addition of water to make it a solution. To ensure efficient etching of copper, the solution must be maintained in a hot state; ammonium persulphate decomposes on heating.
Due to this reason, it is mandatory to add a new solution everytime copper is to be etched and safe handling of the chemical should be observed. The hazardous effect of Ammonium persulphate is that it can cause skin irritation.
Materials required to etch with the ammonium persulphate successfully includes; Chemistry goggle, Gloves, Mask, Glass containers, Distilled water, Scale, Plastic spoon, Ammonium persulfate, Glass stirring rod.
PCB Etching Process
The process of etching involves the careful transfer of the pattern to the metal with the aid of a material that can resist the dissolving action of an acid. Metals are protected in areas where this resist is applied and are etched in areas where they are not resulting in a raised pattern. In this article, a “press ‘n’ peel” paper (PNP paper) would be used to describe the etching process.
The PNP paper is a versatile resist and a type of blue acetate film. The paper has two sides, one side is shiny, and the other side is matte, the matte side is used to transfer patterns or images onto the metal. The pattern will transfer as a mirror image, so if the direction of the pattern is essential or includes lettering, it may be necessary to copy the pattern to clear acetate first and flip it so that it will be reversed on the PnP paper.
Materials used as the resist
Different materials can be used to resist, including:
A black permanent marker and Rubber stamps
Press-on letters and Lace stickers, etc.
Also, we have traditional types of resist, and they include:
1.Lacquer
2.Shellac
3.Nail polish
4.Electrical tape
5.Paint
6.Contact paper
7.Asphaltum
8.Rubber cement
The materials needed for PCB etching will be highlighted, and it is important to note that the availability of materials to work on can lead to a more yielding positive result. The materials include:
1.Ferric chloride
2.PnP paper
3.Metal Shear
4.Jewelers saw
5.Laser printer or carbon-based toner photocopier
6.Brass, copper, or nickel for etching in 18, 20, or 22 gauge
7.Alcohol
8.Iron
9.Heat-resistant surface
10.Scouring pads
11.Black permanent marker
12.Sandpaper
13.Nail polish
14.circuit board shopping, various things might get you confused. Whether you are going for a single-sided PCB, a double-sided PCB, or any other type of PCB, You can Contact paper
15.Nitrile gloves
16.Styrofoam, 1-in. thick
17.Double-sided tape
18.Glass dish or disposable plastic container, minimum 6 in. (15.2cm) square
19.Safety glasses and a Dust mask
20.Apron
21.Baking soda
22.Acetate
23.Brass brush
Steps involved the PCB etching process
1: Transfer your design to the “press ‘n’ peel” paper
Here, the preferred design is transferred to the matte side of the PNP paper with the aid of a photocopier. The photocopier is adjusted in such a way that the darkest image is given without smudging clear areas. The design or image that has been photocopied will serve as a resist on the metal. The ideal heat required to transfer designs or images with the PNP paper is determined just below the temperature at which the backing film on the PNP paper starts to distort or collapse under pressure, and due to this, it is important to run a foretest of the iron to use since they vary in temperature. It is more advisable to use iron set one or two below maximum when transferring the pattern to the metal.
2: Snithe the metal
Often, a jeweler’s saw or metal shears are used to cut the metal to almost fit with the image or design. Make sure the metal is flat and clean its surface with a sandpaper or scouring pad. Rinse with water, dry, and wipe the surface of the metal with alcohol right before attaching the PNP paper, and ensure to hold the metal by its edges while performing this operation.
3: Apply the PNP
When you cut the metal, do not let it fit perfectly with the pattern but make sure to leave a metal border of about 6.5mm around the pattern. Cut out your pattern or image from the PNP paper and place the metal on a heat resistant surface. Position the PnP paper on the metal, with the matte side facing down and apply heat throughout the surface with an iron. During this process, the copper plate becomes very hot revealing the image through the paper’s film backing.
4: Separate the PnP paper from the metal
Wait for some time till the metal cools, separate the PnP paper from the metal and be observant enough to conclude that the pattern has correctly transferred and if otherwise, return the PnP paper to its position and apply heat again until you are satisfied with the result.
5: Get ready to etch
With the aid of a know more about the defects and probable solutions to PCB problems? contact paper, cover the back of the metal and coat the edges to prevent them from etching. Resist like nail polish, etc. can be used. Obtain a piece of expanded polystyrene foam, also known as styrofoam and join it to the back of the metal with double-sided tape. Ensure the area is well ventilated and you are on the apron, eye protection, and gloves throughout the process.
6: Etch the metal
Put a sufficient quantity of ferric chloride into a plastic container to aid floating of the metal, shake the plastic container gently, cover the container and leave the metal for some hours. A shallow etching can be achieved in minutes, usually 35-45.
7: Remove the PnP resist and clean the metal
Avoid removing the metal from the ferric chloride with your bare hands, but rather, wear nitrile gloves or plastic tongs in performing this process. To neutralize the ferric chloride, immerse the metal plate in a solution of 2 cups of water to a quatre cup of baking soda. Rinse in clean water and remove the tape. The PnP should be removed with a scouring pad and acetone and do the final touching with a brass brush and soapy water.
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