This post continues from my previous post, where I developed the Music and Lights PCB using the UV exposure method. Once an etch resistant image of the layout is successfully placed on the Copper board it is time to do the etching. Etching is the process of removing unwanted Copper from a Copper clad board.
The etching solution I am using is called Ferric Chloride, a corrosive chemical that will dissolve exposed Cu and pretty much any metal. It also leaves a stain on pretty much anything it touches. When working with Ferric Chloride, it is very important to be in an area with good ventilation as it tends to produce a strong fume (specially when you just open the bottle or container used to store it)
Compared to the photoresist developing process, the etching process is slow. The amount of time taken to etch the board depends on the board size, temperature, amount of etchant and circulation. I finished etching my board in about 40 minutes.
And these are the steps, continuing from the previous post
Warning: Ferric Chloride is corrosive. Wear safety gloves when handling. Work in a well ventilated area.
Step 20: Pick a plastic container and place the Cu board with the etch resistant layout image inside.
Step 21: Pour Ferric chloride into the container until the board is completely covered. Do not dilute with water.
Step 22: To increase the etching rate agitate the solution every few minutes by tilting the container back and forth. Examine the board and flip the board every 5 minutes for the first 20 minutes or so.
The exposed Cu will start to disappear from the edges first. When the exposed Cu has disappeared from about half of the board start monitoring the process more frequently. If left for too long in the etching solution it will start eating through the etch resist as well.
Step 23: When exposed Cu from both sides of the boards is etched away remove the board from the container and rinse with plenty of cold running tap water. Dry the board with tissue or soft cloth.
As you may notice in the image above, the right side of the bottom PCB layout got a bit eaten away by the etchant. This is because this side was over exposed during the photo development process. Fortunately it is not too bad as the affected area is mostly the ground plane. However, I will have to take extra care when soldering components to ensure that good connections are made.
Step 24: Use tissue paper and nail polish remover to wipe off photoresist from the board and expose the Copper.
Step 25: If necessary, trim the edges of the board with a fretsaw.
Step 26: If you have through-hole components, drill the holes with a PCB drill.
Tip: I used a 1 mm drill bit for larger components like switches and power connector, and a 0.8 mm drill bit for other components.
That’s it! Now in my hands I have a home made PCB for the Music and Lights system.
Now you might be wondering why in the world go through all that trouble to make your own PCB at home when you can get a better one manufactured professionally. I totally agree that it makes more sense nowadays to get your PCB manufactured, plus you will have a solder mask and a nice silk screen too. But making your PCB at home is fun, and you get to control and see the whole process. It is a path with many challenges and finding ways to overcome them is the best part.
Now to the final note about making PCBs at home,
What to do with all the chemicals when you are done with them
You shouldn’t dump used chemicals down the drain, nor flush it down the toilet nor throw in the dumpster. They will destroy your plumbing and could do terrible damage to the ground water and environment.
Safe and easy way to dispose of them is to contact your local hazardous waste disposal company. I store my used Ferric Chloride and photo developer solution in plastic containers, usually the ones they came in, until a sizable portion is ready for disposal.