Faster PCB Etching with Ferric Chloride

At times I am very impatient when I am working on a project and want to assemble a working design. If the design is simple enough I will assemble it on a copper perf board, but often the component count is high enough where a PCB is a much better solution. If the design has a really high component count with lots of surface mount components I will send the board out to a fab house only to have to wait a few days to a month for it to return before finally finishing my project. Sometimes this is much too long. What if I want to have a finished design that night? The solution is etching... more specifically fast etching.

I have been etching my own boards with ferric chloride for years with great success. The only downside to this is time. A larger board will take 20 to 30 minutes (sometimes even longer) to etch in the solution. It also requires agitation to keep it etching effectively by keeping the fresh solution contacting the copper. This requires you to either shake the container of ferric chloride or push the board around constantly in the solution as it etches.

My solution was to have something agitate the board for me.



This was my first test of using a VWR vortexer to speed up the process. This device was designed for a lab environment to hold test tubes, beakers, and such. The lower plate rotated around causing a mini vortex within the containers solution that would be placed on it. I have modified it to hold a glass container full of ferric chloride to agitate the solution for me. The glass container I am using is perfect for the job. It is a food container called 'Glass Lock' and has a tight fitting plastic lid that locks into place on all four sides. Nothing will be leaking out of it. I bought two of them for the lids. One has small holes that I drilled to allow fumes to evacuate while the second lid is unmodified to store the solution.

Ferric chloride also works better when it is warm. To facilitate this I mounted a good sized peltier junction to the bottom with an epoxy heatsink compound and supplied it with a 12V 2A power supply. It heats the solution up to about 110 degrees Fahrenheit, still below the maximum ferric chloride recommended temp of 135 degrees.

The VWR vortexer as it arrived has an adjustable speed control, the only issue was it had a minimum speed of 1200rpm. This is much too fast for what I needed. Opening up the unit I found two adjustable resistors that let you adjust the minimum and maximum speeds of the motor. I was able to adjust it all the way down to a nice ~200 rpm, perfect to keep the ferric chloride in motion.

In goes the PCB:



With the lid locked on and the vortexer switched on, I checked the board every five minutes.



Total etching time was about 12 minutes, less than half the time of any previous etching I have done. After a quick sanding here is the finished board before tin plating:



Not perfect, but not bad for less than an hour and a half time. I had the design drawn up in eagle in about 45 minutes, the rest was transferring the design to the copper and etching.

Future improvements will be to add a second peltier device to get the solution up to a higher temperature and to also add a digital temperature gauge to make sure the solution does not get too hot.

Custom PCB for Toshiba TCM8230MD Camera

I recently purchased a few small TCM8230MD CMOS cameras made by Toshiba from SparkFun. I plan on using the camera for some machine vision experiments as they are controlled by an I2c bus and have an 8 bit parallel video out with sync and clock. This makes them very microcontroller interfacing friendly. I plan to use a higher end PIC micro to receive the picture data and process the received video frames. The only issue is that I didn't realize how small these cameras actually are until I tried to use one.

My first attempt at soldering didn't go so well as the solder pads on this device are extremely small. Since no breakout board is available and the lead spacing on this device appears to be non-standard, I went for a custom PCB design.

I made the initial pattern in Eagle using the dimensions from the datasheet to space the solder pads for it, than drew simple traces to solder pads for two headers. I then used the instructions here to transfer the trace layout to a copper PCB.


A nice thing about this simple board is that I didn't have to worry abut mirroring the layout when printing as the orientation of the camera doesn't matter. Once the board was etched in Ferric Chloride, it looked like this:


Not bad for a quick design, there was one weak trace that was etched too much but a little solder will fix that. One note about etching, It took much longer to etch than anticipated. About 20 minutes was needed with me agitating the board for the last 10 minutes.

A reflow procedure was used to solder the camera down, I did it with an electric skillet. After reflow, a quick test showed no shorts and inspection of the pins to pads looks good. I plan on starting to use it tonight.

Now that I have made the board, I would have changed a few things. I should have made pin 1 on the camera line up with the standard pin 1 location on the board. I should have also made all the header pins along one side of the board instead of two so I could use right angle headers to mount the camera vertically. I also didn't forget to drill the holes in the board for the headers, I purchased new PCB drill bits online and they have not arrived yet. I'll just solder jumpers to the pads for now. Yes i'm impatient.