PCB making process update: Easy PCB at home
The process in which I used to make PCBs at home has changed a lot in these recent months.
Now I use Eagle CAD program to draw the board designs. The free version of Eagle allows to design 2 layer boards within 80mmx100mm size for non-commercial use. You can download Eagle software from http://www.cadsoftusa.com/downloads/
Later someday I’ll show how to extract a nice printable layout from Eagle PCB design for both copper layers and for legends.
I’ve found that Canon LBP2900B printer gives best ink concentration required for PCBs when compared to other printers like HP P1007 which I’ve used before.
Now I use glass epoxy copper laminates. I’ve used both phenolic paper laminates as well as glass epoxy ones and have found that the glass epoxy ones are better.
The G.E ones are surely priced double than the P.P laminates, but the G.E ones are durable and tough enough to bear much heat applied to the PCB during toner transfer or solder leveling or any other rough handling.
The POP ones bend and become very soft that they can be bend forever or break if those are exposed to the heat I use. The strength comes to GE ones from the fact that they are made of glass fibre cloth’s thin layers adhered one layer with another by some kind of epoxy resin.The same technique is used to make the tough and lightweight enclosures for aeroplanes above which a thin sheet of aluminum is layered.
Oh and all responsibilities for uneven exposure in photos to my camera’s flash. 😛
Below you can see I’m using a 10cm x 10cm copper clad board and a somewhat smaller size PCB design. The PCB pattern is printed upside down with a laser printer to a common photopaper. I’ve found that regular glossy photopapers makes better transfer than any other papers like magazine paper, etc. In my locality 20pcs of such papers cost only 80.
For transferring the toner to the pre-sanded copper laminate, a laminator as well as a household Iron can be used. In case you are using laminator, preheat it to 200°C and once pass the blank copper laminate through it and in second time, pass the copper laminate(careful, it’ll be hot) with the PCB layout facing down to the copper side. Then third pass the set again by rotating it 90° angle, that is you pass it this time left to right instead of up to down.
If you are using a iron, make it preheat to 80% maximum heat setting (cotton). Then when the iron is heated, press it to the copper laminate to heat it up and after 5-6 seconds, remove the Iron and put the PCB layout facing down towards the hot copper. Then again press the paper with the Iron at same heat settings. Be sure to heat it evenly in all sides and corners by dragging the iron in the plane. Do this until you see the white paper started turning into little brown. Stop by then. As my experience it takes 30-90 seconds depending on the board size.
No matter which heat source you’ve used, you need to cool he PCB slowly by putting it inside a book and press ing the book hardly. This will ensure there is no air gap between melted toner and PCB that might cause some toner to stick to the paper and not the copper.After 2 minutes, take the PCB out and gently peel the paper from the PCB. Don’t soak it in water as you might knew. No soaking in water is needed for these papers. Also soaking and peeling by fingers will require much time, but you can peel the paper off the PCB in few seconds and what you’ll get is shown below. If there is any breakage in toner, you’ll see small traces of black ink into the paper (See below), just fix those areas with any permanent CD/OHP marker.
After cutting a good visual inspection is necessary to find any broken tracks, etc and it’s the last time you fix them by marker pen.
Then I dip the PCB to a plastic container partially full with ferric chloride. I don’t throw used chemicals but store it by closing the lid of the container and always use used etchant and add fresh etchant to it whenever it becomes very weak.
After etching completes in around half an hour, it’s time to clean the PCB in tapwater. Use much water to completely remove any residuals of the etchant. True inspection of the board can be done by seeing it through light.
Now it’s time to transfer the legend to the top of the PCB. Here the same steps are performed as it previously done while transferring the toner for PCB tracks.
After cleaning the toner from the bottom of the PCB, the PCB looks real shiny like gems.
Next, I drill the holes using my hand drill. Unfortunately the small holes needed 0.8mm drillbits but I had 1.2mm in stock so the drilling obviously isn’t looking good, but it will work anyways.
Next step is tinning/soldering the track of the PCB to prevent the copper from oxygen/water from environment. Since this particular design had copper plane, it’s nearly impossible to neatly solder the pcb with soldering iron. For tinning, you need to solder here and there randomly with soldering iron. Then add lots of flux to the coppers and cover the PCB bothside with paper and pass it through 250°C heated laminator 4 times from each side totaling 16 passes. If you are using iron, heat it at maximum level and drag the iron over top paper and just drag it for 2-3 minutes. A lots of smoke will come from this step as all the flux will be used an the top paper will become brown burnt color.
Skip this step if you’ve used paper phenolic laminate because they cant bear this much heat and will be puffed into layers.
When this completes, remove paper from bothsides (the bottom paper was used to protect the legend from any scratches) and clean the PCB with a old toothbrush and Kerosene and you’ll end up with a nice looking PCB like the one below.
Now it’s time to put components and soldering them to get the project donw for which the PCB is made.
About the project: This in one of my upcoming projects and this will be published in this site in few weeks.