Protecting your PCB

A completely cleaned PCB.
This will teach you how to protect you PCB foil pattern from oxidation. I am using a unetched PCB for demonstration. You would be doing this AFTER you etched you PCB.


















I used a cotton bud, you could get an appropriate brush to do the same. The trick is using clear varnish to the tracks BEFORE soldering. Here i am applying varnish to to top part of the PCB.


















This is what it looks like after the varnish is applied. It takes about 2 to 4 hours for the varnish to completely dry. This depends on how concentrate your varnish is. You can mix thinner in your varnish to dilute it if it takes too long. Also i do not recommend a very thick coat.

















This is what the PCB looks like after a few days. Oxidation set in. Notice the part of PCB varnished is not affected.




















This is the best part. Varnish not only protects your PCB, it also acts as flux which you don't have to wash off.



















Top view of the solder joint. It perfect. So it protects your PCB and functions as flux. You can solder while the varnish is not yet dry, but it tends to be sticky. So take care. Oh...if you don't want to get high while varnishing, use appropriate protection.















73.

Cleaning PCB

To remove of oxidation, grease from PCB

Any grease or oxidation will make it difficult for the solder to stick. If your PCB is unclean, the best way to clean it is to get some household veinger, pour in a container large enough to place your PCB in. Add half teaspoon of salt and stir it. Add half cup of water. Then place the PCB in this bath solution and stir/shake the container for about 1 minute or so... You should have a extremely shiny and a bit smelly copper. Rinse under running water. Dry and start soldering. This tip was given to me by 9M2CF, Uncle Chow.

Etch tank

Get a small fish aquarium to use as an etch tank. Big enough to place your biggest PCB into it. This one is 8"x5". Also get some air tubing and suckers to hold the tubing to the base of the tank.
You can get a small air pump, as displayed, or get a bigger one...More power, more bubbles. :-)
Heat one end the the air tubing with an open flame and then seal it using pliers.
This is what is looks like after it is sealed.
Using a fine sewing needle make holes in the tubing towards the sealed end. If holes are big, the bubbles will be big, I prefer many smaller holes and finer bubbles. Make holes the length of the tank.
Use the sucker the hold the tubing do the base of the tank.
I made a cover from cardboard and made a hole for tubing to fit thru. the board was cut at the back about 2" and rejoined using masking tape.
The cover is more of a protection from the bubbles splashes escaping the tank and staining anything around it.
Use water to test the tubing, once satisfied the the bubbles, (size of bubbles and the length of tubing where the bubbles released), drain water and replace with Ferric Chloride.

 

The tank is use to speed up the etching process. I tape a length of string one the back of the PCB and let it float on the etching solution. You will know it is done when you can see the PCB design  Refer to my older post.

I stopped using the air stone as it does not last and disintegrates over time.  You can also purchase from fish shops air tube that produces fine bubbles. Where is the fun in homebrewing in doing that... :)

PCB Part 5 (Soldering addendum)

:) Left this part out.

After you have soldered your components and tested your board. Now for the finishing touch. You can lacquer the Bottom of the PCB. My friend Basir uses florescent yellow spray paint and gives a light coat. This prevents the copper from oxidizing. Though not required, its recommended you do it. Other option is that you tin the PCB before soldering. I cannot get an even coating and don't like the way it looks. Getting a tinning solution for a neater even coat is another option but too expensive.


Also checkout this link on protecting PCB.

PCB (Part 5 Soldering)

Part 5 (Soldering)

And now, for the final chapter in PCB making, soldering. Though it may seem complicated, it is actually very easy. The best way to get a perfect joint is to practice, practice and more practice. You need a good soldering iron, solder remover (sucker), soldering lead, flux, “Helping hands”, soldering iron stand and metal clippers.

Remember, a higher wattage iron does not mean it get hotter faster. 20 to 30 watts is sufficient. A good iron to get is Hakko Presto or Dash. The soldering lead should be the fine 0.5mm type. Never scrape the tip of the iron. Wipe on damp natural sponge to clean it. Once you are done soldering, don’t force cool the iron, let it cool down naturally.

Any grease or oxidation will make it difficult for the solder to stick. If your PCB is unclean, the best way to clean it is to get some household veinger, pour in a container large enough to place your PCB in. Add half teaspoon of salt and stir it. Add half cup of water. Then place the PCB in this bath solution and stir/shake the container for about 1 minute or so... You should have a extremely shiny and a bit smelly copper. Rinse under running water. Dry and start soldering. This tip was given to me by 9M2CF, Uncle Chow.

It is entirely up to you to cut the component leads to size before or after you solder. I find it neater to do it before. Mount the component on the PCB. Touch the tip of the hot iron on both the component lead and the pad then touch the other side of the component lead and pad with soldering lead. Let it melt and flow around. Remove the lead and then the iron. Always clean the tip of the iron before and after soldering on a damp natural sponge..

That’s all there is to it. If you find that doesn’t work too well, dip the tip of the iron in flux for a microsecond, and then solder. Or melt a tiny bit of lead on the tip of the iron and solder the component lead.

I suggest that you practice on a vero board (strip board). Use discarded network or phone cable. Practice until your soldering is perfect. The whole process of soldering takes less than 2 seconds. You know you have a good solder joint when it is cone shape and shiny.

When soldering PCB ALWAYS solder the lower components first, example: jumpers (if any), resistors, diodes, transistors, capacitors, etc.

Check orientation of polarized components BEFORE you solder. ie diode, cap, transistor, IC.

	Strip board and some network wires for soldering practice
	Helping Hands are great for holding up project and a extra one can even be used to hold component in place while you solder.
	Top two joints are example of bad soldering. Bottom two joints are ideal

This concludes my lessons on PCB making. Thank you for your support. As usual, should have any questions, leave me comments.

Things to remember:

• When doing PCB layout, take into account for housing/casing.
• Label and store toxic chemicals in high and dry places where children cannot reach.
• Print in 600dpi or higher resolution.
• Examine printout for shorts and open circuit.
• Dispose of used developer in a safe manner.
• Examine etched PCB for shorts and open circuit.
• Always drill smaller holes first. For double sided PCB drill before you etch.
• Mount low components first.
• Soldering should not take more than 2 seconds per pad.

Additional stuff i left out... :)

Part 4 Etching and Drilling

Etching.

Before I continue, I want you to give yourself a pat on your back for job well done. J The etching process is same regardless of method used to transfer the pattern on PCB. Now; for the dirtiest part of the whole PCB making process.

The etchant is FeCl_3. Also know as Ferric Chloride. It can be obtained from any respectable electronic shop. Don’t get the solution. Buy the crystals and make the solution yourself. It costs less than RM5 for the crystals. WARNING: FERRIC CHLORIDE STAINS MAKE SURE IT DOES NOT SPILL ON YOUR CLOTHES, FLOOR OR ANY WHERE ELSE. The ratio for mixture is 1 to 3. You need hot water and a plastic container to mix the etchant. Use the whole packet, dissolve it. FeCl₃ is very toxic. The container with ferric chloride must be labeled and store in a safe place.

For etching, pour some in a deep container (used ice-cream container) until half full. Pour the balance in a bottle and label it. Container must be large enough to fill your largest project PCB. FeCl₃ is reusable, so don't dispose of it after use. Leave it in the container and cover it.

The etching process should not take too long, about 5-10 minutes. Depending on your solution strength. To speed up the process, get an aquarium air pump, air stone, some tubing and some suckers. Place the air stone in the container with the etchent. Tape a string to the top of the board. Place the board so it floats on the etchent. Then turn on the air pump. Within 5 to 10 minutes, you PCB should be ready. If left too long in the etchent, your tracks might dissolve. And if not long enough, your excess copper wont dissolve. 

It's a good idea to check the PCB every 5 minutes or so, if you are not sure. Once etching is done., Check the PCB for shorts and open circuit. The green layer of UV sensitive coating will still be on the tracks. Soldering with coating on is not recommended, because it takes the lead sometime to stick and the joint is not clean. This coating can be removed by rubbing isopropyl alcohol.

	FeCl3 Anhydrous
	The mixed, solution. Keep extra in bottle and label it.
	Air pump, air stone and sucker. Is optional, but increases etching time.
	Place PCB face down in and let it float. Turn on air pump.

Drilling


This is easy on the phenolic board. But a but difficult on the FR4. I use a high speed motor for RC toys and got the bits from Pasar Road (again).
You can use a 9V battery to power the drill, but i use an old PC power supply, modified, for my projects. Make sure the bit doesn't wobble when drilling. It usually does at high speed. I am using 0.8mm and 1mm bits. Couldn't find the 0.7mm bits. For double sided PCBs, drill the pads before you etch. For faster and cleaner drilling, use a Dremel high speed drill with flexi hose.

	The drills used.
	My PSU to drive the drills and test projects.

Next Part 5 .... The conclusion.

PCB Part 3 UV

Part 3

Before I continue, Let me tell you what you will learn and need in this chapter.

• UV PCB (Photo sensitive PCB)
• a little about the tracing paper
• constructing a simple UV exposure box
• constructing a PCB exposure unit
• mixing and using the developer solution
• doing a test exposure

The UV PCB

The photosensitive UV PCB comes in this packing.

The UV PCB can be obtained from Maplin at Pasar Road or any respectable electronics shop. This PCB has a special chemical coating that is sensitive to UV. This come is Paper Phenolic, FR4 Glass epoxy and CEM3 Glass epoxy. Also comes in various sizes. One board of 150mm x 300mm should last for quite a lot of small to medium size projects.

Tracing Paper

The paper we will be printing on for UV transfer is tracing paper. This is not the normal tracing paper, but a thicker kind. Used for plan printing. 1 A1 sheet of this paper cost me RM$2 and cuts into 8 A4 sheets. Remember print at 600dpi or higher resolution.

Tracing paper cut into A4 sheet.

UV Exposure Box

This you have to construct. You can opt to get a UV specially made for PCB transfer, more $$$.$$ or get the cheaper version. The difference is the time taken for exposure, 60-90 seconds compared to 5-7 minutes. Installing a 2^nd UV tube, about 2 to 3 inches apart decreases your exposure time to 2-4 minutes depending on your setup.

WARNING: Avoid yourself from exposure to UV.

	My simple UV exposure box Dimensions: 24” x 10” x 8”
	Inside lined with aluminum foil for reflecting back UV downward. This actually decreases the exposure time.
	Warning: Exposure to UV can damage you eyes. When lit, this is what it looks like when on.

PCB Exposure Unit

This is actually a glorified term for something that holds the PCB and the printout together. You can buy this, again at Pasar Road. To build one, you need a rectangle wooden chopping block, a photograph frame with glass, some small hinges, sponge and some kind of locking mechanism.

	Top view of the unit. The green stuff is the sponge. My unit measures 8” x 6”, with an exposure area of 6.5” x 4.5”.
	I lined the inside of the unit with aluminum foil.
	The locking hook. This is closed when PCB is in the unit so that the printout pushes down on the PCB.
	Back view. Small hinges required. Also notice that I have added legs to make it closer to the UV light.

Mixing the developer

Before I proceed any further, you will need to make a developer solution. What the developer does is, it washes away the photosensitive coating exposed to UV. You will then be left with the pattern that you printed.

The Developer

WARNING! WARNING! WARNING! The developer solution is extremely caustic. It is made from NaOH (Sodium Hydroxide) or in English, caustic soda. Keep out or reach of children and store in high place. The ratio required for developing is 7gm NaOH to 1 liter of water. My solution is 10 times more concentrated, 70gm to 1 liter. I use 20ml of 10X solution and add 180ml of water. This way I don’t have make the solution every time is need to use it. Keep the solution in a thick plastic container like empty milk or fabric softener bottle and label it! Store the flakes in an air tight container and label it. I honestly don’t know where to get NaOH flakes from. I know someone who knows someone who got it for me. If you want them, and eyeball often enough, I will help you get some.

	NaOH Flakes
	10X Developer. 70gm:1liter ratio. Remember to label the container.
	View on the other side
	Make sure the label is large. In case someone mistakes it as drinking water.

Your first exposure

OK, I have done my schematics and printed your PCB foil on tracing paper and made my developer. But for how long should I expose my PCB under the UV? To find this out, you need to do a test exposure. Download this test pattern. Remember, paper is placed with printed (toner side) on copper. By doing this you have mirrored your image. Cut PCB and paper to size and tape edges of paper to PCB. Normally you would not need to tape, but for this exercise you do. Once you have taped the test pattern to the PCB, use a business card, to cover numbers 1 – 9. Place in your PCB exposure unit. Expose No 10 to UV for 1 min. Then move to card to cover 1 -8, and expose for 1 minute. Repeat until No 1 is exposed for 1 minute.

Now you have a 10 minutes exposure test. If you have a high end UV, expose in blocks of 10 or 15 seconds.

This test determines you best time of exposure. Next time use this time to develop your PCB projects.

	Printout of my old test pattern
	Taped to the PCB on the edges.
	Excess tape on the back.
	Exposing No 10 to UV and covering the rest.
	Exposing No 9 and 10 to UV and covering the rest. Continue exposing every column for 1 minute.

Developing

Pour 20ml of 10X developer into a plastic container large enough to hold your PCB. An old ice-cream container will do. Then add 180ml of water to the developer. Remember always mix chemical to water and not the other way around. Place your PCB in the developer bath and in 10 to 15 seconds it should be developed. If not, try lightly shaking the container. If still nothing happens, remove the PCB, either by hand or if you have sensitive skin, you latex gloves or plastic tweezers. Take some 10X solution using a straw. Put 2 or 3 drops of it in the bath. Stir the bath and place the PCB back in. But if you measurement for the developer was correct, you should not have any problems.

	Using an old mixture bottle for measuring.
	Place the PCB in the bath and lightly shake the container.
	1-5 minutes is underexposed. Tracks are not visible or blurred. 6-8 minutes is good 6 being the fastest. 9-11 minutes is overexposed. Tracks are getting thinner and dimmer.

That’s all there is to it. Developing a PCB should not take more than 7 minutes. If you want faster results, use transparencies. Exposing time is much shorter; I got 3 minutes for best results compared to 6 minutes. But are more expensive. Remember to use transparencies for laser printer and not ink-jet printers. Those are not heat resistant and will damage you laser printer. Also 2 UV's decreases exposure time. The bath solution is not re-useable. So dispose of it, flush it down the toilet or the drain.

Now I have to go and prepare the next Chapter, Etching. As always, should you have any queries, leave me comments.

Next Part 4

PCB Part 2 (Printing)

Now that you have become familiarize with your PCB software, it time to learn about printing.

Before you print your foil pattern, let me tell you a little about the transfer method. You can use the toner transfer method or UV method. Since the toner transfer method is explained below, i will in detail tell you about the UV method.


Toner Transfer
The toner transfer method is done by using Inket Photo quality glossy paper.This method has been well illustrated by my good friend Basir (9W2BSR) and you can download his step by step guide on the toner transfer method. Reminder do not mirror the foil pattern.


Printing
I do my printing on tracing paper, the one used for plan printing. Or you could print on transparencies, which will result in faster transfer time. Set your Diptrace to mirror text only. Print the foil pattern only, selecting bottom layer from the print preview option. DO NOT MIRROR PCB FOIL PATTERN!

Or you can use Inkjet printer with transparency.

Next PCB Part 3

PCB part 1

Road to making a Printed Circuit Board

Before teaching how to make your first PCB, I will first outline what the steps involved are to make a PCB. These steps will be broken down in different posting. If i post everything in one posting, there will be too much to read and you might get bored. :)

1. Schematics design.
1. Convert to PCB.
2. Printing Foil (PCB).
3. Transferring Foil to PCB.
4. Etching.
5. Drilling.
6. Soldering.

Some topics will expand into different sub topics.

1. Schematics design.

Before you even try to make a PCB, you first need software to draw the tracks. From what I noticed on the net, most people prefer to use Eagle. You can try it out, but I use Diptrace.

Though I like the Eagle's component database, they way to locate a component is much easier than in Diptrace, but that’s all I like about it. I feel Diptrace is easier to use. Give both a try and see which one suit you best. Eagle has a limitation of 4" x 3", double layer PCB, while Diptrace has 300 pins double layer limitation. I have a friend working in a publishing company, and does his foil design in Illustrator. If you like, there even are templates available on the net for doing your foil patterns in Microsoft Paint. What is boils down, choose one that you are comfortable with. Whatever references I make will be to Diptrace. Or you can try others like TinyCad, Protel.Design Spark...

With either Diptrace or Eagle, you can draw your schematics. Then from your schematics you convert the can than play around with your components placement on the board for best routing of the traces. Or you can do manual routing.

If you get Diptrace, download the tutorial file. Go thru is and in no time you will be creating your own schematics, components and component pattern. It took me less than a day.

It is easier to start when you already have a project on mind. If you don’t have a project in mind, check the net for some simple projects, draw schematics in your software. Try playing around with component placement so that you don’t need jumpers. Sometimes jumpers are unavoidable, but for simple circuit there should not be any jumpers.

I think that should be enough for now. Next posts will cover PCB.

73's.

Next PCB Part 2