DIYPCB.com is intended to be a source of information for electronics and robotics hobbiests who want to produce quick turn prototype PCB's in their home shop.
If you've come here with a circuit board design ready and are looking for information on how to produce the PCB, start under the section titled Chemical Etching.
If you're looking for information about how to design and lay out a printed circuit board you should start under the section titled Circuit Board Design.
Thanks for visiting and enjoy the site.
My early experience with hobby PCB Design
The first circuit board I ever designed was way back in my first year of high school. I remember bieng almost obsessed with the idea of making it very small. At the time my teacher discouraged the idea. I'm sure he was impressed by my initiative, but he knew the reality of how complicated miniaturization makes the process. I’m confident autorouters and pcb design programs were around at the time. However, in a poorly funded public school things like cad software might as well not have existed. The classwork was done on a sheet of graph paper and then completed on a mac. Our class only had one computer to share between thirty to forty students so as much of the work had to be done manually as was possible.
The computer was not equipped with cad or design software. I don’t even remember it having a color monitor. The actual design was all done by hand on the graph paper before we students ever got to use the computer. What we did use the computer for was a simple paintbrush program. It was about the equivalent of the paint program that comes included with windows today. The paint software had the most basic set of features. Copy, Paste, Pencil, Eraser. The instructor had created a file with icons of some basic pad layouts and saved it so we could copy them. We would paste a picture of the pads to match what we had drawn and then use the pencil and eraser tool to draw traces. The final step on the computer was to print the design out on a dot matrix printer. From there we darkened the lines with black ink to produce our camera ready artwork.
The best piece of advice I can offer from this experience is to use the space available to you. Just because all of your components will fit into one square inch of board space doesn’t mean they have to. Think about where your board will be used. If you’ve got plenty of room to mount a 4×6 board its only added frustration to try and shrink it down. Over the years plenty of my DIY projects have suffered and failed due to my unwillingness to spend a few extra bucks doing it right. FR4 circuit board stock is not expensive. I'm ashamed to admit how many times I’ve spent hours trying to shrink a project down so I could fit two of them onto a piece of blank copper clad. I’ll admit that if you are going to mass produce your design it makes sense to optimize your design. However, if you are only making a few one off's don't waste time shrinking things down.
Basic Circuit Board Layout Principals
Let me start by saying that as a hobbiest, I’ve never designed a board that needed more than two layers. Even at the two layer stage things can become complicated. I think the first step in designing a good circuit board is starting from a good design. The schematic design if well made will have the parts of the circuit segregated. A quick look at those parts will let you visualize and sketch a block diagram.
Lets use a small microcontroller circuit that records and plays back sound as an example. This board would likely be built from multiple building blocks. One section would be devoted to the power supply. Another would be the microcontroller itself and its support components. A third section would be a timing circuit with either an oscillator or a time chip. The last section would be an amplifier with speaker and microphone connections. Every large circuit is essentially a group of smaller circuits interconnected. If you go back to your schematic and gain an understanding of the building blocks in your circuit the design process will simplify itself.
Circuit board design is an art. Nobody can tell you how to make good art. However, Having written that, I can say it is still pretty easy to spot a bad piece of work.
A good portion of a design comes from visualizing where the board will be used. Plan out mounting holes, heat sinks, and visualize the flow of the circuit. Put inputs at one edge of the board and outuputs at the other edge. Inbetween the input and output chain together the building blocks that make up your circuit. Then adjust things to add your personal artistic touch. Aim for a design that has everthing where it makes functional sense. Finally take the time to sign your work. A logo embedded in the copper will put the perfect finishing touch on your work. Including your signature does serve a purpose. Nobody likes to admit they did a bad job. By signing your board you force yourself to do your best. A really good design boils down to a matter of personal pride.
Component Placement
To start placing components on your pcb design, you should already have a block diagram. At this point its time to move from the paper and pencil stage to a piece of computer software. For my designs I use Eagle Layout Editor by Cadsoft. Cadsoft has a great business model where they kindly allow us to use their software for education. In the layout portion of the software input your schematic so the program knows what pins of what components should be interconnected. The technical term for this is creating a net list. As you switch over from the schematic portion of the software the netlist and ratsnest diagram is automatically generated.
Once you have your parts imported into the design software you will get what is known as a rats nest. A rats nest is a jumble of interconnected parts that shows all of your connections as a straight line from one point to another. This is where you begin component placement. Start by dragging all of the parts in each block of your block diagram to a pile near where you want that block to be in your design. Then begin arranging indivdual parts by spreading them out from each pile.
Bypass Capacitors, by design are used to filter the supply current to power hungry IC’s. If your design uses bypass capacitors, They should be placed as close as possible to the chip they are filtering. Other components may require special placement as well. Voltage regulators, Heat Sinks, ect.
One of the things that separates an amature board from a professional looking one is the care taken in placing the parts. It is an aesthetic standard to line resistors up into banks like chairs on the deck of a ship. Simmetry is the key. Microchips that come in a DIP dual inline package should all have pin one facing the same direction. The positive side on electrolytic capacitors should all face the same way. These are just guidelines. If it takes turning a chip around backwards or mounting a part on the bottom of the board to simplify your design, go for it. One thing to remember though is that later on when you or someone else assembles your board if just one chip is backwards the chance of soldering it in wrong goes way up. Design for simplicity.
Circuit Board Markings
Since we are dealing with hobbiest level pcb’s, the odds on getting a screen printed component marking layer aren’t real good. You could do it, but the effort is far more than its worth. Instead make an effort to put markings right on the copper layer to help keep things simple. Normally microchips in the DIP package have pin one marked by changing the shape of the pad for that pin. The standard method is to have all rectangular pads and then make pin one an oval. For capacitors use a small plus sign next to the positive pad or change the shape of one pad.
As you are placing your components be sure to leave clearance around mounting holes. Often mounting the board requires hardware. Washers, nuts, bolts and posts can short a trace if you don’t plan ahead for them. Also be sure to leave space to sign your work. You can draw your insignia right in the Eagle software if you like.
If you insist on having clear printed board markings it is possible to make them using the toner transfer method. What is required is to repeat the transfer process one additional time using a mirrored sheet after the copper FR4 board is fully etched and cleaned. Its difficult to get toner to stick to a rough copper surface. Getting the transfer to stick to the smooth epoxy fiberglass board is worse. I find its rarely worth the additional effort.
Making Multilayer PCB's
At this stage you should have a strong idea of the form factor your board will need to be and how your components are going to fit. Once your design reaches a certain level of complexity it becomes impossible to route all of the traces onto just one layer. If the design you are working on goes past this point you have a decision to make.
If your board is just barely too complex to route on a single layer the best option is to still make it a single layer board. Line up the traces that would have to go onto the second layer so they are a short straight line between vias, and wont interfere with coponent placement. Then use jumpers to connect traces that were impossible to run. You will have to find the right balance here for how many jumpers is too many. Going from a single layer board to a multilayered PCB really complicates the process. If you would have to solder in a few hundred jumpers a multilayer pcb design is clearly better.
A VIA is a trace that passes through the board to connect separate board layers. You can reduce the number of via’s by using components legs to connect different layers. If you were having a rapid turn board house produce your pcb's you would find that they charge more the more vias you have. It is an intensive process to drill between layers and plate the holes with copper so connecting the layers raises your board cost. We're doing the board making ourselves, but the concept is the same. More crossing between layers means a more difficult board to produce.
There isn’t a whole lot to know about multilayer boards. If you can handle routing the copper trace across one layer I’m sure you can figure out how to run it down to a second layer and back up. The process is fairly intuitive. Multilayer design is a method to improve routing density. Things get complicated if you get into buried vias, blind vias, and through hole plating. Those subjects are beyond hobbiest grade printed circuit board manufacture. Even with the most complicated designs I have done I have never needed to go beyond two layers. One practical piece of advice I can offer is to check your design carefully. Thingss get mirrored when you put traces on the opposite side of the PCB and that leads to errors that are difficult to spot.
PCB Laminant Selection
If you reach the point where you must use two or more layers your first obstacle to overcome is how to align the circuit traces on both sides or layers of the board. A typical piece of blank stock is known as FR4 copper clad. The FR4 is the name of the fibreglass material inside and copper clad is the copper sheet that is affixed to the face of it. FR4 comes in various thicknesses and can have copper on just one or on both sides. In addition the thickness of the copper varies.
A PCB Stackup can allow a hobbiest to produce a multilayer pcb. Two to six layers and blind vias are possible but you have to be pretty resourceful to make something like that work. At that level its probably time to start thinking of using a boardhouse. The trick is to select a very thin fiberglass stock and produce each layer independant of the others. Each layer gets stacked up and interconnected to create the multilayer board.
If you plan to etch your board using a chemical process the thinner the copper is the better. The etchant dissolves the copper, so the less time your board spends in the etchant the less likely it will dissolve enough to break a trace. Thinner copper dissolves more quickly so your board spends less time in the bath. Certain design applications will be an exception and require you to have thick traces. The more copper present the less resistance there is in the traces. High current projects need the extra copper to dissapate the heat and limit the trace resistance.
My own personal choice for laminant is a thin FR4 and single sided stock. If I need a two sided board I make both sides as separate boards and then join them. I stick with the thin copper layer as I haven’t ever really had a need or desire to work with high current in any of my hobbiest projects. If you do decide to use a laminant with copper on both sides there are various tricks to to getting the two layers to line up. One is to drill through the board and use a pin to line up the artwork. Another is to cut the board to size and then make the two pieces of artwork oversized so they overlap the edges of the board. Then tape the two pieces of artwork together with the board stuck between them.
Chemical Etching Safety Tips
Before you get started etching circuit boards there are a few things you should know about chemical safety. This section applys to both personal safety and environmental safety. While this page contains my suggestions and tips, it by no means should be concidered complete or authorative. I urge everyone to use due diligence. Before using any chemical familiarize yourself with its proper usage.
- Always wear appropriate safety glasses. Use goggles when using chemicals.
- Search for, Print, and Read the MSDS sheet for every chemical you buy.
The M.S.D.S. Materials Safety Data Sheet is available for every chemical you can buy and contains handling instructions, safety risks, emergency procedures, allergy information, ect.
- Wear a smock or apron to protect clothing.
- Keep your working container inside a liquid tight tray so spills can be contained and chemicals recovered.
- Avoid fumes by working near an open window or outside if possible.
- Clearly mark containers you have mixed etchant in. Use spray paint and then a black marker.
- Store chemicals in a locked metal cabinet. Preferably with ventilation to the outdoors.
- Never dispose down the drain or into the ground. There is always a way to recycle it.
- Don't use ferric chloride etchant.
Ferric Chloride is recycleable but will require it be sent to a specialist to recycle it. It is not a hobbiest frendly chemical.
- Do use Peroxy-Hydrochloric based etchant.
It is a little more work to maintain, but a peroxide hydrochloric acid etchant can be reconstituted and reused indefinately. A small amount will last a typical hobby user a lifetime because it can be stored and re-used forever.
Process Overview
The process of manufacturing a do it yourself printed circuit board can be broken down into several easy steps.
- Prepare the blank copper clad substrate.
- Print the mirrored artwork onto a transfer material
- Transfer the artwork onto the bare copper pcb stock
- Prepare the pcb etchant solution
- Submerse the prepared board in the etchant and agitate.
- Strip away transfer material.
- Drill holes for board mounting and through hole components.
optional: Print and transfer board markings onto the finished board.
optional: Tin the traces to prevent corrosion.
Preparation of the bare copper PC Board
Thinking way back to my electronics courses in high school I learned a few tricks that have become second nature now. Back then we didn't use toner transfer to make pcb's but at least one of the tricks we learned in preparation of the copper board suits the toner transfer process quite well. A Scotch Brite pad and Ajax Cleanser are just about the perfect tool for preparing the surface.
When you purchase PCB laminant it will likely be coated with something to keep the copper from rusting. This coating is probably not visible and is likely a thin oil or wax. Before you can iron the toner onto the copper this coating has got to go so the toner will stick. Even if you could find a chemical to remove the coating, without abrasion, the surface of the copper is too smooth. A quick scrub with a scratchy cleanser will remove the coating, make microscopic grooves in the copper surface and remove any oil on the board from your hands.
You will probably want to wear rubber gloves once you have cleaned the board as simply touching it will transfer oils from your hands to the surface of the copper. This may seem like overkill at first, but once you've tried it you will discover its true. You can actually see your fingerprints on the board when you touch it even with clean hands. Back in school we used this technique to get a light sensetive film to adhere to the copper. It works equally well with toner and makes the difference between a half transferred image and a near perfect board.
I've often read the suggestion to use steel wool as an alternate. It is my understanding that using steel wool works equally as well but the idea may have drawbacks. Someone suggested that microscopic bits of steel become embedded in the copper and that they will promote rust and lead to premature failure of the PCB. I've never seen it happen though and I find it hard to believe the effects could be that profound. So if you don't have a scotch pad and cleanser on hand you might try steel wool.
Printing the artwork onto a transfer sheet
When making a hobbiest PCB board there are a few tools that are essential. The first of these tools is a laser printer. For my own use I have a laserjet 1012. It is not the ideal printer for the job but you can achieve good results even without a great printer. You can take your artwork to a copy center and have them print or copy it for you if you don't have access to a laser printer. There is no way to do a toner transfer using an ink jet print. The reason is simple, in order to transfer the toner your printer has to actually use toner!
The method I use to create the transfer is fairly simple. First I setup the eagle cad software to print just the traces pads and vias on one side of the board. I print a copy on plain paper using all black and check that it comes out correct. Next I cut a small piece of inkjet photo paper just larger than the image and use a laser label to stick the edges of the photo paper over the image. Then I reload the paper into the printer and run the job again.
I feel its important to note at this point that yes I am using inkjet paper in a laser printer! No it wasn't designed for that. Glossy photo paper has a coating designed to soak in ink and make it appear glossy. This coating does not soak in toner so when you print on gloss inkjet paper with a laser printer the toner doesn't stick to the paper very well. Normally one would not use inkjet paper in a laser printer for exactly that reason. What we're doing is exploiting that normally unwanted property.
I've read dozens of arguments and suggestions on what exactly makes the best photo paper to use. In my experience I've found that practically every photo paper I've tried works as long as the board is well prepared and the ironing process is done well. I've even had some measure of success using an inkjet transparency. As a general rule though the cheaper the photo paper the better. Since we are exploiting a flaw in the paper a low budget paper often has more of a flaw to exploit.
One final suggestion on printing the transfer. If you are using a home laser printer play with the settings a bit. The objective is to get the copy as dark as possible. Turn off toner saver mode, ect. A darker copy wastes more toner, but thats exactly what we want. A thick layer of toner on the printout gives us more material to work with during the re-melting process.
Ironing the transfer onto the copper
The second essential tool for producing PCB's at home is a heat lamiation machine. Now I realize that not everybody is going to have one of these. Yes you can do the iron on process using an actual iron. For me the laminator is essential because I achive results with it that I could only hope for heating the transfer manually.
If you've ever taken a physics class one of the fundimental things you probably learned is how pressure is distributed over an area. you can hammer a steel nail through sheet metal because the hammer hits the large surface and the force is focused and magnified on the smaller point. Why did this turn into a physics lesson? If you take an iron and press it flat against the transfer and against the pcb the amount of force you can apply is distributed across the two surfaces. Even if you press with all your might this limited force may not be enough to bond the toner to the copper very well.
One approach to get enough force is to use the tip of the iron and go over the entire board one trace at a time. It requires some skill and its tedious, but it does work. The method that a lamnating machine uses to focus the energy is to press the two surfaces between two wheels. All the force is applied at the point where the wheels meet in a straight even line across the board. If you are too cheap to buy a laminator you can simulate this effect by pressing the board and transfer sheet against a rolling pin with the iron and rolling the point of contact across the board.
For my own use I have an Ibico EL12-II. I Use it on its hottest setting and send the board through with no carrier sheet. After a dozen or so passes through with the board at various angles I have a strong bond between the copper and the toner. After this I peel the photo paper back and the toner usually just breaks off the paper and stays on the copper. This break off effect happens when you use the right paper and have a good transfer. If you have a good bond but you can't achive the break off effect the next best thing is to soak the board in water until the paper starts to come apart. Then scrub the board with a toothbrush until you've rubbed all the wood pulp (paper) out of the toner.
Once I have the toner on the board the final step is to "touch up" the image. Anywhere you can see through the toner the acid will eat through the copper. In school we were taught to use a sharpie marker to touch up. It works but not very well. They make specialty pens for this, but I don't have one. A few years back sharpie came out with an industrial sharpie that is chemical resistant. It works somewhat better but still isn't perfect. What I've found works the best is finger nail polish. I take a metal pin and dip it into a bottle of nail polish, then dab it onto anywhere that needs a touch up. Nail polish is a pain to use but it never gets eaten by the etchant like a pen does.
Preparation of the copper etchant solution
There are tons of great resources on the web with information on chemistry and there are even lots of pages that explain about specifically the etchant formuala I reccomend. Since I'm no chemist I feel its best to resign the detailed chemical analisys to a higher power which you can find here. There is an alternate resource with detailed information about disposal of peroxy-hydrochloric etchants and information on how to precipitate the copper back out of the solution here.
Back in my school days we used Ferric Chloride. While we didn't have the advantage to use fancy pc's we did have the right equiptment to handle the ferric chloride and the school handled the proper disposal of the stuff. Sadly now just about anybody can by ferric chloride off the shelf of the local radio shack but there's no ready provision to properly dispose of or recycle the stuff. For those reasons and numerous others I like many other electronics hobbiests reccomend the use of a copper chloride etchant.
A simple home-brew copper etchant can be made by mixing one part muratic acid with two parts dilute hydrogen peroxide. Muratic acid is about 30% hydrochloric acid and about 70% water. Consumer grade hydrogen peroxide is about 3% hydrogen peroxide and about 97% water. There's no need to buy concentrated chemicals. A more dilute etchant is actually safer for hobby use. The muratic acid can be found in the paint section of a hardware store. It is used to clean concrete before painting or staining it. Last I checked it was about $7 a gallon. Peroxide can be found at any grocery store that has a pharmacy. Its used as a topical antiseptic and costs about $2 a pint.
You will want to mix these chemicals outside as the fumes from the acid are quite strong. Never pour peroxide into the acid, always pour the acid into the peroxide. Once combined the result will be a clear bubbly liquid and a very powerful etchant. Take a small bit of copper and dissolve it in the solution before attempting to etch your first PCB. The solution will turn a light green when its fresh and ready to work. While its clear it will etch so fast that it will probably ruin your project. Once its light green it should etch at a reasonable rate. As the etchant gets saturated with copper it will turn darker and darker until its almost brown and isn't very effective anymore.
This is the greatest thing about peroxy-hydrochloric etchant... Leave it out in the open air or bubble air through it and it will regenerate back to a light green etchant. If you don't want to wait you can add hydrogen peroxide to instantly regenerate the etchant, but that will dilute the solution a bit. This solution will continue to regenerate and work until all of the acid in the etchant is used up. Then the copper will all be turned into Copper Chloride, a blue crystal salt that can be dried out and disposed of as solid waste. As a hobbiest chances are you will never use the etchant enough to wear it out to the point of needing disposal. This etchant can be stored and re-used for all of your projects for years to come. Even if you managed to expend the acid in the etchant completely, you can allow the water to evaporate a bit and add a bit more muratic acid to revitalize the solution.
Preparation of the copper etchant solution
The actual process of etching the PCB laminant isn't very complicated. If you do alot of boards there are methods to speed up the process. Most of these methods involve the design and construction of an etching tank. I don't believe most electronics hobbiests really have need of a full blown etching tank. However knowing the principals that make an etch tank effective is still a good thing.
As the acid comes into contact with the bare copper it combines to form a copper chloride ion. The ion is dissolved in the water so what we see is the solution slowly turning a darker green color. The factor that inhibits the rate at wich the etchant works the most is the formation of this copper chloride and the rate at which it dissolves into the water. In simple terms, as soon as the copper meets the acid it forms a copper chloride film over its surface and that film prevents the copper underneath from getting exposed to the acid. As the copper chloride dissolves more copper is exposed and the process repeats.
In order to speed up the etching process what we need to do is to get this copper chloride film away from the copper and expose fresh acid to the surface. This is the basic purpose of an etchant tank. Some use a method where the board is suspended in the air, they spray etchant onto the board and allow it to run off. Others use an aquarium air stone to make bubbles. The bubbles agitate the solution which moves the copper chloride around and makes it dissolve faster. The air stone method has the added benefit of introducing oxegyn to the solution so the etchant is regenerating as it is etching.
Another factor that effects etching time is the amount of dissolved copper in the etchant. This is easy to see with peroxy-hydrochloric etchant because the solution gets darker as it gets weaker. Simply having more etchant will make the process go quicker because you will have a better ratio of copper to etchant. I personally would rather wait a little longer than store gallons of green poison in my garage. For my own projects I simply place the board into the solution in a clear plastic container and swish it around once or twice a minute until its done.
As a final tip on etching, you should resist the temptation to rub the board with your rubber glove. Rubbing the board does make it etch faster by physically moving the copper chloride film away from the surface. The toner is often weakend by the acid and it may rub off as you are rubbing the board. It is sad to spend hours making and touching up a good, ready to etch blank and then ruin it bieng impatient. Wait the extra five minutes for it to etch on its own.
Completing the PCB Fabrication Process
Once the board is etched all that remains is to clean off the toner, drill out the holes and put your project together. To remove the toner acetone will do the trick. Acetone is the basic ingredient in finger nail polish remover. Chances are you've got some in the house. In the professional PCB industry the standard is to nickel plate the copper traces then cover the board with a green plastic soldermask. The nickel plating doesn't serve any purpose as far as the electrical charactaristics of the board are concearned. Rather it is a combination of rust proofing and an etch resist all in one step. There really isn't a hobbiest equivalent to this nickel plating and soldermask process. To protect your project so it will last for years to come the most economical solution is to "tinn" the traces.
The process of tinning the traces gets its name from coating the copper traces with tin metal. Thats a fancy way of saying you take the soldering iron and go over each trace one at a time with some solder to give it a thin non-rusting metal coating. In the image on this page I've included a United States Coin to give you an idea of the scale and detail you can achive easily using the toner trasfer method for making PCB's. The logo I've embedded into the board is so fine that when I attempted to tin it parts of it started melting off the board.
To fend off any questions in advance the circuit above is my layout for the L.I.R.C. project. Its a small infra-red reciever that allows me to control the mouse pointer on my pc with a universal remote control. This is just one of the thousands of interesting projects that can be found on the web that are easily done with a simple home made DIY PCB. A while back I got rid of my computer monitor and have been using my LCD tv for both my PC and television viewing. A natural evolution of this has been that I watch more and more video from online video services. Having the ability to pause the movie without getting up and walking over to my desk brings the convience of standard television viewing to online video services.
I want to end this page of DIYPCB.com by saying thank you to anyone and everyone who has read through my site this far. I also want to take a minute to let those of you who have an electronics related website know that I appreciate it if you link to diypcb.com and to thank you in advance for doing so. Be safe, Have fun, and Good Luck.
Practical Soldering Project Kit
Long before I ever made my first Printed Circuit Board I got started building a project kit similar to this one. In fact my mother still keeps it in her cedar chest full of memorabilia. A radio kit like this one teaches not only the fundamentals of practical soldering but also how to read schematic diagrams. I highly reccomend a Radio kit like this as your first electronics project because it gives you a sense of accomplishment. The first time you turn it on and the radio actually works you realize that electronics is something you really can learn.
130 in 1 electronic project kit
This electronic project kit takes me back more years than I care to remember. I got one of these for christmas when I was in grade school. I dare say that a kit like this was the one thing that really set the course in my life. I probably would have take a much different path had I not discovered my thirst for knowledge at an early age. While this project kit can be seen as a simple toy its much more than that. It awoke an interest in me to want to be an engineer and a thirst for knowledge about electronics and computers. I would reccomend a project kit as a gift for any child whom you want to see succeed in life. If the child is old enough to read they're old enough to start setting the seed of inspiration.
Electronics Projects for Dummies
Don't let the name fool you, the dummies series of books are phenominal. They manage to convey advanced knowledge in a manner that those of us who arent genius can understand. Once you have fostered an interest in electronics you will find the thirst to do and know more is there. A project book like this one just might be the inspiration you need.
If you're not quite ready to design a radio but you want to have a bit of fun while increasing your knowledge buying an electroncs project book is a good choice. Make that book a dummies book and you're sure to find fun projects that a beginner can handle.
More Electronic Gadgets for the Evil Genius
If you've developed a good thirst for knowledge and you are looking a good way to show off what you know a more advanced project book is in order. Those of us who've been nerds for a while know that the greatest joy in a nerd's life is to show off something that makes our fellow nerds jealous envious and curious.
The book "More Gadgets for the evil genius" is pretty much your typical electronics project book with a twist. The twist is that the projects this book focuses on are the kind will make your intellectual friends scratch their head in awe. If you've done the beginner stuff and you're ready to try something that really shows off what you can do, give this book a try.
