PCB Exposure Boxes And Driller
Hello Everyone
I know it has been a while and I have been keeping a low profile, but for the last several months I have been designing and building new equipment for the electronics hobbyist and enthuiast. More specifically, I have been designing and building an exporsure box and a cnc pcb driller for small size circuit boards, with dimensions 3 X 4 inch or less.
In the spirit of a little market research and to get the vibe of the general Parallax community, I have a question for you guys.
I know it has been a while and I have been keeping a low profile, but for the last several months I have been designing and building new equipment for the electronics hobbyist and enthuiast. More specifically, I have been designing and building an exporsure box and a cnc pcb driller for small size circuit boards, with dimensions 3 X 4 inch or less.
In the spirit of a little market research and to get the vibe of the general Parallax community, I have a question for you guys.
Comments
-Phil
The cnc driller leadscrews have a 4 1/16" travel for both x and y axes. So realistically it could accommodate 3.05" boards
My original intention was to adapt to the stock DATAK 3" X 4" presensitized boards, with various adapter plates for both the driller and the exposure box to accommodate smaller size boards.
It is my goal to develop a small, inexpensive system that will produce repeatable results, making it more affordable and appealing to the hobbyist.
Bruce
The new Propeller BOE is coming out soon, too. We just finished the last prototype as well. It's also in the 3x4 size. I now remember Phil's 3.05" x 4.00" boo-boo - not sure if that's still a problem with our boards or if we've gone to 3x4 consistently. You see, Phil has been around Parallax for a long time and he maintains a digital snapshop in his non-volatile memory. I'll ask our PCB layout engineer Thomas Bauer to shed some light on this part.
Ken Gracey
Thanks for your input.
That is a key argument for doing just the opposite. Learning how to layout your own PCB definitely takes a certain amount of time as it does with learning any new software. After learning how to use the software, a person must be able to get around the parts libraries rather quickly to avoid wasting more time, therefore it is a good idea for a person to create custom libraries of the parts they use most often. Dependant upon the given type of prototyping method, once you overcome the previously mentioned problems, it will save you an enormous amount of time which is usually spent on cutting, stripping, and soldering jumper wires and such. Besides the fact that it is much neater layout.
Considering that a person must design circuitry anyhow in order for a device to work, why not use a graphical program to represent the circuitry? That way you have easy to read and understand documentation and you can easily produce a board yourself or have a board house do it for you, if you so desire. It sure beats circuitry on a napkin.
Ken, I learned my lesson the hard way. I was using pre-made circuit boards and using a lot of jumper wires to make my connections. I had six duplicate boards, and soldering them all took a lot of time.
In the photo below, you will find my reason for creating custom made circuit boards. These boards drove me nuts.
With the machines that I am currently in the process of making, and once a design has been completed, I would imagine that a board could be ready for solder in about an hour (also dependant upon how in depth a person want to go, e.g. solder mask, through hole plating, etc...). And keep in mind there are no unnnecessary joints to solder.
Once I finish these new machines, you just may change your mind and start taking the time to layout your boards with software.
On second thought, just start a junk design and start learning the software. A minute spent here and there learning how to use PCB design software can go a long way in saving you time in the long run.
Once again, this is just my opinion
Bruce
Most all of our legacy products in the 3x4 form factor are actually 3.05 x 4.00. This size continues today due to the potential of mounting hole alignment issues with any mechanical enclosures or heatsinks. (Plus, any PCB Design Engineer who gets an additional 50 mils of space for routing will fight tooth and nail before giving it back) LOL
When talking about the Propeller BOE, there is so much circuitry that I had to shoe horn into that board that I couldn't reduce it by 0.050 if I had to. By providing the customer with as many options as we possibly could in a design of that magnitude, every square mm was used, and then some.
Boy Bruce, talking about exposing, developing, and etching takes me way back. My very first board that I made, built and tested was an RF (controlled impedence lines) amplifier for use on cellular towers. Keeping the etchant solution from reducing the width of the 50 ohm lines was very tricky and very time consuming. With today's cheap board houses I wonder if anyone is still etching their own boards?
Thomas
Thanks for the info, I sure appreciate it. I don't suppose you have an extra one of those shoe horns laying around that you would be willing to sell. Sounds like a very nice to tool for PCB layout.
As I mentioned to Ken, I am and will be documenting everything. I am attempting to build some fairly sturdy machinery as cheaply as possible. From that point, I will further be exploring and documenting the use of off the shelf chemicals to develop and etch the boards as cheaply as possible to further reduce costs. For example, I will be using hydrogen peroxide 3% and muriatic acid to develop the boards, and Rooto Crystals of Household 100% Lye Drain Opener (caustic soda/sodium hydroxide) for etching.
For hobbyists that do a lot of prototyping, this should be very interesting.
@Leon
I can't wait to get both prototypes of the machinery complete for testing. I really want a nice driller for small boards, but this double sided exposure box looks pretty promising also. So what are you doing for the drilling process Leon?
I use sodium hydroxide from the local hardware store for development, and hot ferric chloride for etching, rocking the container manually. Etching take about 5 minutes.
I use a small Minicraft drill and stand, similar to a Dremel, with reduced shank tungsten carbide drills. It's not very good on FR4 boards, as the drills break very easily, but it's OK with the CEM-1 paper composite laminate that I mostly use. With surface-mount boards there isn't much point in using CNC.
This is my UV exposure unit:
http://www.leonheller.com/Photos/UV%20unit.jpg
Yea I suppose devices are going more towards surface mount, but I believe there is still enough market out there for through hole devices to make it worth while, especially for the beginners.
Once I get the driller complete, here is the drill/grinder that I am going to attach to the z-axis. I have not purchased one just yet, so I am hoping that it does not have too much runout. I just wish I could find a nice, slender, and reasonably priced electric 1/8" grinder, but until I do, I am hoping this item will be a good choice.
http://www.harborfreight.com/1-8-eighth-inch-air-micro-die-grinder-47869.html
Bruce
Bruce
http://www.screenweb.com/content/selecting-right-glass-exposure-units?page=0%2C0
Bruce
I would have to say I both agree and disagree. If you read the article, you will have a better understanding why it is better and more economical to use low iron glass, especially if you are using uv bulbs.
Additionally, it all depends on the film or photoresist. Just for an example, as can be seen in the link below, mg chemicals for their Dry Film - Negative states a UV wavelength range 315 to 400 nm
http://www.mgchemicals.com/products/416dfr.html
Using wikipedia as a source, "Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths, whereas silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm".
They don't provide a percentage for wavelengths between 300nm and 350nm, but we are definitely declining after 350 nm.
http://en.wikipedia.org/wiki/Ultraviolet
So yes, this film could be exposed through single strength glass without any protective coatings, however it would be more productive and more economical to expose this same film through low iron glass. Using 1/8" Starphire Ultra-Clear glazing as an example, it allows 89% of uv transmission. I am uncertain of the wavelengths possible, but I know it will provide more uv transmittance, as stated in the document linked above. The more uv transmitted, the shorter the exposure time and thus faster production and longer bulb life.
http://www.ppg.com/corporate/ideascapes/SiteCollectionDocuments/10060%20Monolithic%20DataR.pdf
Bruce
I've got a couple of very high-power UV tubes that would probably only take a minute or so, but they are rather dangerous, and would need to be completely enclosed.
It may not matter to you or me, but it might matter to someone else. I currently have my panes cut from single strength glass, and I am certain that it will be sufficient for me. However, I am working on a product that I intend to sell, and I want it to be the best that it can be for the money invested.
Bruce
I agree, I will offer both options, single strength glass and Starphire Ultra-Clear, and allow the customer to choose.
Bruce
According to that document, there is a 25% increase in production.
Believe me, I intend to test
Bruce
I have longer/thinner boards, but it would be adapted easily..
I made small boards at home (stamp size).
What scares me the most is drilling holes... supposing a project with a propeller DIP and a handful of connectors would be a pin to drill..
A home solution will also require a little bit of extra work when routing, considering the holes are not plated, but for sure worth the effort.
Massimo
As mentioned, I am developing a drilling system for 3 X 4 boards, actually 4 X 4 could be obtained. As for through hole plating, please refer to this site, there is a lot of information there for PCB fabrication.
http://www.thinktink.com/
Thanks for your input.
Bruce
I like the idea of this, and I also like that someone else is making it happen! 4" by 4" would be very useful. Last week I sent off a 2.7x3.4" single sided board which is the largest for many years.
Just one comment, the equivalent product ("Riston") available here is in 6" x 6" squares rather than 3"x4". I don't know whether that matters, but perhaps it would be nice if there was extra room at least on one axis. This could also be useful for step and repeat functionality on your future designs ...
Thanks for the support
I believe I have an excellent design for a small exposure box, and this design limits the board size to 3 X 4, but it is capable of simultaneous two side exposures. The design for the pcb driller is meant to coincide with the exposure box. The driller could actually accommodate 4 X 4, but that is not my intention. The reason that the driller is 4 X 4 instead of 3 X 4 is because I only want a single design for both X and Y stages of the driller. I believe this will be faster for production as compared to retooling to accommodate different size stages. In other words, the cost of one extra inch of lead screw and base material versus the cost of retooling.
I realize there are size restrictions with my designs, but I am not pursuing a commercial market or large projects. For those folks that are not encumbered by the size restrictions, these two pieces of equipment should be both economical and easy to use.
The exposure box is a do-it-yourselfer project. I am providing free detailed project plans, a well written description, and photos. I will be selling the exposure plates and hardware packages that coincide with my detailed design and instructions. There will be two stock size exposure plates, which are 3 X 4 and 2 X 4, and custom made exposure plates will also be available for a small reasonable fee. The reason behind the individual or custom exposure plates is to allow perfect and precise alignment of artwork from the top of the board to the bottom of the board. The instructions and the kits should be available on the internet in just a couple of days. After getting all the proper parts, the average do-it-yourselfer should be able to assemble one of these exposure boxes in just a couple of hours, and all the parts will cost somewhere between say $60 and $100.
EDIT: It is also worth noting that the exposure box has an exposure plate holder that will accommodate many different sizes of custom made exposure plates, just as long as the board requirement is less than 3 X 4.
Bruce