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Schematic to pcb layout, or Gerber

Discussion in 'General Electronics Discussion' started by bigkim100, Sep 28, 2021.

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  1. bigkim100


    Apr 17, 2013
    I have a relatively straightforward circuit (in my opinion ) that I would like to make several pcbs of...even if its just the track layout, just to print out and make my own boards (with Transferrable laser paper on a copper clad board). I only need 4 or 5 boards, so I dont know if its worth getting a manufacturer involved.
    Alternately, how much would someone here charge to make me pcbs?...drilled as well (If someone can do the board, without the drilling, I can drill it if need be).
  2. Fish4Fun

    Fish4Fun So long, and Thanks for all the Fish!

    Aug 27, 2013
    bigkim100 ...

    You are probably best off having the boards made by a PCB prototype MFG. If you aren't in a hurry, China offers very reasonable prototype quantity boards but expect 4-8 week lead times ... If you are in a hurry (you probably don't have time to make your first PCB) and you should look at the US based prototype mfgs. $500 and two weeks for five PCBs may sound like a lot and seem pretty slow, but it is improbable you could get your first 5 PCBs made any faster/cheaper DIY ... (and certainly not the same quality).

    That being said....

    I make a fair number of 1-off boards for my projects, but it is a labor born of a combination of impatience and spare time. I use a CNC router to cut the traces, slots and drill the holes. A "Simple" Single-Sided PCB (couple of ICs, some headers & passives) generally takes 6+ hours to "CAD", Cut, Drill & Populate ... Double-Sided PCBs take considerably longer ... I generally opt to build Single-Sided "Daughter Boards" that connect to a Single-Sided "Main PCB" using headers rather than mess with DS PCBs ... when I absolutely HAVE to HAVE a DS PCB I generally make the Top Side and Bottom sides on separate pieces of Single Sided PCB material 0.031 thick and use 0.020" solid copper "VIAs" to connect the two PCBs (No Through-Hole Plating). This process requires the addition of VIAs anywhere you would "normally" use component leads to carry a trace from top to bottom.

    I can cut traces down to ~10mil with ~10mil spacing, but I generally try to make traces as wide as possible. For instance, on 100mil through-hole components, I typically CAD the traces 90mil wide leaving 10mil spacing between them ... When I cut them I generally end up with 15mil-20mil spacing ...

    For this type of PCB I use a 60 degree "V-Bit" to cut the traces which means the actual spacing is determined by the depth of cut. If I am doing 50mil or smaller surface mount ICs then I use a 30 degree or even 15 degree "V-Bit" to reduce the "over cutting", but with these V-Bits you have to cut very slowly (5ipm) and be very careful that the PCB is level and that your depth of cut is as shallow as possible ... it also helps to use 1/2oz copper rather than 1oz or thicker ... A 2"x2" SMD PCB with 50 traces on it might take 2 hours or more to cut with a 15 degree V-Bit where a 4"x6" PCB with through-hole components and 100 traces on it might take 15 minutes to cut with a 60 degree V-Bit (20ipm - 30ipm).

    Drilling is FAST ... typically ~ 1 second per hole. Generally the slowest part of drilling is changing bits.

    Small Slots & Cutouts can be sped up considerably by "drilling" holes prior to milling ... For something like a Through-Hole power jack the slots are only 30mil x 100mil ... but to cut through a 0.060" PCB with a 0.8mm end mill is slow and slots can take upward of a minute per slot ... if you "pre-drill" the slots you can cut the time to mill them by 50% or more without worrying about breaking the end mill.

    As to using Toner Transfer Paper ... I know there are many people who have had good results using this method; however, I am NOT one of them. It too is a tedious process that requires meticulous attention to detail. Because it is a multi-step process, there are multiple learning curves that plague progress before you can get a reasonable facsimile of a PCB.

    While getting the toner to transfer properly is the most noted stumbling block, it is by no means the only hurdle. Assuming you eventually make a descent transfer, you then get the opportunity to try your hand at etching.

    Regardless of your choice of etchants, there are caveats and these typically require multiple etching attempts to get right.

    Na2S2O8 (sodium-persulfate) is perhaps the most user friendly etchant ...

    FeCl3 (Ferric Chloride) is a long-time favorite because it is very fast and etches clean when it is fresh, but it is messy to work with and is consumed fairly rapidly ...

    HCL + H2O2 is popular on the internet for the DIYer AND in production ... It is simply Hydrochloric Acid + Sodium Peroxide which in reality is just a precursor for CuCl2 (Cupric Chloride) ... Popular with the DIYer because it is economical and easily sourced ... the downside is relatively slow etching with more "undercutting" than FeCl3 or Na2SO8.

    Assuming you have managed to successfully transfer your toner to your PCB enough times to get through the Etching process, you now come to the "Drilling" process. If people mention this step it is generally a passing reference to a drill press that seems largely ignored by most readers. While PCB drills are not nearly as expensive as they once were, they are very fragile and using them in a drill press with more than ~0.002" TIR will quickly turn $20 worth of PCB drills into $0.50 of scrap carbide. Yes, this means the $100 drill press from Harbor Freight is NOT a great drill press for drilling PCBs. Granted, the Harbor Freight drill press is an improvement over ANY handheld drill; however you will still end up with broken dill bits. (Note: PCB Drills are designed to run @ 20k+ RPM, running them at "normal speeds" greatly diminishes their durability & longevity).

    Assuming you have navigated the gauntlet thus far, we come to the final hurdle ... "tinning" your freshly made PCB ... This is one of those hurdles most newbies either rush or skip altogether, either way the results are generally bad. Cleaning the copper is critical. Not only will you need to clean the etch-resist (toner) from the traces, but you also need to remove any oxidation and then strip away any residual oils.

    Use Acetone to remove the resist.

    Use a Scotch-Brite pad or 400 grit wet/dry sand paper with some Dawn Dish Detergent and water to polish the copper and remove any oxidation.

    Wash with warm soapy water & dry with a paper or cloth towel. (Avoid Touching the copper)

    Apply Acetone with a CLEAN paper or cloth towel.

    Dry with a different CLEAN paper or cloth towel.

    Assuming you don't have a and electroplating tank, a standing-wave tinning tank AND that you don't have tinning solution....

    Apply a thin layer of flux to all of the exposed copper using a CLEAN paper or cloth towel. (Water soluble flux is easier to clean up).

    Use a soldering iron and some solder to carefully coat all of the copper, don't worry about puddles, blobs or covered holes.

    Rinse & Dry the PCB (use soap & water if you used water-based Flux, otherwise use Acetone).

    If you have a vacuum de-soldering tool clean up any covered holes, puddles and blobs .... Otherwise, use De-Soldering wick. If you have a High-Temp heat gun you can speed this process up by heating the entire PCB up until all of the solder is liquid, then quickly grab it with a pair of plyers and give it a sharp whack on a hard surface ... done right this will remove 90%+ of the excess solder instantly.

    The final step is to check for solder bridges from the tinning process. Use a Multi-Meter set to "Continuity"... place one lead on any trace or pad, and place the other lead on ALL the adjacent traces/pads (one at a time). Do this for EVERY TRACE/PAD!! There is nothing worse than getting a PCB completely populated and then powering it up only to find there is a direct short on the PCB (most of the time you assume there is a bad component and don't even start looking at the PCB until you have removed all of the components) ... DO NOT SKIP THIS STEP!

    If you aren't going to populate the PCB immediately it is best to store it in an air-tight plastic bag.

    So, in short, I would suggest you finish the Gerber files and get them to a PCB mfg :)

    Hope it helps!

    Martaine2005 likes this.
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