First PCB - Is it possible to be too ugly to work?

Discussion in 'The Projects Forum' started by jerseyguy1996, Apr 20, 2011.

  1. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    I am creating the circuit laid out on page 5 of this document:

    http://focus.ti.com/lit/ug/sluu023b/sluu023b.pdf

    It is my first attempt at designing a pcb. I used ExpressPCB in this attempt. I started out trying to be all neat about my component placement and traces but towards the middle and end I was literally just sticking components wherever there was some unused real estate on the board. Is there a limit to how convoluted and spaghetti looking a board gets before you start running into problems? The layout is shown below. That is the bottom copper layer. The top copper layer is a solid copper layer that serves as a ground plane.
     
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  2. Wendy

    Moderator

    Mar 24, 2008
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    The green layer is the top layer, not a good thing.

    When I get home I'll show you my latest project, but you can see another attempt on my How I make PCBs thread. Come to think of it, I did not show the Express files directly. I also made the PCB mirrored the wrong way because I had selected the wrong layer the first time.

    How are you planning on making this PCB? Toner transfer, photographic, or other?
     
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  3. JDT

    Well-Known Member

    Feb 12, 2009
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    Yes, unusual colour scheme but I've seen plenty worse layouts. I seem to spend a lot of time getting all my resistors into neat rows, have all my ICs pointing the same way and all my tracks neatly parallel with 45deg corners. It won't make any difference to the performance but it makes me feel good!

    Only 1 comment on your layout: Why is LED1 the opposite way round to the others? Easy to make a mistake on insertion. Especially if it's someone else doing the assembling.

    PS: I design PCB's as part of my job and one day I was looking round Camden Market in London with my family and there was a stall selling things made out of blank PCBs. Earings, lampshades, clipboards, etc. And there was one of my PCB's! Could not believe it. Turns out that the PCB manufacturing companies often make more that you order and the leftovers get sold as scrap. So I add a copyright notice now.
     
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  4. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    Oy! I'm still trying to figure out the software but it refers to the green layer as the "bottom copper layer" and the red layer as the "top copper layer". It is easy enough to change the color scheme.

    I read through your entire thread a few weeks ago when I first started attempting to etch my own pcb's. Excellently written by the way! I tried using wax paper but it was not transferring enough of the toner to the board. I think it was probably because my iron was not as hot as your laminator. I have had pretty good luck using the toner transfer method with the iron and magazine paper. Unfortunately it was actually transferring too much toner for the PCB that I was trying to etch. Toner was bleeding into the spaces between the tracks and ground plane. That is why I decided to design it myself so that I could make bigger pads and more space between tracks.
     
  5. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    LED 1 was turned the other way originally because it was the only way to make the connection based on an earlier placement of the tracks. I had rearranged some things and notice now that I can turn it back around and still make the connection. Thanks for catching that for me!

    Great story about your PCB! Pretty sure mine ain't gonna be ending up in any earrings :)
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    OK, I am going to zip my latest project and attach it here. It isn't finished. I have a schematic and the resultant PCB file.

    Have you drawn a schematic and linked it to the PCB? When you click on a pad it will show all the other pads you need to go to.

    You'll note I try to round the corners with 45° angles. Sometimes 90° angles don't etch so well.
     
  7. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    I usually spend alot of time contemplating device layout, with the intent on finding the least tangle, and because I typically work with single layer, the least jumpers. Much will depend on your methods, as resolution allows, or disallows certain spacings. I use corel draw for my layouts, and have a file of pads, intersections, etc for import. I use 45 degree corners over 90s, and right angled connections are filleted. I always find though, that those last few control traces can take some pretty wild paths.
     
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  8. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    Nice looking PCB! I didn't draw a schematic because I was in a hurry(trying to get this done while on vacation this week) although now I wish I had so that it could keep track of all of my connections for me. As it is I plan to sit down with the schematic and print out of the pcb and number each connection on both to make sure that I don't miss anything. I will be changing all of my 90 degree angles to 45 degree angles.
     
  9. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    That has been my experience as well. It starts out all neat and orderly and by the end I am just trying to weave the traces through the components wherever there may be an opening. This was actually the third iteration of this pcb.
     
  10. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    @ jerseyguy1996 quote, "The top copper layer is a solid copper layer that serves as a ground plane."

    If you are using that as the ground plane, just make sure that where each through hole is that isn't meant to connect to ground has an etched pad or area around it. If not all of your components will be short circuited! Not a good thing.

    If making a two sided board, you can also run your V+ supply rails on that side. That will open up more area for your signal traces. But remember to give a etch out line around these V+ traces also.
     
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  11. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    That is part of the process of using the PCB software. Making a schematic first with the soft ware makes the PCB layout easier. some of the programs(Diptrace, PCBArtist) will give you a sample component placement and trace layout from the schematic.
     
  12. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    Made a couple of fixes. Rounded off all of my corners and changed the colors to more accurately match standard convention. I have also included an image of the top layer as well. I am using thermal pads to connect to the ground plane versus solid pads. What is the difference between the two?
     
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  13. Fenris

    Active Member

    Oct 21, 2007
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    Hi There

    Thermal pads are used when you solder a component to a large plane of copper. The thermal pad is easier/quicker to solder because you don't have a solid plane of copper sucking up the initial heat.

    I have just made a PCB for the Tony Vanroon PS3010 circuit and it has large areas of copper that the components solder to. I have modified it to have thermal pads to ease the soldering on these large copper areas.

    I only learnt what they were for in the last 2 months.... I'm 44 :D

    regards

    Fenris
     
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  14. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    This has all been great advice! I checked the schematic against the PCB and I am pretty confident that I have all of my connections routed correctly and to the proper pads. The circuit is a battery charger. Would a resistor work in place of the battery to initially test it out?
     
  15. russpatterson

    Member

    Feb 1, 2010
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    Just so you have all the information. Eagle is a good program for PCB design. The free version lets you make small PCB's. There's some good tutorials, and forum chat, on SparkFun for it. SparkFun BatchPCB is an inexpensive service for PCB fabrication. They panelize multiple designs and get them made in China. So it takes ~3 weeks turnaround.

    The downside to Eagle is the learning curve and quirky interface. The upside is that when you're done you have industry standard Gerber files so you could have your PCB fabricated anywhere. So if you have daydreams of mass production that's a benefit.
     
  16. SgtWookie

    Expert

    Jul 17, 2007
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    One item I try hard to avoid is running a trace through a pad. I much prefer having pads at the "ends" of traces, for similar reasons as to why you use thermal pads on large ground planes. It's far easier to overheat a pad causing it to "lift" from the board if you have a trace going through the pad; a lifted pad means a ruined board.

    Sometimes it's very difficult to avoid, for example your R10 connection to the IC's pad that continues on to one of the LEDs. However, places like Q1, R12, R14 are very easy to have the trace junctions placed away from the pads, like you did with the right side of R19.
     
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  17. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    Oh man there are a bunch of those that need fixin.:mad:
     
  18. SgtWookie

    Expert

    Jul 17, 2007
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    Sorry guy. Better that you know about it beforehand then wonder why your pads are getting lifted.
     
  19. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Hola Jersey,

    Sorry but if you suspect (or you are convinced) that it is ugly/wrong do not come here to ask. It is a futile excercise.

    First work it out to your satisfaction (no matter how wrong you could be) and then come here and ask for opinions.
     
  20. Wendy

    Moderator

    Mar 24, 2008
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    I will disagree with that last statement.

    The OP asked for feedback, which he got from many users who had experience in this part of the hobby. This is much better than going ahead and then asking what went wrong. I didn't take what he said negatively, even remotely. It is always frustrating to find out you have a lot of work left when you thought you had finished.
     
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