PCB Designing

Discussion in 'General Electronics Chat' started by insanity_embraced, Aug 16, 2010.

  1. insanity_embraced

    Thread Starter New Member

    Aug 11, 2010
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    Hi
    I am designing a PCB layout of my project, i m very new in this, so i am using EXPRESSPCB , as i found it very easy to use.
    the problem is that, i have 2 IC's, and their pins are connected in such a manner that if i try to make connections between them, atleast 1 or 2 connections overlap each others, i tried many different paths but couldnt figure it out.
    I have attached a Screenshot of what i m doing.

    Please Advise
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Yes this is why people use double sides or multilayer boards...
    There is a possibility that you can route traces through the pins of the IC's assuming your required clearances can be met.
    If you are trying to make this board be a single layer only then you will have to create holes for wire jumpers to connect over traces so they don't touch..
     
  3. insanity_embraced

    Thread Starter New Member

    Aug 11, 2010
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    how can i use double sided boards ??
    secondly if i have to use jumpers, then what the difference left in PCB or veroboard..
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    The way to connect traces on either side of the PCB is through a special pad called a "via". You will find several sizes in the pads library.

    ExpressPCB has an introductory tutorial. You can get some useful tips about layout from it. A double sided board is easy to make and avoids using jumpers.
     
  5. Markd77

    Senior Member

    Sep 7, 2009
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    The traces connecting 7, 10 and 16 on the lower chip in the second picture could all run under the chip, and the problem trace on the top one that runs all round the board could go under the chip too. I think that would solve it.
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    beenthere,
    Vias are really not required as the component is a through hole component. Vias are only required for surface mount devices or in areas where you don't have access to through holes already and simply want to switch/run a trace to the other side of the board.
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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    I do not agree. Vias are used to change from one layer to another on the circuit board. It does not matter if you use SMD or hole mounted components. A hole if we should look at it strictly is something that is defined on schematic level linked to a a component package type. A via on the other hand is something that is defined on the PCB level. Not related to information on schematic level. This is true also for the hobbyist. Then making home-brew PCBs most of us can not make plated-through hole boards. So vias can be quite unpractical. As we have solder the through hole connection with a wire. Easy to forget. The trick is to try to swap layer on at through hole components.
    Then I make PCBs also as hobbyist, I always use use the schematics as the main reference for nets. All components also test-points and holes, are defined on the schematics. If I change something I always go back to the schematics do the changes and then import the changes into the PCB.
     
  8. insanity_embraced

    Thread Starter New Member

    Aug 11, 2010
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    please tell me how to make double sided pcb.
    or is it a good way to make connections under the chip, like one person said above on this post ?

    also its just 1 IC im showing, i have 6 same couple of IC's to connect in the same way,, few of them get input from other too.
     
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
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    My software requires you to set the number of layers or it just assumes 2 when it autoroutes.
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Not sure what you don't agree about... Vias are not needed for the OP's issue as the required traces can be run without vias. Vias simply add cost to a circuit board and can decrease its reliability. Reliability is decreased because the through hole plating is not nearly as structurally sound as a circuit board trace. Through hole plating is the first to crack with thermal cycling. If you use a components through hole instead of a via you increase reliability as the soldering process will fill at least 75% of the hole further strengthening the holes wall plating. If they aren't needed you don't put them. If you need them you do.. Vias are 100% needed for SMT boards as you don't have the luxury of using a through hole components already existing hole to allow access to the non component side of a board and 99% of the time you will need at least a double sided board when using surface mount components.
     
  11. marshallf3

    Well-Known Member

    Jul 26, 2010
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    More than once an intermittent problem has been solved by soldering short stubs of wires through vias, however over the years the reliability of vias in commercially created boards has greatly increased.

    Obviously due to the way they're made a home hobbyist can't make their own vias, they're stuck with coonecting two points on opposite sides of a board with wire.
     
  12. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I see via issues quite often on commercial boards. Either voids creating during the fabrication process or cracks due to thermal cycling,etc... Part of my job is to design circuit boards.. I only use vias when there is no other choice. 99% of my work is through hole components. When routing a circuit board I usually make the first pass with "no vias allowed". If the board cannot be routed like that then I typically only allow as few vias as possible.

    My trick of the day...For a home hobbyist I would recommend using rivets to create vias..
    Or simply using wire jumpers on single sided boards. Most PCB programs have built in functionality for using wire jumpers when vias are needed or traces cannot be fully routed on a single layer.
     
  13. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Aren't a lot of those pop rivets made from aluminum? It doesn't play well in contact with copper.

    Even brass rivets have caused problems in the past. Ages ago GE made a 9" color TV called the "Porta Color" and every via on the board was indeed a brass rivet. 99% of the problems they developed (aside from their cheesy compactron tubes) were caused by those rivets. It was time consuming but you could repair most of them by simply soldering copper wire through all of them.

    Point is, if you must use vias on a home etched board just expect to solder wires through them.
     
  14. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Well I wouldn't use rivets in a professional application... But yes aluminum pop rivets work just fine for vias.. (again for a homebrew prototype)
    Galvanic action typically requires an electrolyte like water/salt water,etc... A typical homebrew product will not have corrosion issues for many many years (much longer than most electronic component lifespans).
     
  15. retched

    AAC Fanatic!

    Dec 5, 2009
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    I find it rather easy to do at-home-vias.

    I use the through-wire-via. A dab of solder on the top side with the wire through the via, then flip, solder and trim flush-ish. If you REALLY want to, you can use a rotary tool or the like to grind the solder joint bump FLAT so it looks nice.
     
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