Eyelets

Discussion in 'The Projects Forum' started by capnray, Jan 14, 2012.

  1. capnray

    Thread Starter Member

    Jul 3, 2010
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    2
    Alas, I have digressed and am in need of eyelets for a project here, PTH is not easily done without a plating lab. I have designed and fabricated a 2 sided motor driver PCB. I was able to find eyelets for the base and emitter of my TO-3 transistor, however I have failed to find a source for eyelets for the 6-32 collector connection, any help is greatly appreciated.
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    By 6-32 I assume you mean screws. One accepted standard for PCB mounting is the use of an internal star washer between the nut and the PCB trace. Direct mounting to the board without the use of an eyelet, in other words.

    Sockets are another option

    [​IMG]
     
  3. capnray

    Thread Starter Member

    Jul 3, 2010
    59
    2
    Yer never too old. I never considered sockets, blindly designed the board as PTH...go figure. Now I need the eyelets, and YES for a 6-32 screw. My traces can handle 15A, top and bottom, the transistor is capable of sourcing 30A...I need both sides connected. Thanks for the socket suggestion, I think I'd have a smokey failure at this current flow with he minimal connection of a socket.
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    A plated through hole is not needed to create a connection between both sides of the PCB. A pre-tinned wire(or 2 or more) is inserted and soldered on both sides. Proper matching of wire gauge and hole size will create normal looking solder joints that match the look of the board overall.

    I've repaired a large number of Delco and Philco car radios and in the early evolution of the amps they used multiple TO-3 style transistors mounted on electrically live heatsinks with the use of thermal grease. The connections to the transistors was made with normal stranded copper wire of large gauge, 12 or 14 I believe. The wire ended in a deep socket connector that simply pushed over the pin of the transistor. This practice changed and evolved pretty quickly as transistors matured.

    The point is that the methods of mounting are almost limitless. Some being easier for repair work and others better for long term use and reliability, but a pain to remove or repair.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    This is a case where plating the hole leads to no increase in current carrying ability!

    The thru hole for the collector screw is larger in diameter then the screw itself, least the screw not pass thru the PCB. Thus you cannot depend on the walls of the hole touching the screw.

    Washers, especially of the star type, may be the better way to assure a connection from screw to a PCB land.
     
  6. capnray

    Thread Starter Member

    Jul 3, 2010
    59
    2
    Kermit, Ernie,

    Thanks for the suggestions, gives me more ideas. Lacking PTH ability, I use tinned wire for vias, however I have decided that it would get a tad messy if I used many of these for the TO-3 screws. A PTH (actually two PTH) would connect traces on top and bottom and, yes there is no guarantee that the screws would contact the sides of said hole. The "top to bottom" connection of the PTH would give sufficient conductivity when the screw is connected to the bottom side, an eyelet would be better.
    However, since this is a "quick and dirty" design and I did not calculate the power dissipation from rise and fall times, I will be using a heatsink. That and the associated hardware will use the screws (may need longer ones) will connect both sides and also provide an air gap under the sink.

    Thanks to both of you, Ray.
     
  7. capnray

    Thread Starter Member

    Jul 3, 2010
    59
    2
    The wife is taking a writing class, so we made the journey to Evansville this AM. After, we pigged out at Pizza Hut, right next to a JOANN FABRICS store. Both wife and stepdaughter were sure I'd find what I needed... they were correct. Brass belt eyelets are nearly the right size for the 6-32 screws and will even work with the existing board. Since this driver can be used for other projects I will modify the artwork to allow for the slightly larger part (eyelet).
     
    ErnieM likes this.