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thru-hole pad design

sheepdog

Hi....first post on this forum.

I'm new to OrCAD, working on a fairly simple design.  I have my schematic complete in Capture and I am currently working on designing footprints for all parts in order to generate a valid netlist to port over to PCB Editor (v16.2).  90% of my parts are SMT...I found the design process for SMT symbols pretty straightforward.  I'm now getting into designing footprint symbols for my thru-hole parts and I'm getting stuck.

In pad designer, I'm not quite sure how to properly define the sizes for thermal relief and anti pad.  Looking through some of the supplied .pad files in the ...pcb/pcb_lib/symbols directory, I see many thru-hole .pad files, but they all vary so much, I'm not sure what a good "standard" would be.

For example, say I am designing a simple two layer board.  I have a part with two leads that will mount thru hole.  Say the nominal lead diameter is 24 mils.  I'll add ~6 mils to the nominal to find the proper hole diameter, which works out to 30 mils.  So I figure a good pad diameter for the top and bottom of the board would be twice the finished hole, or 60 mils. 

So now I attempt to design a .pad file for this:

- two etch layers, two mask layers, type is "through"
- hole type is circle drill, plated, with a 30 mil drill diameter
- for the top layer ("BEGIN LAYER"), I define regular pad as "Circle 60" and anit pad "Circle 70" (since I want a 5 mil annulus around the pad, right?).  Does thermal relief need to be defined here?
- What do I enter for the "DEFAULT INTERNAL" layer, regular, thermal relief, and anti pad
- I define the bottom ("END LAYER") the same as the top ("BEGIN LAYER").
- How about SOLDERMASK_TOP/BOTTOM, PASTEMASK_TOP/BOTTOM?  Does anything need to be defined there?

I've had a hard time finding a good tutorial on thru-hold pad design.  Any help/comments would be much appreciated.

Parents
  • hi, in our way, the definition of the pads depends on the fabrication
    house. the pad definition must be in accordance of what the fabrication
    house can manufacture. it differs with every fabrication house. good
    day, eric

    pakistan wrote:
    >
    > I can tell you my way of defining most of the pads.
    >
    > if I had lead size of 24mils I add 6mils in defining drill size the I
    > add 10mils annular ring so the actual pad having 30mils drill and 50
    > mils pad size. add 10 mils in antipad and thermal relief and then copy
    > this stuff in all layer except solder mask. define solder mask 10 mil
    > larger then pad size.
    >
    > It is my practice I am also relatively new to allegro. so if any one
    > knows the better way correct me.
    >
    > Regards
    >
    > Tanveer
    >
    >
    >
    >
    > You received this email because you subscribed to notifications for
    > the Cadence PCB Design Forum. To unsubscribe, log in, go to forums,
    > and change your forum subscriptions.
    >
    > http://www.cadence.com/community/forums/ForumSubscriptions.aspx
Reply
  • hi, in our way, the definition of the pads depends on the fabrication
    house. the pad definition must be in accordance of what the fabrication
    house can manufacture. it differs with every fabrication house. good
    day, eric

    pakistan wrote:
    >
    > I can tell you my way of defining most of the pads.
    >
    > if I had lead size of 24mils I add 6mils in defining drill size the I
    > add 10mils annular ring so the actual pad having 30mils drill and 50
    > mils pad size. add 10 mils in antipad and thermal relief and then copy
    > this stuff in all layer except solder mask. define solder mask 10 mil
    > larger then pad size.
    >
    > It is my practice I am also relatively new to allegro. so if any one
    > knows the better way correct me.
    >
    > Regards
    >
    > Tanveer
    >
    >
    >
    >
    > You received this email because you subscribed to notifications for
    > the Cadence PCB Design Forum. To unsubscribe, log in, go to forums,
    > and change your forum subscriptions.
    >
    > http://www.cadence.com/community/forums/ForumSubscriptions.aspx
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