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Proportional Through-hole Padstacks

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jameshead View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jameshead Quote  Post ReplyReply Direct Link To This Post Posted: 21 Aug 2012 at 8:49am
I've mentioned this on the SMART group e-mail list as well.  A good PCB fabricator mentioned that using laser direct imaging can accommodate a 0.075 mm radial annular ring for drilled hole diameter (not finished hole diameter) on an outer layer for "no breakout" condition but would recommend 0.125 mm radial for inner layers in the same pad stack.
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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 21 Aug 2012 at 9:10am
I have heard from Gary Ferrari at this years IPC APEX conference that the IPC-2221 and 2222 are being overhauled and will be released before the next IPC APEX conference in San Diego, CA in early 2013. But I don't see any release notification here - http://www.ipc.org/CommitteeDetail.aspx?Committee=D-31B
 
All I can say is that the Proportional Via Padstacks have been used in production by CADPRO on over 2,000 PCB layouts and Wind River (now Intel) and all their PCB Layouts before we released it to the public in 2004 via PCB Libraries, Inc.
 
No fabrication shop or EE engineer has ever complained of problems and many of the designs we did went into high volume production.
 
Download the paper on PCB Design Optimization Starts in the CAD Library -
 
Here is a picture from the presentation regarding inner layer shifting & annular ring -
 
 
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plinder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote plinder Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 2012 at 10:43am
The Footprint names for Mounting Holes look different than the last version of LP Wizard.  What naming convention do you plan on carrying forward for Mounting Holes?
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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 2012 at 11:54am
Mounting Holes will not make it into the PCB Footprint Expert.
 
All ANSI and ISO Mounting Holes will be available in every CAD format for free download soon.
 
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Vladimir.Stoyanov View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vladimir.Stoyanov Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 2012 at 11:41pm
Hi Tom,
 
Do you release the through-hole component families to select from IPC 7251 3-Tier?
 
I prefer to use Least level for all my PTH components.
 
Regards,
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Tom H View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 02 Oct 2012 at 7:23am
The PCB Footprint Expert supports the unreleased IPC-7251 through-hole standard but I prefer "Proportional Padstacks" because they cover all 3-Tiers.
 
The IPC-7251 has fixed annular rings for each tier, regardless of the hole size.
 
The Proportional Padstack annular ring gradually increases with the hole size. So small holes use the Least annular ring, medium size holes use Nominal annular ring and larger hole sizes use the Most annular ring. Then there's a point where the hole size is larger than 2 mm (80 mils) and the annular ring gradually gets even larger than the IPC-7251 standard.
 
So Proportional Padstacks meet or beat IPC-7251. The theory is simple. If a through-hole component lead has a large diameter it's for a reason. It might need to carry a lot of current or the component may be tall and requires stability or the component may be heavy and require support. All of these reasons require a larger annular ring which allows more solder.
 
Example: in the case of a large component lead that carries current, this will increase the temperature as the board functions and the large annular dissipates heat. If you use the Least Environment with the small annular ring, it's less solder and less heat dissipation.
 
Note: I've used the Proportional Padstacks on over 1,000 PCB layout designs for both prototype and production boards and never had a manufacturing problem or a field problem. It's proven to be a very reliable padstack.
 
Here is the IPC-7251 table for Axial Lead components:
 
 
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Vladimir.Stoyanov View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vladimir.Stoyanov Quote  Post ReplyReply Direct Link To This Post Posted: 02 Oct 2012 at 11:49pm
Dear Tom,
I made terrible mistake - for PTH I use Most level, not Least. Even with this level I receive a mumble from our plants. For PTH footprints I use Excel table from PCB Matrix, but it is quite old. Do you have an update of this table?



Thanks a lot!
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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 2012 at 7:01am
All of the latest updated tables, charts and rules are for free download here - http://www.pcblibraries.com/forum/pcb-library-construction-guidelines_forum30.html
 
Or here -
 
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Vladimir.Stoyanov View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vladimir.Stoyanov Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 2012 at 9:46pm
IPC-7251_Padstack_Charts.xls

Dear Tom,
Now I see that I can attach a file. I just asked you for update of this table. I don't want to use Least neither Nominal level for PTH. Can you help me?
Kind regards,
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nick B Quote  Post ReplyReply Direct Link To This Post Posted: 04 Oct 2012 at 3:26pm
Please download the latest PTH Padstack Reference Calculator from HERE.
 
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