Proportional Through-hole Padstacks

 

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 -

http://www.pcblibraries.com/forum/pcb-library-optimization-presentation-free_topic468.html 

 

Here is a picture from the presentation regarding inner layer shifting & annular ring -

 

 

 

All ANSI and ISO Mounting Holes will be available in every CAD format for free download soon.

 

 

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:

 

 

 

Or here -

http://www.pcblibraries.com/Downloads/