Gary- great idea, IPC needed to expand it list of component land
patterns.
Having choices between HDI footprints and relaxed (typical)
designs is something
most of us designers have to constantly do on our own. I
work in an environment
where 40% of my designs require changes to footprint designs
(Both IPC and Supplier)
to accommodate for lack of real-estate.
Missing footprint option in new IPC-7351 format.
Descretes need a design showing VIP (via in pad)
configuration. Most people trying this in design would agree
via should be located off center from the pad. For power
inductance reasons we place them on the
inside edge of pads. So vias are as close to each other as
practical. I know this could be a reach for IPC
to join in on this concept, but it is here to stay. HDI
design require this concept to work.
Since the council has both fabrication and assembly members
they should show how they prefer
VIP technology.
Greg Scott
Cray Inc.
Rob Legg wrote:
> That's what I like about standards. No ambiguity, good resale value
> and low-cost maintenance for the end user. RL
>
> ----- Original Message -----
> From: Gary Ferrari
> To: [log in to unmask]
> Sent: Thursday, April 18, 2002 7:15 PM
> Subject: Re: [TN] IPC SMT FOOTPRINT DESIGN GUIDLINES VS
> SUPPLIERS
> I would like to address a few of the comments that have
> been made.
>
> First, when the same component parameters and design fillet
> goals are input into the current web based calculator they
> should yield the same land pattern as listed in the RLP
> section. We have on occasion found an error in the component
> data listed in the hard copy or web calculator and have made
> appropriate corrects. Any discrepancies found should be
> reported to John Perry at IPC.
>
> Second is that the calculator is based on the same
> principles as found in the hard copy of the standard. It is
> true that land patterns for the newer components may not
> have been tested as the earlier ones were. But in many cases
> the basic principles remain untouched. However, the land
> pattern committee does approve each new pattern based on an
> assessment culled from their own experiences with that
> component as well as input from other industry sources.
>
> The last issue is that the 782 land pattern committee is
> currently working on a complete revision to our land pattern
> document. I would point out that one should not perceive the
> revised document as an indication that there is something
> wrong with the current land patterns. This effort is
> addressing new component families as well as a new concept
> going forward.
>
> The new standard will be identified as IPC-7351 and will be
> of a format that provides slash sheets for the various
> component families. This will enable new component additions
> to get released in a much more timely fashion. The standard
> will contain four columns of data for each component. The
> first column will be the existing 782 pattern data. The next
> three will represent minimum, median and maximum
> applications. All component types not currently in 782 will
> be released to this new format. AS we move forward, we will
> NOT be adding data under the 782 columns for components not
> currently listed in the current 782.
>
> As a general point of information, you will find that the
> current 782 land patterns will fall someplace between the
> minimum and median columns. What is important to recognize
> is that compromises were taken to reach the smaller sizes
> and it will be quite apparent where they were made. It would
> be wise for the designer to obtain approval from those
> affected by the compromises before using the smaller sizes.
>
> The first release will contain the current 782 listed
> components with additional component slash sheets released
> in rapid succession thereafter.
>
> Regards,
>
> Gary Ferrari
> Executive Director
> IPC Designers Council
> (860) 350-9300
> Fax (413) 771-5386
>