IPC-2581 Panel: A Spirited Discussion on PCB Data Transfer Formats
By Richard Goering - October 2, 2011
A lively panel discussion Sept. 29
revealed that PCB designers have some
strong opinions about the data formats
that convey design intent to
manufacturing. Several audience members
expressed support for the Gerber data
format that has been around for over 30
years. But other audience members and
panelists agreed that a more intelligent
and up-to-date format is needed, and
that an open industry standard called
IPC-2581 appears to be the best way
forward.
The panel, titled "Data Transfer in
the 21st Century," was held
at the PCB West conference in Santa
Clara, California. The moderator was
Mike Buetow, editorial director of the
UP Media Group. Panelists were as
follows, shown left to right in the
photo below:
- Hemant Shah, product marketing
director, Cadence
- Rick Almeida, founder and
director of marketing, DownStream
Technologies
- Max Clark, product marketing
manager, Valor division, Mentor
Graphics
- Dana Korf, director of product
engineering, Sanmina-SCI
- Gary Carter, CAD engineering
manager, Fujitsu Network
Communications
The panel's purpose was to introduce
the new
IPC-2581 Consortium, a group of
OEMs, EDA companies, and electronics
manufacturers whose collective aim is to
accelerate the adoption of IPC-2581.
Cadence played a leadership role in
establishing this consortium and has
been joined in it by Zuken, another
major PCB CAD provider. Other members
are shown in the graphic below.
The following background will help
set some context for the panel:
- The Gerber format began
in the 1960s as a way to describe
information sent to photo plotters.
RS-274X, or Extended Gerber, is
still widely used today.
- ODB++ (Open Data Base)
was created by Valor Computerized
Systems starting in the 1990s and
promises to be an "intelligent"
format that captures all information
needed for assembly and fabrication.
Mentor bought Valor in 2010 and now
makes ODB++ available through
partnership programs.
- GenCAM was conceived by
the IPC, a PCB standards
organization, in 1997 as a
replacement for the Gerber format.
- IPC-2581 was developed as
an "intelligent" data format that
aimed to combine the best of ODB++X
(no longer available) and GenCAM.
Version 1.0 was released in 2004 and
the standard is currently being
updated.
Perhaps the most important point to
remember is that while the Gerber format
can transfer image data, it does not
transfer stackup data, materials, design
intent, or a netlist. IPC-2581 provides
a complete transfer of design data and
promises to save millions of dollars
that are wasted today by managing
multiple files in different formats.
Time to Move Up from Gerber?
Shah opened the panel discussion by
noting that while Gerber is a proven
format, "it really does not have the
intelligence customers need today to
communicate design data to
manufacturing." One thing it lacks is
netlist information - manufacturers have
to do a lot of reverse engineering to
get that, he noted. An audience member
noted that an IPC standard netlist file
can be sent with Gerber data. Shah
responded that "the beauty with IPC-2581
is that it's all in one file."
A few audience members expressed
concern that IPC-2581 or ODB++ might
send out information design teams don't
want to convey, but Shah noted that
designers can control what data goes
out, and Clark gave a similar assurance
for ODB++. When an audience member said
he saw no reason to use ODB++, given
that fabricators still want Gerber
files, Clark responded that "there's a
tremendous risk when you provide
low-level machine driven formats. A lot
of reverse engineering is done on those
files, more than you'd probably like."
Later in the discussion, an audience
member said that there will still be a
need to support Gerber as a "least
common denominator" format, and declared
that "when we output Gerber every fab
house in the world can read that data."
Clark's response: "Yeah, but using that
logic we should go back to Morse Code."
"The push for IPC-2581 is not that
Gerber is a bad thing," Almeida said.
"Using IPC-2581 or ODB++ lets us
consolidate on a common format to bring
data back and forth, as opposed to
multiple file formats from multiple EDA
vendors." Korf said that Sanmina-SCI
manufactures several thousand designs
per week, and that there's a lot of
extra work involved in comparing and
checking all the diverse files that come
in with Gerber data. With ODB++, a lot
of that checking goes away.
Offering a user perspective, Carter
noted that "the vision I have for
IPC-2581 is beyond Gerber replacement,
it's intelligence. I want to control my
IP. I don't want information that's not
necessary going to an overseas
fabricator somewhere." He also cited the
need to work with his "counterpart" on
the manufacturing side so that both have
the same information. "I've got it in
Cadence [Allegro] and he's got it in his
tools," Carter said.
IPC-2581 or ODB++?
Given that both IPC-2581 and ODB++
are presumably "intelligent" data
exchange mechanisms, why IPC-2581? Clark
said that ODB++ has thousands of users,
and is available to other PCB CAD
vendors (including Cadence and Zuken)
through a partnership program. But it's
still a proprietary format owned by
Mentor, and several audience members
challenged that status.
"As an Allegro user, I have to go to
the Mentor web site to get an ODB++
translator," said one. "That always
bothered me. The people writing
translators are not the best suited to
do that." Said another: "You have to
sign a non-disclosure agreement with
Mentor. That's not fair."
Clark responded that "our concern is
that if it just proliferated, there
would be variances and it would become a
non-standard. Our concern is that if we
make it publicly available, the format
could run amok." Shah replied that
single-entity control is a good idea,
but it should be through a standards
body such as the IPC.
"You have to license it [ODB++], it's
not open," Almeida said. "That's why
we're looking at 2581. We need to rely
on something that's neutral, where
nobody has a vested interest in changing
the format."
One audience member had a practical
concern. ODB++ is the database of a
commercial tool, he said, and when the
tool changes, the format may change. He
cited an example in which a vendor in
China had an older version of ODB++ and
couldn't read the current one. "I'm
thinking 2581 will be more stable," he
said. "I'm hoping 2581 catches on."
Will Mentor support IPC-2581? "Right
now our strategy is all focused around
ODB++," Clark responded.
Why a Consortium?
Given that IPC has already ratified
IPC-2581, why is a consortium needed
now? Dieter Bergman, technical director
of the IPC, spoke from the audience
about the formation of IPC-2581. He
noted that it "doesn't work as a
standard unless there's an industry
group that wants to do it. It's an
opportunity to really take a giant step.
Thank God some of the CAD companies were
ready to do this and found support for
it. We will support it to the nth degree
and if something is not right we'll fix
it."
Shah said that Cadence helped launch
the IPC-2581 Consortium based on
customer demand. "There's a huge demand
from customers to have something that's
open and neutral," he said. Thanks to
the consortium, he noted, "we can demo a
design data exchange between Cadence and
Zuken."
"We think [IPC-2581] is going to be
the format of choice going forward,"
said an audience member. "Not only does
it include everything needed for the
industry, but it's very dynamic and easy
to upgrade the format to what we need."
My Perspective
First let me express great admiration
for the venerable Gerber format, which
has been around longer than almost
anything in EDA except maybe SPICE
simulation. But PCB designs are much
more complex than they used to be,
there's far more data going into
manufacturing, and it's time to move on
to a format for the 21st
century. A number of companies in the
PCB design and manufacturing flow,
including Cadence and several large
OEMs, are betting on IPC-2581 and are
working hard to move it forward.
More information about the consortium
and about IPC-2581 is
available here.
Richard Goering
