Jeffrey,
I would agree I also find it much easier in library part creation & routing
using metric. I would also agree, it is not really only the problem of fab vendors
supposedly not liking metric (I haven't had one complain yet though if I send them all metric data/drawings), it is also all our own mechanical groups
which of course feed us our board outlines & height keep out
requirements that seem to resist going metric. Especially when fitting
a board into a phone plastic body getting all the wacky dimensions usually for
mounting bosses & keypad locations.
Like you said incoming inspection also people not used to dealing with metric too.
I also agree with Suzy's practices.
But I am of the camp we should all be going metric.
Bob
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of [Jeffrey] [Jenkins]
Sent: Monday, March 19, 2012 4:37 PM
To: [log in to unmask]
Subject: Re: [DC] IPC APEX Designer's Day
Hi Tom,
Unfortunately it seems in the DOD world, we are the servants to several masters. What I find, and it doesn't matter the division or company I'm working with, is that the mechanical drawings (1st master)are still using an inch based system. The component vendors (2nd master) are in general metric, with the exceptions of some unique specialized devices. To handle this I use and have seen several other places use a systems outlined below which is similar to Susy's email.
* Board outline and any critical placement that is driven by mechanical needs are completed using the inch system
* Part creation is done in the primary or "dominant" dimensions of the source drawing, typically metric
* Part placement and trace routing are done in metric, using a similar setup to Susy's below. I use the .025mm (about 1mil) step size up to 2.5mm (about 100mil) for most routing and spacing. I have cheat sheets of all values up to 100mil on each side of my monitor for quick reference.
* Drawings are done in inches as our QA and mechanical all do inspections in inches.
Why am I routing in metric? Actually I've found it easier as all the escapes of most modern ICs are set up for metric. After a while, I find it pretty easy to swap between the two systems, and find metric to be more flexible.
So why am I doing the drawings in inches when metric at this point would probably be easier? I've done both, and it seems that no matter what, I often have vendors (not all, but some) return questions back...in guess what, inches. I went back and forth on this fence for a while and asked several vendors their take and the general consensus was, "well.. we convert them all to inches because it's what we are used to and what's preferred on the floor." Perhaps this is the 3rd master?
But this does seem to raise the question as to what incentive is there for the pwb vendors to change and rewrite their processes when they have them dialed in using inches? Forcing the IPC standards to metric only doesn't really seem to have been the answer. Nor does having the designers try to drive the vendors to do so, because that seems to have had little effect. They don't seem to be driven by anyone to do so
I think adding both dimension systems to the standards as you have indicated is currently the best solution. But until all parties agree (mechanical, vendors, designers, standards) to switch to metric, we're going to be riding this fence for a good long while.
That’s my $02. Right or wrong, I've learned to live in both worlds.
Best Regards,
-Jeffrey
Jeffrey A. Jenkins CID+/CIT
Designer PCB Staff-CA || L-3 Linkabit || Ph: 858-552-9832 || [log in to unmask]
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Susy Webb
Sent: Monday, March 19, 2012 12:37 PM
To: [log in to unmask]
Subject: Re: [DC] IPC APEX Designer's Day
Hi Tom,
I am quickly becoming a metric gal! I have a tendency to design the library part in the units which it is dimensioned in on the data sheet. If it is done in both, you can almost always tell which is the "dominant" dimension by which one is the "most rounded number". That is almost always metric these days... especially if it's BGAs, QFNs, and QFPs.
I always encourage people to at least try to designing in metric when I give my presentations because I believe that is the direction we are all going... sooner or later. I often suggest they switch over using the 05mm grid equivalents that you and the IPC suggest, for example....
0.050 mm = 0.0019” = 2 mil
0.100 mm = 0.0039” = 4 mil
0.125 mm = 0.0049” = 5 mil
0.150 mm = 0.0059” = 6 mil
We deal with a variety of fabricators and have never had any issues at all in either measurement. One thing I DON'T do is have the database in one set of units and the fab drawing in another set. Now THAT is confusing and I have to fight that battle at work all the time with the mechanical people.
BTW... Have a blast in Sydney! It's a WONDERFUL place too visit and the conference is a good one! Last year I was there and all my slides were in english units even though I was saying to design in metric. One of the attendees raised his hand and asked why I didn't change that. (I said because of lack of time.) Well, they use metric... and I have since changed all my slides to show both sets of dimentions!
That's my $.02 worth!... a confirmed fence straddler... at least in presentations!
Best Regards,
Susy Webb
---- Tom Hausherr <[log in to unmask]> wrote:
> Gilbert,
>
> That is great news! Now I have to give my presentation to the Orange
> County, CA IPC Designer's Council in an upcoming meeting to see if you
> are an isolated case or if the trend is finally turning. I'll get
> together with Scott McCurdy to set up a date in the near future to
> come up and visit your DC chapter to present and gather information.
>
> For everyone in the San Diego, CA area, I will be giving my
> presentaiton for the IPC San Diego Designer's Council Chapter meeting
> at the Del Mar Electronics Show on May 2, 2012 in the afternoon. Hope to see you there.
>
> And for those in the Dallas, TX and Phoenix, AZ area IPC Designer's
> Council, I'm coming your way this fall to discuss this topic. See you then!
>
> I can't forget the PCB designers in Australia. I'll be in Sydney
> speaking at the ElectroneX (SMCBA) convention, September 12 - 13
> giving the same presentation and gathering information.
>
> And all of you PCB designers in the Silicon Valley / Bay area, I'll
> see you at PCB West on September 25th to present and gather information.
>
> Tom
>
>
> -----Original Message-----
> From: Gilbert Mayandia [mailto:[log in to unmask]]
> Sent: Monday, March 19, 2012 10:14 AM
> To: '(Designers Council Forum)'; 'Tom Hausherr'
> Subject: RE: [DC] IPC APEX Designer's Day
>
> Thank you Tom,
>
> We are now using millimeter from footprint design all the way to the
> Fab Dwg. Thanks to you.
>
>
> Gilbert Mayandia
> PCB Designer
> STEC
> Santa Ana, CA U.S.A.
>
>
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
> Tom Hausherr
> Sent: Monday, March 19, 2012 9:52 AM
> To: [log in to unmask]
> Subject: [DC] IPC APEX Designer's Day
>
> Hi Everyone,
>
>
>
> I posted my IPC APEX "Designers Day" Power Point presentation on "PCB
> Design Optimization Starts in the CAD Library" here -
> https://console.mxlogic.com/redir/?hRT76bKfCS4TTS7PhOCr01bm87O8hScLFO-2ZoJGV9qNvlL3O_xWRiWtQkNmtlFmsU76XYyUqenAkmkXL6XCWC8v4KxZ94ov6RmUmAu2FbmU02rhd79EVsudEIIFEL6zBxOVJBcS2_id41Fr3x8QKCy0d2MAq810b3g36y0e-Aycfyq9W6y0eQIrDUvf5zZB0SyrhdI9LLIfLFCTZgV
>
>
>
> This presentation contains recommendations for adding PCB library
> drafting elements such as Silkscreen and Assembly Outlines, Polarity
> marking, Reference Designator sizes, Local Fiducials, round-off
> resolution update and the implementation of Mil Units for the upcoming IPC-7351C standard.
>
>
>
> One note on the Mil Unit subject. As PCB Designers, we have been
> taught DFM (Design For Manufacturing) rules during our entire career.
> For the past 10 years I have been all over the world promoting PCB
> Designers to transition to the metric measurement system and revealing
> why the metric system is superior for PCB design layout. However, our
> PCB fabrication shops prefer Mil unit Gerber or ODB++ data, drill
> data, fabrication drawings and layer stack-ups, panel sizes, material
> thicknesses, etc. The global electronics industry including component
> manufacturer's, CAD vendors, fabrication, assembly, mechanical and PCB
> design is split down the middle on this subject. I believe it will
> remain this way until the PCB fabrication process completely transitions to metric.
>
>
>
> I've been on the open market contracting PCB layout for DOD companies
> and they're ALL doing mil unit PCB design. Most PCB design service
> bureaus are doing mil (inch) based PCB layout because that's what
> their customers are asking for. I've submitted employment resumes to
> firms all over the USA to seek employment and the vast majority of them are doing mil unit PCB layout.
> At this year's IPC APEX conference there was a large crowd at the
> Designer's Day event and when I asked the question "How many of you
> are doing metric PCB layout?" only a couple people raised their hand.
> When I asked "How many of you are doing PCB layout in mil units?" the
> vast majority of the attendees raised their hands. When I asked people
> why they still do PCB layout in mil units the majority say "because
> our fabrication shops prefer mil units and we are big on Design For Manufacturing (DFM)".
>
>
>
> Most people in our industry refer to chip capacitors and resistors
> after their inch based names 1206, 0805, 0603, 0402 and not the IPC
> metric names 3216, 2012, 1608, 1005. All CAD vendors create their
> default software installation in mil or inch units (not metric).
> Popular PCB fabrication shops default to mil unit presentations in
> their private seminars to their customers or at IPC symposiums. Are we
> being brainwashed or are we in a state of chaos?
>
>
>
> I applaud IPC, JEDEC, NIST and the component manufacturing industry
> for fully transitioning to the metric unit system, but I fear that
> things are more messed up than ever before in our industry. Being
> split into two measurement systems is not exactly optimizing the
> electronics industry. So I propose that IPC go back and add mil
> dimensions in all of their standards to eliminate the confusion in
> dealing with dual measurement systems. IPC needs to recognize that a
> vast majority of the PCB industry is not transitioning to the metric
> unit system and that we need standards that are applicable to our
> profession today. Download my Power Point presentation from
> "Designer's Day" and you'll get a good taste of the metric / mil state of the PCB library industry.
>
>
>
> That's my opinion, what's yours?
>
>
>
> Best Regards,
>
> Tom
>
>
>
> Tom Hausherr
>
> President
>
> PCB Libraries, Inc.
>
> 13730 Sorbonne Court
>
> San Diego, CA 92128
>
> 858.592.4826 Office
>
> 858.859.5371 Cell
>
> [log in to unmask]
>
>
>
>
>
>
>
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