10 Replies Latest reply on Feb 20, 2009 1:26 PM by Jerry_Suiter

    Assembly and Silkscreen Reference Designator text for small packages

    Jerry_Suiter

      Hello,

       

       

       

      I have a question for the users specific to Assembly and Silkscreen Reference Designator text within small cells, like 0201 packages which are only 0.024 by 0.012 in size.

       

       

       

      Do you have Assembly and Silkscreen Reference Designators built within these cells?

       

       

      If so, is the text size so small that the strings are not useful for visualization? 

       

      How is this text used during the design process if it’s very small?

       

       

       

      Regards,

       

      Jerry Suiter

      ExpeditionPCB/XtremePCB Product Marketing Manager

        • 1. Re: Assembly and Silkscreen Reference Designator text for small packages
          yu.yanfeng

          Jerry,

          This is a good question! To very small componet, I suggest an auto-sizing Text.

          Yanfeng

          • 2. Re: Assembly and Silkscreen Reference Designator text for small packages
            Jack

            We don't bother with silkscreen for such small discretes, but we create assembly drawings that show everything. . Unfortunately, it is often difficult to read, so our assembers request we print the BoardStation "PLACE" layer to PDF, which shows all parts with RefDes as large as possible inside the placement border. Still difficult to read for small parts, but "zoomable", right? . I wish others would post how they deal with this... good question. . onward thru the fog, Jack .

            • 3. Re: Assembly and Silkscreen Reference Designator text for small packages
              bbpcbdesign

               

              Hi,

               

               

              I don't use silkscreen for such small discretes.

               

               

              I create a detailed assembly drawing using DXF output, to obtain a text searchable pdf.

              Assembly Refdes are not readable but they are searchable.

               

               

              Auto sizing text ( auto sizing using Placement Outline or assembly outline ? ) could be useful since is not easy to choose the right text height size while you create the cell.

              For example R100 require more space than R1 and you don't know till you place the cell into pcb.

              So, autosizing text could be usefull.

               

               

              Bortolo

               

               

              • 4. Re: Assembly and Silkscreen Reference Designator text for small packages
                Jerry_Suiter

                Hello,

                 

                So in the case of Expedition PCB, you would have no Silkscreen graphics for these very small components and you would create documentation based on the Assembly graphics correct?

                 

                The reason I asked the original question is because we are thinking that the Silkscreen and Assembly graphics are not very useful during placement.  So we are considering adding a new Placement Reference Designator to identify parts during placement that is always right reading, never mirrored and is the size of the Placement Outline.  The problem is for these small parts the Placement Outlines are so small the text would not be readable.  However I think for normal parts, having only the Placement Outline and this new Placement RefDes displayed would be much better than having Silkscreen or Assembly RefDes displayed.  We would make the maximum size for this Placement RefDes around 150th in height so it does not get too big. 

                 

                Any comments to improving placement by creating a new more dynamic Placement RefDes?

                 

                Regards,

                 

                Jerry Suiter

                ExpeditionPCB/XtremePCB Product Marketing Manager

                • 5. Re: Assembly and Silkscreen Reference Designator text for small packages
                  bbpcbdesign

                  Hi Jerry,

                  ....The reason I asked the original question is because we are thinking that the Silkscreen and Assembly graphics are not very useful during placement.

                   

                  It depends of what Assembly Drawing you create...

                  Attached an image from a very very simple board.

                  Even if you don't believe it, it's not so time consuming create ( with macros, dxf...) such detailed Assembly drawings.

                   

                  Regards

                  Bortolo

                  • 6. Re: Assembly and Silkscreen Reference Designator text for small packages
                    strangd

                    Hi Jerry:

                     

                    I hope that you are not assuming that there is only one Placement Outline per footprint cell.  And please pay attention to the database size limitation that some people are bumping into before adding more data to every part if that data may be redundant.

                     

                    I place the silkscreen graphics much like I would for a 0402.  The line width may be smaller but I don't be in the business of predicting print capabilities of future equipment.  Place the parts and delete the aperture size photoplotter draws later on.  If the contract calls for all parts to have markings, then use a different color soldermask as the screening tool.  Or laser etch the marking.

                     

                    Assembly drawings get a detail view blow-up if you need to see all of the markings at the drawing level.

                     

                    Dwain

                    • 7. Re: Assembly and Silkscreen Reference Designator text for small packages
                      Jerry_Suiter

                      Dwain,

                       

                      I fully understand that Expedition PCB supports multiple placement outlines and expect this not to be an issue.  We have other similar situations where we need to account for multiple placement outlines so this is not new to our development. 

                       

                      As for your statement about database size limitation, I would like to understand the details behind your statement so I can respond.  I have been working with this software since its inception and might be able to provide some insight to this issue if I have more information.  Specific to the proposal, this would not increase the database size on disk at all since we will dynamically build the graphics on startup just as we do today for Pin Numbers/Types.

                       

                      I understand some customers will place silkscreen graphics for these small devices.  Can you tell me what font size your using for the RefDes?  Also, is the size of this text difficult to read when you’re doing placement manipulation?  Also, once physically silkscreened on the board, is this text readable or does it get jumbled up with other silkscreen graphics? 

                       

                      Your information has been very helpful.  It was interesting to see that you used different color soldermask as a screening tool. 

                       

                      I know this response has been long but I have one more question since everyone has been so helpful to provide information.  During placement or placement manipulation, is there anyone using the assembly graphics as a reference?  If so, how is it used to aid placement?

                       

                      Regards,

                      Jerry Suiter

                      ExpeditionPCB/XtremePCB Product Marketing Manager

                      • 8. Re: Assembly and Silkscreen Reference Designator text for small packages
                        strangd

                        Good day Jerry:

                         

                        I have attended two users' group presentations were the company had to strip out the CES data in order to get the database small enough for the board to load and be processed.  For myself, I have not hit that point but I have been close enough that I had Windows Task Manager | Performance up and running so that I could see when I was getting too close to max'ing the memory.  I would shut down and re-start.  I would imagin that the same people that keep asking when there is going to be a 64 bit version of Expedition are having this problem more than I.  From time to time, this has been discussed on the monthly conference calls.

                         

                        I have been working with this software since the VAX days, through the Clipper based PCB Engineer/AT Designer and into the Windows based VeriBest and Mentor Graphics products.

                         

                        I put a RAID drive system into my workstation years ago to handle the loading of large Expedition database sizes and the video that edit.  And I don't care how big the database is on the hard drives.  I start to care when the software builds a board database in RAM and that database size runs into the limits set by Windows 32.  The graphic frame displayed on my screens use to be of a fixed size and would be constructed from the RAM database. ( Pulling frame information from the hard drive, even a RAID, would be too painful to the end user.)  One would guess that the move to OpenGL might have more than a couple of video frames worth memory used but still, it is the RAM limitations that drive the problem.

                         

                        I don't remember using text less then 0.005".  Even on a MCM.

                         

                        I zoom in when placing and routing the boards.  The size of the REFDES text has not been material to me.

                         

                        No one picks up one of these boards and tries to read the silkscreen without aid.  The Pick and Place setup guy zooms in the camera over one part at a time and adjusts the CAM placement data to the pads on the surface of the board.  In the images that I have seen during this operation, 2 or 3 mil objects were clearly visible.  The build-up and re-work benches at this company all have visual magnifiers with cameras which the techs use even to place and solder 0402s.  And Yes, they would like to have a REFDES in the field of view.

                         

                        Dwain

                        • 9. Re: Assembly and Silkscreen Reference Designator text for small packages
                          yu.yanfeng

                          Hi Dwain,

                           

                          I fully agree with you!

                           

                          I also saw the memory footprint of Expeditionpcb is so big to reach 2G Limit to most of our designs. Compared to Allegro, Expeditionpcb consumes 1.5X more memory than Allegro and performance is slower. That is a big weakness of Expeditionpcb. I hope Mentor can take cares on this issue. We have designed boards with nearly 15K net ( 50K pins) and 3.5K nets be constrainted, the design can be loaded with CES enabled in the box with 2G Memory. Windows can support a maxium of 3G application space, Hope next 32bit release of Expeditionpcb can use 3G memory space before a 64bit roll out. Today, some of PCB tool have 64bit version to support more complicated design, for example, Ansoft's Siwave, Sigrity's OptimizePI and Flotherm etc.

                           

                           

                          Yanfeng

                          • 10. Re: Assembly and Silkscreen Reference Designator text for small packages
                            Jerry_Suiter

                            Hello Dwain,

                             

                            It’s good to see someone who has a long history like myself with the old Intergraph products.  I still remember back in 1990 working on the VAX to PCB Engineer translator and the old InterPro dual monitor workstations.  Boy, we have come a long way..

                             

                            Your information on how you use silkscreen during the design phase and post design after manufacturing has been valuable to me.  We are not making any changes in this area so don’t be alarmed by my questions.  I was just trying to understand how people cooped with such small text graphics.

                             

                            Also, I appreciate the detailed information on your concerns about the memory footprint of Expedition PCB.  I think your questions are important enough to justify another thread on the topic.  Let me write something up and I will post it next week.  I will cover the topics you have raised as well as the response from Yanfeng on the same topic.  Look for it next week.

                             

                             

                            Regards,

                            Jerry Suiter

                            ExpeditionPCB/XtremePCB Product Marketing Manager