<runs from the from screaming hysterically -- WHY do i do this for a living?> At 08:05 AM 7/10/2008, you wrote: >Just a few thoughts on inner layer shifting. > >1. Don't forget Pythagoras and the proverbial >True Hole Position - .001" misregistration in >the X and .001" in the Y can be .00141" at 45°. This concept > works with holes, pads and clearances etc. >2. Consider that the drilled holes, ablated >holes and layers are all independently tooled >and shift independent of each other. >3. Hole to hole registration can vary due to drill deflection, drill walk etc. >4. Image feature to image feature may move due >to uneven expansion of the dielectric or the art >work. This uneven expansion may be due to physical > deformation or uneven thermal expansion. >4. Sequential lamination adds the vagrancies of >layer shift by variation sublam to sublam registration. >5. Back drill, counter bore and secondary drill >operation add another layer misregistration >particularly if the secondary drill is producing tooling > holes. >6. Over-etch and under-etch can effect line >width and spacing that may appear to be a shift >in layer when in fact the issue is variation in feature size. >7. Improper artwork compensation to accommodate >process variation can produce what appears to be >layer shift but in fact is improper sizing. >8. Mixing materials, uneven builds, grain >direction (warp vs. weft) all can produce registration issues. >9. Nonfunctional pads in every layer may >aggravate drill and image registration. >10. Glass style and epoxy ratios may affect registration. >11. Humidity can have an effect on artwork and image registration. >12. Tooling methods, round alignment holes >verses slots, aligning in the center verses the >edge of panel will affect layer shift. > >To know if you have inner layer shift, I >believe, you need to consider possible causes of >misregistration. For example the inner layer may >not be shifted, it may be that the drilled holes >are shifted. You have to choose what you >consider to be you reference point, drill hole >or layer one image etc. and consider the registration to that. > >All that being said, reasonable etch back should >not have a significant role or be significantly >affected by, inner layers shifting. > > >Paul Reid > >PWB Inc. > > > >-----Original Message----- >From: TechNet [mailto:[log in to unmask]] On Behalf Of Kathy Kuhlow >Sent: Wednesday, July 09, 2008 4:07 PM >To: [log in to unmask] >Subject: [TN] PCB Inner layer shifting > >I was just reading and got to thinking about PCB >inner layer shifting. Now I realize that this >can be caused by registration issues but here >are the questions I can't readily answer: > >1) Is it possible to cause inner layer shifting >on only signal layers during the assembly >operations or will this be seen in the PCB fabrication testing? > >2) Can inner layers that create opens or shorts >be latent or would the effect be seen immediately? >3) Would inner layers that do shift all shift >the same way? In other words would I get the >same opens/shorts? What would be the proportion >of possible affected if not all? >4) Would the PCB stresses caused by lamination >not be released prior to the PCB test or is >there enough residual stress still in the PCB at >time of assembly to cause an issue? >5) How would you know if you have inner layer shifting? > >I was just reading about etch back and some the >test data related with the process, is this part >of the driver to develop this process? > >Kathy Kuhlow >6980 Professional Parkway East >Sarasota, FL 34240 >Phone: 941-907-1000 ext 8248 >Mobile: 320-267-5549 >Email: [log in to unmask] > > >--------------------------------------------------- >Technet Mail List provided as a service by IPC >using LISTSERV 15.0 To unsubscribe, send a >message to [log in to unmask] with following text >in the BODY (NOT the subject field): SIGNOFF >Technet To temporarily halt or (re-start) >delivery of Technet send e-mail to >[log in to unmask]: SET Technet NOMAIL or (MAIL) >To receive ONE mailing per day of all the posts: >send e-mail to [log in to unmask]: SET Technet >Digest Search the archives of previous posts at: >http://listserv.ipc.org/archives Please visit >IPC web site >http://www.ipc.org/contentpage.asp?Pageid=4.3.16 >for additional information, or contact Keach >Sasamori at [log in to unmask] or 847-615-7100 ext.2815 >----------------------------------------------------- > >--------------------------------------------------- >Technet Mail List provided as a service by IPC using LISTSERV 15.0 >To unsubscribe, send a message to [log in to unmask] with following text in >the BODY (NOT the subject field): SIGNOFF Technet >To temporarily halt or (re-start) delivery of >Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) >To receive ONE mailing per day of all the posts: >send e-mail to [log in to unmask]: SET Technet Digest >Search the archives of previous posts at: http://listserv.ipc.org/archives >Please visit IPC web site >http://www.ipc.org/contentpage.asp?Pageid=4.3.16 >for additional information, or contact Keach >Sasamori at [log in to unmask] or 847-615-7100 ext.2815 >----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------