Craig It would help to know what material is being used, and the frequency specified for measurement of phase delta. Scott -- Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC Craig Sullivan wrote: > Hello, > > > I have a 2 part problem. Our customer has informed us they are seeing phase > errors in the assemblies we build for them. The requirement is all channels > need to have a phase delta of < 14.5 degrees. In other words, the max phase > - the min phase across 48 channels. > > > > Part 1 of the problem is a phase delta in excess of 30 degrees. We have > found the root cause of this problem to be PCB delamination. > > > > Part 2 of the problem is the phase delta around 15-18 degrees. This is > usually brought back into tolerance by changing an SMT capacitor. > > > > Finding the root cause of part 2 is proving to be rather challenging. > Originally the specification was < 8 degrees. When the customer started > seeing failures, they increased the specification to < 14.5. When they saw > even more failures in addition to the delam, they finally brought it to our > attention. > > > > In my opinion the stripline construction "should" be rather forgiving. It's > 1/2 oz, 19.4 mils wide surrounded by ~18 mil dielectrics on each side. > Though one of my concerns is each trace length is around 14.5 inches and is > serpentined. In addition, no two serpentine designs exhibit the exact same > pattern. > > > > Another concern I have is the channels are spread across 3 different layers > in the stackup (16 channels each on layers 2, 7, and 11). The PCB is 12 > layers. > > > > Layers 2 and 11 have the same stackup: > > ==================== Ref > > 18 mil core > > -------------------- Signal > > 5.8 mil pp > > 6 mil core > > 5.8 mil pp > > ==================== Ref > > > > Layer 7 is slightly different: > > ==================== Ref > > 12 mil core > > 5.8 mil pp > > -------------------- Signal > > 18 mil core > > ==================== Ref > > > > Also to toss another variable in the mix. This board is completely round > with each channel beginning at the perimeter of the PCB and equidistant from > the next channel. So with that said, I am aware of the trace orientation in > regard to weave/glass/resin now becomes a factor as well. > > > > So my question to the list is: What are some causes of an increased phase > spread? Also, any reference material recommendations are welcomed. > > > > Thank you, > > Craig Sullivan > > Manufacturing Engineer > > MPL Incorporated > > P: 607.266.0480 > > F: 607.266.0482 > > csullivan@xxxxxxxxxx > > > > Export Control: > This message is intended only for the addressee and may contain information > that is company confidential or privileged. Any technical data in this > message may be exported only in accordance with the U.S. International > Traffic in Arms Regulations (22 CFR Parts 120-130) or the Export > Administration Regulations (15 CFR Parts 730-774). Unauthorized use is > strictly prohibited and may be unlawful. If you are not the intended > recipient, or the person responsible for delivering to the intended > recipient, you should not read, copy, disclose or otherwise use this > message. If you have received this email in error, please delete it, and > advise the sender immediately. > > > > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > List technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu