Star-fst-l mailing list

[Yi Yang <yiyang AT ncku.edu.tw>]

Hi Gerard and Zhenyu,

I checked with the vendor yesterday. 

Yes, this vendor did work with soft PCB before, but they will perform this baking procedure only by request. They said normally they will receive the PCB in the vacuum bag, and they will do the soldering right after open it. 

They was also surprised when they saw our hybrid without using vacuum packaging, and I didn't ask for the baking procedure. 

In anywise, this will be fixed in the future.

Cheers,

Yi

+++++++++++++++++++++++++++++++++++++++++++++++++++
Yi Yang, Associate Professor
Department of Physics
National Cheng Kung University
Tainan, 701 Taiwan
E-Mail: yiyang AT ncku.edu.tw
Tel: +886-6-2757575 ext.65237
Fax: +886-6-2747995
Group Web: http://phys.ncku.edu.tw/~yiyang
+++++++++++++++++++++++++++++++++++++++++++++++++++

On Fri, Oct 18, 2019 at 7:17 AM Zhenyu Ye <yezhenyu2003 AT gmail.com> wrote:

Hi Gerard, I did not expect mounting R/C/connectors onto hybrid would be a problem, since it must have been done on a daily basis by many vendors. But surprises seem to arise everywhere. Maybe Yi can find out why the assembly vendor did not follow such a “standard” procedure. Has the vendor done assembly work with hybrid PCBs before?

Zhenyu

> On Oct 17, 2019, at 4:53 PM, Gerard Visser <gvisser AT indiana.edu> wrote:
>
> hi Zhenyu, Jianing,
>       I am surprised that the assembly vendor did not bake the hybrids no matter how they may have been packed. It is my understanding that would be standard procedure for multilayer flex circuits, see e.g. https://urldefense.proofpoint.com/v2/url?u=https-3A__blog.epectec.com_why-2Dpre-2Dbake-2Dflex-2Dpcb-2Dprior-2Dto-2Dassembly&d=DwIDaQ&c=aTOVZmpUfPKZuaG9NO7J7Mh6imZbfhL47t9CpZ-pCOw&r=8ygAAI6gQzVe9hFCRdEAO5MwBJh2ID34fiwLpV3P1Xo&m=giOH7RS5Xa-xGGwScwvBQl-StfhXSE1nzFUC09bfW3U&s=p4gT8sQiokgPYN24qO4W4TTOdaeXD9Xlq1OvlsXrdWw&e=  . (I do not have a copy ($$) of the IPC standards mentioned there but perhaps BNL/Mike can access them somehow?) It seems to me if your assembly drawing references IPC standards (as is probably best) then the vendor ought to know about all this and get it right.
>       Anyway, with heightened awareness on their part now it should be good for the future, I am confident. Storage in vacuum packs would be beneficial of course but probably does not eliminate the need to bake. (I am not sure about that.)
>       Sincerely,
>
>               Gerard
>
>
> On 10/17/2019 5:31 PM, Zhenyu Ye wrote:
>> Minutes:
>> Attendees: Elke, Han-Sheng, Jianing, Krishan, Mike, Prithwish, Zhenyu
>> *** Mechanical structure: We went through Yi’s slides w/o his presence. Some questions were already communicated to him by email. Other questions were asked:
>> 1. Elke: what causes bending of the structure and how the vendor is going to fix it?
>> Because Yi was not present to answer this question, ZY explained his understanding based on the brief discussion with Yi on Tuesday (Yi, please correct me if I am wrong). The bending was believed to be caused by unevenly distributed material during injection and formation. The vendor was going to add additional injection points and distribution tunnels. This is not mentioned in Yi’s slide, but instead they are going to add a rib to strengthen the structure.
>> 2. Elke: What caused the bubbles in the hybrids? Is baking hybrids at 120 degree a standard procedure? Do we have documents from the vendors on the recommended procedure and/or requirements
>> ZY answer for Yi: The company in Taiwan to do the soldering thinks that the bubbles may be caused by water vapor intrusion during the transportation. They expected hybrids sealed in vacuum bags to prevent it from happening during transportation and storage, but this was not the practice done by the Chinese vendor, which made the hybrids.
>> Jianing: after communicating the “bubble” issue with the Chinese vendor, they recommended baking hybrids at 120 degree C for 2 hours before soldering. JIaning will try to get the recommended handling and soldering procedure from the hybrid vendors. She will also ask the vendors to use vacuum bags. She has contacted two vendors (the old + a new ones) to make new outer hybrids with modified APV positions, and the new vendor to make new inner hybrids. The latter will need the confirmation from ZY that the 0.528mm shift is not a problem for wire-bonding at Fermilab.
>> *** hybrids
>> Jianing: The delivery time for new hybrids from the old vendor is 2-3 weeks, and 3-4 weeks from the new vendor.
>> ZY: unless the 0.528mm shift is found to be an issue, we should stick to the current inner hybrid design.
>> *** Module assembly
>> ZY met the Fermilab engineers and technicians on Wednesday. They confirmed that 0.011mm shift for sensor-APV bonding pads for the outer region won’t be a problem. The technician does not think the 0.528mm shift for the inner region is a problem either, but she will double check. Also started discussing fabrication of the assembly fixture, e.g., machine shop options, materials, etc.
>> *** F2F meeting at BNL for forward upgrade
>> The STAR management started discussing the need to hold a 2-3 day workshop on Spin/Forward upgrade in early 2020 (e.g. January)
>>> On Oct 15, 2019, at 5:10 PM, Zhenyu Ye <yezhenyu2003 AT gmail.com> wrote:
>>>
>>> Dear all,
>>>
>>> We will have a meeting starting at 9am BNL time this Thursday Oct 17.  The meeting agenda and bluejeans info can be found at https://drupal.star.bnl.gov/STAR/blog/yezhenyu/forward-silicon-tracker-weekly-meeting
>>>
>>> 1. News - All
>>> 2. Mechanical Structure - Yi Yang, Han-sheng Li
>>> 3. Hybrid - Jianing Dong
>>> 4. Module Assembly - Zhenyu Ye
>>>
>>> If you have other updates and items for discussion, please add them to the agenda.
>>>
>>> Thanks and Best,
>>> Zhenyu
>>>
>>>
>> _______________________________________________
>> Star-fst-l mailing list
>> Star-fst-l AT lists.bnl.gov
>> https://lists.bnl.gov/mailman/listinfo/star-fst-l
> _______________________________________________
> Star-fst-l mailing list
> Star-fst-l AT lists.bnl.gov
> https://lists.bnl.gov/mailman/listinfo/star-fst-l

_______________________________________________
Star-fst-l mailing list
Star-fst-l AT lists.bnl.gov
https://lists.bnl.gov/mailman/listinfo/star-fst-l