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["Capotosto, Michael" <capotosto AT bnl.gov>]

Gerard, 

I've checked with John Hammond, we do have access to some IPC specs, but none 
applicable to flex boards.

--Mike

-----Original Message-----
From: Star-fst-l <star-fst-l-bounces AT lists.bnl.gov> On Behalf Of Zhenyu Ye
Sent: Thursday, October 17, 2019 7:18 PM
To: Gerard Visser <gvisser AT indiana.edu>
Cc: star-fst-l AT lists.bnl.gov
Subject: Re: [Star-fst-l] Weekly FST meeting - 10/17/2019

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-track
>>> er-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
>>> 
>>> 
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