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[Zhenyu Ye <yezhenyu2003 AT gmail.com>]

Hi Gerard,

My previous statement of vendor opening a larger area than design was a 
misinterpretation of what Jianing told me.
My understanding was that the first version of hybrid from the first vendor 
did not have the exposure (this is what we see from prototype #1 and #2), and 
that the production version of hybrid from the second (new) vendor had the 
GND exposure because of limited precision to open the insulation layer. I did 
not realize that this was already in the design of the new hybrid. To me, it 
could be better to have the insulating layer cover GND.

So far we have 12 modules mounted with APV, there are a couple of issues with 
some of them, but none is related to this operation. 

Zhenyu

> On Feb 10, 2021, at 10:32 AM, Visser, Gerard <gvisser AT indiana.edu> wrote:
> 
> hi Zhenyu,
>    That larger opening is there in the design, see attached screenshot. It 
> is not a vendor mistake.
>    And, I think that the coverlayer is not to be considered reliable 
> insulation anyway. So the issue (IMHO) is overlap of the epoxy and the 
> other conductors. For sure at the time of the hybrid reviews, I stated that 
> I couldn't speculate how much overflow of the epoxy there might be, and I 
> asked for the experts on the chip die attachment to review this point.
> 
>    Anyway, it is what it is, I think the rework plan is probably fine in 
> practice. I am completely confident the tech(s) will remove the copper 
> carefully and check their work. Hopefully they don't have to reject any.
> 
>   Sincerely,
> 
>        Gerard
> 
> 
> 
> From: Zhenyu Ye <yezhenyu2003 AT gmail.com>
> Sent: Wednesday, February 10, 2021 11:14 AM
> To: Visser, Gerard <gvisser AT indiana.edu>
> Cc: Star-fst L <star-fst-l AT lists.bnl.gov>
> Subject: Re: [Star-fst-l] FST slides from Monday
>  
> Hi Gerard, 
> 
> I must have a bad memory, because I don’t remember this request. Review of 
> the design of the hybrid or of any of the detector is not their 
> responsibility. Even if one reviews the layout, one would not find this 
> because by design the GND copper should be covered by insulation layer, but 
> the vendor opened a larger window so that parts of the GND is exposed. 
> 
> Zhenyu
> 
> > On Feb 10, 2021, at 9:34 AM, Visser, Gerard <gvisser AT indiana.edu> wrote:
> > 
> > hi Xu, Flemming,
> >   Interesting.
> >    I feel I must point out, I asked (several times) that we should ask 
> > Fermilab Sidet people to review the hybrid layout files, specifically 
> > because these other copper areas in the layout looked to me too close to 
> > the die attach pad. I believe I was told that the layout was examined and 
> > it was fine. Clearly, that's not the case. Oh well.
> >    Reworking every hybrid in this manner is not zero risk.
> > 
> >    Gerard
> > 
> > p.s. On slide 6 - extra noise in cooling test - the cooling tube was I 
> > hope grounded to T-board according to plan. Right? (If not, there is risk 
> > of permanent damage, not only of higher noise.)
> > 
> > 
> > From: Star-fst-l <star-fst-l-bounces AT lists.bnl.gov> on behalf of videbaek 
> > <videbaek AT bnl.gov>
> > Sent: Wednesday, February 10, 2021 9:15 AM
> > To: Star-fst L <star-fst-l AT lists.bnl.gov>
> > Subject: [Star-fst-l] FST slides from Monday
> >  
> > Hi Xu,
> > 
> > Are your slides from Monday's meeting available? I do not see them on 
> > the meeting page.
> > 
> > best Flemming
> > 
> > 
> > -- 
> > Flemming Videbaek
> > senior scientist
> > videbaek @ bnl.gov
> > Brookhaven National Lab
> > Physics Department
> > Bldg 510D
> > Upton, NY 11973
> > 
> > phone: 631-344-4106
> > cell     :  631-681-1596
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