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Re: CDC Electronics Assembly
Hi Yves and Curtis,
Apparently this email could not be delivered. Sorry if you are receiving
duplicates.
Regards,
Fernando
Fernando J. Barbosa wrote:
> Hi Yves,
>
> I think I am missing which PCB you are referring to. The connector
> assembly is attached to the Plexiglass from the straw side with screws
> attached from the outside and pressing the connector on the plenum
> side of the Plexiglass (the threaded inserts will be an integral part
> of the connector). The screws also have a washer and o-ring seal. The
> CDC can then be rotated vertically and the sealant applied around the
> connectors and between the connectors and the Plexiglass. It should
> make a very nice seal. The conformal seal on the connector assembly is
> to prevent leaks through the electrical pins on the connector.
>
> Regards,
> Fernando
>
>
>
> Yves Van Haarlem wrote:
>> Hi Fernando,
>>
>> Thanks for the drawing. I was actually thinking of sealing the pcb in
>> the endplate which would be much easier to seal than the connector.
>>
>>
>> Cheers,
>> Yves
>>
>> /--------------------------------
>> / Yves Van Haarlem
>> _--~~--_ /
>> /~/_| |_\~\ / Carnegie Mellon University
>> |____________| / Department of Physics
>> |[][][][][][]|:= / Wean Hall room 8404
>> __| __ |__ \ Pittsburgh, PA 15213
>> | ||. | == | | \ USA
>> (| ||__| == | |) \
>> | |[] [] == | | \ Tel.: +1 412 268-6949
>> | |____________| | \ +1 412 641-9252
>> /__\ /__\ \ Fax.: +1 412 681-0648
>> ~~ ~~ \-----------------------------------
>>
>> On Wed, 13 Aug 2008, Fernando J. Barbosa wrote:
>>
>>> Hi Yves,
>>>
>>> The shield is at HV (1800 V) and the inner conductors are at the
>>> same HV but with the series resistors; the signals are decoupled
>>> from the inner conductors with HV caps to the preamps. In the
>>> drawing, pins 13 and A13 are labeled HVshield. So, the potential
>>> between the shield and the inner conductor is about zero.
>>>
>>> I attaching the new PCB option with the updated drawing. It seems we
>>> have email problems.
>>>
>>> Regards,
>>> Fernando
>>>
>>> Yves Van Haarlem wrote:
>>>> Hi Fernando,
>>>>
>>>> I see, this brings me to the RG-174 cable - so we plan to put the
>>>> shield to ground and the signal part to 1800V - the cable is not
>>>> being spect to do that, right. Now we leave the shielding to float,
>>>> before we put it to 1800~V as well.
>>>>
>>>> If in the final design we leave the ground of the cables floating
>>>> then we do not have a problem with the PCB feedthru. If we plan to
>>>> connect also the cable grounds I believe we can make enough real
>>>> estate on that feed-through pcb to solder the signal part on one
>>>> side and the cable grounds on the other side of that pcb and have
>>>> one more solder pad for the grounding to the endplate. Asuming that
>>>> the feedthru pcb is as broad as the new EDAC connector is long. The
>>>> old EDAC connector is half as long and has 13 solder leads per
>>>> side, that times 2 gives us 26 solder leads on both sides of the
>>>> feed through pcb.
>>>>
>>>>
>>>> Cheers,
>>>> Yves
>>>>
>>>>
>>>>
>>>> /--------------------------------
>>>> / Yves Van Haarlem
>>>> _--~~--_ /
>>>> /~/_| |_\~\ / Carnegie Mellon University
>>>> |____________| / Department of Physics
>>>> |[][][][][][]|:= / Wean Hall room 8404
>>>> __| __ |__ \ Pittsburgh, PA 15213
>>>> | ||. | == | | \ USA
>>>> (| ||__| == | |) \
>>>> | |[] [] == | | \ Tel.: +1 412 268-6949
>>>> | |____________| | \ +1 412 641-9252
>>>> /__\ /__\ \ Fax.: +1 412 681-0648
>>>> ~~ ~~ \-----------------------------------
>>>>
>>>> On Wed, 13 Aug 2008, Fernando J. Barbosa wrote:
>>>>
>>>>> Hi Yves,
>>>>>
>>>>>
>>>>> Yves Van Haarlem wrote:
>>>>>> Hi Fernando,
>>>>>>
>>>>>> Thanks a lot for the drawings. Some questions:
>>>>>>
>>>>>> What is meant by the Conformal Seal? Does it refer to make the
>>>>>> connector gas tight with glue? The problem with those new
>>>>>> connectors is that the space between solder leads and connector
>>>>>> are larger compared to the previous (smaller) one which makes
>>>>>> that much more difficult. We even do not know yet if it is
>>>>>> possible with the smaller connectors.
>>>>> There are adhesives with different viscosities for this purpose
>>>>> but we need to try them. I will test with the connectors you are
>>>>> sending me. The choice of the adhesive is very important in terms
>>>>> of its chemistry so that we don't end up with polymerization
>>>>> (aging) inside the straws.
>>>>>>
>>>>>> Going back to the PCB-feedthrough design. The argument was that
>>>>>> when you solder the wires (coming from the straws) to it, they
>>>>>> would make a 90 degree angle with that PCB. Could we not make
>>>>>> solder pads on that PCB (like you have for SM components) so that
>>>>>> the wires can be soldered at 0 degrees. Those PCBs with wires can
>>>>>> be prepared before detector assembly and we can use the new
>>>>>> connector on the other side of that PCB.
>>>>> Yes, this is a possibility. The issue with this approach is that
>>>>> we need to solder all over the shield (300 degrees?), not just at
>>>>> the shield/PCB interface. If we don't, the wires on the shield
>>>>> will be all over the place. However, we could just solder at the
>>>>> shield/PCB interface and then use a conformal coat of adhesive. We
>>>>> need to check this. Maybe two small PCBs, one for each row on a
>>>>> connector?
>>>>>
>>>>> Regards,
>>>>> Fernando
>>>>>
>>>>>>
>>>>>> Cheers,
>>>>>> Yves
>>>>>>
>>>>>>
>>>>>>
>>>>>> /--------------------------------
>>>>>> / Yves Van Haarlem
>>>>>> _--~~--_ /
>>>>>> /~/_| |_\~\ / Carnegie Mellon University
>>>>>> |____________| / Department of Physics
>>>>>> |[][][][][][]|:= / Wean Hall room 8404
>>>>>> __| __ |__ \ Pittsburgh, PA 15213
>>>>>> | ||. | == | | \ USA
>>>>>> (| ||__| == | |) \
>>>>>> | |[] [] == | | \ Tel.: +1 412 268-6949
>>>>>> | |____________| | \ +1 412 641-9252
>>>>>> /__\ /__\ \ Fax.: +1 412 681-0648
>>>>>> ~~ ~~ \-----------------------------------
>>>>>>
>>>>>> On Tue, 12 Aug 2008, Fernando J. Barbosa wrote:
>>>>>>
>>>>>>> Hello everyone,
>>>>>>>
>>>>>>> Following discussions with Yves and Slava, I have attached two
>>>>>>> pdf drawings describing the assembly process. Note that these
>>>>>>> drawings are not to scale.
>>>>>>>
>>>>>>> Please provide feedback. Board design will proceed with the new
>>>>>>> EDAC connector.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Fernando
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Fernando J. Barbosa wrote:
>>>>>>>> Hello everyone,
>>>>>>>>
>>>>>>>> I have attached a pdf describing the edge card connector from
>>>>>>>> EDAC. This is similar to the one Gerard suggested but in 0.156"
>>>>>>>> contact spacing. The connector part number is 307-030-500-202,
>>>>>>>> which is a 30 contacts on dual row with a HV rating of 1800 V
>>>>>>>> AC rms, Thermoplastic Polyester insulator and $3.05. I
>>>>>>>> searched for similar connectors and Sullins also has a similar
>>>>>>>> one rated at 1800 V DC but with a different insulator (PPS
>>>>>>>> Ryton). However, the cost for the Sullins part is five times
>>>>>>>> higher at ~$15. The EDAC connector is stocked at Newark.
>>>>>>>>
>>>>>>>> Now for the assembly details which are based on Slava's
>>>>>>>> drawings. Slava, I would appreciate if you could email your
>>>>>>>> drawings to those on this distribution list.
>>>>>>>>
>>>>>>>> The assembly attempts to minimize the cable length from the
>>>>>>>> straw to the connector:
>>>>>>>>
>>>>>>>> 1. 24 RG-174 cables are prepared as follows:
>>>>>>>> a. Strip both ends so that there is the center conductor for
>>>>>>>> soldering, insulation of center conductor, braid and outer
>>>>>>>> insulation. Each is about .125 long so there are steps
>>>>>>>> (different diameters).
>>>>>>>> b. On the straw side, prepare as is now planned with solder
>>>>>>>> ball and conductive rubber. Maybe a heat shrink piece could be
>>>>>>>> applied to secure the conductive rubber cylinder and cover the
>>>>>>>> shield in one step.
>>>>>>>> c. On the connector side, slide each of the 24 cables into a
>>>>>>>> small copper plate (perhaps a bit less than .125 thick) with 24
>>>>>>>> holes and solder the shield braids at the exit of the holes.
>>>>>>>> The shields will all be connected together to the shield HV and
>>>>>>>> to 2 connector pins. Solder each of the 24 center conductors to
>>>>>>>> the connector.
>>>>>>>>
>>>>>>>> 2. The connector has 24 pins connected as in 1.c above, the
>>>>>>>> next 2 adjacent pins connect to the copper plate to the shield
>>>>>>>> HV, as in 1.c above. The next two pins are left unconnected and
>>>>>>>> insulated or cut. the final 2 pins are soldered to a cable to
>>>>>>>> attach to the endplate for grounding (ground on card is
>>>>>>>> connected to endplate in this way.
>>>>>>>>
>>>>>>>> 3. The back side (soldered connections) is sealed with the
>>>>>>>> proper viscosity sealer and with low out-gassing
>>>>>>>> characteristics (no silicone here). The finished part forms the
>>>>>>>> connector assembly.
>>>>>>>>
>>>>>>>> 4. Connect all the cables from all the cable assemblies to the
>>>>>>>> straws and endplate (grounds).
>>>>>>>>
>>>>>>>> 5. Attach dummy boards with straps to the edge card connectors
>>>>>>>> on each of the cable assemblies.
>>>>>>>>
>>>>>>>> 6. Position the gas plenum Plexiglass cover and feed all the
>>>>>>>> straps through their respective holes on the Plexiglass cover.
>>>>>>>> Slide this cover while pulling or straightening the straps
>>>>>>>> until the cover touches the connectors. Attach the connectors
>>>>>>>> with screws, washer and neoprene seal washer.
>>>>>>>>
>>>>>>>> 7. Rotate CDC so that connector side is at top.
>>>>>>>>
>>>>>>>> 8. Apply sealer (see 3 above) around each of the
>>>>>>>> connectors/plexiglass holes.
>>>>>>>>
>>>>>>>> In this way, we only need a short distance between the straws
>>>>>>>> and the gas plenum cover. This is not very elaborate but I can
>>>>>>>> provide a drawing if necessary to better explain this
>>>>>>>> technique. Please note that if one of the wires in the straws
>>>>>>>> brakes and shorts tripping the HV, all the 24 channels in the
>>>>>>>> group will be off. This is required because the shields are
>>>>>>>> also at HV and the RG-174 is not rated for this level of HV.
>>>>>>>> So, this is inherently safe.
>>>>>>>>
>>>>>>>> There will also be an aluminum plate or aluminized mylar cover
>>>>>>>> over the whole gas plenum and grounded for shielding.
>>>>>>>>
>>>>>>>> Please provide feedback so we can finish the design of the HVB
>>>>>>>> PCB. The HVB PCB will have the HV distribution network, the
>>>>>>>> connections to the preamp card connector, grounding, etc. The
>>>>>>>> preamp card, as in the FDC, is removable from the HVB.
>>>>>>>>
>>>>>>>> Regards,
>>>>>>>> Fernando
>>>>>>>
>>>>>
>>>
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adr:Suite #10, 12B3;;12000 Jefferson Ave.;Newport News;VA;23606;USA
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