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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brian Ellis <[log in to unmask]>
Date:
Wed, 12 Dec 2012 16:32:40 +0200
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That's an old chestnut from someone pine-ing for attention and making an 
ash of it. You maple the other leg to make me sycamore often. Will lower 
your blood pressure and spruce you up, woodn't you know?

Brian

On 12/12/2012 15:54, Douglas Pauls wrote:
> I am guessing that wasn't a poplar component in Russia.
>
> Ok Hillman, I have the Whittaker virus.  Just come over and shoot me now.
>
> Doug Pauls
>
>
>
> From:   Inge Hernefjord <[log in to unmask]>
> To:     <[log in to unmask]>
> Date:   12/11/2012 04:39 PM
> Subject:        Re: [TN] Polymer Lid
> Sent by:        TechNet <[log in to unmask]>
>
>
>
> When you say that, Joyce, I remember a practical joke we played 30 years
> ago. We were pretty good at so called 'hybrids', RF type, ceramic
> substrates mounted in machined Kovar packages. We made a couple of
> packages
> of wood and sent them to an expo in USA. On the stand's wall you could
> read
> that this was a way to lower the costs essentially. Caused many smiles and
> also serious questions. They were stolen last day, and we chuckled "
> russians".  This was in the days humor was larger part of the daily work
> than it is today.
> Inge
>
> On 11 December 2012 15:19, Joyce Koo <[log in to unmask]> wrote:
>
>> Why not metal lid? With such a low volume, can't be the cost.
>> --------------------------
>> Sent using BlackBerry
>>
>>
>> ----- Original Message -----
>> From: Steven Creswick [mailto:[log in to unmask]]
>> Sent: Tuesday, December 11, 2012 08:44 AM
>> To: [log in to unmask] <[log in to unmask]>
>> Subject: Re: [TN] Polymer Lid
>>
>> Ken,
>>
>> I did not mean to imply that this would create a seal to keep moisture
> out,
>> but simply to point out that an enclosed volume of gas will expand when
>> heated.  If one is not prepared for this, it can cause surprises.
>>
>> We did things like this in the hybrid industry over 30 years ago, using
>> ceramic substrates and ceramic shells/lids.  Definitely NOT hermetic,
> but
>> served their purpose for industrial applications.
>>
>> I believe that Zytel is a glass reinforced polyamide.  Not familiar with
>> this particular one, but my experience with LCP's has been that they can
>> offer greater temperature resistance, but likely cost more....
>>
>> Try it before you buy it!  Get some samples from the folks cited.
>>
>>
>> Steve Creswick
>> Sr Associate - Balanced Enterprise Solutions
>> http://www.linkedin.com/in/stevencreswick
>>                           616 834 1883
>>
>>
>>
>> -----Original Message-----
>> From: Kenneth J. Wood [mailto:[log in to unmask]]
>> Sent: Tuesday, December 11, 2012 8:19 AM
>> To: 'TechNet E-Mail Forum'; 'Steven Creswick'
>> Subject: RE: [TN] Polymer Lid
>>
>> The units are not airtight and some small amount of moisture is
> inevitable
>> /
>> acceptable.
>> The linx guys got back to me and said that they use Zytel HTNFR52G30
>> Polyimide for thier lids.
>> Any thoughts?
>> Ken
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
>> Sent: Monday, December 10, 2012 7:20 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Polymer Lid
>>
>> Ken,
>>
>> Also consider that if you seek to create an enclosed cavity, the air
> inside
>> that cavity will expand during heating and sometimes create blow holes
> in
>> the 'seal' during heat cure of the adhesive.  Similarly, during reflow,
>> depending upon the adhesive used, you can 'pop' the lids off.
>>
>> I've encountered situations in the past where a small hole was left in
> the
>> lid to avoid the 'over pressurization scenario' and then 'sealed'
>> post-reflow.
>>
>> Can you use a deep drawn metal lid as opposed to a folded type metal
>> lid/shield?
>>
>> You could use a logo on sticker to cover the vent hole afterwards...
>>
>>
>> Steve Creswick
>> Sr Associate - Balanced Enterprise Solutions
>> http://www.linkedin.com/in/stevencreswick
>>                           616 834 1883
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Kenneth J. Wood
>> Sent: Monday, December 10, 2012 6:58 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Polymer Lid
>>
>> Bob,
>> I'm using a metal lid for the larger size modules now and it is a pain
> to
>> say the least to solder them on manually.
>> One of the issues in the past was liquids getting under the lid during
>> cleaning.
>> That's why I wanted a plastic lid with no seams that could be filled
> with
>> goo and glued down.
>>
>> These units are supplied as a module to end uses so they have to have
> the
>> lids on from us.
>>
>> Ken
>>
>> -----Original Message-----
>> From: Robert Kondner [mailto:[log in to unmask]]
>> Sent: Monday, December 10, 2012 6:48 PM
>> To: 'TechNet E-Mail Forum'; 'Kenneth J. Wood'
>> Subject: RE: [TN] Polymer Lid
>>
>> Kenneth,
>>
>>    Yes, I looked at your link so now I see better. Your users will be
> doing
>> a
>> reflow.
>>
>>   So you need a thermoset lid. Glue it on with a silicon and I think you
> are
>> set except maybe for cleaning.
>>
>>   I would imagine your customer will clean their boards which would tend
> to
>> trap fluids under the lids. So then you get into the area of filling and
>> sealing? That is a mess. It gets worse as you have SMT leads coming off
> the
>> PCB. If you can place filling holes in the PCB you can get the right
> amount
>> of material in the unit except for the filling of voids. I played with
> this
>> once and using a vacuum fixture to removed voids can cause a mess. You
> need
>> to vacuum then fill with the vacuum applied. Then reintroducing air
> fills
>> voids as air pushed down through the fill holes.
>>
>> A mess to fixture.
>>
>> You might look at cavist.com as they do low temp thermoplastics, maybe
>> they
>> can do a low temp thermoset so you can encapsulate soldered modules.
>>
>> Or consider metal cans? :-)
>>
>>   Getting the right amount of fill material to provide a filled sealed
>> device
>> is very difficult.
>>
>> Bob K.
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Kenneth J. Wood
>> Sent: Monday, December 10, 2012 6:04 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Polymer Lid
>>
>> Bob,
>> Thanks for your help on this.
>> Quantities are 1,000 to 50,000 per year and the lid needs to be glued on
>> before it ships to the end users.
>>
>> Ken
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
>> Sent: Monday, December 10, 2012 5:58 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Polymer Lid
>>
>> Kenneth,
>>
>>   I looked into this some years back and any material that "Stands Up" to
>> reflow temps would be difficult to form. Injection molding would
> probably
>> be
>> impossible but ask, don't take my word.
>>
>>   At all costs is there any way to add it as a last step addition to a
>> finished PCB?
>>
>>   How many are you talking about?
>>
>>   I did have some plastic parts made from a thermoset. It was black
> material
>> and I forgot the trade name. It was probably just a phenolic material.
> Not
>> sure how well it takes reflow temps. If you need help contact me off
> line,
>> I
>> will get you a sample. I had some 2 x 4 inch boxes and cover made.
>>
>> Bob K.
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Kenneth J. Wood
>> Sent: Monday, December 10, 2012 5:30 PM
>> To: [log in to unmask]
>> Subject: [TN] Polymer Lid
>>
>> Hi all,
>> I need to design a polymer lid that gets glued on top of a square PCB.
>> The lid will be 0.66" x 0.66" by 0.20" (maybe 0.025" wall thickness)
> with a
>> flat top so I can have the company logo and part number printed on it.
>> The PCB itself is a system that gets soldered to a main board by way of
>> castellated holes.
>>
>> My question is, what lid material should I use since this unit must go
>> through a reflow over?
>>
>> I assume a vacuum formed CPVC lid would melt right?
>>
>>
>> The unit is somewhat similar in mechanical characteristics to a Linx
> module
>> like the TXM-xxx-es
>>
>> https://www.linxtechnologies.com/resources/data-guides/txm-xxx-es.pdf
>>
>>
>>
>> Thanks
>> Ken
>>
>>
>> _____________________________________
>> Kenneth J. Wood
>> Saturn PCB Design, Inc.
>> [log in to unmask]
>> www.saturnpcb.com
>>
>>
>>
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