Inge, I wondered where we got that wooden hybrid! :-) Steve C -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord Sent: Tuesday, December 11, 2012 5:36 PM To: [log in to unmask] Subject: Re: [TN] Polymer Lid 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. 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