We cured Ag glass at +225C. Depended on Silver to rest ratio. I don't
remember the Silver %age, but we were surprised that it was printable.
Inge
On 4 June 2013 13:18, Steven Creswick <[log in to unmask]> wrote:
> Mike,
>
> I seem to recall that many of the 'cure'/sintering temperatures for the Ag
> glasses were in the 250-310°C, at their lowest. Were developments made
> that
> allowed them to come down below that?
>
> Steve C
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner
> Sent: Tuesday, June 04, 2013 6:45 AM
> To: [log in to unmask]
> Subject: Re: [TN] Conductive epoxy to install SMT parts
>
> HI Inge
> Attached is an old presentation (early 1990's) on conductive adhesives,
> which you might like to add to your Dropbox archive. Technically it has
> stood up remarkably well, so is still a good primer for solder engineers. I
> apologise though for its garish appearance.
>
> Silver glasses seem to have fallen from the mainstream (together with
> ceramic packages and so on). Sod's Law now says someone more informed will
> say opposite.
> They were a seemingly obvious candidate to revisit as a Pb-free, Au-free
> alternative to high Pb content die attach solders, but were set aside again
> as the glass component could not be made lead free.
>
> Best Wishes
>
>
>
> Mike
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
> Sent: Monday, June 03, 2013 10:26 PM
> To: [log in to unmask]
> Subject: Re: [TN] Conductive epoxy to install SMT parts
>
> .........................................so by and large you
> > can't just switch to an other suppliers functional equivalent as you
> > can with solders, you will need to
> revalidate..............................."
>
> I learned that the hard way by much embarrassment and pain....
>
> Q: is Silver glass discussed and reviewed? I used that in a Space
> application for its low outgassing and resistance against high operation
> temp as well as high electric conductivity
>
> Inge
>
>
> On 1 May 2013 15:16, Watson, Howard A <[log in to unmask]> wrote:
>
> > Eva,
> >
> > I was also researching conductive epoxies and found a paper here:
> > http://www.masterbond.com/whitepaper/electrically-conductive-adhesives
> > I had to register to access it. I don't endorse this company in any
> > way, but maybe this paper will help you in some way.
> >
> > Good luck!
> >
> > Howard A. Watson
> >
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Eva J
> > Sent: Tuesday, April 30, 2013 4:20 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Conductive epoxy to install SMT parts
> >
> > Thank you very much
> >
> > Indeed it is a difficult situation with limited solutions for our
> > specific application.
> >
> > Onward TechNet Soldiers!
> > Eva J
> >
> >
> > On Tue, Apr 30, 2013 at 5:07 PM, Mike Fenner <[log in to unmask]> wrote:
> >
> > > Well the basic laws of physics and chemistry haven't changed. The
> > > plethora of papers at that time does identify the issues very well
> > > and explain what is needed. The reason for that burst of effort was
> > > that Ag conductives - iso or anisotropic - were seen as a possible
> > > alternative process in the light of the looming lead ban.
> > > I was involved in such a project (at a somewhat low level
> > > technically, more marketing orientated). Our conclusions were the
> > > same as most others. First that at least three breakthroughs would
> > > be needed to have anything like a drop in adhesive replacement for
> > > solder. Second that the use of adhesive interconnects would continue
> > > to grow, but by designing for adhesives not by designing an adhesive to
> be a solder.
> > > The lead ban would just tilt the balance of choice slightly more
> > > away from solders. We do still solder of course.
> > > Overall the issues now are the same as then. They are better
> > > addressed in newer products by a number of sequential incremental
> > > developments in process and in in-service performance. Newer
> > > products can have snap cure schedules which give comparable thermal
> > > exposure in processing, maybe less. They can contain oxide reduction
> > > additives, and corrosion inhibitors and so on to increase reliable
> > > conductive bond life and maintain mechanical integrity.
> > > Conductivity is still relatively poor. Thermoplastics do overcome
> > > one of the biggest draw backs which is reparability but not without
> > > performance costs.
> > > So modern products can be closer to solders in service and may well
> > > be good enough, but this is conditional on component surfaces being
> > > optimised for bonding not soldering. Process parameters will also
> > > need to be adjusted for the way the products behave. For example
> > > what you print is what you get, so No self alignment and so on.
> > > It may be that you could use a low temp soldering process, if not
> > > then of course use adhesives, but do speak with suppliers to obtain
> > > optimum product and process conditions. Keep in mind that each
> > > adhesive/process will be application specific, so by and large you
> > > can't just switch to an other suppliers functional equivalent as you
> > > can with solders, you will need to revalidate.
> > >
> > >
> > > Regards
> > >
> > > Mike Fenner
> > > Bonding Services & Products
> > > M: +44 [0] 7810 526 317
> > > T: +44 [0] 1865 522 663
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Eva J
> > > Sent: Monday, April 29, 2013 1:59 PM
> > > To: [log in to unmask]
> > > Subject: Re: [TN] Conductive epoxy to install SMT parts
> > >
> > > Conductive epoxy is being considered as an electrical and mechanical
> > > bond since the component can not withstand reflow temperatures. The
> > > future application will be an ENIG finish on PCB with gold finish on
> > > the component termination. Late 80s and even 90s papers would be
> > > outdated as materials have changed. So no one is aware of recent
> > > papers regarding conductive epoxy?
> > >
> > > Thanks
> > > Eva
> > >
> > >
> > > On Sun, Apr 28, 2013 at 7:41 PM, Mike Fenner <[log in to unmask]> wrote:
> > >
> > > > It's not totally clear why you want to adhesive bond instead of
> solder.
> > > Are
> > > > you looking to adhesive bond special devices to otherwise
> > > > assembled
> > > boards?
> > > > There maybe ways to solder using repair techniques for example.
> > > > If you wish to use adhesives you will need to consider conditions
> > > > of use, service life, and in production surfaces to be bonded as
> > > > well as max process temp and time. These will be different from
> solders.
> > > > Generally adhesive bonds are not as strong as solder, and in
> > > > non-hermetically sealed
> > > packages
> > > > service life can be shorter (but maybe sufficient in either case).
> > > > As already said epoxies do not bond well to tin or tin based alloys.
> > > > Gold is also a low energy surface and will give low bond strengths
> > > > with
> > > adhesives.
> > > > So bond strength could be an issue, this is in addition to any
> > > > problems that might arise from the Ag:Sn interface. Some suppliers
> > > > do claim to have addressed the long term conductivity issues.
> > > > Do keep in mind that whereas adhesives can be classified into
> > > > generic types, (epoxies, silicones, acrylates etc) they are all
> > > > supplier unique within that classification. This means you will
> > > > need to check or verify product performance claims with every
> supplier.
> > > > [This is not like solder pastes where although flux chemistry may
> > > > be supplier specific, a solder alloy
> > > such
> > > > as Sn63 is not.]
> > > > You will need to observe the cure schedules in the supplier data
> > > > sheets, treating them as minimum times/temps at the bond line or
> > > > the product will not develop data sheet properties.
> > > >
> > > > Regards
> > > >
> > > > Mike
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven
> > > > Creswick
> > > > Sent: Thursday, April 25, 2013 3:31 PM
> > > > To: [log in to unmask]
> > > > Subject: Re: [TN] Conductive epoxy to install SMT parts
> > > >
> > > > Eva,
> > > >
> > > > You should ask the formulator for this information. Really
> > > > attempt to
> > > nail
> > > > them down and get them to provide real, and detailed data - one
> > > > real live part types.
> > > >
> > > > In general, it is quite difficult to get most adhesives to adhere
> > > > to the diverse surfaces finishes presented in SMD work, at
> > > > temperatures that the SMD assembler [and components] will
> > > > tolerate. Making it more flexible is only one factor to consider.
> > > >
> > > > Mechanical, thermal, or other environmental stresses typically
> > > > quickly
> > > show
> > > > the weak links.
> > > >
> > > >
> > > > Side note - if "cured" over the weekend, I suspect that it is more
> > > > of a humidity cure RTV than an "epoxy" based system. Do you smell
> > > > acetic acid [vinegar] during cure? = bad idea. Or do you smell
> > > > more
> > of an alcohol?
> > > =
> > > > okay. Silicones have a nasty way of tending to migrate to places
> > > > you
> > > don't
> > > > really want them to go... switches, connectors,
> > > >
> > > > Can your production live with a 48-72 hr cure?
> > > >
> > > > I would be sure to ask the formulator whether the material has an
> > > > epoxy backbone, or a silicone backbone so that I could get a
> > > > better grasp of
> > > its
> > > > mechanical properties. I am assuming that if it is a silicone,
> > > > under normal conditions, it will already be above its Tg, and
> > > > therefore already in it 'high expansion' state. I also make the
> > > > generalization that it will
> > > remain
> > > > flexible until down in the -20 to 0°C range [subject to the
> > > > specifics of the material]
> > > >
> > > > Steve C
> > > >
> > > > -----Original Message-----
> > > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Eva J
> > > > Sent: Thursday, April 25, 2013 10:01 AM
> > > > To: [log in to unmask]
> > > > Subject: [TN] Conductive epoxy to install SMT parts
> > > >
> > > > I am looking for guidance on conductive epoxy selection for
> > > > components on PCBs. I heard that there is a formulation of
> > > > conductive epoxy with
> > > silicone
> > > > as a filler that is more flexible. Do you know of any studies or
> > > > evaluations available on conductive epoxy for electronics?
> > > >
> > > > We attached a 4 pin LGA component that has gold finish
> > > > terminations to a HSAL finished PCB. We syringe dispensed the
> > > > conductive epoxy to the land pattern. Optically machine placed
> > > > part and allowed the conductive epoxy
> > > to
> > > > cure over the weekend.
> > > > During environmental stress test ( hot / cold cycling) one joint
> > failed.
> > > > All of the LGAs were removed and what we found is the component
> > > > came off way to easily.
> > > >
> > > > I would like to continue using conductive epoxy to mount special
> > > > application
> > > > SMD's: however reliability is a concern. Any words of wisdom?
> > > >
> > > >
> > > > __________________________________________________________________
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