[SI-LIST] Re: soldering plastic balls
- From: "Lars Juul" <write2larsj@xxxxxxxxx>
- To: "steve weir" <weirsi@xxxxxxxxxx>
- Date: Tue, 5 Jun 2007 16:13:26 +0200
Just went one link deeper.
It seems that they're also trying to flog their product to us, claiming the
solder ball sphere is much more uniform in size for these balls, making it
possible to make a controlled impedance for the package/board interconnect.
However, I'm not convinced, as
a) You need to place the balls awfully close to come even close to a Z0 of
50 Ohms. My bet is that you'd have a significant risk of shorting the balls
in a production environment. They might aim for a higher impedance, which
might lessen the Z0 mismatch, I suppose.
b) In order for this to make sense, you need to somehow avoid the huge,
clumsy through vias that are normally seen on bga substrates. I am guessing
that the impedance mismatch caused by the package through vias is much more
significant than what you gain from having a controlled impedance across
your solder joints to the board. The vendor does in fact show a
microwave-like module with the circuitry on the same side as the solder
balls, which makes sense. But, honestly, how many would employ such a design
for standard high volume surface mount components? (apart from TBGAs, I
guess)
2007/6/5, Lars Juul <write2larsj@xxxxxxxxx>:
>
> Hi Steve,
>
> I'm surprised to hear that the primary objective with the plastic core
> balls is to equalize the resistance over frequency, as Sekisui write on
> their product page:
>
> ( http://www.sekisui-fc.com/eng/html/jissou/product/jipr_02.html)
> ...
> Micropearl SOL is a solder plated true sphere with a plastic core and was
> designed for mounting chips to circuit board. Unlike conventional solder
> balls which often cracks under the heat cycle test,
> ...
>
> They go on to show graphs with how much longer these solderjoints will
> hold in temp cycle tests comparison to SnAg alloys, which I feel is very
> relevant in these RoHS times.
>
> However, it's true that at high frequencies the current flows on the edge
> of the conductor (in closest possible proximity to your return current), and
> that the lack of conductor diameter will lead to increased resistance closer
> to low frequencies, but I doubt that it will act as a good loss equalizer (I
> might be wrong, I guess)
>
>
> 2007/6/5, steve weir <weirsi@xxxxxxxxxx>:
> >
> > Lars, the idea of the plastic balls is that they have only a thin outer
> > conducting layer and therefore the resistance remains much more uniform
> > and therefore equalizing loss across a broad frequency range.
> >
> > Steve.
> > Lars Juul wrote:
> > > Hi David,
> > > I would call up your packaging vendor and ask them to make a test
> > build with
> > > ball samples from Sekisui on existing 10 Gbps BGAs, provided the ball
> > attach
> > > tool is suitable for this. This is usually the stumbling block, as
> > this is
> > > very expensive in NRE.
> > >
> > > Alternatively, it's worth exploring if you make a manual ball attach
> > > (possible if the packages are for small form factor 10Gbps CDRs, for
> > > instance) by printing solder paste on the package lands first, and
> > then
> > > manually place the balls on the paste by a trained person with a
> > steady
> > > hand. I assure you, crazier things have been made.
> > >
> > > On the other hand, my only concern with this kind of balls would be
> > the
> > > suitability for them in the power supply, as I imagine the current
> > carrying
> > > capabilities are somewhat limited if you have a plastc core on the
> > inside.
> > > (I don't think it's possible to attach solid solder and plastic balls
> > on
> > > specific lands on the package in a high volume setup, yet)
> > >
> > > PS: you're asking whether they work at 10GHz, which is a single
> > frequency
> > > point, I think it's feasible to use plastic core balls for a
> > narrowband
> > > application, but if it's broadband from 0 to 10e9 Hz you're driving
> > at, I'd
> > > say, try it out in practise first to see if it flies, then make a full
> > wave
> > > or macromodel of package afterwards to feed the chip I/O designers.
> > >
> > > Have fun.
> > >
> > > Best regards,
> > > Lars
> > >
> > > 2007/6/5, david stern <dan1_st@xxxxxxxxx>:
> > >
> > >> hello all
> > >>
> > >> I was looking for bga soldering balls technology for an
> > >> application working at 5GHz to 10GHZ and and found
> > >> soldering plastic balls from SEKISUI. Did somebody work with them at
> > >> 10Ghz?
> > >>
> > >> Thanks
> > >>
> > >> David
> > >>
> > >>
> > >> ---------------------------------
> > >> Moody friends. Drama queens. Your life? Nope! - their life, your
> > story.
> > >> Play Sims Stories at Yahoo! Games.
> > >>
> > >> ------------------------------------------------------------------
> > >> To unsubscribe from si-list:
> > >> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> > >>
> > >> or to administer your membership from a web page, go to:
> > >> //www.freelists.org/webpage/si-list
> > >>
> > >> For help:
> > >> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >>
> > >>
> > >> List technical documents are available at:
> > >> http://www.si-list.net
> > >>
> > >> List archives are viewable at:
> > >> //www.freelists.org/archives/si-list
> > >> or at our remote archives:
> > >> http://groups.yahoo.com/group/si-list/messages
> > >> Old (prior to June 6, 2001) list archives are viewable at:
> > >> http://www.qsl.net/wb6tpu
> > >>
> > >>
> > >>
> > >>
> > >
> > >
> > > ------------------------------------------------------------------
> > > To unsubscribe from si-list:
> > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> > >
> > > or to administer your membership from a web page, go to:
> > > //www.freelists.org/webpage/si-list
> > >
> > > For help:
> > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >
> > >
> > > List technical documents are available at:
> > > http://www.si-list.net
> > >
> > > List archives are viewable at:
> > > //www.freelists.org/archives/si-list
> > > or at our remote archives:
> > > http://groups.yahoo.com/group/si-list/messages
> > > Old (prior to June 6, 2001) list archives are viewable at:
> > > http://www.qsl.net/wb6tpu
> > >
> > >
> > >
> > >
> > >
> >
> >
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
