FreeLists / si-list / [SI-LIST] Re: soldering plastic balls

[steve weir <weirsi@xxxxxxxxxx>]

Lars, the technique of using only an outer layer conductor for HF 
equalization is well established.  There is a nifty interposer connector 
technology that uses tiny silver plated nickel balls.

Regards,


Steve.
Lars Juul wrote:
> 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 <mailto: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
>     <mailto: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
>     >>
>     >>
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