Phil,

A number of patents have addressed this problem in recent years and not
all use the words fatigue resistant in the title. Some techniques will
refine the grain size, which, as already mentioned, usually have only a
temporary effect. However, other elements can be added which slow down
the inevitable grain growth during the joint life. Grain growth is
increased by longer time, higher temperature and by mechanical
stressing.

I hope that this helps a little .

Roger Bilham

In article <[log in to unmask]>,
[log in to unmask] writes
>My (very limited) knowledge of so-called fatigue-resistant soldersis that
>they are fairly normal eutectic solder alloys, but the particle size and
>shape is carefully controlled, and the paste has a number of dopants added.
>The overall effect is that FRS's have a slightly lower melting point than
>normal and produce very fine-grained solder joints.
>
>My feeling about them is that they only prolong the inevitable a little -
>the joints will still tend to coarsen with time and temperature, and
>intermetallic layers wil also grow. It's highly debatable whether the extra
>cost of this type of solder is cost effective in terms of extending solder
>joint life.
>
>There is some info on the WWW about FRS's, but not a lot.
>
>Peter
>
>
>
>Phillip Hinton <[log in to unmask]>   18/09/2002 10:55 AM
>Sent by: TechNet <[log in to unmask]>
>
>Please respond to "TechNet E-Mail Forum."; Please respond to Hintpwb1
>
>              To:  [log in to unmask]
>              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
>              Subject: [TN] Theramal Fatigue Resistant Solder
>
>
>
>
>
>
>
>
>All
>
>In a presentation given by Tom Scimeca of Florida Cir Tech (time unknown)
>on lead free solder he shows a graph on page 43 in which he graphs fatigue
>of a "Sn63 Thermal Resistant Solder" compared to "Standard Sn63" and a
>Sn/Cu with nickel (Nihon Superior Sn100C).  Does anyone know what the
>"(Sn63) Thermal Resistant Solder" is
>
>Phil Hinton
>520-745-1013    .
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--
Roger Bilham
Roger Bilham Consultancy
Tel: +44 (0)20 8467 8819
Fax: +44 (0)8700 548 613
Mobile +44 (0)7 941 122 446

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