If I read this correctly you are soldering the body of a device with high
temp and the leads are reflow soldered at a later time with a lower temp
alloy.  I see no technical reason why both could not be soldered
simultaneously.  As for performing two reflow cycles on a solder joint
soldered with paste this is not an unusual condition and is performed
regularly in commercial applications.  The risk with reflowing twice is
there will be more intermetallic formation due to the collective dwell time
at liquidus of the joint(s)reflowed twice.  In a commercial application
where there are minimal thermal and physical loads on the device a double
reflow usually does not pose a problem.   In an environment subject to
thermal cycles, shock, vibration, or in an RF application the intermetallic
could pose some risk.  In either case, only testing can prove the product
is robust enough for the process.
Denis Meloche
Heraeus Cermalloy

At 10:48 AM 8/28/97 PDT, you wrote:
>Technetters,
>
>        Currently, we are using high temp solder to attach leads on the
>component body of a surface mount device.  The customer will use standard
>63/37 to attach the other end of the lead to the board.  Historically, we
have
>used the high temp solder to prevent reflow on the component when the board
>goes through the IR oven.  The leads are attached around the edge and pinch
>the board.
>
>        Now the question for all the experts.  Does anyone see a problem with
>using the same solder for both attachments?  Or, does anyone see a problem
>with a second reflow of the solder on the component?
>
>        I hope this makes sense, and thanks for any input.
>
>Glenn Pelkey
>Quality/Reliability Engineer
>Maxtek Components Corp.
>
>