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June 2004

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 23 Jun 2004 07:48:48 -0400
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You could develop a profile with a 20 second excursion from 200 through 205
and back and stay above 180 for a minute. It would be a ramp up and down at
about .5 degree per second.  205-180=30 30x2=60 205-200=5 and back 5x2=10
10x2=20. But, what happens to the parts on the board that are difficult to
heat? That part may have to be hand soldered.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Lance Mayes
> Sent: Tuesday, June 22, 2004 5:15 PM
> To: [log in to unmask]
> Subject: [TN] Reflow Profile(Temperature and Times)
> Importance: High
>
> Technetters Hello again;
>
> We are having a problem with a Token crystal oscillator.
> During the month of April there was a fallout spike of plus
> 10% from testing in manufacturing.  The supplier was
> contacted and some defective components returned.  After
> their evaluation they indicated that the components were
> damaged due to over-heating.  They attached a copy of the
> desired temperature profile we should be using.
>
> We ran the mole through the oven and came up with the real
> profile (note, the thermocouple was attached to the body of
> the resonator).  They are having trouble actually
> interpreting the wording of the spec, especially when
> compared to the recommended profile for the solder paste.
>
> The component spec has a cautionary note as follows:
> "Heating conditions shall be within 20 seconds at +230 deg C
> min, but peak temperature shall be lower than +240 deg C.
> The profile figure shows a breakout above +200 deg C and
> states the maximum time above 200 should be 20 seconds.  The
> two statements together seem confusing and we are asking for
> some clarification.
>
> To add confusion to the issue the solder paste spec:
> Qualitek 670I No-Clean Paste (Sn63/Pb37) shows a recommended
> profile for reflow of Minimum Temp 205 deg C ranging from
> approx. 180 deg C with a minimum time of 60 seconds.  Again
> it appears using this paste we cannot meet the component
> reflow profile?
>
> We then looked at our current profile and found the following:
>
> We are above 200 deg C for about 45 seconds, the peak
> temperature is 218 deg C.
>
> Any help/comments would be appreciated.
>
>
>
>
>                         P.  Lance Mayes

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