Ken,

I'm going to open a can of worms with this one, and I'm sure will get
plenty of responses.

The target peak for SAC305 is 253 C for most applications. (245 C is too
cool).

You should be above 217 C for 45 to 90 sec.

But 217 C is not the temp you should worry about, it's really somewhere
around 235/7 C which is where the solder melts to other metals, (wetting
temp). If you are not over the wetting temp long enough you will
experience poor wetting, especially with OSP, where you need to be near
the "longer" end. You should stay over 235 C for 30 to 45 seconds.

Now the kicker here is, that if your oven has poor thermal capacity, you
can see a temp difference across the board of as much as 30 to 35
degrees C if you are soldering a component like the 775 Socket T and
trying to get the underside to melt.

That means other solder joint temps in a bad oven could hit 285 C,
(don't ask about the component body) which is unacceptable for most
components that are rated at 260 C.

If your oven cannot maintain at least +/- 10 degrees C across the PCB on
your heaviest boards/components (+/- 5 degrees C on regular LF product)
you should replace it. 10 years ago I would have said +/- 3 degrees C,
but I have been soldering some weird stuff lately, :<)
 

  



 

 




 

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Kanaiyalal Patel
Sent: Tuesday, October 11, 2005 7:10 PM
To: [log in to unmask]
Subject: [LF] Leadfree Processing temp requirement

All,
Has IPC modified the document related to component spec from process
point of view such as reflow and wave. I forgot the document number.

This document is being used by supplier/manufacturer to make parts that
can withstand needed Leadfree reflow/wave temperature. Few of my
suppliers' parts are rated around 240c max and I think that is too low
for leadfree process. Can someone provide the temp numbers withour
buying a IPC spec for urgent requirements?

Any help will be appreciated.

re,
ken Patel


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