Hi Ken:
                Is this the first time that you run this board through the wave? If it is not  and there was no issues like this in previous runs, then it might have to do with too many hits by the drill during PCB manufacturing. There is a stress built in the board and the level of stress added by the wave causes measles. Another reason might be that PCB manufactures are getting cheaper material that does not bond as good as previous products. Prebaking the boards to 190 F for 4 hours may help.
        Regards,
        Ramon

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Morse, Carrie
Sent: Thursday, June 16, 2005 2:11 PM
To: [log in to unmask]
Subject: Re: [TN] Measling Conundrum


My recommendation is to try to figure out where within the wave process
the measling is happening (preheat?  Or over the Wave?)

Also...attach some TC's and see what the time and temps are.

-Carrie 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken
Sent: Thursday, June 16, 2005 9:54 AM
To: [log in to unmask]
Subject: [TN] Measling Conundrum

My question of the day sort of reminds me of a Steve Gregory type
question. It just doesn't make sense but still it's happening ;-)

We have a board that has standoff's cone swaged into it. They are not
roll swaged or pressed in hard. They still spin after they are swaged
in. We mask the hole in the center with temporary solder mask to protect
the threads. We run it through the wave solder with the following
parameters:
The topside board temp through wave is about 280 degrees F. 
Conveyer speed of 2.5 FPM
Solder temp at 460 degrees F
Bottom preheater 2 is at 275 F
Bottom preheater 1 is at 360 F
Top preheater is at 300 F

When the boards come out we have measling around the standoffs.

Now for the Steve part of the equation. If we hand solder the standoffs
into the board they do not develop measles. We tried to make measles and
using two soldering irons and staying on the solder joint for about 38
seconds we finally got a few around the pad but not enough to be
rejectable.

So... Why is the wave solder causing these standoffs to measle and not
hand soldering?

Thanks,

KennyB

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