Following from the EMPF HelpLine in Indianapolis, prepared by Pat Kane:

There may be some concern about the accuracy of the profile info.  Have the
mole unit checked and calibrated to insure that it is working properly.

Secondly, there is no info as to what the "defects" are that using the
pallet seems to correct.  The use of the pallet will have an effect on the
profile info.  The profile should be determined with the pallet and
without.  Also the loading of the preheat chamber will effect the profile.
If the board is profiled with only one board in the tunnel, then when he
runs production and sends boards maybe 10 inches apart, the combined mass
of the boards and the pallets will "cool" the profile.

Thirdly,  there seems to be an indication of insufficient flux activation
(blow holes and outgassing).  The flux may be applied too heavy and not
activated correctly before entry into the wave bath.  Is the application
foam of spray?  The preheat temps here again would greatly play into the
activation parameters being met.

I would start investigation by insuring the calibration of the mole to
properly profile.  Next, make sure that the thermocouples are attached to
the test board in both dense and sparsley populated areas.

Look at a board after the preheat chamber, but before it has entered the
wave bath.  Compare the amount of flux ( current status) to the amount of
flux when the profile has been verified.

Lastly,  the blow hole situation could be caused by moisture absorbtion if
the boards are stored for a long period of time in an uncontrolled area.
Try prebaking at 100C for 4 hours just prior to processing.  Allow the
boards to cool to room temp before starting the assembly process.


>----------
>>From: [log in to unmask] (MR MARK A WARYCKA)
>>Date: Fri,  1 Nov 1996 23:43:58, -0500
>>Subject: wavesoldering mixed tech boards
>>
>>Good Day,
>>
>>         This is a request for some assistance on a wavesoldering
>>problem that we are currently experiencing on some mixed technology
>>boards that we process. The boards have surface mount top and bottom
>>and when the process is set to wave the bottom side with no defects
>>we are experiencing a problem with some top side surface mount IC's
>>de-soldering! I have tried using soldering pallets set at
>>approximately  a 30 degree angle with some success but it slows down
>>the processing time and the top side components still come loose.
>>Initial profiling indicates that the top side of the board is showing
>>temperatures below the eutectic point of the solder paste being used.
>>When the boards are processed without the pallets the defect rate
>>increases dramatically but the incidence of topside component des-
>>soldering decreases! The wavesolder machine is a T/D Nu-Era with
>>dancer wave and the flux being used is Kester 2331-ZX. Topside
>>preheat temperatures just prior to wave entry are around 185 degrees
>>F.
>>
>>      Another question is in regard to voids and blowholes occurring
>>on a PTH board that is auto-inserted. Just can't seem to get rid of
>>them. The boards are inspected at incoming for voids in the plated
>>thru holes. Profiling indicates that all process parameters are
>>correct. Any ideas?
>>              From: Mark A. Warycka
>>                       Process Engineering Manager
>>                       Electronic Systems, Inc.
>>                       Sioux Falls, SD

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