> Ray Turner wrote:

 > We have been wave soldering SOIC and SOJ packages for quite some 
 > time, but recently we are finding solder balls flattened like pancakes 
 > underneath these devices after wave solder. The package stand-offs are 
 > the standard 8-10 mils for the SOICs and 25-26 mils for the SOJs and 
 > we have not been able to identify any process or material changes that 
 > may be causing this phenomenon.

We have designed several PCB's that utilize the wave soldering process to solder
large active devices on the board. We were first made aware of this phenomenon as
we tested the PCB's and detected a short between two signals. Upon further observation 
we discovered that solder had found its way under the device and shorted two vias that
were also under the device. We were able to determine that this phenomenon only occurredon the leading edge of the board as it goes through the wave. We were able to make
several adjustments and the phenomenon disappeared.

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\_                                                                        \_
\_  Todd J. Zorn                          Email:     [log in to unmask]  \_ 
\_  Technical Analyst - PCB Design                                        \_
\_  The Allen-Bradley Company                                             \_
\_  1201 South Second Street                                              \_ 
\_  Dept. J8751, Control Logic            Phone:     (414) 382-3971       \_ 
\_  Milwaukee, Wi. USA 53204              FAX:       (414) 382-3737       \_
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