I'm assuming that a ramp, soak, spike profile will reduce voiding as opposed to a ramp to spike. I was wondering however if anyone has done any experiments (void reduction) with round apertures vs. square apertures in a windowpane pattern?  Thanks



Regards,

Steve Vargas

 

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-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wettermann

Sent: Monday, January 08, 2018 12:51 PM

To: [log in to unmask]

Subject: EXTERNAL: Re: [TN] solder voids - QFN belly pad



Once the criteria is determined for the max voiding percentage the most common suspects we have found, from a process standpoint  are:



1. Type of paste / flux chemistry



2. Thermal Profile



3. Printing reduction in the center ground - ie the print pattern



Certainly vias in the pad will cause the situation to be very complicated as well will very large center ground patterns relative to the part size.



Bob Wettermann





On Mon, Jan 8, 2018 at 10:26 AM, Guy Ramsey <[log in to unmask]> wrote:



> We are having trouble with a lot of boards.

> We are seeing excessive voids like the ones on page 18 of this 

> presentation.

>

> https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=

> 0ahUKEwj27JnJ38HYAhUF5YMKHWYICvcQFggpMAA&url=https%3A%2F%

> 2Fwww.eptac.com%2Fwp-content%2Fuploads%2F2012%2F06%2Feptac_

> 07_18_12.pdf&usg=AOvVaw2OX6J_YRqkuNUNNgDBvmwZ

>

>

> The vias are filled and plated. Anyone seen this, resolved it?

>

>

> Guy

>







--

Bob Wettermann

BEST Inc

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Cell: 847-767-5745