Please also share the x-ray images of the QFNs. Wondering voids create during the reflow process or induce to PCB design (Via-Fill-Plated-Over, VFPO)


________________________________
From: TechNet <[log in to unmask]> on behalf of Steve Golemme <[log in to unmask]>
Sent: Saturday, 3 August 2019 5:45 AM
To: [log in to unmask]
Subject: Re: [TN] Jumping QFNs

If you can, please record a video and post it on youtube. I'd love to see
that!

Best,
Stephen Golemme
Electrical Manufacturing Engineer
650-214-5647
go/ees-consulting
x.company


On Fri, Aug 2, 2019 at 2:23 PM Robert Kondner <[log in to unmask]>
wrote:

> Hi,
>
>  I would vote that the flux is popping them  with bubbels. You might try
> reflowing a few on a hot plate. Mke sure the hot plat is hot so the temp
> rise is faster than that in the oven.
>
> Bob K.
>
> -----Original Message-----
> From: TechNet <[log in to unmask]> On Behalf Of Guy Ramsey
> Sent: Friday, August 2, 2019 2:32 PM
> To: [log in to unmask]
> Subject: [TN] Jumping QFNs
>
> We are experiencing a bout of QFNs that jump off the pads, even off the
> assembly during reflow.
> The parts are handled in accordance with J-STD-033.
> The boards are complex multilayer sequential lamination with thousands of
> vias, blind, buried, and through hole. All exposed vias are filled and
> plated,with ENIG finish.
> We bake the boards 10 hrs at 105C.
> Solder paste is FCT WS159 . . . I know, I know.  The Peregrine parts don't
> solder well unless the flux is crazy active.
> Any ideas on why about 2-5 percent of the parts jump off the pads or
> assembly completely?
> Can this be just a solderability problem?
>