If my memory is correct, there was an article by Phil Zarrow in
Circuit Assembly in 1996 or 1997. The formula in that article was the
ratio of the package weight (in gram) to the total pad area (in square
inch) was no greater than 30. Please correct me if I am wrong.
Yuan Li
Research Associate
CAMPmode (Center For Advanced Manufacturing and Packaging of Microwave,
Optical and Digital Electronics)
University of Colorado at Boulder
http://saagar.colorado.edu/~liy
(303)492-0481
On Thu, 22 Jan 1998, Nicholas Kane wrote:
> Can you tell what the formula is please?
>
> Thankyou
>
>
>
> At 14:02 21/01/98 -0800, you wrote:
> >Steve,
> >
> >I would say that you do want side 1 to reflow as it goes through the oven a
> >second time. Depending on the paste you use, there are going to be
> >different metal types within the paste and you do not want parts of the
> >paste going to liquidus without all the paste going liquidus. I think that
> >may sound a bit confusing, but essentially, either you keep the bottom side
> >below the plastic range or you want it to go all the way into the reflow
> >range - put simply: going halfway is bad.
> >
> >Then you of course run into problems with components falling off. That's
> >when you use the formula (as I am sure you know) using component mass and
> >pad surface area with surface tension of the paste at liquidus. If the
> >math shows your parts will fall off then you need to get the glue going.
> >
> >If I can help further, you can contact me directly.
> >
> >Douglas Bennett
> >Sales Engineer
> >Heraeus Amersil, Inc.
> >770-623-5630 ext 4225
> >[log in to unmask]
> >
> >
> >
> >At 03:40 PM 1/20/98 -0500, you wrote:
> >>All,
> >>
> >>We have a new board coming up that will be 6.3" x 9.3" with 30-40 fine pitch
> >>(20 mil) per side (mostly PQFP, couple TSSOP). Board will be 6-8 layers,
> >>.062 thick,
> >>~400-500 total components, 2 compliant pin connectors.
> >>
> >>Can I ask any of you who are processing boards with similar density what
> >>your reflow process
> >>is? Will I have problems with a straight 2-sided reflow process or should I
> >>look at
> >>fixturing to keep side 1 from reflowing when side 2 is reflowed? We have a
> >>Conceptronics
> >>HVN-102 (7-zone) reflow oven. We do not have glue-dispensing capability at
> >>this time.
> >>
> >>Next generation of this product will have equal number of BGA on both sides,
> >>what do
> >>I need to be concerned about other than the rework process? Thanks for any
> >>inputs...
> >>
> >>Steve
> >>
> >>
> >>----
> >>Steve Schrader
> >>VP Manufacturing
> >>Patton Electronics Co.
> >>http://www.patton.com
> >>
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> >
> Nicholas Kane
> Axion Australasia
> Suite 3, 651 Canterbury Road
> Surrey Hills
> Victoria 3127 Australia
>
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