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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