Also on this subject, It should be added that with no-clean fluxes, the added flexibility of more zones can increase yeild via more control of the profile.
You can imagine with the process window tightening, unless you have more control, you might start missing the target. With a no-clean process, your oven can become your best friend, or your worst enemy!
-----Original Message-----
From: MIME :[log in to unmask]
Sent: Wednesday, November 12, 1997 7:45 PM
To: [log in to unmask]
Subject: Re: [TN] length of reflow oven
Once in a while you might need oven with longer and more zones. One time, We
had thick board, densely populated and had mirror image QFP's of big sizes.
In that case, we have to order reflow fixture to control the heat and to
prevent the falling of the already reflowed components. This fixture
(non-metal, high temp material) was kind of heavy and thus worked as a heat
sink too, meaning you may not be able to accomplish reflow on top side with
less # of zones as you have to increase the ramp-up rate very high to
achieve reflow within 5 zones.
You might find problem on thicker board (above .093") to achieve desirable
reflow profile for single reflow. There are some customers who pay more
attention to thermal profile. It is worth going for 7 zones.
re,
ken patel
At 07:41 PM 11/12/97 +0100, D. Terstegge wrote:
>Hello Technet,
>
>Does anyone know a good reason, besides the possibility of having a
>higher throughput-rate, to invest in a 7-heating-zone reflow oven (with
>forced convection) instead of a similar machine with only 5
>heating-zones ?
>
>Daan Terstegge
>
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______________________________________________________
Ken Patel Phone: (408) 490-6804
575 Cottonwood Dr. Fax: (408) 490-6859
Milpitas, CA 95035 Beeper: (888) 769-1808
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