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January 2009

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Subject:
From:
Lee Whiteman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 6 Jan 2009 17:27:27 -0500
Content-Type:
text/plain
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text/plain (113 lines)
Eli,

Tell your engineer that it is a Best Manufacturing Practice (BMP) to use
both top and bottom side heaters. Even if there is a 5C difference
between both sides, with BGAs on the board I would be very skeptical
about not using the bottom side heaters as my esteemed colleagues
indicated.

Lee Whiteman, PMP
Senior Member Engineering Staff
L-3 Communications East
Telephone: (856) 338-3508
FAX: (856) 338-2906
E-Mail: [log in to unmask]
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eli Sarig
Sent: Tuesday, January 06, 2009 3:16 PM
To: [log in to unmask]
Subject: Re: [TN] Question about bottom heaters of reflow oven

Hi,

Thank you for your quick reply!
I really don't want to use only the top heaters. One of my engineers
insists
that the bottom heaters are not necessary. I know about the warping
problem
and the possible cracks. But he measure only 5 C differences between
both
sides. It is over 2 mm board populated with BGA components?


2009/1/6 Steve Gregory <[log in to unmask]>

> Hi Eli!
>
> I have a couple of questions; you say that you measure *almost* the
same
> temperature on the top and bottom, how much is almost?
>
> My second question is; why would you only want to use the topside
> heaters?
>
> Steve
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Eli Sarig
> Sent: Tuesday, January 06, 2009 1:16 PM
> To: [log in to unmask]
> Subject: [TN] Question about bottom heaters of reflow oven
>
> Hi all,
>
> My question is related to the necessity of down heaters in the reflow
> oven.
> When we solder double sided boards, we *can* create a suitable reflow
> profile using *only* the top heaters of the oven.
> In that case, the bottom heaters remain at room temperature. We
measure
> almost the same temperature on top and bottom of the board.
> Are there any limitations or problems that might happen using this
kind
> of process?
>
> Thanks,
>
> Eli.
>
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