Hi Brian
Agree, the chiller you engage only when pushing limits , depends on top
load componentry .
Brian , enlighten me :
165, 175, 160 (dip?) , 160(why?), 185, 245, ?(no cooling?) .
Somehow my Indium profile looks different .
What is the reason for dwell on 160 2x, and how do you cool ?
With ALL bottom zones blowing ambient ; the separation is nice indeed .
Can you get me an info on what ( in 'C's ) is achievable ?
thanks
Paul Klasek
http://www.resmed.com
> ----------
> From: ETS[SMTP:[log in to unmask]]
> Sent: Thursday, 25 June 1998 2:10
> To: [log in to unmask]
> Subject: Re: [TN] ASSY: BGA sanity check
>
> Dear Jerry,
>
> As a reflow manufacturer of course I want to brag but I also do not
> blame
> you for your hesitation. The weight of most BGA's outwieghts the
> surface
> tension of the solder paste. However, as Mr. Klasek pointed out,
> reflow CAN
> be avoided on the bottom side of the board. I am sure that you have
> heard
> before that once solder has been reflowed once the melting point of
> that
> solder increases to a higher temperature. This is where I have to
> differ
> with Mr. Klasek, we have not found chillers to be necessary. After
> reflowing
> the BGA's on the top side and inverting the board, we run the assembly
> through an ETS CUREFLOW that has both top and bottom convection
> heating. We
> use a profile that uses standard temperatures on all 6 top zones
> (165C,
> 175C, 160C, 160C, 185C, 245C) and then set all bottom zones to ambient
> temperature (or room temperature). This creates differential heating
> on the
> assembly by heating the top side of the board and cooling the bottom
> side
> of the assembly. This creates a big enough temperature delta to keep
> the
> bottom side components from reflowing a second time.
>
> Of course this method requires two passes through the reflow oven
> whereas if
> all the BGA's where on the top of the board you might be able to
> solder both
> sides with a single pass through reflow.
>
> If you would like to discuss this further I can be contacted at
> [log in to unmask]
>
> Sincerely,
>
> Brian Stumm
>
>
>
>
>
> >Hello, TechNet....
> >
> >Soldering (inline convection furnace) BGA's on both sides of a board
> is
> >beyond my own experience, but it seems to violate a principle (at
> least an
> >imaginary one) related to the controlled collapse, or perhaps liquids
> under
> >tension.
> >
> >For a board design using 3 commercial BGA packages (PBGA 256,
> eutectic
> >balls on 1.27 mm pitch), am I obstinately blocking the path of
> progress by
> >requesting that this package style be confined to only one surface of
> a new
> >board design?
> >
> >If you are doing this today and it is a piece of cake, go ahead and
> brag;
> >but I would prefer to hear that caution is well advised, i.e. tales
> of
> >misery, shame and corporate disaster resulting from such mistakes.
> ;-)
> >
> >
> >cheers,
> >
> >
> >
> >
> >Jerry Cupples
> >Interphase Corporation
> >Dallas, TX USA
> >http://www.iphase.com
> >
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