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March 1997

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Subject:
From:
Allen Hertz <[log in to unmask]>
Date:
Fri, 07 Mar 1997 14:50:52 -0500 (EST)
Content-Type:
TEXT/PLAIN
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TEXT/PLAIN (92 lines)
Karl,
During the development of the part (PBGA) and subsequent production, we dipped 
the component in flux (Originally Dupont 9554 then Kester 247 Vehicle), placed 
and reflow the part. Then the assembly went through a Terpine cleaner. This 
process cleaned a large percent of the flux under the component. At that time, 
any misaligned parts (not reflowed to pads) washed off. We finally progressed to 
no-clean and improved our placement processes to six Sigma.

There are several new paste vehicles that will work, some suggestions (not 
endorsements!) are still the Kester 247 and Multicore NC 73 or 402-01 for lower 
residue. 

Regards,
Allen

_______________________________________________________________________________

Subject: Re: Cleaning of BGA

From:    [log in to unmask] at ftl03

Date:    3/7/97  12:49 PM




Guenter,

How do you check for this on a finished assembly, since the
rest of the board is very clean and likely to still pass a
general ionic contamination level determination procedure?

Is there an approved cleaning method for assembled boards
with BGAs, or is no-clean flux the only option?

Regards,
Karl Sauter


----- Begin Included Message -----

Date: Fri, 7 Mar 1997 14:12:32 +0100
To: [log in to unmask]
From: [log in to unmask] (Guenter Grossmann)
Subject: Re: Cleaning of BGA
Resent-From: [log in to unmask]

Hi Poh

In my opinion there is no way to clean the solder joints underneath a BGA.
You might even worsen the situation because the polymer matrix of the flux
residues close to the edge of the BGA will be cracked in a cleaning agent.
This solution is washed underneath your BGA and will contaminate the inner
row of balls even worse than they where before. Additionally, if you have
tracks underneath your BGA, the SIR between the tracks will be affected
with all the rubbish you wash under the component. We made trials with
QFP's, where we saw that residues are washed underneath the component but
that the rinsing operations where not able to remove the sauce accumulating
underneath the package.

Best regards

Guenter Grossmann


----- End Included Message -----



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