James,

        IPC-A-610 (section 4.1) defines solder ball acceptability as a given
diameter (less than 0.13 mm) and quantity per area (5 balls allowed per
600mm2 )

        I agree with the adjustments to the stencil thickness and aperture
shape.  I have had very good results with round or oval apertures on
discrete devices.  This, with a 0.005" stencil has relieved many of my
headaches.  This also improved my paste deposition quality on fine pitch
devices (0.020").

Good Luck


Richard Elensky
Sr. Manufacturing Engineer
[log in to unmask] <mailto:[log in to unmask]>

Tel:  559-292-1111  x246
Fax:  559-292-9355

Dantel
2991 North Argyle Ave.
Fresno, CA, 93727
Visit our web site at:
http:// www.dantel.com <http://www.dantel.com>


        ----------
        From:  Marsico, James [SMTP:[log in to unmask]]
        Sent:  Wednesday, September 26, 2001 12:45 PM
        To:  [log in to unmask]
        Subject:  [TN] SOLDER BEAD SURVEY

        Ok... Here we go again.  We are experiencing solder beads found
UNDER chip components.  The following questions are for all SMT assemblers
(this info would be very helpful to me):
        1)      Do you look for solder balls under chip devices?
        2)      Do you find them?
        3)      Do you rework this anomaly?
        4)      What workmanship criteria are you working to (i.e.
MIL-STD-2000, IPC-610, other)?

        Thanks in advance,
        Jim Marsico
        Senior Engineer
        Production Engineering
        EDO Electronics Systems Group
        [log in to unmask] <mailto:[log in to unmask]>
<mailto:[log in to unmask] <mailto:[log in to unmask]> >
        631-595-5879


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