PoP (package on package) and vapor phase technology
the smallest ΔT at short dwell times of the As a surface
board in the condensing vapor. Thermal finish, ENIG
transfer is independent of form, color, offered good solder-
mass and mass distribution of the PCBA. ability, increasingly
Detailed x-ray inspections were significant strength
performed on each BGA group, looking and a considerably
for evidence of solder bridges, voids and improved board
Affordable, intelligently designed x-ray
open connections. Voids were measured finish.
using RINCON measuring software and Visual inspec-
inspection systems since 1983.
found compliant with IPC-7095 where tion under 40, 150,
the accepted voiding area is less than 25% 600 and 1200X
Patented real-time x-ray imaging
(the percentage of joint cross-sectional area magnifications re- technology that creates high resolution,
occupied by the void). Voiding was mainly sulted in 100% first
compact systems.
caused by flux out-gassing within molten pass yield (FPY) for
solder joints. (These bubbles form and pop all BGAs that used
open when they either grow too large or Multicore LF318M
migrate to the edge of a joint; upon solidi- DAP solder paste
fication, the bubbles become voids.) While under VP reflow.
cross-sectioning was not perfectly centered All five BGAs
on the BGA balls, the solder joints exhib- (U1, U5, U8, U11,
ited in the analysis met all requirements and U15) were suc-
of IPC-610 Revision D for component cessfully tested for
alignment, voiding, solder ball spacing and continuity.
connection (Figure 1). All criteria for
Cross sections of the components that this process were
used Multicore LF318M DAP solder paste satisfied with excel-
together with VP reflow indicate adequate lent test results.
solder volume and uniformity (Figures 2
and 3). The calculated solder volume used
is within 5% of the solder volume that
should normally occur on a production
To learn more, go to:
surface mount line.
www.GlenbrookTech.com
references:
1. Munroe, C., “Beating
the RoHS Heat,” Circuits
Assembly, March 2008.
2. Wooten, R., “Vapor
Phase vs. Convection Re-
flow Technology” SMT,
July 2009
Dan Coada is a process/
manufacturing engineer
with EPIC Technologies. He
can be reached at coaddc@
epictech.com.
Figure 4. Vapor Phase profile that has been used to reflow the boards.
www.globalsmt.net Global SMT & Packaging – September 2009 – 13
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