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Disclosed is a method for the prevention of solder ball/paste misalignment using a single screen that can be used for flux printing, solder ball placement, and reflow. Benefits include improved yield.
English (United States)
This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately
61% of the total text.
Method for the prevention of solder ball/paste misalignment
using a single screen that can be used for flux printing, solder ball
placement, and reflow
Disclosed is a method for the prevention of solder ball/paste
misalignment using a single screen that can be used for flux printing, solder
ball placement, and reflow. Benefits include improved
� � � � � Ball grid array (BGA)
solder balls misalign after solder paste and solder ball reflow. The
misalignment reduces the ball-attach module yield. A method for preventing this
problem is required.
� � � � � Conventional ball
attachment uses different screen and jig for flux printing and ball placement
respectively. The picking up of the screen at flux printing causes insufficient
flux coverage and volume. As a result, a jig is used for solder ball placement.
However, picking up the jig after this process causes the detachment of balls.
Additionally, the solder balls are left unguided at reflow, causing ball
movement (see Figure 1).
� � � � � A solder bump/ball
can become misaligned from the substrate pad after the reflow soldering process
(see Figure 2). Solder ball misalignment during the reflow process reduces the
ball joint yield. Ball misalignment is due to poor flux coverage, flux
misalignment, or solder ball misplacement. No conventional solution exists for
this problem. All misaligned units are rejected.
� � � � � The disclosed method
is a screen/jig for flux printing, ball placement, and reflo...