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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

IP.com Disclosure Number: IPCOM000012936D
Publication Date: 2003-Jun-11
Document File: 3 page(s) / 102K

Publishing Venue

The IP.com Prior Art Database

Abstract

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.

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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 yield.

Background

        � � � � � 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.

Description

        � � � � � The disclosed method is a screen/jig for flux printing, ball placement, and reflo...