Enhanced Polymer Passivation Layer for Wafer Level Chip Scale ...

Figure 4.3 The test board with the individual bonding site and its close-up view
4.2.2 Die Placement
Pick-and-place machines are used to place surface mount devices onto printed circuit
boards. They are used for high speed, high precision placing of a broad range of electronic
components. In general, the die placement cycle is composed of four steps: 1) pattern recognition
of the substrate using local or global fiducials; 2) picking of the die; 3) die imaging and theta
correction; and 4) die placement. In direct chip attach applications, the dies are sorted prior to
the attachment, and presented for placement via either waffle packs or tape & reel. In most cases,
flux dispensing and die placement operations are performed on one machine. Approaches to
accomplish the fluxing process include: 1) flooding the chip site by dispensing the flux, and then
place the chip; and 2) dipping the die into a thin film of flux to coat the solder balls and then
placing the chip onto the substrate. There are several key considerations for the die placement
such as the placement speed, force of placement, material properties of the flux, die metrics (size,
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