Browse Prior Art Database

Method for an off-center microvia

IP.com Disclosure Number: IPCOM000029167D
Publication Date: 2004-Jun-16
Document File: 4 page(s) / 154K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an off-center microvia. Benefits include improved functionality and improved reliability.

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Method for an off-center microvia

Disclosed is a method for an off-center microvia. Benefits include improved functionality and improved reliability.

Background

      The size of chip components is decreasing. Chip scaling is accomplished with via-in-pad (VIP) printed circuit board (PCB) technology. However, voids generated during the via-in-pad processing, amplifies the solder joint reliability issue. No conventional solution exists.

              The conventional pad design includes a microvia located in the center of the device pads. The location of the microvia causes the void formation directly underneath the component terminal (see Figure 1).

 

              Crack propagation for chip components initiates at the bottom of the chip component’s terminal and extends at a 45-degree angle towards the fillet edge (see Figure 2). Cracking initiates at the bottom of the component terminal due to the solder joint undergoing high shear force because of the lower standoff (see Figure 2).

      A solder void in the crack propagation path reduces the cross-sectional area of the solder joint. However, the void poses a risk of early failure in solder joints during thermal cycling. The crack propagation path is longer in photo 1 as compared to photo 2 (see Figure 3). The solder void within the crack propagation path shortens the crack length before the full crack occurs (see Figure 4).

Description

      The disclosed method is a via-in-pad (VIP) design away from the center of the device pads (off center) and underneath the component terminals. This location provides a longer crack path and increases the solder-joint’s life.

      The disclosed method removes the void formation within the solder region or offsets the solder void formation from the crack propagation path. A longer crack propagation path is provided within the solder region and subsequently increases the fatigue life of the chip component.

              The key element of the method includes a microvia located away from the center of the chip component pads and inclined away from underneath the component terminals.

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