Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Method for asymmetric double-folded stack chip-scale packages

IP.com Disclosure Number: IPCOM000033134D
Publication Date: 2004-Nov-29
Document File: 3 page(s) / 171K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for asymmetric double-folded stack chip-scale packages (ADFS-CSP). Benefits include improved functionality and improved performance.

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 53% of the total text.

Method for asymmetric double-folded stack chip-scale packages

Disclosed is a method for asymmetric double-folded stack chip-scale packages (ADFS-CSP).  Benefits include improved functionality and improved performance.

Background

              The conventional double-folded CSP technology extends the single fold stack chip-scale package (FS-CSP) technology by doubling the allowable number of  traces to connect the top and bottom package. The method improves the power delivery and signal integrity by reducing the trace length of the FS-CSP. However, the precision alignment requirements for the conventional double-folded CSP limits the manufacturing capability (see Figure 1).

              The problem with the conventional double-fold package is that the top package ball-out must align to the folded substrate land pad precisely to make good electrical connection. The control of folding process is very critical. If the gap between the two sides is too wide or narrow, the balls can not be align to the land pad correctly, which causes electrical connection problems with top package. When the gap between the ends of the fold is too wide, one side of the balls is misaligned with the pads (see Figure 2).

Description

              The disclosed method is a double-fold package structure with an asymmetric fold substrate (see Figure 3). The bottom package is placed on the substrate in an off-center location. The substrate is folded on both sides. One fold is shorter with one or more rows of large landing pads. The other fold is longer with rest of the landing pad for connection to the top package. The top package is attached to the folded substrate. Due to a dual ball-out structure for the short fold side of the substrate, the alignment of the double fold is not critical. The connection can be achieved through either ball to the large landing pad.

              With the asymmetric double-folded package, the...