Split Solder Pad for Flip-Chip Testing Prevention
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Solution Overview
Problem
Existing flip-chip packaging techniques do not effectively prevent testing of an integrated circuit die after packaging, as solder balls can still enable electrical connections between test and VSS bond pads, allowing unintended testing.
Innovation Solution
A split solder pad design with two half-disk portions, where the test bond pad is connected to one portion and the VSS bond pad to the other, allowing testing only when no solder ball is present, as the solder ball merges these connections, disabling the test circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a dedicated test bond pad is provided for testing the die, then testing capability is enabled, but the die can be tested unintentionally after flip-chip packaging operation
Solution Approach 1:
The solder pad is divided into two separate portions: a first portion connected to the test bond pad and a second portion connected to the VSS bond pad. This segmentation allows the test function to be enabled only when no solder ball is present, while preventing unintended testing after packaging when the solder ball bridges both portions and grounds the test bond pad.
2Reliability
If a solder ball is placed on the solder pad to ground the VSS bond pad, then the test bond pad is merged with VSS bond pad disabling test circuitry, but the ability to test the die is lost
Solution Approach 1:
The electrical connection state of the test bond pad dynamically changes based on the presence of a solder ball. When no solder ball is present, the test bond pad is accessible for testing. When a solder ball is placed during packaging, it automatically grounds the test bond pad through the second portion of the solder pad, disabling test circuitry and preventing unintended testing.
3Ease of operation
If the test bond pad is connected to a separate pad, then testing is always possible, but cannot prevent testing after packaging
Solution Approach 1:
The first portion of the solder pad is merged with the test bond pad connection, and the second portion is merged with the VSS bond pad connection. This merging allows the solder ball to simultaneously ground both the VSS bond pad and the test bond pad, effectively disabling testing capability after packaging while maintaining it before packaging.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents integrated circuit die testing after flip-chip packaging by ensuring the test bond pad and VSS bond pads are electrically connected only in the absence of a solder ball, effectively grounding the VSS bond pad and disabling the test circuitry when a solder ball is placed, thus preventing unintended testing.
Implementation Method 1
solder balls establishing electrical connections between the solder pads 17 and the tracks 14
Data Source
Figure 1~6
AI summary
The invention relates to an electronic system comprising: - an integrated circuit die (10') having: • at least 2 bond pads (20, 37) • a redistribution layer, said redistribution layer having: - at least a solder pad (19') comprising 2 portions (33, 34) arranged to enable an electrical connection between each other by a same solder ball placed on said solder pad (19'), but electrically isolated of each other in the absence of a solder ball on the solder pad (19') - at least 2 redistribution wires (22, 23, 39), each one connecting one of the 2 portions (33, 34) to one of the 2 bond pads (20, 37), a second bond pad (37) connected via a second redistribution wire (39) to a second portion (34) of the solder pad (19') being dedicated to testing said integrated circuit die (10') - a grounded printed circuit board track (24), a solder ball (35) being placed between the solder pad (19') and the printed circuit board track (24).