Interposer Stress Relief for BOC Package Delamination

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Solution Overview

Problem

Conventional ball grid array type board on chip packages face reliability issues due to delamination between contact pads and insulation layers caused by material mismatch and stress concentration, which existing improvements in metal line designs and materials have not adequately addressed.

Innovation Solution

Incorporating an interposer between the IC chip and the board, with holes to expose contact pads, and using bonding wires to connect them, which absorbs stresses and reduces delamination by transmitting them to the interposer, thereby improving the structural integrity and reliability of the package.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If contact pads are concentrated on the center of the IC chip to achieve electrical connection, then electrical connectivity is improved, but stress concentration and delamination occur between contact pads and insulation layer

Engineering Contradiction:

Improveelectrical connectivityVSAvoidbonding strength between contact pad and insulation layer

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent introduces an interposer as an intermediary component between the IC chip and the board. The interposer includes a stress relief layer that absorbs and distributes the thermal expansion stress, preventing direct stress transmission to the contact pads and insulation layer interface. This mediator structure resolves the contradiction by maintaining electrical connectivity through the interposer while protecting the vulnerable bonding interface from stress-induced delamination.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the material parameters of the interposer, specifically using a material with a thermal expansion coefficient matched to the IC chip substrate. This parameter matching reduces thermal stress differential during temperature cycling, thereby preventing stress concentration at the contact pad interface while maintaining electrical connectivity through the interposer structure.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If adhesive material is used to adhere the board to the IC chip, then structural assembly is simplified, but delamination occurs due to stress concentration around contact pads

Engineering Contradiction:

Improveassembly processVSAvoidbonding reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The interposer acts as a mediator between the adhesive material and the IC chip contact pads. By placing the stress relief layer of the interposer between the adhesive and the contact pads, the interposer absorbs the stress that would otherwise concentrate at the adhesive-contact pad interface, preventing delamination while maintaining the simplicity of adhesive-based assembly.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If metal lines and contact pads occupy more than 60% of the IC chip center region, then electrical connection density is improved, but stress-induced delamination increases

Engineering Contradiction:

Improveelectrical connection densityVSAvoidstress-induced delamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The interposer serves as a protective intermediary that shields the densely packed metal lines and contact pads from stress-induced delamination. The stress relief layer of the interposer absorbs thermal expansion stresses, allowing high-density electrical connections to be maintained in the center region without suffering from stress concentration problems.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The interposer effectively reduces delamination between the contact pads and insulation layers, enhancing the reliability and grounding performance of the board on chip package, and minimizing defects caused by stress-induced delamination.

Implementation Method 1

the interposer effectively reduces delamination between the contact pads and insulation layers, enhancing the reliability and grounding performance of the board on chip package, and minimizing defects caused by stress-induced delamination

Methodology Applied

Scientific EffectStress absorption: Absorption (physical)

Data Source

PatentUS7923296B2Board on chip package and method of manufacturing the same

Publication Date: 2011.04.12 SAMSUNG ELECTRONICS CO LTD

AI summary

A ball grid array type board on chip package may include an integrated circuit chip having an active surface that supports a plurality of contact pads. An interposer may be adhered to the active surface of the integrated circuit chip. At least one hole may be provided through the interposer to expose the contact pads. A board, which may have a first surface supporting a plurality of metal lines, may have a second surface adhered to the interposer. The board may have an opening through which the contact pads may be exposed. A plurality of bonding wires may connect the contact pads to the metal lines through the opening.