IC Package Stub Trace Termination for Security

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Solution Overview

Problem

Existing integrated circuit (IC) packages with exposed copper traces at the side edges of substrates are vulnerable to unauthorized access, allowing attackers to probe and potentially manipulate IC buses, despite security measures like data encryption.

Innovation Solution

The integration of stub traces that terminate 200 micrometers inside the substrate perimeter, made invisible through an etching process using a pattern mask and acid, prevents exposure of these traces, enhancing security by making it difficult for attackers to access IC buses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If copper traces are extended to side edges of substrate to facilitate electroplating, then electroplating process is simplified, but security is compromised as traces become visible and accessible from the side

Engineering Contradiction:

Improveelectroplating processVSAvoidunauthorized access to IC buses

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The copper trace is segmented into two parts: the functional trace that connects to the bond pad, and the stub trace that extends toward the side edge but terminates before reaching it. This segmentation allows the trace to facilitate electroplating while preventing unauthorized access, as the stub trace is isolated and not visible from the side of the package.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stub trace is positioned in a specific spatial dimension - extending from the functional trace but terminating 200 micrometers inside the substrate perimeter. This dimensional positioning ensures the trace serves its electroplating function while remaining invisible from the side edge, effectively using spatial arrangement to resolve the security conflict.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If stub traces extend to side edge to facilitate electroplating, then manufacturing is easier, but attackers can probe exposed traces

Engineering Contradiction:

Improveelectroplating facilitationVSAvoidsecurity of IC buses

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The stub trace is designed to extend toward the side edge in advance to facilitate the electroplating process, but terminates 200 micrometers inside the substrate perimeter before reaching the edge. This preliminary extension provides sufficient electrical path for electroplating while preventing the harmful outcome of exposed traces that attackers could probe.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If copper traces are made visible for manufacturing purposes, then electroplating is facilitated, but access to IC buses becomes possible

Engineering Contradiction:

Improveelectroplating processVSAvoidsecurity vulnerability

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

Different portions of the copper trace structure have different properties: the functional trace portion is fully connected and visible for manufacturing, while the stub trace portion extends locally to facilitate electroplating but terminates before becoming visible from the side. This local differentiation in trace visibility and connectivity resolves the contradiction between manufacturing ease and security.

Inventive Principle:

Principle #3Local quality

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 solution effectively secures IC buses by ensuring that stub traces are not visible from the side of the IC package, thereby protecting sensitive transactions and preventing unauthorized access to electrical signals.

Implementation Method 1

The PCB substrate panel is then completely submerged in an acid or solution that eats away the exposed metal through the openings

Methodology Applied

Scientific EffectChemical etching: Oxidation

Implementation Method 2

Bond pad 16 is normally electroplated with a layer of gold because of the excellent conductive and mechanical properties of gold

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS8049324B1Preventing access to stub traces on an integrated circuit package

Publication Date: 2011.11.01 MAXIM INTEGRATED PROD INC

AI summary

An integrated circuit (IC) package includes a printed circuit board (PCB) substrate and a plurality of package attachment terminals. The package attachment terminals are used to conduct electrical signals from a die that is attached and bonded onto the PCB substrate. The PCB substrate has a side edge and includes a plurality of electrically-conductive paths. Each one of the plurality of paths includes an electroplated bond pad, a trace, and a stub trace. The die is connected to the bond pad and the trace couples the bond pad to a respective one of the package attachment terminals. The stub trace is used to facilitate the electroplating process. The stub trace extends from the trace and terminates at a distance away from the side edge. The stub trace is not visible from the side of the IC package and therefore prevents access to IC buses on the package.