Unplated Leadframe IC Packaging with Selective Plating

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Solution Overview

Problem

The increasing complexity and cost of semiconductor chip packaging, driven by the need for compact electronic devices, has not been effectively addressed by existing technologies, which rely on expensive pre-plated leadframes and complex processing steps, leading to high material costs and inefficiencies.

Innovation Solution

A method involving an unplated leadframe with contact protrusions, where a solder resist is deposited and etched to form contact pads and traces, followed by a trace protection layer and recess formation, allowing direct deposition of external connectors without pre-plated materials, thereby reducing costs and improving efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If pre-plated leadframe is used, then adhesion and protection are improved, but material cost increases

Engineering Contradiction:

ImproveadhesionVSAvoidmaterial cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies preliminary protective plating on specific areas (contact pads and traces) before the etching process. This pre-plating serves as a protective layer during manufacturing while allowing selective removal to create the final circuit pattern, thus ensuring adhesion and protection without requiring complete plating of the entire leadframe, reducing material cost.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements plating only in specific locations where electrical connection and protection are needed (contact pads and traces), rather than uniformly plating the entire leadframe. This localized plating approach maintains necessary adhesion and protective properties while significantly reducing expensive plating material consumption.

Inventive Principle:

Principle #3Local quality

2Reliability

If complete plating process is applied, then protection is improved, but processing time increases

Engineering Contradiction:

ImproveprotectionVSAvoidprocessing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent extracts and removes the plating layer from areas where it is not needed after the protective function has been served during etching. By selectively removing plating from non-critical areas, the process achieves necessary protection during manufacturing while reducing total processing time compared to maintaining complete plating throughout all subsequent steps.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The plating is applied preliminarily only where needed for protection during etching, rather than applying complete plating and then maintaining it throughout all processing. This preliminary, selective plating reduces the overall processing time while still providing necessary protection during critical manufacturing steps.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If complex multi-step process is used, then manufacturing precision is improved, but device complexity increases

Engineering Contradiction:

Improveetch precisionVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies different processing treatments to different areas of the leadframe - plating is applied only to contact pads and traces that require precise etching, while other areas remain unplated. This localized approach achieves necessary manufacturing precision for electrical connections while simplifying the overall process by eliminating unnecessary plating and removal steps from non-critical areas.

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

This approach reduces material costs, decreases product lead time, increases etch efficiency, and enhances production reliability by eliminating the need for expensive plating and unnecessary processing steps, while improving the pad pitch and adhesion of external connectors.

Implementation Method 1

depositing a solder resist on the contact protrusion

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 2

forming a contact pad and traces by etching the unplated leadframe

Methodology Applied

Scientific EffectEtching: Ablation

Implementation Method 3

depositing an external connector directly on the top surface of the contact pad

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS9190349B1Integrated circuit packaging system with leadframe and method of manufacture thereof

Publication Date: 2015.11.17 STATS CHIPPAC LTD

AI summary

An integrated circuit packaging system and method of manufacture thereof including: providing an unplated leadframe having a contact protrusion; depositing a solder resist on the contact protrusion; forming a contact pad and traces by etching the unplated leadframe; applying a trace protection layer on the contact pad and the traces; removing the solder resist; forming a recess in the trace protection layer by etching a top surface of the contact pad to a recess distance below a top surface of the trace protection layer; and depositing an external connector directly on the top surface of the contact pad.