Non-electrolytic Plating of Semiconductor Package Leads

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Solution Overview

Problem

In semiconductor packaging, the formation of reliable and inspectable solder connections between singulated package leads and a printed circuit board (PCB) is challenging due to inconsistent wetting of solder paste on exposed lead tips, which hinders visual and automatic optical inspection.

Innovation Solution

A non-electrolytic plating operation is performed on exposed lead tips during the saw singulation process to create a wettable surface, using a plating solution that acts as a coolant-lubricant, resulting in consistent fillet formation during surface mount assembly, enabling visual and automatic optical inspection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional singulation process is used without plating, then manufacturing process is simpler, but solder connection reliability is poor

Engineering Contradiction:

Improvesolder connection reliabilityVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by performing non-electrolytic plating on the exposed lead tips during the saw singulation process itself, before the actual soldering operation. This advance preparation of the lead surface ensures proper wetting and reliable solder connections without requiring separate post-singulation plating steps, thus improving reliability while controlling process complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent merges two previously separate operations (saw singulation and plating) into a single integrated process. The non-electrolytic plating is performed concurrently with the saw singulation by applying plating solution to the exposed lead tips during cutting, eliminating the need for separate plating equipment and process steps, thereby improving reliability without significantly increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If plating is performed after singulation, then solder wetting is improved, but manufacturing time increases

Engineering Contradiction:

Improvesolder wetting consistencyVSAvoidmanufacturing cycle time

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent performs the plating action preliminarily during the singulation process itself, so that by the time the packages are ready for soldering, the lead tips are already plated and ready for optimal solder wetting. This eliminates waiting time and sequential processing, maintaining high productivity while achieving consistent solder wetting.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuity of useful action by maintaining the plating solution application throughout the saw singulation process. The plating occurs continuously as the saw cuts through the packages, ensuring that all exposed lead tips receive uniform plating coverage without interrupting the singulation workflow, thus improving solder wetting consistency without extending manufacturing cycle time.

Inventive Principle:

Principle #20Continuity of useful action

3Manufacturing precision

If non-electrolytic plating is performed during saw singulation, then solder fillet formation is consistent, but process complexity increases

Engineering Contradiction:

Improvefillet formation consistencyVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the plating process with the existing saw singulation operation by applying non-electrolytic plating solution to the exposed lead tips during cutting. This integration utilizes the same equipment and process flow, adding minimal complexity while achieving consistent fillet formation through uniform plating coverage on all lead tips.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the plating method from traditional electrolytic plating to non-electrolytic plating, which can be applied more easily during the sawing process. This parameter change allows plating to occur during singulation without requiring complex plating equipment, thereby achieving consistent fillet formation while minimizing increases in process complexity.

Inventive Principle:

Principle #35Parameter changes

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 ensures reliable and consistent formation of solder fillets on exposed lead tips, facilitating effective visual and automatic inspection of surface mount assemblies and ensuring reliable electrical connections.

Implementation Method 1

performing a non-electrolytic plating operation on exposed lead tips of individual packages from the array of package sites as the array of package sites is saw singulated

Methodology Applied

Scientific EffectNon-electrolytic plating: Deposition (physical)

Implementation Method 2

using a plating solution that acts as a coolant-lubricant

Methodology Applied

Scientific EffectCooling: Cooling

Implementation Method 3

using a plating solution that acts as a coolant-lubricant

Methodology Applied

Scientific EffectLubrication: Lubrication

Data Source

PatentUS9224651B2Method for plating a semiconductor package lead

Publication Date: 2015.12.29 NXP USA INC

AI summary

A method of forming a packaged semiconductor device includes loading an array of package sites in position for saw singulation, saw singulating the array of package sites, and performing a non-electrolytic plating operation on exposed lead tips of individual packages from the array of package sites as the array of package sites is saw singulated.