Dual Solder Interconnects for Fine-Pitch Bridge Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As microelectronics packaging technologies scale down, challenges arise from solder bridge formation and low yields due to warpage-associated incomplete solder joint formation between integrated circuit dies and package substrates during thermal compression bonding operations.
Innovation Solution
A dual solder metallurgy method is employed, where two solder layers with disparate liquidus temperatures are used, with a touch-and-bond process forming partial solder joints that are later reinforced to prevent solder bridging and ensure complete bonding, utilizing an underfill material to confine the solder and prevent it from flowing to neighboring bond pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If interconnect dimensions are scaled down to achieve ultrahigh density architectures, then package footprint and thickness are reduced, but solder bridge formation incidence increases
Solution Approach 1:
The solder joint formation process is segmented into two distinct stages: a first reflow stage that forms an initial solder joint, and a second reflow stage that completes the solder joint. This segmentation allows each stage to be optimized independently, with the first stage creating a barrier that prevents solder bridge formation while the second stage ensures complete bonding, thus resolving the contradiction between reduced pitch and solder bridge prevention.
Solution Approach 2:
The invention changes the thermal parameters by applying two different reflow temperature profiles at two distinct stages. The first reflow stage uses a temperature profile that forms a partial solder joint sufficient to prevent bridging, while the second reflow stage uses a different temperature profile to complete the joint. This parameter change approach allows prevention of solder bridges while achieving complete bonding.
2Strength
If thermal compression bonding is used to bond dies to substrates, then bonding is achieved, but warpage-associated incomplete solder joint formation occurs
Solution Approach 1:
The invention performs a preliminary thermal compression bonding operation that brings the die and substrate into contact and forms an initial solder joint before the final reflow stage. This preliminary action establishes proper alignment and contact, preventing warpage-associated incomplete joint formation while maintaining bonding strength. The initial joint serves as a foundation that ensures complete bonding in the subsequent reflow stage.
3Quantity of substance
If FLI pitches are decreased to increase density, then ultrahigh density architectures are achieved, but solder bridge formation increases
Solution Approach 1:
The solder joint formation is divided into two stages: a first reflow stage that creates a partial joint sufficient to prevent bridging between closely spaced interconnects, and a second reflow stage that completes the joint. This segmentation enables the process to handle decreased FLI pitches by ensuring that solder is contained during the critical formation phase, thus achieving ultrahigh density while preventing solder bridges.
4Device complexity
If single-stage reflow is used for simplicity, then process complexity is reduced, but solder bridge formation and incomplete joint formation occur
Solution Approach 1:
The invention divides the reflow process into two distinct stages with different temperature profiles and durations. The first reflow stage is optimized to form a partial solder joint that prevents bridging, while the second stage completes the joint. Although this increases process complexity compared to a single-stage approach, it successfully prevents solder bridge formation and ensures complete bonding, resolving the contradiction between process simplicity and reliability.
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 method effectively prevents solder bridging and ensures high-yield, complete solder joint formation by using a temporary bond to stabilize the die-substrate interface before forming a permanent bond, enhancing the reliability and density of ultrahigh-density interconnects.
Implementation Method 1
reflowing the first layer to form a partial solder joint between the first bond pad and the second bond pad
Implementation Method 2
reflowing the second layer to form a complete solder joint between the first bond pad and the second bond pad
Implementation Method 3
utilizing an underfill material to confine the solder and prevent it from flowing to neighboring bond pads
Data Source
AI summary
An apparatus, comprising an integrated circuit (IC) package having at least one solder bond pad, a die having at least one solder bond pad, wherein the die is bonded to the IC package by at least one solder joint between the at least one solder bond pad of the die, and the at least one solder bond pad of the IC package, and an underfill material between the IC package and the die, wherein the at least one solder joint is embedded in the underfill material, and wherein the at least one solder joint comprises a first metallurgy and a second metallurgy.