Chip-to-Substrate Assembly With Hot Underfill for Fine-Pitch Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenges of interconnecting chips with high-density bump interconnection to organic laminate substrates include connector pitch limitations, nearest neighbor shorting, and thermal strain-induced misalignment due to coefficient of thermal expansion (CTE) mismatch, which hinder data transfer and connection reliability, especially at sub-55 μm pitches.
Innovation Solution
The method involves bonding a semiconductor chip to an organic laminate substrate using solder, dispensing underfill without cooldown, and curing it at elevated temperatures, while using solder caps on both pillars and pads to accommodate warpage and reduce thermal excursion, and applying volatile tacky adhesive to ensure proper alignment and underfill without intermediate cooling steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If chip connector pitch is reduced to increase data transfer density, then data transfer capability is improved, but thermal strain-induced misalignment increases due to CTE mismatch between chip and substrate
Solution Approach 1:
The patent applies preliminary action by dispensing underfill material between the chip and substrate before the thermal bonding process. This underfill layer is pre-positioned to compensate for upcoming thermal expansion differences, maintaining connector alignment throughout the bonding process even at reduced pitches.
2Speed
If connector pitch is reduced to increase interconnection density, then data transfer capability is improved, but nearest neighbor shorting risk increases
Solution Approach 1:
The patent uses underfill material as an intermediary substance dispensed between connectors before bonding. This underfill acts as a mediator that maintains proper spacing and alignment between adjacent connectors, preventing nearest neighbor shorting while enabling higher density interconnections.
3Ease of manufacture
If underfill is dispensed after cooldown from bonding temperature, then underfill application is simpler, but thermal strain causes misalignment before underfill can protect connectors
Solution Approach 1:
The patent reverses the conventional sequence by performing the preliminary action of dispensing underfill before thermal bonding rather than after cooldown. This ensures alignment protection is in place before thermal strain occurs, solving the contradiction by prioritizing precision over procedural simplicity.
4Reliability
If solder amount in C4 bumps is reduced to prevent nearest neighbor shorting, then shorting risk is reduced, but connection strength decreases
Solution Approach 1:
The patent introduces underfill material as an intermediary that enables reduced solder amounts in C4 bumps. The underfill provides structural support and stress distribution, allowing smaller solder volumes that prevent shorting while maintaining adequate connection strength through the combined support of solder and underfill.
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 enhances solder connection reliability, reduces thermal strain, and maintains alignment, enabling efficient data transfer and connection at sub-55 μm pitches by minimizing nearest-neighbor shorting and misalignment.
Implementation Method 1
bonding a semiconductor chip to an organic laminate substrate using solder
Implementation Method 2
Underfill reducing thermal strain and protecting chip connectors from shear stress during cooldown from solder bond to room temperature
Data Source
AI summary
An exemplary method includes at a bonding temperature, bonding a semiconductor chip to an organic laminate substrate using solder; without cooldown from the bonding temperature to room temperature, at an underfill dispense temperature, dispensing underfill between the semiconductor chip and the organic laminate substrate; and curing the underfill within a range of temperatures above the underfill dispense temperature. Another exemplary method includes depositing a first solder on pads of an organic laminate substrate; contacting a second solder on pillars of a semiconductor chip to the first solder on the pads of the organic laminate substrate; and solder bonding the semiconductor chip to the organic laminate substrate.