Die Packaging Using Tape Apertures for Void-Free Solder Joints
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Solution Overview
Problem
The existing methods for attaching semiconductor dies to substrates are slow, prone to voiding, and face challenges with underfill materials that are difficult to handle due to high filler loading, low filler loading issues, and susceptibility to solvents, which can lead to mechanical or electrical joint failures, especially as the pitch of die pads becomes finer.
Innovation Solution
A tape segment with apertures is applied over the die, allowing conductive elements to be inserted and bonded to the die's contacts, which are then aligned with substrate pads and bonded using heat treatment, eliminating the need for an underfill layer and providing a consistent standoff and stress relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If underfill material with high filler loading is used, then the material provides strong mechanical connection and heat dissipation, but it flows slowly into the space between die and substrate
Solution Approach 1:
The patent applies preliminary action by pre-positioning the die on the substrate using a pick-and-place machine with precise alignment, eliminating the need for slow underfill flow to establish mechanical connection. The die is attached directly in the correct position before any adhesive curing, resolving the contradiction between needing strong mechanical connection and maintaining fast process speed.
2Speed
If underfill material with low filler loading is used, then the material flows quickly into the space between die and substrate, but it becomes subject to popcorning
Solution Approach 1:
The patent eliminates the underfill flow step entirely by using preliminary die placement with pick-and-place equipment. The die is positioned and attached directly without requiring adhesive flow, thus achieving fast processing speed without the risk of popcorning that plagues low filler loading materials.
3Ease of operation
If the die is moved towards the substrate during underfill dispensing, then the solder balls can push the adhesive out of the way, but the alignment may degrade and the die may float on the underfill material
Solution Approach 1:
The patent performs preliminary alignment using a pick-and-place machine that positions the die with high precision before attachment. The die is placed directly onto the substrate in the correct position, eliminating the need to move the die during adhesive dispensing and preventing alignment degradation or die floating.
4Reliability
If the existing underfill attachment procedure is used, then the die can be attached to the substrate, but the process is slow and causes a bottleneck in production
Solution Approach 1:
The patent uses preliminary die placement with automated pick-and-place equipment to attach dies to substrates directly without the slow underfill flow and curing process. This preliminary attachment method achieves both high reliability through precise positioning and high productivity by eliminating process bottlenecks.
Solution Approach 2:
The patent extracts and eliminates the underfill material and curing step from the attachment process. By removing this time-consuming step while maintaining attachment reliability through direct die placement, the patent resolves the contradiction between attachment reliability and production speed.
5Reliability
If subsequent process steps expose the underfill layer to solvents, then the solvents may cause voiding or bubbling within the cured underfill
Solution Approach 1:
The patent extracts and eliminates the underfill material from the process entirely. By using direct die attachment without underfill, the patent avoids the problem of solvent-induced voiding while maintaining joint integrity, thus resolving the contradiction between joint integrity and compatibility with subsequent solvent-exposed processes.
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 enhances the reliability of solder joints by preventing voiding and mechanical stress, ensures consistent spacing, and reduces the risk of joint failure, while being faster and more robust than traditional methods, particularly for fine pitch flip chips.
Implementation Method 1
the conductive elements are bonded to the die pads by a heat treatment
Data Source
AI summary
A method of attaching a die to a substrate is disclosed. A major surface of the die has an array of electrical contacts, and is covered with a tape segment having an array of apertures in register with the contacts. Solder balls are inserted into the apertures. The die is positioned against a substrate with the solder balls in register with the die pads on the surface of the substrate, and a heat treatment process is performed to bond the conductive elements to the corresponding bond pads.