Semiconductor Die Bonding via Pre-coated Carrier Pad
Solution Overview
Problem
Existing methods for attaching a semiconductor die to a leadframe face challenges such as difficult alignment, adhesive instability at higher temperatures, and the need for specialized handling and coating processes, which complicate the secure bonding and encapsulation of semiconductor devices.
Innovation Solution
A method involving a carrier pad with a pre-coated first adhesive bonded to the leadframe and a flowable second adhesive applied to the carrier pad for aligning and bonding the semiconductor die, allowing for accurate alignment and secure attachment without the need for adhesive application on the die or leadframe, using thermosetting adhesives that remain stable post-curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a die is coated with adhesive prior to bonding, then the die can be bonded to the leadframe, but the coating and handling becomes difficult and requires specialised machines
Solution Approach 1:
A carrier pad is introduced as an intermediary component between the die and the leadframe. The carrier pad is pre-coated with adhesive in a controlled manner, and both the die and leadframe are bonded to the carrier pad. This mediator approach allows the adhesive to be applied in a controlled environment rather than directly on the die, simplifying handling and eliminating the need for specialised coating machines.
2Ease of manufacture
If thermoplastic adhesives are used for bonding, then bonding can be achieved, but the adhesives become unstable at higher temperatures
Solution Approach 1:
The adhesive type is changed from thermoplastic to thermosetting adhesive. Thermosetting adhesives undergo a chemical curing process that creates a cross-linked network structure, providing stability at higher temperatures. This parameter change in the adhesive's chemical properties resolves the temperature stability issue while maintaining bonding effectiveness.
3Manufacturing precision
If alignment is performed before bonding, then accurate positioning can be achieved, but the process becomes more complex and time-consuming
Solution Approach 1:
The carrier pad is pre-coated with adhesive in advance, creating a stable base before the die and leadframe are positioned. This preliminary preparation allows for easier and more accurate alignment since the adhesive is already in place on the carrier pad, and the components can be positioned without the complexity of simultaneous multi-component alignment.
4Reliability
If adhesive is applied to the die or leadframe, then bonding can be achieved, but specialised coating and handling machines are required
Solution Approach 1:
The carrier pad serves as an intermediary that is pre-coated with adhesive. Instead of applying adhesive directly to the die or leadframe (which would require specialised machines), the adhesive is applied to the carrier pad in a controlled manner. This allows standard handling equipment to be used for positioning the die and leadframe onto the pre-coated carrier pad, simplifying the manufacturing process.
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 enables accurate alignment and secure bonding of the semiconductor die to the leadframe, reduces the complexity of handling and temperature stability issues, and allows for independent production of sub-assemblies, enhancing the efficiency and reliability of semiconductor device assembly.
Implementation Method 1
using thermosetting adhesives that remain stable post-curing
Data Source
AI summary
Methods and resulting devices are disclosed related to attaching a die to a leadframe. One such method includes initially bonding a carrier pad which is pre-coated with a thermosetting first adhesive to the leadframe. The carrier pad can be electrically non-conductive. The first adhesive can be raised to its thermosetting cure temperature by heating the leadframe to a temperature just above the thermosetting cure temperature of the first adhesive. A thermosetting second adhesive which is liquid at room temperature can be applied to a second major surface of the carrier pad, and the die can be placed on the second adhesive and aligned with the leadframe. The second adhesive can be raised to its thermosetting cure temperature to bond the die to the carrier pad, and in turn form a bonded assembly.