Bismaleimide Underfill Resin Composition for Low-Voids and Adhesion
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Solution Overview
Problem
Conventional underfill materials face challenges in achieving a balance of low-void property, chip adhesiveness, tackiness, transmittivity, and flux activity due to rapid curing of radical polymerizable monomers, instability during storage, high water absorption, and insufficient metal joint formation, which affect the reliability and productivity of semiconductor devices.
Innovation Solution
A resin composition comprising a bismaleimide compound, a radical polymerizable resin or compound, and a curing accelerator, optionally with a thermosetting compound, inorganic filler, and an organic compound with flux function, to enhance adhesiveness, mobility, and flux activity while maintaining low voids and good visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a radical polymerizable monomer is used as the main resin in pre-applied underfill material, then the material cures quickly, but the mobility of the adhesion site is rate-controlled before sufficient bonds form with the chip surface, resulting in insufficient low-void property and chip adhesiveness
Solution Approach 1:
The patent changes the chemical composition parameters by using a bismaleimide compound with specific molecular structure (formula 1) combined with radical polymerizable resin containing citraconimide, vinyl, maleimide, (meth)acryloyl, or allyl groups. This compositional parameter change allows the material to maintain both fast curing speed and sufficient mobility for adhesion, resolving the contradiction between curing speed and chip adhesiveness
Solution Approach 2:
The patent creates a composite material system combining bismaleimide compound (A) with radical polymerizable resin or compound (B) and curing accelerator (C). This composite approach allows the bismaleimide compound to provide structural stability and adhesion while the radical polymerizable component enables fast curing, simultaneously achieving both fast curing speed and reliable chip adhesiveness
2Ease of manufacture
If conventional underfill materials are used, then they can fill the gap between chip and substrate, but they exhibit high water absorption and instability during storage
Solution Approach 1:
The patent modifies the chemical composition parameters by selecting specific bismaleimide compound structures and radical polymerizable resin types that inherently possess low water absorption characteristics. This parameter change maintains the filling capability while improving storage stability and reducing water absorption issues
3Reliability
If epoxy compounds are used in underfill material, then adhesion is improved, but the material reacts with flux component, reducing flux activity and metal joint formation
Solution Approach 1:
The patent uses bismaleimide compound as an intermediary material that provides adhesion functionality without the harmful side reactions of epoxy compounds. The bismaleimide structure acts as a mediator between the chip/substrate surfaces and the flux component, maintaining both adhesion and flux activity for proper metal joint formation
4Productivity
If the underfill material cures rapidly, then productivity is improved, but the material cannot embed in surface unevenness of the chip, resulting in insufficient anchor effect
Solution Approach 1:
The patent applies preliminary action by formulating the underfill material with specific viscosity characteristics and chemical composition that enable it to first embed into the surface unevenness of the chip before curing occurs. The bismaleimide compound and radical polymerizable resin combination provides sufficient working time for embedding while maintaining fast curing speed, ensuring both productivity and reliable anchor effect
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 resin composition achieves a balanced performance in low-void property, chip adhesiveness, tackiness, and flux activity, ensuring reliable semiconductor device assembly with improved handling and insulation reliability.
Implementation Method 1
a bismaleimide compound (A) containing a constituent unit represented by formula (1) and maleimide groups at both ends of the molecular chain; a radical polymerizable resin or compound (B) other than the bismaleimide compound (A)
Implementation Method 2
a curing accelerator (C)
Implementation Method 3
the mobility of the adhesion site of the compounded silane coupling agent is rate-controlled by the main resin that has been polymerized before forming a sufficient number of bonds with the silanol groups on the surface of the chip
Data Source
AI summary
A resin composition containing a bismaleimide compound (A) containing a constituent unit represented by the following formula (1) and maleimide groups at both ends of the molecular chain, a radical polymerizable resin or compound (B) other than the bismaleimide compound (A), and a curing accelerator (C), wherein the radical polymerizable resin or compound (B) contains at least one selected from the group consisting of a citraconimide group, a vinyl group, a maleimide group, a (meth)acryloyl group and an allyl group.