Semiconductor Package Assembly Using Opposed Warpage Compensation
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Solution Overview
Problem
Semiconductor apparatuses face assembly challenges due to warping, particularly when using a lead frame bonded via solder joints, leading to unstable bonding and assembly difficulties.
Innovation Solution
A semiconductor apparatus design that includes a base plate with initial downward convex warpage, an insulating circuit board with upward convex warpage, and a case enclosing the semiconductor device, where the warpage forces of the base plate and circuit board cancel each other out, stabilizing the assembly and reducing warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat metal base plate is used for assembly, then the base plate structure is simple and easy to manufacture, but the base plate and structure over it warp in upward convex direction during assembly, making assembly difficult
Solution Approach 1:
The base plate is pre-formed with a downward convex curvature before assembly. This preliminary shaping creates a restoring force that counteracts the upward warping tendency during assembly, allowing the structure to self-correct and maintain flatness without requiring complex real-time control during the assembly process.
Solution Approach 2:
The base plate is designed with an initial downward convex curvature that generates a restoring force opposing the upward warping force that occurs during assembly. This preliminary anti-action prevents the net warping effect, ensuring the assembled structure remains flat without requiring additional corrective measures.
2Ease of manufacture
If the insulating circuit board is assembled without warpage compensation, then the assembly process is simple, but the lead frame cannot be appropriately bonded through solder joint due to warpage
Solution Approach 1:
The insulating circuit board is pre-formed with an upward convex curvature before assembly. This preliminary shaping creates a restoring force that counteracts the downward warping tendency during assembly, ensuring the board remains sufficiently flat to enable proper solder joint bonding of the lead frame without requiring complex real-time adjustment during assembly.
Solution Approach 2:
The insulating circuit board is designed with an initial upward convex curvature that generates a restoring force opposing the downward warping force during assembly. This preliminary anti-action prevents excessive warpage that would otherwise prevent proper lead frame bonding, ensuring reliable solder joints while maintaining assembly simplicity.
3Ease of manufacture
If components are assembled on a flat surface without warpage compensation, then the initial assembly is easy, but thermal stress and cracks develop in joint materials during power cycling
Solution Approach 1:
The base plate and insulating circuit board are designed with specific curvature parameters (downward and upward convex respectively) that create restoring forces to counteract thermal expansion and contraction during power cycling. This parameter optimization allows the assembly to accommodate thermal stress without developing cracks in the joint materials, improving power cycle reliability while maintaining ease of initial assembly.
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 design enhances yield and power cycle reliability by stabilizing the assembly process, reducing warpage, and minimizing thermal stress and cracks in the joint materials.
Implementation Method 1
a metal layer 14b formed on a lower surface of the ceramic substrate 14c and fixed on an upper surface of the base plate 12 with a first joint material 13
Implementation Method 2
a semiconductor device 16 having a first surface fixed on the circuit pattern 14a with a second joint material 15
Implementation Method 3
a lead frame 18 fixed on the second surface with a third joint material 17
Implementation Method 4
restoring force acts on the insulating circuit board in a direction of warpage that is convex upward, and restoring force acts on the base plate in a direction of warpage that is convex downward
Data Source
AI summary
A semiconductor apparatus includes: a base plate; an insulating circuit board including a ceramic substrate, a circuit pattern formed on an upper surface of the ceramic substrate, a metal layer formed on a lower surface of the ceramic substrate and fixed on an upper surface of the base plate with a first joint material; a semiconductor device having a first surface fixed on the circuit pattern with a second joint material and a second surface which is an opposite surface of the first surface; a lead frame fixed on the second surface with a third joint material; and a case fixed to an outer edge portion of the base plate and enclosing the semiconductor device, wherein restoring force acts on the insulating circuit board in a direction of warpage that is convex upward, and restoring force acts on the base plate in a direction of warpage that is convex downward.