Micro Surface Mount Device Packaging Using Sacrificial Plastic Carrier
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Solution Overview
Problem
Current micro surface mount device (μSMD) packaging methods are costly due to the expense of carriers and redistribution layer formation processes, necessitating the development of more economical techniques.
Innovation Solution
The use of a plastic carrier with wire bonded contact studs, encapsulation, and redistribution layers formed through cost-effective methods like screen printing, followed by grinding to create a thin, fully encapsulated μSMD package, where solder bumps are attached for electrical connections and additional encapsulant layers provide structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional carriers and redistribution layer formation steps are used, then μSMD packages can be formed, but packaging costs become relatively high
Solution Approach 1:
The patent applies this principle by using a sacrificial carrier that is intentionally designed to be low-cost and temporary. The carrier supports the dice during assembly but is subsequently removed entirely after the encapsulant is applied and the package is singulated. This eliminates the need for expensive, reusable carriers while maintaining manufacturing reliability during the critical assembly phase.
Solution Approach 2:
The patent extracts the carrier from the final package structure. Instead of incorporating the carrier as a permanent component, the process removes the carrier after it has served its purpose of holding dice during assembly. The encapsulant is applied over the carrier-dice assembly, then the carrier is removed, leaving only the encapsulated dice without any carrier material in the final product.
2Length of moving object
If thickness reduction is achieved through carrier sacrifice, then very thin μSMD packages are formed, but carrier structural integrity is compromised
Solution Approach 1:
The patent applies this principle by designing the carrier with sufficient initial thickness and structural strength to support all assembly operations (dice mounting, encapsulant application, grinding, singulation) before it is sacrificed. The carrier is engineered to be strong enough for its temporary duty during manufacturing, then intentionally removed to achieve the thin final package profile.
Solution Approach 2:
The patent performs all necessary assembly actions while the carrier is still intact and providing structural support. Dice are mounted, encapsulant is applied, and singulation grooves are formed all before the carrier is removed. This preliminary completion of all structural requirements enables the subsequent removal of the carrier to achieve thin package thickness.
3Ease of manufacture
If screen printing is used for encapsulant application, then manufacturing cost is reduced, but process precision requirements increase
Solution Approach 1:
The patent applies this principle by designing the encapsulant application process to be self-aligning. The encapsulant is screen-printed directly over the carrier-dice assembly, and the carrier itself serves as the alignment reference. The encapsulant naturally conforms to the underlying structures without requiring complex alignment systems, as the carrier geometry provides inherent positioning cues that simplify the printing 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 approach significantly reduces packaging costs and enables the creation of very thin, fully encapsulated μSMD packages with efficient electrical interconnects, utilizing low-cost equipment and processes like transfer molding and wire bonding, while maintaining structural integrity.
Implementation Method 1
In some preferred embodiments, screen printing is used to apply the encapsulant.
Implementation Method 2
After the encapsulant has been applied, a first surface of the encapsulant and the contact studs are ground such that exposed portions of the contact studs are smooth and substantially co-planar with the encapsulant.
Implementation Method 3
singulation grooves are cut into an exposed top surface of the contact encapsulant layer. The singulation grooves extend into the carrier.
Implementation Method 4
The back surface of the carrier is ground to thin, but not completely sacrifice the carrier. The grinding preferably removes enough of the carrier to reach the singulation grooves.
Implementation Method 5
Each die has a plurality of wire bonded contact studs secured to its associated I/O pads.
Implementation Method 6
After the redistribution layer as been formed, solder bumps may be attached to the redistribution layer to serve as electrical I/O contacts for the resulting packages.
Data Source
AI summary
A variety of improved approaches for packaging integrated circuits are described. In one described approach, a multiplicity of dice are mounted on a carrier (e.g., a plastic carrier). Each die has a plurality of wire bonded contact studs secured to its associated I/O pads. An encapsulant is applied over the carrier to cover the dice and at least portions of the contact studs to form an encapsulant carrier structure. After the encapsulant has been applied, a first surface of the encapsulant and the contact studs are ground such that exposed portions of the contact studs are smooth and substantially co-planar with the encapsulant. In some embodiments, a redistribution layer is formed over the encapsulant carrier structure and solder bumps are attached to the redistribution layer. A contact encapsulant layer is applied over the encapsulant carrier structure to provide extra mechanical support for the resulting packages.