Solder Attach Film for Semiconductor Package Assembly
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Solution Overview
Problem
The existing methods for forming solder balls on semiconductor packages are time-consuming, prone to defects, and costly due to the need for multiple apparatuses and expensive solder balls, especially when forming smaller solder balls to reduce chip size and pitch.
Innovation Solution
A solder attach film comprising a first cover film, a flux layer, and a solder layer, which can be rolled and includes optional barrier ribs, is used to adhere to semiconductor packages or dies, allowing for the formation of solder balls through a simplified process involving gridding and reflowing, eliminating the need for separate flux dotting and solder ball dropping apparatuses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional flux dotting and solder ball dropping apparatuses are used, then solder balls can be formed on substrate, but manufacturing time increases and defect rate increases
Solution Approach 1:
The patent combines flux dotting, solder ball placement, and reflow processes into a single integrated solder attach film that is applied in one step. The film contains both flux and solder balls in predetermined positions, eliminating the need for separate flux dotting and solder ball dropping apparatuses, thereby reducing manufacturing time and improving placement accuracy.
Solution Approach 2:
The solder attach film is prepared in advance with flux and solder balls pre-positioned in their final locations. This preliminary preparation allows all materials to be ready before the reflow process, eliminating the need for sequential operations during manufacturing and reducing both time and defects.
2Volume of moving object
If smaller solder balls are used to reduce chip size and pitch, then packaging size decreases, but manufacturing cost increases
Solution Approach 1:
The patent uses a disposable solder attach film that is inexpensive to manufacture and can be discarded after single use. This eliminates the need for expensive precision dropping apparatuses required for small solder balls, as the film itself carries the solder balls in predetermined positions, significantly reducing manufacturing cost while enabling small chip sizes.
3Ease of manufacture
If multiple apparatuses are used for flux dotting and solder ball dropping, then solder balls can be formed, but initial apparatus cost increases
Solution Approach 1:
The patent merges the functions of flux dotting apparatus, solder ball dropping apparatus, and reflow apparatus into a single solder attach film application process. The film integrates both flux and solder balls, requiring only application and reflow steps, thereby eliminating multiple expensive apparatuses and reducing device complexity.
Solution Approach 2:
The solder attach film serves multiple functions simultaneously: it acts as a flux carrier, a solder ball carrier, and a positioning template. This multi-functionality replaces multiple specialized apparatuses with a single versatile material, reducing initial apparatus cost while maintaining solder ball formation capability.
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 reduces manufacturing time and defects, lowers packaging costs by using a single film to form solder balls efficiently, and eliminates the need for expensive solder ball dropping apparatuses, while enabling precise placement and formation of smaller solder balls.
Implementation Method 1
the flux layer is volatilized and removed
Implementation Method 2
the solder layer is fused and fixed to the electrically conductive pads
Data Source
AI summary
A solder attach film includes a first cover film, a flux layer, a solder layer, and a second cover film, and it can be treated or kept in a roll shape. A solder ball forming method using the solder attach film includes preparing a semiconductor package or a semiconductor die, adhering the solder attach film, gridding, and reflowing. In the solder attach film adhering operation, the first cover film and the second cover film are removed, and the flux layer is adhered to electrically conductive pads of the semiconductor package or the semiconductor die. Subsequently, in the reflowing operation, the flux layer is volatilized and removed, and the solder layer is fused and fixed to the electrically conductive pads, so that solder balls are formed.