PCB Alignment Mark Layout for Short-Circuit-Free Chip Stacking
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Solution Overview
Problem
The formation of short circuits between alignment marks and coupling pads on a printed circuit board during the mounting of semiconductor chips is a challenge, particularly when different kinds of semiconductor chips are stacked, which can disrupt the precise positioning and electrical connectivity.
Innovation Solution
The design includes alignment marks and coupling pads on the printed circuit board, where the alignment marks are arranged in specific directions and the coupling pads are structured to prevent overlap, ensuring they are electrically disconnected and positioned to avoid short circuits, with the alignment marks guiding the stacking of semiconductor chips to maintain precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alignment marks are formed on the printed circuit board to enable precise chip mounting, then manufacturing precision is improved, but the risk of short circuit between alignment marks and coupling pads increases
Solution Approach 1:
A solder resist layer is introduced as an intermediary insulating layer between the alignment marks and coupling pads. This layer prevents direct electrical contact between conductive elements while allowing the alignment marks to maintain their positioning function, thus resolving the short circuit risk without compromising mounting precision
Solution Approach 2:
The problem is solved by adding a vertical dimension through the solder resist layer covering the top surface. Instead of relying solely on horizontal spacing, the insulating layer provides vertical isolation, enabling precise alignment while preventing electrical short circuits between adjacent conductive elements
2Device complexity
If coupling pads are positioned close to alignment marks for compact design, then device complexity is reduced, but the risk of short circuit increases
Solution Approach 1:
The solder resist layer acts as a mediator that enables close positioning of coupling pads and alignment marks without creating electrical contact. This insulating barrier allows compact layout design while maintaining electrical isolation between adjacent conductive elements
3Adaptability or versatility
If different kinds of semiconductor chips are stacked on the board, then adaptability is improved, but the risk of short circuit between alignment marks and coupling pads increases
Solution Approach 1:
The solder resist layer provides universal electrical isolation that works for all chip stacking configurations. This insulating layer ensures that regardless of chip types or stacking arrangements, the alignment marks and coupling pads remain electrically isolated, enabling versatile chip integration without short circuit risks
Data Source
AI summary
A semiconductor package may include a board, a first semiconductor chip mounted on the board, and a plurality of second semiconductor chips stacked on the first semiconductor chip. The board may include alignment marks on a top surface of the board and which are arranged in spaced apart relationship along a first direction. Each alignment mark includes a first side surface parallel to the first direction and a second side surface parallel to a second direction perpendicular to the first direction. A coupling pad is on the top surface of the board and between adjacent ones of the alignment marks. The first side surfaces may be collinear in the first direction. Each of the second semiconductor chips may include end surfaces, which are parallel to the second direction and are collinear with respective second side surfaces in the second direction.