BGA Surface Mounting Structure with Lead-Defined Well
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Solution Overview
Problem
Existing surface mounting technologies for Ball Grid Array (BGA) face challenges in heat dissipation and soldering failures at the four corners of chip substrates, leading to increased manufacturing complexity and cost, as well as space wastage, due to conventional methods such as metal enhancing layers, virtual balls, and larger solder balls.
Innovation Solution
The proposed surface mounting structure includes a substrate with multiple leads and a passivation layer that defines a well around the soldering pad, allowing solder to be soldered onto multiple surfaces, including lateral surfaces through the well, enhancing heat dissipation and reducing manufacturing complexity and cost by modifying the copper lead layout and passivation layer design without adding new manufacturing stations or components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an extension portion is added to the soldering pad to increase heat dissipation surface, then heat dissipation is improved, but the lateral contact surface between solder ball and soldering pad decreases
Solution Approach 1:
The invention transitions from a single-plane soldering interface to a multi-dimensional soldering structure by creating a well (cavity) around the soldering pad. This allows solder to contact not only the top surface but also the lateral surfaces of the soldering pad, effectively increasing the contact area from two dimensions to three dimensions and improving both heat dissipation and soldering reliability simultaneously.
Solution Approach 2:
The well structure acts as a nested cavity around the soldering pad, with the solder ball positioned within this nested structure. The solder fills the well and contacts the soldering pad from multiple surfaces, creating a nested configuration that maximizes thermal contact while maintaining mechanical strength.
2Strength
If metal enhancing layer is applied to strengthen substrate and prevent wrapping, then substrate strength is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The existing copper leads surrounding the soldering pad are repurposed to serve a dual function: their original electrical connection function and a new structural support function. By configuring these existing leads to form a well structure, the substrate gains anti-wrapping strength without requiring additional metal enhancing layers or manufacturing steps.
Solution Approach 2:
The copper leads are designed to perform multiple functions simultaneously: electrical connection, mechanical support, and structural reinforcement against wrapping. This multi-functionality eliminates the need for separate components dedicated to each function, reducing manufacturing complexity while maintaining substrate strength.
3Reliability
If virtual balls or larger solder balls are applied to increase SMT soldering reliability, then soldering reliability is improved, but chip space is wasted
Solution Approach 1:
Instead of uniformly increasing solder ball size across the entire chip, the invention applies localized modifications only at the four corner soldering pads where soldering failures occur. The well structure is created specifically at these critical locations using the surrounding copper leads, while the rest of the chip maintains its original design, thus improving reliability without wasting chip space.
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 solution effectively addresses soldering failures at the four corners by increasing the cooling rate of soldering pads and improving solder fixation strength, reducing manufacturing complexity and cost, and optimizing chip space usage.
Implementation Method 1
a passivation layer (11) having a first opening (111) disposed corresponding to a top of the first soldering pad (13), so as to expose the first soldering pad (13) and the well (16)
Implementation Method 2
By increasing the lead amount of the first soldering pad, the present invention completes the soldering operation between the solder (such as the tin ball), and the first soldering pad. When being cooled, the first soldering pad will be cooled faster, since the first soldering pad is connected to more leads
Data Source
AI summary
A surface mounting structure applied to a BGA includes a substrate, a first soldering pad, a first lead, a second lead and a passivation layer. The substrate has a top surface for the first soldering pad to be disposed thereon. The first lead has a first end connected to the first soldering pad and a second end. The second lead has a third end connected to the first soldering pad and a fourth end connected to the second end of the first lead. A well is defined among the first lead, the second lead, and the first soldering pad. The passivation layer covers the top surface of the substrate, and has a first opening corresponding to the top of the first soldering pad to expose the first soldering pad and the well. Chip failure resulting from the warp occurring at four corners in the surface mounting procedure is prevented.