LED Connection Pad Structure for Bonding Material Containment
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Solution Overview
Problem
The challenge is to prevent the protruding bonding material from reaching the connection position of the wire wiring when the size of the sealing part is reduced in a vehicle lighting device with LEDs, which is exacerbated by thermal deformation due to temperature changes and increased current, leading to potential disconnection or peeling of the light emitting diode and wire wiring.
Innovation Solution
The solution involves providing a suppression part on the connection pad, such as a concave, membranous, or convex shape, to contain the protruding bonding material, ensuring effective wire bonding even with a smaller sealing part, thereby reducing thermal stress and maintaining connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of the sealing part is reduced to decrease thermal deformation, then the thermal stress on the light emitting diode and wire wiring is reduced, but the distance between the connection position of the wire wiring and the light emitting diode is shortened, causing the protruding bonding material to reach the connection position
Solution Approach 1:
The connection pad is divided into two distinct regions: a bonding region for applying bonding material and a connection region for wire wiring connection. This segmentation prevents the protruding bonding material from reaching the wire wiring connection position, solving the contradiction between reducing sealing part size (for thermal stress reduction) and maintaining ease of wire wiring connection.
2Illumination intensity
If the current flowing through the light emitting diode is increased to achieve higher luminous flux, then the luminous output is improved, but the heat generated during lighting increases, leading to increased thermal deformation of the sealing part
Solution Approach 1:
The sealing part is designed with non-uniform thickness, being thicker at the center and thinner toward the periphery. This local quality variation allows the center region to better withstand thermal expansion from the high-current light emitting diode, while the thinner peripheral regions accommodate thermal deformation, thus enabling higher luminous flux operation with reduced overall thermal stress.
3Area of stationary object
If the region in which the light emitting diode and wire wiring are provided is made small to reduce sealing part size, then the thermal deformation is reduced, but the distance between the connection position of the wire wiring and the light emitting diode is shortened
Solution Approach 1:
The connection pad is divided into two distinct regions: a bonding region for applying bonding material and a connection region for wire wiring connection. This segmentation prevents the protruding bonding material from reaching the wire wiring connection position, solving the contradiction between reducing sealing part size (for thermal stress reduction) and maintaining ease of wire wiring connection.
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 effectively suppresses the protruding bonding material from interfering with wire connections, enhances reliability by reducing stress, and allows for a smaller sealing part, leading to a more compact design with lower manufacturing costs.
Implementation Method 1
when the light emitting diode is turned on, heat is generated and the sealing part expands. When the lit light emitting diode is turned off, the temperature of the sealing part drops and the sealing part contracts
Implementation Method 2
the light emitting diode is bonded to the mounting pad using a bonding material such as a die attaching material and a die attaching sheet
Data Source
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AI summary
The vehicle lighting device (1) according to an embodiment includes a socket (10); a substrate (21) provided on one end side of the socket and having a wiring pattern (21a) that includes a mounting pad (21a1) and a connection pad (21a2) connected to the mounting pad; a light emitting element (22) being chip-shaped and bonded to the mounting pad using a bonding material; a wire wiring (21b) connected to an electrode of the light emitting element and the connection pad; a sealing part (24) covering the light emitting element and the wire wiring; and a suppression part (21a4, 21a5, 21a6) suppressing a component (21a3) of the bonding material protruding from the light emitting element from reaching a position where the wire wiring is connected to the connection pad.