Surface Mountable Semiconductor Device with Raised Thermal Pad
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Solution Overview
Problem
Surface mountable semiconductor devices with insulated metal substrates face challenges in heat dissipation due to high thermal resistance caused by thin dielectric layers, leading to increased junction temperatures, especially in high power density devices, and result in connection defects and uneven substrate surfaces requiring different material amounts for interconnect layers.
Innovation Solution
A surface mountable semiconductor device with electrical connection pads of a first height and a thermal pad of a second height, where the thermal pad is taller than the electrical pads, allowing direct thermal connection to the metal substrate without a dielectric layer, enabling uniform deposition of a conductive interconnect layer for reliable mounting on insulated metal substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin dielectric layer is used to cover the metal substrate, then electrical insulation is achieved, but thermal resistance increases leading to poor heat dissipation
Solution Approach 1:
The invention segments the substrate area into two distinct zones: a first area with a dielectric layer for electrical insulation of electrical pads, and a second area without dielectric layer for direct thermal contact of the thermal pad with the metal substrate. This spatial segmentation allows simultaneous achievement of electrical insulation and thermal conduction in different regions.
Solution Approach 2:
The invention applies different structural qualities to different locations: the first area has dielectric material for electrical isolation, while the second area has no dielectric material to enable direct thermal contact. This local differentiation of material presence allows each pad type to have optimal properties for its function.
2Temperature
If the dielectric layer is removed underneath the thermal pad, then direct thermal connection is achieved, but the substrate surface becomes uneven requiring different material amounts for interconnect layers
Solution Approach 1:
The invention intentionally creates an asymmetric substrate structure where the first area has dielectric layer coverage and the second area is exposed metal substrate. This asymmetric design accepts non-uniform substrate surfaces as a necessary consequence of achieving direct thermal contact in the thermal pad region.
Solution Approach 2:
The invention compensates for the height difference created by dielectric removal by using a raised thermal pad structure that extends vertically. The thermal pad's increased height in the vertical dimension compensates for the missing dielectric layer, allowing uniform interconnect material deposition across both areas while maintaining direct thermal contact.
3Reliability
If different material amounts are used for interconnect layers, then connection to both pad types is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention raises the thermal pad to the same height level as the electrical pads by adding material in the second area, creating an equipotential surface for interconnect deposition. This allows uniform thickness interconnect layers to be applied across the entire substrate surface using standard deposition processes, eliminating the need for complex variable thickness control.
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 configuration ensures easy and reliable thermal connection without additional processing or cost, maintaining high thermal conductivity and reducing the risk of connection defects, thus effectively addressing heat dissipation challenges in high power semiconductor devices.
Implementation Method 1
the thermal pad is in direct thermal contact with the metal substrate... directly bring the thermal pad into good thermal contact with the metal substrate
Implementation Method 2
covered by an electrically insulating dielectric layer... an electrically conductive layer is applied
Data Source
Figure 1~2
AI summary
The present invention relates to a surface mountable semiconductor device comprising at least one semiconductor element mounted on or integrated in a device substrate (1) having a top surface and a bottom surface. One or several electrical pads (2) of a first height and at least one thermal pad (3) of a second height are arranged at the bottom surface of the device substrate (1). In the proposed surface mountable semiconductor device the height of the thermal pad (3) is larger than the height of the electrical pads (2). This allows the mounting of such a device to an IMS with a locally removed dielectric layer in an easy and reliable manner in order to directly connect the thermal pad with the metallic substrate of the IMS.