Molded Interconnection Device LED Connection Without Intermetallic Interfaces
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Solution Overview
Problem
Existing methods for mounting light sources like LEDs on molded interconnection devices (MIDs) in motor vehicle luminous devices face issues with fragile mechanical strength, risk of damage from high temperatures, and reliability due to intermetallic interfaces and oxidation.
Innovation Solution
A method involving a molded interconnection device with a surface comprising an insulating part and electric tracks with a conductive metal layer, where the electronic component's connection means are covered with the same metal layer, and a sequential process of contacting and coating at room temperature to create a durable electrical and mechanical connection without intermetallic interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering technique is used to mount LEDs on MID, then electrical connection is achieved, but mechanical strength becomes fragile due to intermetallic interfaces
Solution Approach 1:
The invention removes the solder paste intermediary from the connection process. Instead of using soldering with flux and reflow processes that create intermetallic interfaces, the patent directly bonds LED connection means to conductive tracks through a mechanical pressing operation, eliminating the fragile intermetallic layer entirely while maintaining electrical connectivity.
Solution Approach 2:
The invention introduces a conductive adhesive as an intermediary bonding material between the LED connection means and the MID conductive tracks. This adhesive provides both mechanical bonding strength and electrical conductivity, replacing the traditional solder joint while avoiding intermetallic interface formation.
2Reliability
If reflow soldering is used to attach LEDs to MID, then welds are produced, but polymer substrate and LEDs are damaged due to high temperatures
Solution Approach 1:
The invention fundamentally changes the temperature parameter of the bonding process. Instead of using reflow soldering temperatures (typically 200-250°C), the patent employs a low-temperature mechanical pressing process at or near room temperature, thereby avoiding thermal damage to the polymer substrate and LED components while still achieving reliable electrical and mechanical connection.
3Reliability
If wire bonding technique is used to connect LEDs to MID, then electrical connection is achieved, but oxidation occurs on tin surface reducing reliability
Solution Approach 1:
The invention applies a protective conformal coating to the conductive tracks on the MID before the bonding process. This preliminary coating creates an oxidation barrier on the tin surface, preventing oxide formation that would otherwise occur during storage and assembly. The coating is applied in advance, sealing the reactive tin surface from atmospheric oxygen.
Solution Approach 2:
The invention uses a thin conformal coating layer as a sacrificial protective barrier. This coating is applied to prevent oxidation during assembly and storage, and can be easily removed or is transparent to the bonding process. The coating serves its protective function temporarily during critical phases and then becomes part of the final assembly structure.
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
The solution provides a reliable and durable connection between the electronic component and the MID, avoiding damage from high temperatures and oxidation, thus enhancing the mechanical and electrical strength and reducing production costs.
Implementation Method 1
The substrate can advantageously be cleaned and its surfaces are activated by a laser, which creates fine roughnesses thereon
Implementation Method 2
A thin film, preferably 0.1 to 0.2 μm thick, of copper, gold, silver, nickel or palladium is then deposited on the laser-activated surfaces, for example by vacuum evaporation or sputtering
Implementation Method 3
A thin film, preferably 0.1 to 0.2 μm thick, of copper, gold, silver, nickel or palladium is then deposited on the laser-activated surfaces, for example by vacuum evaporation or sputtering
Data Source
Figure 1~2
AI summary
The invention proposes a moulded interconnection device (MID) comprising at least one electronic component, for example a light-emitting diode (LED) light source. The electrical and mechanical connections between the light source and the conductive tracks of the MID do not have intermetallic interfaces and are more durable relative to known devices. The invention also proposes a method for assembling a light source on an MID during the production of the latter. Since all of the steps of the method can be carried out at ambient temperature, the risk of damage to the components used is diminished.