PCBgogo

Project Name
Cost effective, high efficiency heat dissipation PCB for high-brightness LED

Project Summary
LED technology has been continually adopted in various lighting solutions including Indoor Lighting, Street Lamps, Advertising Display, and Backlights for LCD TV. Even though high-brightness LED has achieved very high energy efficiency of around 50% versus the 10% of traditional lighting, there is still significant heat being generated in its operation. Without proper thermal management the junction temperature of the LED will quickly increase, leading to shift of color spectrum, reduction of light output and reduction of life-time.To enhance the thermal conductivity, molecular engineering on nano-particle (NP) is conducted to develop a NP-epoxy composite for embedding into traditional PCB. Thermal imaging of assembled PCB is performed to optimize the overall thermal dissipation with LEDs.

R&D methodology
(1) Material Engineering and Characterization
(a) Nanocomposite preparation

PCB with thermal material based on filled epoxy will be the next generation materials and is expected to possess high heat dissipation capability in addition to low coefficient of thermal expansion (CTE) as the accumulated heat from high performance electronic devices should be removed for proper operation. The use of 1% of coupling agent was found to be more effective in increasing thermal conductivity of the composite. Despite the maximum content of the NP allowed to be added into the epoxy is about 30% due to the comparatively high viscosity of the varnish, as low as 10% of the micron-sized NP-filled dielectric is enough to fulfill the requirement of thermal conductivity larger than 1 W/m K and balance other critical properties used for PCB application. We emphasize on selecting BN content with different phases and their effective surface treatment for turning essentially the optical transparency and thermal conductivity.

(b) Thermal and optical characterization
The different optical and thermal properties of different materials contribute to the overall performance of heat dissipation and hence on the reliability. In this proposal, material will be characterised by using thermal analytical equipment, such as a dynamic mechanical analyser, a thermal mechanical analyser, a differential thermal analyser and differential scanning calorimetry.

(2) Thermal imagining for PCB and LED design applications
After determining the thermal properties ofNP-Epoxy Matrix Composite PCB, we will study its effect on high brightness LED application. An approach taken in this design study is to model both through hole LED and SMT LED using FLOTHERM, a computational fluid dynamics (CFD) tool from Flomerics. The results from the simulation are compared to the experimental measurements.

Objectives and Benefits

The objectives of this project are:

1.To develop the NP Epoxy Matrix Composite PCB Materials;
2.To optimize the process parameters to obtain the best composition and geometry of NP Composite material for thermal management;
3.To evaluate the thermal conductivity of NP Epoxy Matrix Composite PCB Materials in high brightness LED applications; and
4.To benchmark the thermal performance of conventional PCB materials versus NP Epoxy Matrix Composite PCB materials.

Deliverable(s)
1. A set of engineering material for PCB and LED encapsulation

1a. NP Epoxy Matrix PCB film with anisotropic heat dissipation

1b. NP Epoxy Matrix Composite recipe with parameters optimization among isotropic heat dissipation, strength and optical transparency obtained after a series of pilot production

2. A set of NP Epoxy Matrix Composite PCB Materials design with specific characteristics including heat dissipation capability, coefficient of thermal expansion, electrical isolation, and cost models.

3. A set of Designs with high brightness LED and the associated PCB Materials design based on accelerated methods for reliability tests.