Thermal Materials : Thermal Substrates : Fans and Blowers : Membrane Switches : Touch Screens

• T-Clad Product Overview
• Dielectrics
  • Selection
  • Characteristics
  • Summary
  • Product Family FAQ's
• Base Metal Layer
• Optimal Design
  • Cost Effective Materials
  • Circuit Design
  • Part Fabrication
  • Design Guidelines
  • Electrical Design
  • Advanced Processes
• LEDs
  • Introduction
  • Temp. Effect
  • PCB Comparison
  • HPL
  • T-Clad PA
  • TIM Solutions
  • Standard Configurations
• Reliability Testing
• Applications
• Specialty Applications
• IsoEdge Heat Plate
• Assembly Recommendations
• Awards and Certifications
• T-Clad Selection Guide
• LED Solutions Brochure
• T-Clad Optimal Design White Paper
• Assembly Resources
  

Dielectrics Characteristics

Electrical Isolation - Power Applications

Dielectrics are available in thicknesses from 0.003" (76μm) to 0.009" (229μm), depending on your isolation needs. See "Electrical Design Considerations" to help determine which thickness is appropriate for your application.

High Power Lighting Applications

HPL is a dielectric specifically formulated for high power lighting LED applications with demanding thermal performance requirements. This thin dielectric at 0.0015" (38μm) has an ability to withstand high temperatures with a glass transition of 185°C and phenomenal thermal performance of 0.30°C/W. For detailed information, call Bergquist Sales or go online.

Thermal Impedance Determines Watt Density

Thermal impedance is the only measurement that matters in determining the watt density capability of your application because it measures the temperature drop across the stack-up for each watt  of heat flow. Lower thermal impedance results in lower junction temperatures. The lower the thermal impedance, the more efficiently heat travels out of the components.

Lower Thermal Impedance = Lower Junction Temperatures

Peel Strength

This chart graphs the stability of the bond strength between the dielectric and the circuit layer during temperature rise. Although bond strength goes down at higher temperatures, it maintains at least 3 lbs/inch (0.53 N/mm) even at 175°C.

Coefficient of Thermal Expansion

ThermoMechanical Analysis (TMA) measures the dimensional stability of materials during temperature changes, monitoring the Coefficient of Thermal Expansion (CTE). Note: In the application, the CTE of the base material is a dominant contributor to thermal mechanical stress. See pages 12-13 for base layer selection."

CTE OF IMS BOARDS - The concerns in exceeding Tg in standard FR-4 materials from a mechanical standpoint should be tempered when using Thermal Clad. The ceramic filler in the polymer matrix of Thermal Clad dielectrics results in considerably lower Z-axis expansion than in traditional FR-4 materials, while the low thickness of the dielectric means significantly less strain on plated-through-hole (PTH) connections due to expansion..

Storage Modulus

This chart depicts the storage modulus of the material over a temperature range. All of our dielectrics are robust, but you will want to choose the one that best suits your operating temperature environment. See “Assembly Recommendations” on pages 18-19 for additional information.

Dielectric Stability

This charts depicts the stability of the dielectric electrical properties over a range of temperatures. The flatter the line, the more stable. Note the stability of our high temperature dielectric, HT to a temperature of 175°C.

Operating Thermal Clad Materials Above Tg

Above the Tg of the material, mechanical and electrical properties begin to change. Mechanical changes of note are a reduction of peel strength of the copper foil, an increase in the CTE, and decreasing storage modulus. There is a potential benefit of relieving residual stress on the dielectric interfaces, in solder joints and other interconnects due to CTE mismatches by choosing a dielectric with Tg below the operating temperature. The dielectric material above Tg is in its elastomeric state (much lower storage modulus), allowing some of the stresses to relax. Changes in electrical properties must also be considered in operation above Tg, although they are typically only important at frequencies above 1MHz. Effects to consider are changes in the permittivity, dielectric loss and breakdown strength of the material.

Important Note: Many Thermal Clad products have U.L. rating up to 45% higher than their glass transition temperature and are used extensively in applications above rated Tg.