DENKI KAGAKU KOGYO KABUSHIKI KAISHA Electronic Materials Division
Low-stress substrate
Metal substrates are widely used in automotive electronics applications, incluiding electric power steering systems.
DENKA successfully developed a new insulating layer suitable for the high heat cycle resistance required in automotive electronics applications.
In conventional aluminum-based metal substrates, due to the difference in thermal expansion between the aluminum base plate and the mounted ceramic chips, heat cycle-induced cracking can occur in the solder joints.
DENKA optimized the insulating layer, eliminated or reduced solder cracking, and improved the heat cycle resistance of a solder by absorbing the difference in thermal expansion with the insulating layer.
Major applications of the EL-1 substrate
- Automotive electronics ECU (electric power steering systems (EPS), etc.)
- Others: applications requiring high heat cycle resistance property
Comparison of properties between the EL-1 substrate and other grades of substrates
| Properties | High thermal conductivity type TH-1 |
General purpose type K-1 |
Low-stress type EL-1 |
|---|---|---|---|
| Thermal conductivity (W/m.k) | 4.0 | 2.0 | 2.5 |
| Glass transition temperature (oC) | 165 | 104 | 57 |
| Insulating layer thickness (μm) | 125 (Y-type) | 100 (Y-type) | 110 |
| Thermal resistance (oC/W) | 0.50 | 0.64 | 0.55 |
| Peel strength (N/cm) | 22.1 | 25.2 | 19.6 |
| Insulation breakdown voltage (kV) | 8.3 | 6.8 | 3.5 |
| Heat cycle Solder crack resistance |
○ | ○ | ◎ |
General properties of the insulating conductive layer of the EL-1 substrate
| Thermal conductivity (W/m.k) |
Glass transition temperature (℃) |
Dielectric constant (at 1 MHz) |
Dielectric loss tangent (at 1 MHz) |
Volume resistance (Ω.cm) |
|---|---|---|---|---|
| 2.5 | 57 | 7.4 | 0.024 | 1x1015 |
Characteristics of insulating material
We developed a high thermal conductivity insulating material TH-1 and are now developing insulating materials with even higher thermal conductivity.
Thermal resistance
The steady-state and transient thermal resistance of the high thermal conductivity insulation material (prototype) and the existing high thermal conductivity insulating material (TH-1) were measured.
2.1 Steady state
Steady-state thermal resistance was measured by the DKK method. As shown in Fig. 1, the high thermal conductivity insulating material (prototype) can significantly reduce thermal resistance.
2.2 Transient state
Transient thermal resistance was measured by the ΔVBE method. As shown in Fig. 2, the high thermal conductivity insulating material (prototype) can significantly reduce thermal resistance as in the steady state.
Reliability evaluation results (Al plate: 2.0 mm; copper foil: 105 μm; insulating layer thickness: 125 μm)
Table 2 shows the evaluation results of short and long-term reliability. The high thermal conductivity insulating material (prototype) is not as good as TH-1 in electrical strength, but shows no significant degradation in its properties.
The high thermal conductivity insulating material (prototype) is under mass-production testing. Please note that the values in the table may be changed.
