When choosing a high-performance PCB laminate you need to consider:
- thermal performance
- low dissipation factor (Df)
- stable Df characteristics
- low Z-axis Coefficient of Thermal Expansion (CTE)
- skew mitigation properties
- characteristics to improve rise times
- jitter reduction
- conductor loss reduction
One of the key characteristics of high-frequency laminate material is the stability of the dissipation factor (Df) since this will tell you how signal losses occur and their distribution across the frequency band of operation.
Also, a stable dielectric constant (Dk) and consequently a stable impedance across the length and width of a substrate is important.
High-frequency laminates display little change in the Dk with variations in temperature over a wide range.
In an RF or microwave circuit, the value of the dielectric constant will impact the PCB’s trace sizes and therefore the size of the PCB. Higher Dk PCB materials can result in smaller PCBs.
The table below displays the key electrical and mechanical attributes of the ISOLA I-Tera® MT40, ISOLA Tachyon® 100G, Panasonic Megtron6, and Panason Megtron7 for ease of comparison.
Attribute | Isola | Isola | Panasonic | Panasonic |
Product | I-Tera MT40 / RF | Tachyon-100G | Megtron7 (R-5785/R-5680) | Megtron6 (R-5775/R-5670) |
IPC-4101E | /102 & IPC-4103 /17 | /102 & IPC-4103 /17 | /91/102 | /91/102 |
Tg – Glass Transition Temperature by DSC – ºC |
190-200 | 200 | 200 | 185 |
Tg – Glass Transition Temperature by TMA – ºC | 175-185 | 180 | ||
Td – Decomposition Temp ºC (TGA) | 360 | 360 | 400 | 410 |
Lead-free Process Compatible | Yes | Yes | Yes | Yes |
Halogen Free | No | No | No | No |
UL Approved | Yes | Yes | Yes | Yes |
Flammability UL94 | V-0 | V-0 | V-0 | V-0 |
Dielectric Constant (DK) / Dissipation Factor (DF) – 1 GHz | 3.37 / 0.001 | 3.40 / 0.002 | ||
Dielectric Constant (DK) / Dissipation Factor (DF) – 2-3 GHz | 3.38 / 0.0028 | 3.04 / 0.0021 | ||
Dielectric Constant (DK) / Dissipation Factor (DF) – Df 10-12 GHz | 3.45 / 0.0030 | 3.02 / 0.0021 | 3.35 / 0.0020 | 3.35 / 0.0040 |
Dielectric Constant (DK) / Dissipation Factor (DF) – Df 20 GHz | 3.45 / 0.0030 | |||
Moisture Absorption (%) | 0.10% | 0.10% | 0.06% | 0.14% |
CTE Z Axis (ppm/ºC) Pre Tg | 55 | 45 | 42 | 45 |
Z-axis Expansion (50-260ºC) (CTE Z Axis) | 2.80 | 2.50 | ||
CTE, X-, Y-axes, Pre-Tg – ppm/ºC | 12 | 15 | 14-16 | 14-16 |
Peel Strength – 1oz (35μm) – N/mm | 1.00 | 0.96 | 0.8 | 0.8 |
T260 | >60 | >60 | ||
T288 – minutes | >60 | >60 | >120 | >120 |
Flexural Strength – ksi | Lengthwise direction – 71.0 Crosswise direction – 58.0 |
Lengthwise direction – 44.0 Crosswise direction – 41.0 |
||
Flexural/Taylor’s Modulus – ksi | Lengthwise direction – 2,857 Crosswise direction – 2,743 |
Lengthwise direction – 2,857 Crosswise direction – 2,743 |
||
Tensil/Young’s modulus – ksi | Lengthwise direction – 3,060 Crosswise direction – 2,784 |
Lengthwise direction – 3,060 Crosswise direction – 2,784 |
||
Tensile strength – ksi | Lengthwise direction – 39 Crosswise direction – 35 |
Lengthwise direction – 30 Crosswise direction – 25 |
||
Volume Resistivity – MΩ-cm | 1.33×107 | 1.33×107 | 1×109 | |
Electrical Strength – kV/mm | 45 | 60 | ||
Surface Resistivity – MΩ | 1.33×105 | 1.33×105 | 1×108 | |
Thermal Conductivity (-100-250ºC) – W/mK | 0.61 | 0.42 | ||
Maximum Operating Temperature – ºC | 130 | 145 |