CLTE-AT and CLTE-XT are related reinforced PTFE candidates, but their suitability depends on the stability and fabrication demands of a specific RF stack. Compare the finished electrical response and reliability evidence rather than choosing by suffix.
Split stability into measurable requirements
Electrical phase stability, dimensional registration and plated-hole reliability are connected but distinct. List the acceptable phase change over temperature, the registration allowance between layers and the required thermal exposure for the assembled board. A favorable laminate expansion value does not prove every one of those requirements by itself.
Read the exact constructions
Use the CLTE-AT and CLTE-XT records to compare property observations with their method, direction and conditions. Confirm thickness and copper options before selecting a model. Ceramic filler, PTFE and glass reinforcement are part of the family architecture, but their broad presence does not imply that the two grades have interchangeable dielectric or fabrication behavior.
Example: a phase-sensitive multilayer network
For a distribution network, simulate equal-function routes on each candidate and include the actual bonding layers. Estimate the phase spread caused by thickness and material variation, then determine which dimensions the fabricator must control. Build representative paths with matched launches so the measurements can distinguish propagation behavior from connectors. Use the phase tool for intuition, then use the relevant multilayer solver for final geometry.
Qualify the thermal and manufacturing sequence
Confirm the supported drill, hole-treatment and lamination route with the fabricator. Include all intended lamination and assembly cycles in the process discussion. Measure electrical response and inspect representative structures before and after the agreed environmental sequence, with consistent conditioning. If the board must maintain an established approval, define the scope of requalification before substituting grades. The test-planning guide provides a framework for connecting the material decision to an acceptance record.
For a replacement, define whether the existing bonding system and press sequence are fixed constraints. If they also change, the trial compares two complete stacks and cannot isolate a laminate-only benefit. Keep that distinction in the engineering report and in any subsequent purchasing approval.
Source-aware property comparison
CLTE-AT
| Property | Reported value | Conditions / source |
|---|---|---|
| Process dielectric constant | 3 | Typical; 10 GHz, 23°C/50% RH; IPC-TM-650 2.5.5.5 clamped stripline; direction is not separately recorded here. Source |
| Dissipation factor | 0.0013 | Typical; 10 GHz, 23°C/50% RH; IPC-TM-650 2.5.5.5; direction is not separately recorded here. Source |
| Thermal conductivity | 0.64 W/(m·K) | Typical; ASTM E1461, through-thickness direction; test temperature not specified in the product table. Source |
| Thermal coefficient of dielectric constant | -10 ppm/°C | Typical; 0°C to 100°C, IPC-TM-650 2.5.5.5 (modified temperature measurement); 10 GHz. Source |
| Water absorption | 0.03 % | Typical; E1/105 + D24/23, IPC-TM-650 2.6.2.1. Source |
Typical reported values are not a purchase specification. Process Dk, design Dk and values measured at different frequencies are not interchangeable.
CLTE-XT
| Property | Reported value | Conditions / source |
|---|---|---|
| Design dielectric constant | 2.93 | Typical; 10 GHz, microstrip differential phase length method, C-24/23/50 conditioning. Source |
| Dissipation factor | 0.001 | Typical; 10 GHz, 23°C/50% RH; IPC-TM-650 2.5.5.5; direction is not separately recorded here. Source |
| Thermal conductivity | 0.56 W/(m·K) | Typical, through thickness; ASTM D5470. The product table does not state test temperature. Source |
| Process dielectric constant | 2.79 at 5.1 mil; 2.89 at 9.4 mil; 2.92 at 20 mil; 2.94 at 30 mil; each ±0.03 | Typical; 10 GHz, 23°C/50% RH, IPC-TM-650 2.5.5.5. Datasheet construction table, page 4. Inch labels retained because paired metric labels are inconsistent. Source |
| Thermal coefficient of dielectric constant | -8 ppm/°C | Typical; -50°C to 150°C, IPC-TM-650 2.5.5.5 (modified temperature measurement); 10 GHz. Source |
| Water absorption | 0.02 % | Typical; E1/105 + D24/23, IPC-TM-650 2.6.2.1. Source |
| Density | 2.17 g/cm³ | Typical; C-24/23/50, ASTM D792. Source |
Typical reported values are not a purchase specification. Process Dk, design Dk and values measured at different frequencies are not interchangeable.
Select the CLTE construction whose measured phase and reliability behavior satisfy the actual multilayer requirement.