Arlon 85N pure polyimide laminate
Arlon 85N PCB: Pure Polyimide, Tg 250 °C+
Arlon 85N is a pure polyimide laminate and prepreg with no epoxy: Tg of 250 °C or more, Td of 407 °C and only 1.2% z-axis expansion from 50 to 260 °C, for boards that live at high temperature.
- Tg (TMA)
- ≥ 250 °C
- Td (5% loss)
- 407 °C
- Z-expansion 50–260 °C
- 1.2%
- T300
- > 60 min
What is Arlon 85N
What is Arlon 85N?
Arlon 85N is a pure polyimide laminate and prepreg system with no epoxy added, blended or reacted. It meets IPC-4101/40 and /41, has a glass transition temperature of 250 °C or more and a 5% weight-loss decomposition temperature of 407 °C, and is bromine-free.
Its low z-axis expansion, 1.2% from 50 to 260 °C against 2.5–4.0% for typical high-performance epoxies, reduces latent plated-hole defects from reflow and device attachment. That is why 85N is used for boards that run hot for long periods: downhole drilling tools, aircraft engine instrumentation, under-hood automotive controls, burn-in boards and industrial sensors.
Properties
Arlon 85N typical properties.
| Property | Value | Test method |
|---|---|---|
| Tg (TMA) | ≥ 250 °C | IPC-TM-650 2.4.24 |
| Td, initial / 5% weight loss | 387 / 407 °C | IPC-TM-650 2.4.24.6 |
| T260 / T288 / T300 | > 60 min | IPC-TM-650 2.4.24.1 |
| CTE (X,Y) | 16 ppm/°C | IPC-TM-650 2.4.41 |
| CTE (Z) < Tg / > Tg | 55 / 149 ppm/°C | IPC-TM-650 2.4.24 |
| Z-axis expansion, 50–260 °C | 1.2% | IPC-TM-650 2.4.24 |
| Dk @ 1 MHz / 1 GHz | 4.2 / 4.0 | IPC-TM-650 2.5.5.3 |
| Df @ 1 MHz | 0.01 | IPC-TM-650 2.5.5.3 |
| Electrical strength | 1450 V/mil (57.1 kV/mm) | IPC-TM-650 2.5.6.2 |
| Peel strength (1 oz) | 1.1 N/mm (6.4 lb/in) | IPC-TM-650 2.4.8 |
| Water absorption | 0.27% | IPC-TM-650 2.6.2.1 |
| Thermal conductivity | 0.2 W/m·K | ASTM E1461 |
| Flammability | UL 94 HB | UL-94 |
When to use
When to choose an Arlon PCB on 85N.
An Arlon PCB built on 85N is the right choice when the board itself runs hot, not just during assembly. Epoxy FR-4, even high-Tg grades, softens and degrades when held above about 150–170 °C for long periods. Polyimide stays mechanically stable well above that, and its low z-axis expansion keeps plated holes intact through wide thermal cycles. Note that 85N is rated UL 94 HB, not V-0; if your product needs a V-0 laminate, tell us at quote so we can review alternatives.
Downhole & energy
Drilling tools and sensors at sustained high temperature.
Burn-in & test
Burn-in boards cycled at high temperature.
Processing
How Arlon 85N is processed.
Polyimide needs its own process window. Following Arlon’s recommendations, inner layers get brown oxide and are baked at 107–121 °C for an hour before lay-up, and prepreg is vacuum-desiccated before lamination. Lamination uses a controlled heat rise and a 218 °C cure held for 120 minutes, then cooling under pressure. Holes are drilled at reduced surface speed with undercut bits for small vias, and desmear uses plasma or alkaline permanganate set for polyimide, with plasma preferred for positive etch-back. Conventional plating is compatible.
- Brown oxide and pre-lamination bake of inner layers
- Prepreg stored at ≤ 30% RH and vacuum-desiccated
- 218 °C, 120-minute cure; cool under pressure
- Polyimide-specific drilling and plasma desmear
- Bake 1–2 hours at 121 °C before HASL or reflow
Prepreg styles
Arlon 85N prepreg styles.
| Arlon part number | Glass style | Resin % |
|---|---|---|
| 85N0672 | 106 | 72 |
| 85N8063 | 1080 | 63 |
| 85N2355 | 2313 | 55 |
| 85N2650 | 2116 | 50 |
| 85N2840 | 7628 | 40 |
Resin-rich styles such as 106 and 1080 fill fine features and heavy copper; 2116 and 7628 build thickness efficiently. We choose the mix with the stack-up so that dielectric thickness, fill and Dk all meet the design.
Comparison
Arlon 85N vs high-Tg FR-4.
| Property | Arlon 85N | High-Tg FR-4 (typical) |
|---|---|---|
| Resin | Pure polyimide | Epoxy |
| Tg | ≥ 250 °C | ≈ 170–185 °C |
| Td (5%) | 407 °C | ≈ 300–360 °C |
| Z-expansion 50–260 °C | 1.2% | ≈ 2.5–4.0% |
| Flammability | UL 94 HB | UL 94 V-0 |
| Relative cost | High | Low |
For boards that only need extra margin through lead-free assembly, a high-Tg FR-4 such as Shengyi S1000-2M or Isola 370HR is far cheaper. For flexible polyimide, see DuPont Pyralux.
RFQ
What to include in an Arlon 85N RFQ.
- Laminate name and grade exactly as on your drawing, or “or equivalent” if substitution is allowed
- Arlon 85N laminate and prepreg (or IPC-4101/40, /41 if an equivalent is acceptable)
- Continuous operating temperature and thermal-cycling range
- Flammability rating required
- Layer count, finished thickness and tolerance
- Impedance targets and reference layers
- IPC class, quantity and schedule
FAQ
Material questions.
What is the Tg of Arlon 85N?
250 °C or more by TMA, per the Arlon data sheet.
What is the decomposition temperature of 85N?
407 °C at 5% weight loss, with initial decomposition at 387 °C.
Is Arlon 85N lead-free compatible?
Yes. It is designed for lead-free soldering and has T260, T288 and T300 above 60 minutes.
What is the dielectric constant of Arlon 85N?
4.2 at 1 MHz and 4.0 at 1 GHz.
Is Arlon 85N halogen-free?
Yes, it uses bromine-free, halogen-free chemistry and is RoHS/WEEE compliant.
What flammability rating does 85N have?
UL 94 HB. If your product needs V-0, ask us to review alternatives at quote.
Ready when your files are
Send your stack-up for a material check.
Upload Gerber, ODB++ or IPC-2581 data. Every quote includes a written engineering DFM review, typically within one business day.