Substrate presets

Select one with .substrate ID in a netlist, optionally overriding any value, e.g. .substrate jlc-fr4-1.6 er=4.3, or describe your own board with .substrate custom h=… er=… [tand=…] [t=…]. See the manual for the syntax.

Values marked † are assumptions rather than published data; each preset lists its assumptions and sources below the table.

#Assumptions, notes and sources

#FR-4

Presets: jlc-fr4-0.4, jlc-fr4-0.6, jlc-fr4-0.8, jlc-fr4-1.0, jlc-fr4-1.2, jlc-fr4-1.6, jlc-fr4-2.0

Assumed:

• loss tangent 0.02 at 1 GHz is a typical FR-4 value; JLCPCB does not publish one
• dielectric h = board thickness − 2 × 1 oz copper; JLCPCB does not publish the 2-layer core thickness, and board thickness tolerance is typically ±10 % — confirm for impedance-critical work

Notes:

• FR-4 εr varies with glass style, resin content and frequency; treat 4.5 as nominal

Sources:

• https://jlcpcb.com/capabilities/pcb-capabilities — FR-4 εr 4.5 (2-layer), thicknesses, min trace/space 0.10/0.10 mm, min via hole 0.15 mm, 1 oz outer copper (accessed 2026-10-18)

#Rogers RO4350B

Presets: jlc-ro4350b-0.508, jlc-ro4350b-0.762, jlc-ro4350b-1.524

Assumed:

• fabrication limits taken as JLCPCB standard 2-layer rules; not published separately for Rogers

Notes:

• εr is the Rogers design Dk 3.66 (recommended for circuit design); the process Dk is 3.48 at 10 GHz, the value JLCPCB quotes
• Df 0.0031 at 2.5 GHz, 0.0037 at 10 GHz
• JLCPCB also quotes finished thicknesses of 0.6 / 0.9 / 1.65 mm for these cores; h here is the core thickness

Sources:

• https://jlcpcb.com/pcb-fabrication/high-frequency-pcb — RO4350B and PTFE materials with Dk/Df, 2-layer only (accessed 2026-10-18)
• https://jlcpcb.com/blog/112-rogers-pcb-ptfe-pcb-high-frequency-pcb-is-available-on-jlcpcb — RO4350B 0.51/0.76/1.52 mm, PTFE 0.76/1.52 mm, 2-layer, 1 oz (post dated 2023-03-09) (accessed 2026-10-18)
• https://rs.jlcpcb.com/static/file/rogers-ro4350b-datasheet.pdf — RO4350B design Dk 3.66, process Dk 3.48 (10 GHz), Df 0.0037 @ 10 GHz / 0.0031 @ 2.5 GHz (accessed 2026-10-18)

#PTFE ZYF255DA

Presets: jlc-zyf255da-0.762, jlc-zyf255da-1.524

Assumed:

• test frequency for Dk/Df not stated by JLCPCB; 10 GHz assumed
• fabrication limits taken as JLCPCB standard 2-layer rules

Notes:

• JLCPCB lists 0.76 / 1.52 mm in one place and 0.65 / 0.9 / 1.65 mm (finished) in another; confirm before ordering

Sources:

• https://jlcpcb.com/pcb-fabrication/high-frequency-pcb — RO4350B and PTFE materials with Dk/Df, 2-layer only (accessed 2026-10-18)
• https://jlcpcb.com/blog/112-rogers-pcb-ptfe-pcb-high-frequency-pcb-is-available-on-jlcpcb — RO4350B 0.51/0.76/1.52 mm, PTFE 0.76/1.52 mm, 2-layer, 1 oz (post dated 2023-03-09) (accessed 2026-10-18)

#PTFE ZYF265D

Presets: jlc-zyf265d-0.762, jlc-zyf265d-1.524

Assumed:

• test frequency for Dk/Df not stated by JLCPCB; 10 GHz assumed
• fabrication limits taken as JLCPCB standard 2-layer rules

Notes:

• JLCPCB lists 0.76 / 1.52 mm in one place and 0.65 / 0.9 / 1.65 mm (finished) in another; confirm before ordering

Sources:

• https://jlcpcb.com/pcb-fabrication/high-frequency-pcb — RO4350B and PTFE materials with Dk/Df, 2-layer only (accessed 2026-10-18)
• https://jlcpcb.com/blog/112-rogers-pcb-ptfe-pcb-high-frequency-pcb-is-available-on-jlcpcb — RO4350B 0.51/0.76/1.52 mm, PTFE 0.76/1.52 mm, 2-layer, 1 oz (post dated 2023-03-09) (accessed 2026-10-18)

#PTFE ZYF300CA-C

Presets: jlc-zyf300ca-c-0.762, jlc-zyf300ca-c-1.524

Assumed:

• test frequency for Dk/Df not stated by JLCPCB; 10 GHz assumed
• fabrication limits taken as JLCPCB standard 2-layer rules

Notes:

• JLCPCB lists 0.76 / 1.52 mm in one place and 0.65 / 0.9 / 1.65 mm (finished) in another; confirm before ordering

Sources:

• https://jlcpcb.com/pcb-fabrication/high-frequency-pcb — RO4350B and PTFE materials with Dk/Df, 2-layer only (accessed 2026-10-18)
• https://jlcpcb.com/blog/112-rogers-pcb-ptfe-pcb-high-frequency-pcb-is-available-on-jlcpcb — RO4350B 0.51/0.76/1.52 mm, PTFE 0.76/1.52 mm, 2-layer, 1 oz (post dated 2023-03-09) (accessed 2026-10-18)

#PTFE ZYF300CA-P

Presets: jlc-zyf300ca-p-0.762, jlc-zyf300ca-p-1.524

Assumed:

• test frequency for Dk/Df not stated by JLCPCB; 10 GHz assumed
• fabrication limits taken as JLCPCB standard 2-layer rules

Notes:

• JLCPCB lists 0.76 / 1.52 mm in one place and 0.65 / 0.9 / 1.65 mm (finished) in another; confirm before ordering

Sources:

• https://jlcpcb.com/pcb-fabrication/high-frequency-pcb — RO4350B and PTFE materials with Dk/Df, 2-layer only (accessed 2026-10-18)
• https://jlcpcb.com/blog/112-rogers-pcb-ptfe-pcb-high-frequency-pcb-is-available-on-jlcpcb — RO4350B 0.51/0.76/1.52 mm, PTFE 0.76/1.52 mm, 2-layer, 1 oz (post dated 2023-03-09) (accessed 2026-10-18)

Fab data change over time. If you rely on a value, check it against the current fabricator documentation and update js/substrates.js (then run npm run docs).