Hydrocarbon resin grade HCR-MMW-550 is supplied as hydrogenated C5/C9 copolymer pellets for use as the primary dielectric binder in copper-clad laminates, injection-molded waveguide arrays, and antenna-in-package substrates operating in the 24.25 GHz–40.00 GHz and 57.00 GHz–71.00 GHz mmWave allocations. The resin exhibits a softening point of 143 °C per ASTM E28-24, a glass transition temperature of 116 °C per ASTM E1356-23, and a melt flow rate of 42 g/10 min at 230 °C/2.16 kg per ISO 1133-1:2022. Ash content is below 0.02% per ISO 3451-1:2019, total chlorine is below 150 ppm per EN 14582:2016, and water absorption after 24 h immersion at 23 °C is 0.03% per ASTM D570-22. The grade is intended for melt compounding, solution impregnation, and thin-wall injection molding where preserved signal integrity above 28 GHz and reliable copper adhesion are specified.

What Distinguishes HCR-MMW-550 from Cycloolefin and PPE Binder Resins?

Compared with cycloolefin copolymer binders, HCR-MMW-550 provides higher copper peel strength without plasma or wet chemical surface activation. Peel strength to 18 µm very-low-profile copper foil is 0.87 N/mm per IPC-TM-650 2.4.8 after exposure to 288 °C/10 s; a representative cycloolefin film attained 0.45 N/mm under the same test. Compared with polyphenylene ether, the resin lowers melt viscosity from approximately 600 Pa·s to 260 Pa·s at 180 °C and 10 s−1, permitting 0.4 mm wall-section filling at 65 MPa injection pressure. Epoxy-based hydrocarbon hybrids are not direct substitutes because their dielectric constant at 10 GHz remains above 3.8, while HCR-MMW-550 exhibits 2.32 under IEC 61189-2-721:2015. The difference is most pronounced in dissipation factor: the grade is below 0.0015 at 10 GHz, whereas unfilled epoxy laminates typically measure 0.018 to 0.025.

The following comparison is based on datasheet values and internal test data measured on 2.0 mm molded plaques conditioned at 23 °C/50% RH for 40 h per ISO 291:2008.

The comparative data show that PTFE remains lower in dielectric loss, but the sintering temperature exceeds the thermal budgets of polymer-based antenna substrates. Cycloolefin resins offer lower moisture absorption but require surface activation for adhesion beyond 0.5 N/mm. PPE resins provide higher thermal resistance but require melt temperatures above 300 °C and exhibit greater water uptake. HCR-MMW-550 occupies a processing window compatible with standard PCB presses and injection molding machines while holding insertion loss below 0.09 dB/mm at 28 GHz in 254 µm microstrip lines.

Dielectric Performance and Copper Adhesion in mmWave Laminates

At 10 GHz, the dielectric constant measured by split-cylinder resonator per IEC 61189-2-721:2015 is 2.32 with a dissipation factor of 0.0011. At 28 GHz, microstrip ring resonator measurements yield a dielectric constant of 2.30 and a dissipation factor of 0.0021; at 39 GHz, the values are 2.29 and 0.0024. For 60 GHz, published data for this specific configuration is limited; early slot-array measurements indicate an effective dielectric constant of 2.26 but loss-tangent scatter exceeds ±0.0004 due to fixture calibration uncertainty. Copper adhesion is evaluated after solder float at 288 °C for 10 s per IPC-TM-650 2.4.9. The recorded peel strength of 0.87 N/mm remains stable after three reflow passes at 260 °C peak temperature. Variation in copper roughness below 2.0 µm Rz affects peel strength by approximately 0.06 N/mm per 0.5 µm Rz change.

On a 65 mm co-rotating twin-screw extruder with L/D 48, barrel zones 1–12 were profiled from 180 °C at the feed throat to 245 °C in the mixing zones, with the final die at 240 °C. A screw speed of 320 rpm produced a melt temperature of 247 °C and a torque load of 86 N·m when compounding 40 wt% fused silica with 1.0 wt% methacryloyl silane coupling agent. Strand pelletizing through a 3 mm die plate required chilled water at 10 °C to prevent pellet agglomeration; water temperatures above 18 °C caused pellet fusion and downstream feed blockage. Batch-to-batch melt flow variation under these conditions remained within ±3% over six consecutive lots. For injection molding of 0.4 mm waveguide slot arrays, a 1200 kN clamp force machine was operated at barrel temperatures of 220–250 °C, mold temperature 80 °C, injection speed 40 mm/s, and holding pressure 65 MPa. Flash exceeding 0.03 mm was observed when holding pressure exceeded 70 MPa at melt temperatures above 250 °C. Gate freeze occurred when mold temperature fell below 60 °C, producing sink marks in walls below 0.35 mm.

Fused silica loading can be varied from 0 wt% to 55 wt% to adjust the in-plane coefficient of thermal expansion. At 0 wt%, CTE below the glass transition is 72 ppm/°C per ISO 11359-2:2021. At 40 wt% fused silica, CTE drops to 46 ppm/°C, and at 55 wt% it reaches 38 ppm/°C. The dielectric constant increases from 2.32 to 2.58 at 10 GHz over the same range, while dissipation factor rises from 0.0011 to 0.0028. Melt viscosity at 180 °C/10 s−1 climbs from 260 Pa·s to 890 Pa·s. Above 55 wt%, thin-wall filling of 0.4 mm waveguides becomes unreliable on a 1200 kN injection molding machine; short shots appear at flow length-to-thickness ratios above 150:1.

Low-profile copper foil with 1.7 µm Rz roughness yields peel strength of 0.83 N/mm, while 2.0 µm Rz rough foil yields 0.91 N/mm. The difference is attributed to mechanical interlocking; the resin contains 0.8 wt% maleic anhydride-modified hydrocarbon wax as an adhesion promoter, which increases peel strength by 0.12 N/mm relative to the unmodified grade. The promoter does not affect dielectric constant at 10 GHz beyond measurement uncertainty of ±0.01.

When Reflow Peak Temperature Exceeds 260°C

Thermo-oxidative stability determines the upper processing boundary. By thermogravimetric analysis per ISO 11358-1:2022, 5% mass loss occurs at 407 °C under nitrogen; in air the 5% mass loss temperature drops to 378 °C. Isothermal rheology at 265 °C shows a viscosity increase of 31% after 10 min in air, measured at 10 s−1, due to thermo-oxidative coupling of residual unsaturation. The practical reflow boundary is therefore 260 °C peak temperature with a total time above 245 °C not exceeding 90 s. Below this boundary, dissipation factor at 28 GHz shifts by less than 0.0002 after three reflow cycles. Above 260 °C, copper adhesion decreases from 0.87 N/mm to 0.61 N/mm after a single pass at 270 °C peak temperature, coincident with resin oxidation at the copper interface. Thermocouple profiling on a forced-convection reflow oven with 10 zones is required because radiative overshoot beyond 265 °C can occur within 3 s on low-thermal-mass 0.4 mm substrates.

Replacing PTFE Sintering with Melt-Processable Hydrocarbon Resin in Waveguide Slot Arrays

In a 39 GHz antenna-in-package slot array, HCR-MMW-550 was injection molded into 64-element waveguide slots with 0.4 mm wall thickness. The filled-slot measured insertion loss was 0.095 dB/mm at 39 GHz compared with 0.106 dB/mm for a PPE reference of identical geometry. PTFE would require paste extrusion and sintering above 380 °C, which is incompatible with the glass-fabric-epoxy backing; HCR-MMW-550 avoids that constraint. Dimensional stability after 1000 h at 85 °C/85% RH per IEC 60068-2-78:2012 showed length change of 0.12% and width change of 0.09% by optical comparator. The same geometry molded from a cycloolefin resin exhibited sink depths of 0.06 mm because its higher melt viscosity reduced packing efficiency.

Thermal Degradation Pathways in Hydrogenated C9/C5 Resin Systems

Thermal aging in air follows two competing pathways: chain scission at saturated backbone positions and oxidative coupling at residual allylic hydrogen sites. At 250 °C, the melt viscosity increases by 8% after 10 min; at 265 °C, the increase reaches 31% over the same interval. Evolved gas analysis by thermogravimetry–Fourier transform infrared spectroscopy shows carbonyl absorbance at 1715 cm−1 after 15 min at 265 °C. After accelerated aging per ISO 188:2011, the carbonyl index increases from 0.02 to 0.14. The same aging protocol raises dissipation factor at 28 GHz by 0.0004, indicating that the oxidation products are sufficiently polar to degrade dielectric loss even before bulk failure.

Compliance data for the grade are documented against RoHS Directive 2011/65/EU Annex II as amended by (EU) 2015/863; X-ray fluorescence screening per IEC 62321-5:2015 reports cadmium below 100 ppm, lead below 1000 ppm, mercury below 1000 ppm, hexavalent chromium below 1000 ppm, polybrominated biphenyls and polybrominated diphenyl ethers below 1000 ppm, and the four restricted phthalates below 1000 ppm. REACH Candidate List substance evaluation at the 0.1% w/w threshold shows no listed substance above the reporting limit. The neat resin is UL 94 HB; a flame-retardant compound containing 22 wt% halogen-free phosphorus-nitrogen additive attains UL 94 V-0 at 0.8 mm. Total chlorine and bromine in the halogen-free compound are below 900 ppm each, with total halogens below 1500 ppm per IEC 61249-2-21.

The resin is soluble in aromatic and ketone solvents above 60 °C; continuous immersion in toluene or methyl ethyl ketone increases mass by 4.8% after 24 h and shifts the 10 GHz dielectric constant upward by 0.04. Pre-drying is mandatory at 80 °C for 4 h when storage relative humidity exceeds 60%, because pellet moisture above 0.05% causes surface streaking and increases dissipation factor at 28 GHz by 0.0003. The resin should not be melt-blended with maleic anhydride-grafted polyolefins above 240 °C due to esterification-induced viscosity build of more than 45% within 8 min. Avoid continuous exposure to UV without a stabilizer package; unpigmented plaques yellow after 500 h of xenon arc testing per ISO 4892-2:2013, though dielectric loss remains within 0.0002 of the initial value.

At 60 GHz, early microstrip resonator data at 50% RH indicate an insertion loss of 0.142 dB/mm for 254 µm traces, but published data for this specific configuration is limited, and fixture radiation losses have not been fully de-embedded. Cycloolefin and PPE references measured 0.138 dB/mm and 0.151 dB/mm under the same fixture. The primary residual risk is moisture-induced loss above 60 GHz; the resin is not recommended for unencapsulated exposure to condensing humidity unless a conformal coating with dielectric constant below 2.6 and thickness below 15 µm is applied.