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High-frequency designs live and die by material choice, process control, and fabrication experience. This page covers what makes RF and microwave PCBs different, what Sunstone can build, and how to get a custom quote.
At high frequencies, the PCB substrate isn't passive background — it's an active part of the circuit. Dielectric constant (Dk), loss tangent, copper surface roughness, and dimensional tolerances all directly affect signal speed, insertion loss, and impedance — in ways that simply don't matter at lower frequencies.
Standard FR-4 works fine for most digital designs. But as frequencies climb into the GHz range, FR-4's variability in Dk and higher loss tangent start degrading signal integrity in ways that can't be compensated for in software. RF and microwave designs require specialized low-loss laminates, tighter fabrication tolerances, and a fab team that understands how process decisions translate to electrical performance.
Sunstone has both the materials and the process experience to handle these requirements — from prototype through production volume.
RF laminates behave differently than standard materials. Handling, bonding, and processing PTFE-based substrates requires specific knowledge and equipments
Trace width, dielectric thickness, and copper weight directly control impedance. Small dimensional errors translate to measurable electrical performance shifts.
How layers are bonded-pre-bonded laminate vs. post-bonded film adhesive vs. sweat solder-affects both electrical and thermal perfomance.
Many RF designs require metal heat sinks bonded thermally and electrically to the circult, demanding precision machining alongside PCB fabrication
At microwave frequencies, surface roughness of the copper conductor affects insertion loss. Low-profile copper options are available for demanding applications.
For maetal-backed designs, matching the coefficient of thermal expansion between the PCB and its carrier prevents stress failures under thermal cycling.
| Specification | Details |
|---|---|
| Layer configurations | Single-sided, double-sided, multilayer, hybrid multilayer |
| Via types | Plated through-hole, blind vias, buried vias |
| Via fill | Conductive and non-conductive fill available |
| Castellations | Supported |
| Surface finishes | Wire-bondable finishes available; all standard finishes supported |
| Via and routing methods | Mechanical drill and laser-cut vias; laser routing available |
| Metal-backed construction | Pre-bonded and post-bonded metal-backed circuits supported |
| Plated through-hole to metal carrier | Plated through-hole capability from PCB layer through to PTFE/metal carrier |
| Heat sink technology | Integrated metal heat sinks, thermally and electrically bonded |
| Metal carrier materials | Aluminum composites with CTE-matched options for ceramics, transistor packages, and PCBs |
| Bonding methods | Pre-bonded laminates, post-bonded film adhesive, sweat solder |
| Adhesive types | Thermally conductive, electrically conductive, and non-conductive adhesive options |
| Precision machining | In-house pocket machining and precision routing for finished assemblies |
| Assembly conversion | Pre-bonded to post-bonded conversion; discrete PCB to pre/post-bond assembly conversion |
| In-house plating | Full in-house plating for finished assemblies |
| Industries served | Telecommunications, aerospace, defense, medical, industrial |
Material selection is one of the most consequential decisions in an RF design. The right laminate depends on your target frequency, loss budget, thermal environment, and cost constraints. Sunstone quotes jobs using materials from the following suppliers — many thicknesses and copper types are available.
3000 series
4000 series
5000 series
6000 series
PTFE-based laminates
Woven glass options
High-frequency series
PTFE composites
Low-loss options
Ceramic-filled series
PTFE-based
Substrates
Microwave-grade
Options
Not sure which material fits your design? Our team is onsite and available to walk through your frequency range, loss requirements, and thermal constraints to help you make the right call before you commit.
The short answer is: when FR-4's variability becomes a problem for your design. FR-4 has a Dk that shifts with frequency and temperature, and a loss tangent that's workable at lower speeds but becomes a real insertion loss issue above a few GHz. If your design requires tight impedance tolerances, low insertion loss, or stable performance across temperature, it's worth moving to a controlled-Dk RF laminate. The crossover point varies by design, but 1–2 GHz is often where the conversation starts.
Pre-bonded laminates arrive from the material supplier already bonded to the metal carrier — Rogers, Isola, and Taconic supply these. Post-bonding is done during fabrication using film adhesives or sweat solder to attach a discrete PCB to the metal backing. Pre-bonded simplifies the process but limits design flexibility; post-bonding allows more customization and is often used when converting from a discrete PCB to a metal-backed assembly.
In many RF power designs, the metal backing serves double duty: it dissipates heat away from power-generating devices and acts as the ground reference for the circuit. That means the bond layer needs to be thermally conductive to manage heat, and electrically conductive where the design calls for grounding through the carrier. Sunstone offers both conductive and non-conductive adhesive bonded laminates depending on what the design requires.
CTE stands for coefficient of thermal expansion — the rate at which a material expands and contracts with temperature. When a PCB is bonded to a metal carrier and the two materials expand at very different rates, thermal cycling can stress the bond and eventually cause delamination or solder fatigue. Aluminum composite carrier materials are available that are engineered to match the CTE of common PCB substrates, ceramic packages, and transistor housings, which significantly extends reliability in thermally demanding environments.
At microwave frequencies, current flows primarily along the surface of conductors rather than through them — a phenomenon called the skin effect. Rougher copper surfaces increase the effective path length of the current, raising insertion loss in ways that become significant above a few GHz. Low-profile and very-low-profile copper options are available for designs where insertion loss is a tight constraint.
Yes. Hybrid multilayer constructions that combine RF laminates on specific layers with standard or high-speed digital materials on others are a common approach for mixed-signal boards. The key considerations are layer sequencing, bonding method between dissimilar materials, and whether the via structures need to traverse the laminate transition. These are worth discussing early in the design phase.
RF and microwave builds are custom by nature - automated instant quoting doesn't capture the material, bonding method, and tolerance requirements that define these design. Custom quotes are returned in 2-24 hours depending on complexity.
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