RO4835 20mil Rogers Laminate 2-layer Immersion Gold Custom PCB

 RO4835 20mil Rogers Laminate 2-layer Immersion Gold Custom PCB

1.Product Overview

This a custom 2-layer rigid high-frequency PCB built on 20mil Rogers RO4835 hydrocarbon ceramic CCL with immersion gold (ENIG) surface finish. Differentiated from generic FR-4 and standard RO4000-series PCBs, this circuit board targets high-volume, high-temperature RF and automotive radar systems, balancing low-loss microwave performance, outstanding oxidation resistance, FR-4-compatible manufacturability, and reliable immersion gold surface treatment.

All fabrication parameters follow IPC-Class-2 industrial reliability standards, with full electrical continuity testing and strict dimensional tolerance control. The content is split into two independent modules: complete PCB product technical introduction and separate, detailed RO4835 copper-clad laminate material knowledge section.

2. PCB Construction Details

The following table summarizes the key manufacturing specifications of this 20mil RO4835 high-frequency PCB:

3. PCB Stackup

The following table details the layer stackup configuration of this 2-layer rigid PCB:

4. PCB Statistics

The following table presents the component and pad statistics for this20mil RogersPCB design:

5.Core Differentiated Product Advantages

5.1 Substrate Material Unique Performance

Different from traditional FR-4 and standardRO4350B hydrocarbon laminates, RO4835 adds proprietary anti-oxidation fillers in resin formula. Long-term high-temperature aging test data shows that after 1000 hours of 150°C thermal storage, its Dk drift is controlled within±0.02, while ordinary thermoset microwave materials produce Dk deviation exceeding±0.07 under the same condition. This feature guarantees stable radar ranging accuracy for automotive under-hood high-temperature working environments. Meanwhile, Dk=3.48±0.05 and Df=0.0037@10GHz deliver ultra-low signal transmission loss, supporting stable operation from 500MHz up to 77GHz millimeter wave frequency band.

5.2 Immersion Gold Surface Finish Optimization

ENIG surface finish is selected instead of HASL, OSP or hard gold plating to match fine-pitch SMT components. The chemical deposition process forms ultra-flat pad surface without uneven tin height, avoiding soldering failure of small RF chips. The nickel barrier layer blocks copper ion diffusion, and thin gold layer prevents pad oxidation during long-term inventory, extending the PCB shelf life to over 12 months under vacuum packaging. Without solder mask coverage on pads, RF signal transmission loss caused by mask dielectric absorption is completely eliminated, a critical optimization for antenna layout.

5.3 Process & Reliability Control Highlights

No blind/buried vias design: Simplifies manufacturing flow, reduces production defect rate and lowers overall cost for mass-volume automotive radar projects;

Low 5/6mil minimum trace/space: Supports compact high-density RF wiring without sacrificing impedance control precision;

20μm thick via plating: Matches RO4835 low Z-axis CTE (31ppm/°C), effectively preventing via barrel cracking after repeated lead-free reflow thermal shocks;

Full 100% electrical testing: Every single board passes continuity and insulation resistance inspection, consistent with IPC-Class-2 acceptance criteria for high-reliability RF equipment.

5.4 Target Application Scenarios

This2-layer RO4835 immersion gold PCB is tailor-made for performance-sensitive high-volume RF products, including automotive 24GHz/77GHz radar sensors, point-to-point microwave communication transceivers, RF power amplifier modules, phased array radar antenna units and general discrete RF component carrier boards. Its balanced high-frequency performance and manufacturability make it a cost-effective upgrade solution replacing RO4350B for long-lifetime outdoor and vehicle-mounted electronic systems.

6. Conclusion of PCB Main Body

This20mil RO4835 double-sided RF PCB achieves a balanced combination of stable high-frequency electrical performance, superior thermal oxidation resistance, cost-efficient FR-4 compatible fabrication and reliable immersion gold soldering surface. The standardized two-layer stackup, precise dimensional and circuit geometric specifications. Compared with competing high-frequency PCB products based on PTFE or ordinary hydrocarbon laminates, it stands out via three core differentiation points: enhanced anti-oxidation substrate formula, mask-free bare-copper RF pad design and low-complexity through-via-only construction. It is a mature mass-production PCB solution for automotive radar and millimeter-wave RF equipment, capable of stable worldwide supply and lead-free assembly compatibility.

Appendix: Full Technical Explanation of RO4835 CCL (Copper Clad Laminate)

1. Basic Material Profile of RO4835

Rogers RO4835 is a thermoset hydrocarbon ceramic-filled CCL belonging to Rogers RO4000 series, developed to solve the long-term oxidation drift problem of conventional microwave laminates at elevated temperatures. It retains nearly identical electrical and mechanical parameters as widely recognized RO4350B, while adding proprietary anti-oxidation resin components. Unlike PTFE high-frequency materials, Rogers 4835 supports standard FR-4 manufacturing processes without special sodium etching via treatment, which greatly reduces production threshold and total manufacturing cost for RF PCB factories. It complies with UL 94 V-0 flame retardant standard, RoHS environmental directives and IPC-4103 slash sheet /11 material specification, fully applicable to lead-free SMT reflow processes without blistering or interlayer delamination.

2. Complete RO4835 Material Performance Data Sheet Table

3. Core Material Feature & Benefit Interpretation

3.1 Remarkably Enhanced Oxidation Resistance

The core competitive characteristic of RO4835 versus other hydrocarbon thermoset materials. Long-term high-temperature exposure will cause Dk and Df rise of ordinary microwave substrates, which distorts RF signal phase and reduces radar detection precision. RO4835’s modified resin formula slows oxidative degradation rate, maintaining stable dielectric properties over thousands of thermal cycles, perfectly matching automotive long service life requirements.

3.2 Low Loss High-Frequency Electrical Property

Ultra-low dissipation factor 0.0037@10GHz minimizes RF signal energy loss during transmission lines, supporting high operating frequency up to millimeter wave bands, ideal for power amplifiers and phased array antenna systems. Tight Dk tolerance (±0.05) enables accurate impedance control for microstrip and stripline circuits, reducing simulation-to-real measurement deviation.

3.3 Excellent Thermal & Dimensional Stability

Tg exceeds 280°C, covering the full temperature window of PCB lamination, etching, solder mask and lead-free reflow. Low in-plane CTE (10ppm/°C X-axis, 12ppm/°C Y-axis) prevents board warpage during processing; low Z-axis CTE (31ppm/°C) eliminates plated through-hole barrel cracking under thermal shock, improving interconnection reliability.

3.4 Mass-Production & Cost Advantages

Compatible with standard FR-4 production lines without special chemical treatment for vias, cutting manufacturing time and extra equipment investment. Available with Rogers proprietary LoPro reverse-treated copper foil option to further lower high-frequency conductor loss, suitable for large-volume automotive radar batch orders with competitive material cost compared with PTFE laminates.

3.5 Additional Reliability Performance

CAF resistance, low moisture absorption rate and UL 94 V-0 flame retardant rating expand its application range to outdoor, vehicle-mounted and power RF equipment with strict safety standards.

4. Standard Specification of RO4835 CCL Raw Material

4.1 Standard Core Thickness

0.17mm (6.6mil), 0.25mm (10mil), 0.51mm (20mil), 0.76mm (30mil), 1.52mm (60mil); non-standard thickness customizable with 0.0033”incremental step.

4.2 Standard Panel Sizes

305×457mm (12”×18”), 610×457mm (24”×18”), 610×915mm (24”×36”), 1219×915mm (48”×36”); customized large panels available upon request.

4.3 Standard Copper Cladding Weight

0.5oz (18μm) HH/HH foil, 1oz (35μm) H1/H1 electrodeposited copper; LoPro low-roughness reverse treated copper foil optional for ultra-low insertion loss demands.

5. Typical CCL Application Matching

• Automotive 24GHz/77GHz millimeter-wave radar sensors & vehicle safety detection modules
• Point-to-point microwave communication transceiver boards
• RF power amplifier and signal matching network substrates
• Phased array radar antenna unit carrier boards
• General industrial high-frequency RF discrete component circuit boards

6. Supplementary CCL Material Diagram Description

The physical structure of RO4835 substrate consists of three layers: double-sided electrodeposited copper foil + intermediate hydrocarbon ceramic dielectric core. The ceramic filler uniformly dispersed in hydrocarbon resin balances low dielectric loss and thermal expansion performance; spread glass fiber reinforcement reduces fiber weave effect which causes signal phase distortion at high frequencies. Compared with FR-4’s epoxy resin system, RO4835’s hydrocarbon matrix delivers far lower Df, while its anti-oxidation modification addresses the biggest reliability pain point of traditionalRO4000 series laminatesunder continuous high-temperature operation.