2. Product Specification Table

Parameter	Value / Description
Layer count	4 layers (6-layer stackup construction)
Material	RT/duroid 5880 + High Tg FR4 hybrid stackup
Finished board thickness	1.0 mm
Board dimensions	90 mm × 80 mm (1 piece)
Inner layer copper (starting)	0.5 OZ
Finished outer copper	1 OZ
Solder mask	Blue
Silkscreen	White
Surface finish	Immersion Gold (2 microinches)
Plated hole copper thickness	25 µm
IPC standard	Class 3 (IPC-3)
Special feature	Controlled depth routing (slot)

Controlled depth routing allows precise cavities or partial slots for component recessing, shielding, or impedance control. The 25 µm hole copper thickness ensures reliable plated through-holes. Immersion gold provides a flat, solderable, oxidation-resistant surface.

3. RT/duroid 5880 Laminate Introduction

RT/duroid® 5870 and 5880 are glass microfiber reinforced PTFE composites designed for exacting stripline and microstrip circuit applications. The randomly oriented microfibers result in exceptional dielectric constant uniformity. The dielectric constant of RT/duroid 5880 laminates is uniform from panel to panel and remains constant over a wide frequency range. Its low dissipation factor extends the usefulness of RT/duroid 5880 laminates to Ku-band and above. The material is normally supplied as a laminate with electrodeposited copper of ½ to 2 ounces per square foot (8 to 70 µm) or reverse treated ED copper on both sides. For more critical electrical applications, rolled copper foil cladding is available. Aluminum, copper, or brass plate cladding may also be specified.

4.Typical Properties of RT/duroid 5880

Property	RT/duroid 5870 Typical Values	RT/duroid 5880 Typical Values	Direction	Units	Condition	Test Method
Dielectric Constant, εr (Process)	2.332.33 ± 0.02 spec.	2.202.20 ± 0.02 spec.	Z	N/A	C24/23/50	1 MHz: IPC-TM-650 2.5.5.310 GHz: IPC-TM 2.5.5.5
Dielectric Constant, εr (Design)	2.33	2.20	Z	N/A	8 GHz – 40 GHz	Differential Phase Length Method
Dissipation Factor, tan δ	0.00050.0012	0.00040.0009	Z	N/A	C24/23/50	1 MHz: IPC-TM-650 2.5.5.310 GHz: IPC-TM 2.5.5.5
Thermal Coefficient of εr	-115	-125	Z	ppm/°C	-50 – 150°C	IPC-TM-650 2.5.5.5
Volume Resistivity	2 × 10⁷	2 × 10⁷	Z	Mohm·cm	C96/35/90	ASTM D257
Surface Resistivity	2 × 10⁷	3 × 10⁷	Z	Mohm	C/96/35/90	ASTM D257
Specific Heat	0.96 (0.23)	0.96 (0.23)	N/A	J/g/K (cal/g/°C)	N/A	Calculated
Tensile Modulus @23°C	1300 (189) X1280 (185) Y	1070 (156) X860 (125) Y	X,Y	MPa (kpsi)	Condition A	ASTM D638
Tensile Modulus @100°C	490 (71) X430 (63) Y	450 (65) X380 (55) Y	X,Y	MPa (kpsi)	Condition A	ASTM D638
Tensile Ultimate Stress	50 (7.3) X42 (6.1) Y	29 (4.2) X27 (3.9) Y	X,Y	MPa (ksi)	-	ASTM D638
Tensile Ultimate Strain	9.8 X9.8 Y	6.0 X4.9 Y	X,Y	%	-	ASTM D638
Compressive Modulus	1210 (176) X1360 (198) Y803 (120) Z	710 (103) X710 (103) Y940 (136) Z	X,Y,Z	MPa (kpsi)	Condition A	ASTM D695
Compressive Ultimate Stress	30 (4.4) X37 (5.3) Y54 (7.8) Z	27 (3.9) X29 (5.3) Y52 (7.5) Z	X,Y,Z	MPa (ksi)	-	ASTM D695
Compressive Ultimate Strain	4.0 X3.3 Y8.7 Z	8.5 X7.7 Y12.5 Z	X,Y,Z	%	-	ASTM D695
Moisture Absorption	0.02	0.02	N/A	%	0.062” (1.6mm), D48/50	ASTM D570
Thermal Conductivity	0.22	0.20	Z	W/m/K	80°C	ASTM C518
Coefficient of Thermal Expansion	22 X28 Y173 Z	31 X48 Y237 Z	X,Y,Z	ppm/°C	0–100°C	IPC-TM-650 2.4.41
Td	500	500	N/A	°C (TGA)	N/A	ASTM D3850
Density	2.2	2.2	N/A	g/cm³	N/A	ASTM D792
Copper Peel Strength	27.2 (4.8)	31.2 (5.5)	N/A	pli (N/mm)	1 oz (35μm) EDC foil, after solder float	IPC-TM-650 2.4.8
Flammability	V-0	V-0	N/A	N/A	N/A	UL94
Lead-Free Process Compatible	Yes	Yes	N/A	N/A	N/A	N/A

5. Typical Applications of RT/duroid 5880

Commercial airline broadband antennas, microstrip and stripline circuits, millimeter wave applications, military radar systems, missile guidance systems, and point-to-point digital radio antennas.

 

6.Fabrication Guidelines for RT/duroid 5880

 

RT/duroid 5880 laminates are shipped in reinforced corrugated cardboard containers with protective sheets. Upon receipt, inspect immediately and report any damage to the carrier and to Rogers' Customer Service within 30 days. Each panel is labeled with product, lot, and sheet numbers; maintain this traceability through storage and processing. Store at normal room temperature (65–85°F / 18–30°C) and humidity. Keep panels sealed in their original polyethylene bags or with adherent sheets to prevent copper oxidation. Stack cartons flat, maximum five high. For panels removed from cartons, store on edge in slotted shelving with clad surfaces vertical; if horizontal storage is necessary, use a flat, clean shelf with soft separator sheets and keep loading below 50 lbs/ft².

 

PTFE materials are softer than standard laminates. Always wear knit nylon or non-absorbent gloves when handling to prevent fingerprint corrosion. If fingerprints occur, remove by bright dipping in dilute hydrochloric acid, degreasing with acetone or MEK, water rinsing, baking at 250°F (125°C) for 60 minutes, then repeating the bright dip. Keep work surfaces clean and dry. Leave protective polyethylene sheets on during shearing, sawing, or punching. Pick panels by two edges only – thin cores lack stiffness and can be permanently creased if handled by one edge. Transport panels on flat carrying trays, interleaved with soft, sulfur-free paper.

 

To remove the self-adhering polyethylene sheet, lay the panel flat, peel back a corner and extend across the short edge, then gently peel horizontally. Remove adhesive residue with a lint-free cloth soaked in isopropanol (70–100%), then rinse with clean water. Remove copper oxides using commercial cleaners and microetchants. Abrasive cleaning (pumice or brush scrubbing) is not recommended because it creates microscopic scratches that can lead to thermal stress cracks; if unavoidable, use minimal pressure.

 

For drilling, avoid smear – PTFE smear cannot be removed, so it must be prevented by tight process control. Use carbide drills with standard geometry and 130° lip angle. Undercut drills may help reduce re-deposited debris. Always use new or precision-repointed drills. Recommended parameters: surface speed 150–250 SFM (45–75 m/min), infeed 0.0015–0.0025 inch per revolution, retract rate 400–500 IPM (10–13 m/min). Stack height (including entry/exit materials) should not exceed 75% of the drill flute length, typically less than 0.240 inch (6.1 mm). Use phenolic composite entry (0.010–0.030") and exit (>0.060"). Tool life: for a stack height of 0.060" (1.5 mm), maximum 300 hits; for 0.120" (3.0 mm), 250 hits; for 0.180" (4.5 mm), 100 hits. After drilling, remove loose debris using vapor or hydro-honing with adequate support of the soft laminate.

 

Before metallization, drilled holes in PTFE require surface activation. Sodium treatment is the preferred method for RT/duroid 5880. Plasma treatment should only be considered if a direct metallization process (instead of electroless copper) is used. Without such treatment, poor metal adhesion or plating voids will occur.

 

7.What Is Controlled Depth Routing?

 

Controlled depth routing, also known as controlled depth slotting or back-milling, is a machining process that creates cavities, slots, or recesses that do not go through the entire board thickness. This feature allows components to be embedded within the board for improved thermal management, reduced signal path length, or shielding. In this PCB, the controlled depth routing is implemented precisely to meet design requirements without compromising the integrity of the hybrid stackup.

 

8.High-Frequency Hybrid PCB with PTFE and FR4

 

This board combines RT/duroid 5880 (a low-loss PTFE composite) with high Tg FR4. Such a hybrid construction is used when a circuit requires superior high-frequency performance on certain layers (e.g., RF or microwave signals) while other layers can use standard FR4 for power distribution, grounding, or lower-speed signals. The PTFE layer provides excellent dielectric stability and low loss up to Ku-band and beyond, while FR4 adds mechanical rigidity and cost efficiency.

 

9.Advantages of Hybrid PTFE+FR4 Construction

 

The hybrid design delivers exceptional high-frequency performance on critical RF paths due to RT/duroid 5880's uniform Dk and low dissipation factor. Cost is reduced by limiting expensive PTFE material to only the necessary layers. The board maintains good dimensional stability and can be machined using standard methods (cutting, shearing, routing) as PTFE composites are not brittle. Additionally, the combination allows for controlled impedance and minimal signal distortion in broadband and millimeter-wave circuits.

 

10.Disadvantages and Considerations

 

PTFE-based materials like RT/duroid 5880 require specialised via preparation (sodium or plasma treatment) before electroless copper deposition, unlike standard FR-4 or hydrocarbon laminates. Hybrid lamination with FR4 demands careful control of temperature and pressure due to different coefficients of thermal expansion. The material is softer than FR4, which can lead to burring or creasing if handling and drilling are not optimised. Abrasive cleaning is discouraged. Overall, fabrication costs are higher than all-FR4 boards, and not all PCB manufacturers are experienced with PTFE hybrid stacks.

 

11.Summary

 

Rogers RT/duroid 5880 4-layer PCB uses a hybrid stackup of RT/duroid 5880 and high Tg FR4 with a finished thickness of 1.0 mm and dimensions of 90 mm × 80 mm. It features 0.5 OZ inner copper, 1 OZ finished outer copper, blue solder mask, white silkscreen, and immersion gold (2 microinches). Hole copper thickness is 25 µm, meeting IPC Class 3. A controlled depth routing feature is included. The RT/duroid 5880 laminate enables low-loss, uniform Dk performance up to Ku-band. Key fabrication guidelines: store at room temperature, handle with gloves, avoid abrasive cleaning, use carbide drills with 150–250 SFM and strict tool life limits (e.g., 300 hits at 0.060" stack height), and perform sodium treatment on drilled holes before metallisation to ensure plating reliability.