Key Characteristics and Applications

CuClad 6700 is a high-performance bonding film developed by DuPont for use in the manufacture of multilayer printed circuit boards (PCBs). Some key characteristics and applications of CuClad 6700 include:

High Bond Strength

CuClad 6700 provides excellent adhesion between laminated layers of PCBs. It bonds firmly to copper and FR-4 laminates, with typical peel strengths exceeding 9 lbs/in. This high bond strength prevents delamination and separation of PCB layers during manufacturing and use.

Dimensional Stability

The bonding film is dimensionally stable during lamination processes up to 400°F. It resists stretching, shrinking, and distortion, allowing for precision alignment and registration of PCB layers.

Low Flow Properties

CuClad 6700 retains its thickness and does not flow significantly during lamination. This prevents pooling around pad areas and maintains consistent dielectric spacing between conductors.

Compatibility

The bonding film is compatible with a wide range of rigid and flexible circuit laminates, including FR-4, polyimide, ceramic-filled PTFE composites, and others. It bonds well to common PCB metals like copper and nickel.

High Reliability

PCBs made with CuClad 6700 demonstrate excellent resistance to thermal cycling, humidity exposure, and other environmental stresses. The sturdy construction prevents conductor fractures and other reliability issues.

PCB Applications

Typical applications of CuClad 6700 include multilayer boards for high-speed digital circuits, RF/microwave circuits, flex/rigid flexible circuits, and high-density interconnect (HDI) boards. The robust bonding enables up to 30-layer PCBs.

Properties and Specifications

CuClad 6700 has the following key properties and product specifications:

Physical Properties

Property	Value
Color	Translucent Amber
Nominal Thickness	0.002 in (2 mil)
Specific Gravity	1.2
Melting Point	280°F

Electrical Properties

Property	Value
Dielectric Constant	3.2-3.8 (@ 1 MHz)
Dissipation Factor	0.024 (@ 1 MHz)
Dielectric Strength	4000 V/mil
Volume Resistivity	>1015 ohm-cm

Lamination Processing

Property	Value
Processing Temperature	375-400°F
Pressure	200-300 psi
Time	60-180 minutes

Shelf Life

• Stable for 2 years when stored sealed at < 40°C

Manufacturing Process

CuClad 6700 bonding film is manufactured through a proprietary process by DuPont. The key steps include:

Step 1 – Raw Material Preparation

The main raw materials are thermoplastic resins, crosslinking agents, and metal adhesion promoters. These components are precisely measured and mixed.

Step 2 – Film Extrusion

The formulation is fed into an extruder and passed through a slit die to form a continuous film with precise thickness. Chilled rolls quench and collect the extruded film.

Step 3 – Surface Treatment

The film surface is treated with electrical discharge or flame exposure to increase surface energy. This enhances adhesion to copper and laminate layers.

Step 4 – Product Winding

The surface-treated film is continuously wound onto rolls, with interleaving layers to prevent blocking. It is packaged to prevent contamination prior to use.

Step 5 – Slitting and Cutting

For end use, the master rolls are slit into desired widths and sheeted into panels matched to PCB dimensions.

Step 6 – Quality Control

Extensive product testing confirms film properties and performance specifications. Dimensional consistency, adhesion strength, electrical properties, and other parameters are verified.

Lamination Process Guidelines

To properly bond PCB layers, CuClad 6700 film should be laminated according to the following guidelines:

Surface Preparation

• Ensure copper surfaces are free of oxides, oils, and other contaminants
• Chemically etch or mechanically scrub surfaces
• Apply chemical coupling agents for maximum adhesion

Lamination

• Use recommended processing temperature, pressure, and time
• Employ vacuum assist if needed to remove air pockets
• Allow sufficient time for adhesive to fully cure

Cool Down

• Cool the laminated board gradually under pressure
• Avoid moisture condensation on cooled boards

Post Lam Processing

• PWBs can be processed after 60 minutes of cooling
• Perform any necessary hole drilling, routing, or patterning

Following these instructions provides properly laminated boards without defects like delamination or blistering.

Lamination Troubleshooting

Issue	Possible Causes	Corrective Actions
Delamination	Insufficient bonding pressure	Increase pressure during lamination
	Insufficient adhesive resin flow	Use higher temperature to improve flow
	Surface contamination	Thoroughly clean copper surfaces before lamination
Blistering	Trapped moisture	Improve vacuum degassing in lamination press
	Excessive resin flow	Reduce lamination temperature
	Inadequate curing	Increase time and temperature to ensure complete crosslinking
Distortion	Uneven pressures across laminate	Use shims to equalize pressure distribution
	Excessive lamination temperature	Reduce temperature to recommended levels

Design Guidelines for Using CuClad 6700

To take full advantage of CuClad 6700 properties in PCB design, the following guidelines should be followed:

Layer Stack-up

• Use between 2 to 6 mil thick prepreg layers on either side of the 2 mil CuClad 6700 core
• Adjust layer count to meet electrical and mechanical requirements
• Minimize asymmetry to avoid curling or twisting

Conductor Spacing

• Size dielectric gaps based on required voltage isolation
• Provide adequate clearance between adjacent traces for leakage and breakdown prevention
• Allow slightly wider spacing for flexible circuits to account for flexing deformation

Hole Size and Spacing

• Use larger hole sizes and spacings when possible to minimize resin clogging
• Avoid high conductor densities around drilled holes
• Allow 1:1 hole size to annular ring ratio for good resin bonding

Copper Weight

• Use 1⁄2, 1 or 2 oz copper cladding on rigid boards
• Reduce copper weight on flex boards, e.g. 1⁄4 or 1⁄2 oz, to improve flexibility

Mask Definition

• Use solder mask to prevent shorts between closely spaced traces
• Apply mask to both sides of double-sided or multilayer boards
• Allow slight mask pullback from edges of conductors

Handling, Storage and Shelf Life

CuClad 6700 bonding film requires careful handling to prevent contamination or physical damage:

• Keep sealed in polyethylene bags until ready to use
• Store horizontally to avoid blocking, pressure marks, and uneven thickness
• Storage temperature should not exceed 40°C
• Use within 2 years of the production date
• Avoid direct exposure to sunlight or excessive humidity

Before lamination, allow the film to equalize to room temperature in the press. Carefully peel back the bag liner to avoid scratching the film surfaces.

With proper storage conditions, CuClad 6700 retains full bonding performance for at least 2 years from the production date. DuPont recommends retesting bonding properties after this period.

Safety and Compliance Information

CuClad 6700 bonding film offers high performance with safe manufacturing and disposal:

• RoHS compliant – contains no lead, cadmium, mercury, hexavalent chromium
• Halogen-free – no intentionally added halogens
• UL 94 V-0 rated for flammability

DuPont provides full safety data sheet (SDS) information for safe handling. Off-gassing, thermal degradation, and combustion byproducts meet stringent environmental standards.

Frequently Asked Questions

Q: Is CuClad 6700 suitable for automotive grade PCBs?

A: Yes, CuClad 6700 meets all requirements for high-reliability automotive electronics applications. It delivers excellent thermal shock resistance, temperature cycling performance, and moisture resistance needed for under-hood and engine control systems.

Q: Can the bonding film be used for flexible PCB applications?

A: CuClad 6700 provides good flexibility and fold endurance when used in multilayer flex boards along with polyimide dielectric layers. It withstands repeated bending without cracking or delaminating.

Q: What is the typical copper surface treatment prior to lamination with CuClad 6700?

A: Lightly brushing or chemical etching to remove surface oxides is usually sufficient. For maximum adhesion, a chemical copper surface treatment like sulfuric permanganate or sodium persulfate microetch is recommended.

Q: Does the material contain any antimony trioxide flame retardants?

A: No, CuClad 6700 does not contain antimony trioxide or any other antimony compounds. It achieves FR-4 flammability rating through brominated resin chemistries.

Q: What is the typical drill life when machining multilayer boards made with CuClad 6700?

A: Excellent drill life is attained due to the thermoplastic properties and absence of inorganic fillers. Up to 1000 hits are typical for standard FR-4 circuit boards. Adjustments may be needed for thicker boards with higher layer counts.