Rogers RT/duroid® and RO4000® series laminates are widely used in high-frequency applications such as RF and microwave circuits. Reliable device attachment and wirebonding are essential for achieving optimal performance and long-term reliability. This guide outlines best practices for attaching devices and performing wirebonding on these high-frequency laminates.

1. Device Attachment Methods

A. Surface Mount Technology (SMT):

1. Materials Compatibility:
   • Ensure the solder paste and flux are compatible with the laminate and device metallization.
   • Use low-residue or no-clean flux for reduced post-solder cleaning.
2. Reflow Soldering:
   • Recommended peak temperature: 245°C–260°C for most RO4000 laminates.
   • RT/duroid materials may require lower temperatures due to their lower thermal expansion coefficients.
   • Use a controlled ramp-up and cool-down profile to minimize thermal stresses.
3. Thermal Management:
   • Employ heat sinks or thermal vias for high-power devices to manage heat dissipation.

B. Adhesive Attachment:

1. Conductive Epoxies:
   • Use for components sensitive to thermal stresses.
   • Ensure even application to avoid air gaps that can compromise electrical or thermal performance.
2. Curing:
   • Follow manufacturer’s recommendations for curing temperature and duration.
   • Avoid over-curing, which can degrade the adhesion strength or laminate surface.

2. Wirebonding Notes

A. Bonding Surface Preparation:

1. Cleaning:
   • Ensure surfaces are free of contaminants such as dust, oils, or oxides.
   • Use an isopropyl alcohol (IPA) wipe followed by an ionized air blow to clean the bonding areas.
2. Surface Roughness:
   • Ensure the laminate’s copper surface has an adequate roughness for strong bond adhesion.
   • Light abrasion or microetching can enhance surface bonding strength.

B. Bonding Methods:

1. Thermosonic Bonding (Gold Wire):
   • Ideal for high-frequency laminates with low thermal expansion coefficients.
   • Recommended bond force: 50–150 g (varies with wire diameter).
   • Ensure bonding temperature (150°C–250°C) is compatible with the laminate’s thermal limits.
2. Ultrasonic Bonding (Aluminum Wire):
   • Suitable for RT/duroid materials due to their low modulus.
   • Bonding pressure: 0.5–1.5 N, with moderate ultrasonic energy.
3. Ribbon Bonding:
   • For applications requiring higher current-carrying capacity.
   • Minimize bonding stress by optimizing ultrasonic energy and time settings.

C. Bond Quality Verification:

• Conduct pull tests or shear tests to confirm bond strength meets application requirements.
• Inspect for cracking, delamination, or weak bonds under a microscope or X-ray.

3. Challenges and Mitigation Strategies

Challenge	Mitigation Strategy
Delamination during soldering	Pre-bake laminates at 120°C–150°C to remove moisture
Thermal expansion mismatches	Use adhesives with matched coefficients of thermal expansion (CTE)
Wirebonding failures	Optimize bonding parameters to match material properties
Surface oxidation of copper	Use protective coatings like ENIG or OSP finishes

4. Best Practices for Long-Term Reliability

1. Environmental Protection:
   • Apply conformal coatings or encapsulants to protect bonds and devices from environmental degradation.
2. Thermal Cycling Tests:
   • Conduct thermal cycling to ensure bonds withstand operational temperature ranges.
3. Material Compatibility:
   • Ensure adhesives, solder, and wires are compatible with the laminate and operational environment.

Proper device attachment and wirebonding techniques are essential for ensuring the reliability and performance of circuits built with RT/duroid and RO4000 series laminates. Adhering to these guidelines will help mitigate common challenges and enhance the overall quality of high-frequency applications.