What to Consider When Buying Thermal Pads - Selection Guide for Makers & Engineers

Overview: what thermal pads do and when to use them

Thermal pads are soft, thermally conductive interface materials used to bridge air gaps between heat-generating components (ICs, power devices, MOSFETs) and heatsinks, metal chassis, or cooling plates. They are an alternative to thermal grease and gap-filling compounds when repeatable thickness, easy placement, and electrical isolation are priorities. For South African makers, students and technicians, choosing the right thermal pad balances thermal performance, mechanical compliance, electrical properties and local availability.

Common use cases

• PCB components where planarity is uneven or there is a small gap to a heatsink
• Enclosures and chassis-mounted cooling for power supplies and motor drivers
• Prototyping and education projects where pads allow easier rework than adhesive pastes

Key specifications to check

• Thermal conductivity (W/m·K) - higher values conduct heat better but may be firmer.
• Thickness (mm) - choose to fill the specific gap without compressing fully.
• Hardness / compliance (Shore or durometer) - softer pads conform to uneven surfaces.
• Electrical properties - electrically insulating versus electrically conductive pads.
• Operating temperature range and dielectric strength for safety in power electronics.

Quick comparison: thermal pad types

For hands-on purchases, compare categories such as heatsinks and thermal interface materials on the Communica site to match pad thickness with your heatsink mounting method. Visit the Collections page or browse the All Products index for product ranges and stock status.

Selection checklist

• Measure the actual gap in millimetres. Choose a pad slightly thicker than the gap so it compresses 10-30% under clamping.
• Estimate heat dissipation (watts) from the component to calculate allowable temperature rise using thermal resistance.
• Decide on electrical insulation; for exposed leads choose an electrically insulating pad.
• Confirm operating temperature limits for your environment (e.g., solar/wind controllers may see higher ambient temperatures in South Africa).

Simple thermal calculation

Use this basic relation to estimate temperature rise across the pad: Delta T = P × Rth, where P is power dissipated (W) and Rth is thermal resistance (K/W). Thermal resistance for a pad depends on thickness, area and thermal conductivity. As a rule of thumb, thinner pads and higher conductivity lower Rth. For example, a 2 mm pad at 2 W/m·K with 1 cm2 contact area has a higher Rth than the same material at 1 mm thickness.

If you need component-level advice or to confirm stock for a course or class, Communica's branch locations and trading hours can help with local collection and VAT invoicing; see the where to find thermal management products page.

Practical examples and troubleshooting

Example 1 - Small power regulator on a hobby PCB: A regulator dissipates 1.5 W and the heatsink contact area is 2 cm2. Choose a 1 mm insulating silicone pad with thermal conductivity around 2 W/m·K. Estimate Delta T = P × Rth; lower pad thickness reduces Rth and keeps junction temperature down. For student labs, stock common thicknesses (0.5 mm, 1 mm, 2 mm) to cover most assemblies.

Example 2 - High-power MOSFET assembly

For higher-power devices where you need better heat transfer, consider a graphite or carbon-enhanced pad with conductivity >5 W/m·K, but confirm whether it is electrically conductive. If the pad is conductive, use insulating washers or an insulating pad layer under the device to prevent shorts.

Troubleshooting common issues

• Over-compression: If the pad is compressed too thin, contact pressure may be uneven-choose a firmer pad or thicker nominal value.
• Insufficient thermal performance: If temperatures remain high, reduce pad thickness, increase pad area, or upgrade to higher conductivity material.
• Electrical shorts: Verify pad is specified as electrically insulating before use near exposed pads or leads.
• Aging and creep: Some soft pads may flow over long service periods; for long-term installations, consider phase-change pads or higher-durometer materials.

Compatibility and accessory guidance

Match pad thickness to your heatsink mounting hardware. When using screws or clamps, ensure the clamp force is sufficient to compress the pad into good contact without damaging components. For repeatable builds or education kits, pre-cut pads and adhesive-backed options simplify assembly. Communica stocks thermal pads and related accessories from multiple brands - check the buy-thermal-management-accessories list to find alternatives and datasheets.

Local availability, procurement and classroom use

When planning workshops or procurement for tertiary courses, order with lead times and VAT invoicing in mind. Communica offers account quotes and VAT invoices for educational institutions and procurement teams; check company background and services on the where-to-find-electronic-component-suppliers page for guidance on bulk ordering and branch collection options. For quick browsing of available parts, start at the electronic-component-suppliers.

Final selection tips

• Always confirm electrical insulation if working near exposed copper or leads.
• Keep a small inventory of common thicknesses and conductivities for rapid prototyping; approximate costs in South Africa vary by material and brand-expect ranges rather than fixed pricing.
• For production runs, request sample material datasheets and consider environmental conditions (high ambient temperature regions require conservative choices).

Sources

• Thermal interface material overview - Wikipedia
• Calculating thermal resistance - Omega Engineering
• Thermal management techniques for PCBs - Analog Devices