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How to Choose the Right Thermal Adhesive for Electronics: A Complete Engineering Guide
In the internal structural design of electronic products, space utilization is particularly critical. Sheen Technology's TIV series thermal adhesives offer excellent insulation, thermal conductivity, and bonding properties, significantly reducing the space occupied by fasteners such as screws or clips within electronic components. This perfectly resolves the challenge of securing heat sinks to heat-generating components.The Sheen team assists you in selecting the optimal thermal adhesive for your application through comprehensive analysis of adhesive composition types, specifications, selection criteria, and comparative evaluations against thermal tape solutions.
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Understanding Thermal Adhesive Chemistry
Thermally Conductive Epoxies (Rigid Bonding)
Epoxy-based thermal adhesives are ideal for achieving high-strength permanent bonding, but they are rigid and brittle. Once cured, their high hardness makes them impossible to open, hindering rework and repair.Silicone-Based Thermal Adhesives (Flexible Bonding)
Silicone adhesives are flexible thermal bonding agents, retaining pliability even after curing. While offering lower bonding strength compared to epoxy, they provide reworkability.Polyurethane Thermal Adhesive
Polyurethane thermal adhesives feature a softer material with good adhesion properties. Their bonding strength falls between epoxy and silicone adhesives. However, they exhibit poor high-temperature resistance and produce a non-smooth surface after curing.Key Technical Specifications for Selecting a Thermal Adhesive
Thermal Conductivity and Bond Line Thickness (BLT)
Thermal resistance R″ = t / k (where t = BLT). Relying solely on the k value (W/m·K) is misleading. The primary factors determining thermal resistance are the BLT thickness and thermal conductivity. Under identical or higher thermal conductivity conditions, thinner materials may exhibit superior performance. Conversely, thicker materials with higher thermal conductivity may still exhibit inferior performance.Shear Strength and Mechanical Reliability
As a functional structural adhesive, clearly define the loads the material must withstand before selection. Shear strength is measured in MPa (megapascals) or psi. Select thermal conductive adhesives based on strength requirements.Curing Time and Manufacturing Throughput
Thermal adhesive curing time impacts production efficiency. Therefore, selection must consider production requirements. Sheen Technology's TIV series thermal adhesives offer validated curing times:- Single-component thermal adhesives: Surface dry in 5-10 minutes, full cure in 24 hours at room temperature.
- Two-component thermal structural adhesives: Room-temperature curing or accelerated heating for rapid curing.
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Sheen Technology TIV series thermal adhesives
| TIV series | TIV800-10 | TIV800-12 | TIV800-15 | TIV800-20 | TIV800-26 | TIV800-30 |
| Surface drying time(min) | 5~10 | 5~10 | 5~10 | 5~10 | 5~10 | 5~10 |
| Natural curing time(H) | 24 | 24 | 24 | 24 | 24 | 24 |
| Hardness(ShoreA) | 40~60 | 40~60 | 40~60 | 40~60 | 40~60 | 40~60 |
| Bonding strength(Mpa) | ≥1.5 | ≥1.5 | ≥1.5 | ≥1.5 | ≥1.5 | ≥1.5 |
| Operating temperature(℃) | -50~200 | -50~200 | -50~200 | -50~200 | -50~200 | -50~200 |
| Thermal conductivity(W/m·k) | 1.0 | 1.2 | 1.5 | 2.0 | 2.6 | 3.0 |
| PU series | PU4500-A-10AB | PU4500-A-15AB | PU4500-A-20AB |
| Hardness(ShoreA) | 55±5 | 70±5 | 60±5 |
| Density(g/m³) | 1.87 | 1.87 | 2.45 |
| Tensile strength(Mpa) | 17 | 16 | 14 |
| Elongation at break | 60% | 15% | 30% |
| Shear strength(Mpa) | 16 | 10 | 9.5 |
| Thermal conductivity(W/m·k) | 1.0 | 1.5 | 2.0 |
| Operating temperature(℃) | -40~85 | -40~85 | -40~85 |
Thermal Tape vs Adhesive: Which Method Wins?
Thermal Adhesive
When surfaces are rough or uneven, liquid thermal adhesive is required to better fill gaps, expel air, and enhance thermal efficiency. Additionally, thermal adhesive is necessary for functional bonding applications.Thermal Tape
Thermal tape offers uniform thickness, and if speed and production efficiency are considerations, thermal tape is more suitable, especially for projects with flat thermal interfaces and less demanding performance requirements.Reworkability Considerations
- Tape: Prone to residue during repair, difficult to remove, requires heating and peeling.
- Epoxy Resin: Difficult to remove, permanent structure hinders repair.
- Silicone : Though challenging to remove due to its flexibility, it can still be cut away.
Best Practices for Thermal Adhesive Application and Common Failure Modes
Application Practices
- Ensure Cleanliness: Surface contamination is the primary cause of adhesive failure.
- Define Bonded Layer Thickness (BLT): BLT significantly impacts material performance.
- Thermal Adhesive Curing: For Sheen Technology's TIV Series two-component thermal adhesives, rapid curing via heating enhances thermal performance and production efficiency.
Failure Modes
- Delamination: Interface separation, typically caused by inadequate cleaning.
- Creep/Flow: Occurs when material is not fully cured, common in uncured thermal pastes but rare in structural adhesives.
- Pumping: Uncommon in adhesives but may occur during thermal cycling of semi-cured gels.
Frequently Asked Questions
Q: Can thermal adhesive be used to bond CPU coolers?A: Generally not recommended. CPU coolers are heavy and require high mounting pressure for optimal performance. We suggest using thermal paste with mechanical clips for secure attachment. Adhesives are permanent and will prevent future upgrades.
Q: Is thermal adhesive conductive?
A: Most standard thermal adhesives use ceramic fillers and are insulating. However, silver-filled epoxy resins exist for specific grounding applications. Always consult the datasheet to verify the “volume resistivity” parameter.
Q: How do I remove thermal adhesive?
A: Sheen engineers note that removal difficulty varies by adhesive composition. Thermal double-sided tape is relatively easier to remove, but all methods carry a risk of damaging components.
Q: Should k-value or BLT value be prioritized in applications?
A: BLT value is typically more critical—both must be optimized simultaneously. Set the k-value based on BLT value/pressure requirements.
Q: Can conductive adhesive replace heat sink fasteners?
A: Only feasible if mechanical loads remain within the adhesive's shear strength range; requires validation through vibration testing.
Selecting the appropriate thermal adhesive requires evaluating factors such as material structure, performance characteristics, and production efficiency. Each material type has its advantages and disadvantages, so it is also essential to assess whether the material meets the requirements for the specific application.
Need a permanent bonding solution that keeps components cool? Contact the Sheen Thermal team today for high-shear thermal adhesives customized to your project's needs.
