2025-03-28
Mechanical structure characteristic
mechanical structure characteristics
First, mechanical structure characteristics
1.1 Encapsulation architecture type
| Encapsulation form | Structural feature | Mechanical strength index | Typical application scenario |
| Lamp type | Epoxy coated + metal leads | Bending strength <5N | Pilot light, decorative lighting |
| SMD type | Ceramic/metal substrate + silicone package | Shear strength >10N/mm² | Backlight, general lighting |
| COB type | The multiple chips are directly bound to the aluminum substrate | Strong thermal mechanical stress tolerance | High power lighting |
| CSP type | Bracket less chip-level package | Excellent impact resistance | Miniature display, car lights |
1.2 Key mechanical parameters
- Wire bonding strength: Gold wire bonding force >5g (MIL-STD-883 standard)
- Package hardness: silica gel package Shore hardness is usually A50-70
- Coefficient of thermal expansion (CTE) matching:
The CTE difference between the chip (7ppm/℃) and the substrate (6-20ppm/℃) should be less than 5ppm/℃
Two.Mechanical properties of materials
2.1. Packaging material performance comparison
| Material type | Elastic modulus (GPa) | Fracture toughness (MPa·m¹/²) | Maximum operating temperature |
| Epoxy resin | 2.5-3.5 | 0.6-1.0 | 120 ℃ |
| Organic silica gel | 0.01-0.1 | 0.3-0.5 | 200 ℃ |
| Glass package | 70-90. | 0.7-1.2 | 500 ℃ |
2.2 Mechanical properties of substrate materials
- Alumina ceramics: bending strength 300-400MPa, thermal conductivity 25W/mK
- Aluminum nitride ceramics: bending strength 350-450MPa, thermal conductivity 180W/mK
- Aluminum substrate: tensile strength 150-200MPa, CTE 23ppm/℃
Third, environmental mechanical reliability
3.1 Vibration and shock test standards
| Test type | Condition parameter | Acceptance standard |
| Random vibration | 20-2000Hz, 10Grms | No structural damage |
| Mechanical impact | 1500G, 0.5ms half sine wave | Electrical properties change <5% |
| Drop test | 1.5m height free fall | Appearance intact |
3.2 Thermal mechanical reliability
Temperature cycle test:
- After 1000 cycles at -40℃~125℃, the light decay is less than 10%
- Main cause of failure: welding joint cracking caused by CTE mismatch
Thermal shock test:
- Liquid Nitrogen (77K)←→ Boiling water (373K) Fast switching
- Passed 500 test requirements
Four.Failure mode and mechanism
4.1 Typical mechanical failure
- Lead breakage: Metal fatigue due to vibration (following the Coffin-Manson model)
- Package cracking: Thermal stress induced interface delamination (JEDEC JESD22-A104 standard)
- Solder joint failure: Creep fatigue interaction (Darveaux model prediction)
4.2 Accelerated life model
Among them:
- Nf:Number of failure cycles
- Δεp:Plastic strain range
- Q:Activation energy (Gold wire bond contract 0.5eV)
five.Advanced mechanical technology
5.1 Stress resistance design
- Flexible interconnection: Copper column convex points instead of gold wire bonding (spacing <50μm)
- Stress buffer layer: Add silicone rubber transition layer (reduce interface stress by 40%)
5.2 Miniaturization technology
- 3D package: Chip stack thickness <0.5mm
- Embedded LED: directly packaged inside the PCB (60% thickness reduction)
Six. Test and standard system
6.1 Key test methods
- X-ray inspection: Observe the internal bond line topography (resolution <1μm)
- Acoustic microscope: Detection of package delamination defects (accuracy 50μm)
- Micro force tester: Measuring solder joint shear force (accuracy 0.1g)
6.2 International standards
- IEC 62031: General safety requirements for LED modules
- MIL-PRF-19500: High Reliability LED military standard
- JESD22-B104: Mechanical impact test specification
seven.Engineering application guide
Selection suggestion:
- High vibration environment: CSP or COB package is preferred
- High temperature environment: Choose aluminum nitride substrate + silicone package
Design criteria:
- Keep the CTE matching difference <3ppm/℃
- Avoid 90° sharp Angle structure (50% reduction in stress concentration factor)
Failure analysis:
- Thermal mechanical stress is simulated using finite element analysis (FEA)
- Implementation of Weibull distributed reliability prediction
Mechanical parameter curves for specific package types (such as SMD device vibration fatigue curves) or more in-depth failure case studies are available!
For more knowledge about LED industry, please pay attention to our LIKELIGHT.If you are not sure which LED fixture is best for your project or need help with layout configuration, contact us LIKLEIGHT, we are a professional manufacturer of LED lamps in China;we have engineers and 24 hours customer service for you.Phone:+86-755-23328395, Email :contact@like-light.com,Wechat/WhatsApp:86-132-66666-320.
