With many computers, the heating effects of solar radiation are more taxing than material degradation. Computers are generally manufactured with metal enclosures. On the other hand, LCDs may suffer from both heating effects and material degradation. Coatings may degrade somewhat with color changes but the impact of plastic becoming brittle, for example, does not apply to a computer. A computer used outdoors can become very hot with the subsequent impact on keeping the internal components within operating temperature specifications.
The maximum surface and internal temperatures attained by materiel will depend on:
- the temperature of the ambient air.
- the intensity of radiation.
- the air velocity.
- the duration of exposure.
- the thermal properties of the materiel itself, e.g., surface reflectance, size and shape, thermal conductance, and specific heat.
Material can attain temperatures in excess of 60°C if fully exposed to solar radiation in an ambient temperature as low as 35 to 40°C. Paint color and composition can have a major impact on surface temperature.
810G Method 501.5 (High Temperature) mentions Method 505.5 as a factor to consider (Aggravated solar) when determining effects of high temperature. In addition, Method 503.5 (Temperature Shock) also references 505.5 in section 2.3.1 for ‘Climatic Conditions’.
The impact of solar radiation heating effects include:
- Jamming or loosening of moving parts.
- Weakening of solder joints and glued parts.
- Changes in strength and elasticity.
- Loss of calibration or malfunction of linkage devices.
- Loss of seal integrity.
- Changes in electrical or electronic components.
- Premature actuation of electrical contacts.
- Changes in characteristics of elastomers and polymers.
- Blistering, peeling, and de-lamination of paints, composites, and surface laminates applied with adhesives such as radar absorbent material (RAM).
- Softening of potting compounds.
- Pressure variations.
- Sweating of composite materials and explosives.
- Difficulty in handling.
Trimble Kenai®, Yuma® 2, Nomad® 1050, Juno® T41 and Ranger™ 3 all passed the Solar Exposure Test 505.5, Procedure II for prolonged solar exposure.