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Norland Electronic Adhesives 123THGA ("NEA 123THGA") is a single component, low outgassing, adhesive that cures tack free in seconds to a tough, resilient polymer when exposed to ultraviolet light. It is recommended as an extremely fast and efficient way to tack, fill, seal or bond precision components or wires in place. With this system, a drop of adhesive is used to form a bridge between the component or wire, and the substrate. Exposure to UV light quickly cures it, and holds the component in place. Useful applications for NEA 123THGA include HGA bonding, wire tacking, chip capacitor bonding, glob top, and tamper proofing adjustable components.
The unique advantage of this adhesive is that even though it cures in seconds, it is extremely stable when not exposed to ultraviolet light. Norland 123THGA is sensitive to the whole range of UV light from 320 to 380 nanometers with peak sensitivity around 365 nanometers. Cure time is dependent on light intensity and thickness of adhesive layer. The adhesive has been designed to be spot cured in small areas with hand held or desk top UV light sources that are safe and easy to use.
| HAND HELD | MANUFACTURER | APPROX. CURE TIME |
| Opticure LED 200 |
|
5-10 seconds at 1/2 inch |
| Opticure 4 Light Gun |
|
90 seconds at 1/2 inch |
| DESK TOP | MANUFACTURER | APPROX. CURE TIME |
|
40 minutes at 6 inches |
Faster cure times are possible with medium pressure vapor lamps (typically 200 watts/linear inch). These are most commonly used in conveyorized applications because the light must be shielded from the operator. These types of lights are available from companies such as American Ultraviolet or Fusion UV Curing Systems.
In addition to the UV cure, Norland 123THGA contains a latent heat catalyst that can quickly cure areas that do not see the ultraviolet light. The catalyst allows the adhesive to cure in 10 minutes at 125° C in a convection oven, or 3 hours at 80° C. Faster cure times are possible with infrared ovens. Temperatures less than 60° C will not appreciably activate the adhesive. The advantage of the heat cure is to bring partially cured adhesive to full cure to get the maximum physical properties of the adhesive. The heat cure is not required if all the adhesive receives proper exposure to UV light.
NEA 123THGA has very good adhesion to glass, metals, printed circuit boards and many plastics. Since the cure is very exothermic, the adhesive should be allowed to cool back to room temperature before adhesive testing begins.
Typical Properties of NEA 123THGA
| Temperature Range | -150 to 150° C |
| Viscosity | 465,000-515,000 cps |
| Elongation at Failure | 25% |
| Modulus of Elasticity (psi) | 321,000 |
| Tensile Strength (psi) | 3,790 |
| Hardness - Shore D | 80 |
| Dielectric Constant (1 MHz) | 3.852 |
| Dissipation Factor (1 MHz) | 0.040 |
| Volume Resistivity (ohm-cm) | 1.7 x 10 to the 15 power |
| Surface Resistivity (ohms) | >1.0 x 10 to the 15 power |
| Dieletric Strength (volts/mil) | 814 |
| Arc Resistance (sec) | 100 |
NASA Outgassing Test, ASTM E-595-90
Type of Cure % TML % CVCM % WVR\
UV-Cure (only) 1.74 0.03 0.20
UV-Cure plus 125 ° C/12-min 1.55 0.03 0.22
TML = Total Mass Loss. CVCM = Collectable Volatile Condensable Material. WVR =Water Vapor Regain.
To remove uncured adhesive from substrate use an acetone or alcohol moistened cloth. The cured adhesive can be removed by prying the drop with a knife edge or soaking in a solvent combination of 90 parts methylene chloride and 10 part methanol.
CAUTION: Norland Electronic Adhesive 123THGA may cause skin irritation and prolonged contact with skin should be avoided. If contact occurs wash well with soap and water. Use in well ventilated area.
Store in a cool dark place. CAUTION: Do not freeze material. Never expose the bulk material to high heat or ultraviolet light. It can generate an extremely exothermic reaction.
