| 摘要 |
A method and encapsulation material for encapsulating the solder joints of an IC device mounted on the substrate of an electronic circuit assembly. The encapsulation material is formulated to be sufficiently opaque to x-radiation to enable the use of x-radiation imaging techniques to detect air pockets and voids in the encapsulation material that might degrade the fatigue life properties of the solder joints encapsulated by the encapsulation material. For the purpose of enhancing the fatigue life properties of the solder joints, the encapsulation material contains a filler material dispersed in a polymeric material, such as an epoxy, such that the encapsulation material is characterized by a coefficient of thermal expansion approximately equal to that of the solder joints. The filler material contains a sufficient amount of an element to render the encapsulation material opaque to x-radiation. Generally, suitable elements are those having an atomic number of at least about 35, such as lead, barium, zirconium, mercury, bismuth, tantalum, tin and tungsten. The element may be present as an oxide, particularly if the filler material is glass microspheres.
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