Reliability of metallized ceramic packages

Thin-film circuitization on a dry-pressed alumina ceramic substrate has been a popular approach to developing low-cost ceramic quad flat pack (CQFP) and pin grid array (PGA) packages in the industry. Such material/process sets have also been suggested for simply designed low-cost ball grid array (BGA) packages. Due to the nature of processes involved in manufacturing, and due to handling, these metallized ceramic packages can occasionally possess circuit-line abnormalities. At the present time, all modules with such circuit-line abnormalities are eliminated since they are believed to affect the long-term reliability of the product. The goal of this paper is to understand what impact the circuit-line abnormalities have on the reliability of the metallized ceramic packages. The reliability assessment is carried-out through environmental stress tests correlated with elastic-plastic three-dimensional (3-D) finite element (FE) analyses of idealized circuit line abnormalities. Ninety-three parts with circuit-line abnormalities were thermally cycled between 0/spl deg/C and 100/spl deg/C. Ninety one of these parts survived over 5000 cycles of the test. The FE models showed that the stresses in the circuit lines with abnormalities were mostly elastic over the test temperature range, and so the failure of these circuit lines with abnormalities was governed more by the physics of high-cycle fatigue than by low-cycle fatigue. The tests and models indicate that metallized ceramic substrates are robust under thermal cycling and circuit-line abnormalities caused by manufacturing processes do not reduce the useful life of the product.