No abstract

No abstract

The effects of sintering process conditions on the size shrinkages of low-temperature co-fired ceramic (LTCC) substrate were investigated. The process variables investigated were thickness of the stacked raw tapes, lamination pressure, lamination-pressure holding time, pre-heating time, debinding time, sintering dwell time, and sintering temperature ramp. Results revealed that the size shrinkage percentage of the LTCC samples in the lateral directions was always smaller than that in the thickness direction. The lateral shrinkage deviations were less than 2.1% for all the experiments conducted in this study. Pre-heating time, lamination-pressure holding time, debinding time, sintering dwell time and sintering temperature ramp had almost no effects on the lateral size shrinkage of the LTCC samples, and the average of the lateral shrinkage values was 15.3%, with a standard deviation of 0.17%. Lamination pressure and stacked raw-tape thickness had effects on the lateral size shrinkage of the LTCC samples, and empirical equations for calculation of the size shrinkage values were obtained by curve fitting.

A challenge in selecting and applying lead‐free solders lies in separating the influences of materials' properties, fluxes and processes to obtain robust assembly conditions that are compatible with PCB finishes and all component terminations. This paper discusses simple steps towards establishing a lead‐free assembly process. With reference to results of solder paste spread and wetting tests and component solderability tests, some of the current limitations in applying standard test methods to lead‐free evaluations are highlighted.

PurposeThe purpose of this paper is to present the results of experiments performed to attach silicon dies (chips) to low‐temperature co‐fired ceramic (LTCC) substrates with Ag or AgPd pads using SnAgCu or SnPb solder and the results of the characterization of the solder joints.Design/methodology/approachLTCC substrates were fabricated by stacking and laminating four green tapes with the top layer screen‐printed with Ag or AgPd paste to form pads. Silicon die sizes of 1 × 1 mm and 2 × 2 mm with electroless nickel immersion gold plated were soldered to 2 × 2 mm pads on the LTCC substrates using SnPb or SnAgCu solder. The solder joints were then characterized using X‐ray, die shear, energy dispersive X‐ray and scanning electron microscopy techniques.FindingsThe joints made by AgPd pads with SnAgCu solder provided the best results with the highest shear strength having strong interfaces in the joints. However, the joints of Ag pads with SnPb solder did not provide high‐shear strength.Originality/valueThe findings provide certain guidelines to implement LTCC applications. AgPd pads with SnAgCu solder can be considered for applications where small silicon dies need to be attached to LTCC substrates. However, Ag pads with SnAgCu solder can be considered for lead‐free solder applications.