Embodiments of the present disclosure are directed to techniques and configurations for an integrated circuit (IC) package having an underfill layer with filler particles arranged in a generally random distribution pattern. In some embodiments, a generally random distribution pattern of filler particles may be obtained by reducing an electrostatic charge on one or more components of the IC package assembly, by applying a surface treatment to filler to reduce filler electrical charge, by applying an electric force against the filler particles of the underfill material in a direction opposite to a direction of gravitational force, by using an underfill material with a relatively low maximum filler particle size, and/or by snap curing the underfill layer at a relatively low temperature. Other embodiments may be described and/or claimed.