A process window defines combinations of settings that consistently meet visual, dimensional, and mechanical requirements. Designed experiments and capability data make the window repeatable across lots and tools.
Pull and shear strength reflect bond formation, wire properties, geometry, and failure mode. Improvement requires interpreting where the sample fails, not simply increasing the measured force.
Non-stick-on-pad defects can result from contamination, oxidation, poor capillary condition, weak ultrasonic transfer, pad damage, or incorrect setup. Structured checks prevent random parameter changes.
Bond force, ultrasonic energy, time, temperature, tool condition, and material quality interact to form the bond. A robust recipe creates adequate deformation and intermetallic contact without pad damage.
Gold, copper, silver, and aluminum wires differ in conductivity, hardness, oxidation behavior, cost, and process requirements. Diameter, coating, pad finish, and package environment also affect selection.
Ball bonding is fast and commonly uses gold or copper wire, while wedge bonding supports aluminum wire, lower loop profiles, and directional geometries. Product design and materials determine the best method.
A reflow profile should activate flux, limit thermal shock, create complete wetting, and avoid excessive intermetallic growth. Preheat, soak, time above liquidus, peak temperature, and cooling rate all matter.
SAC alloys are widely used, while low-silver, bismuth-containing, tin-copper, and specialty alloys address cost or temperature needs. Selection should consider reliability, melting range, finish compatibility, and rework.
Production reliability improves through compatible finishes, controlled paste printing, stable reflow, suitable joint geometry, cleanliness, and feedback from inspection and reliability data.