Derating Nominal Equipment Speeds for Mixed Package Electronics Assembly Line Balancing
Derating nominal placement speeds based on package mass, feeder width, and vision complexity is required to establish accurate line balance and cost models.
Mixed Package Assembly
Hybrid Assembly
Production lines must often handle boards that feature a wide variety of component types and sizes. In a single pass, mixed package assembly involves the placement of tiny passive chips alongside integrated circuits. This diversity requires the pick and place machine to change nozzles and adjust vision parameters frequently.
The process challenges the ability of the line to maintain a high speed while ensuring accuracy for every part.
Process Complexity
Stencil design becomes difficult when small components require thin solder paste and large components require thick deposits. Multi-level stencils or solder preforms are used in mixed package assembly to provide the correct volume of alloy for each pad. The reflow profile must also be carefully managed to avoid overheating small parts while ensuring large parts reach the required temperature.
Heavier components may require higher placement force than delicate sensors. These competing requirements often lead to compromises in the overall process window.
Defect Risk
Solder balling and tombstoning are common when the thermal mass varies greatly across the board. Success in mixed package assembly depends on sophisticated software that can optimize the placement sequence for speed and safety. Rigorous inspection is necessary to verify the solder fillets on disparate joint types.