Microchip makers and their equipment suppliers are chasing greater scale and breadth as slower growth, rising competition and technology shifts exert new pressures across the electronics industry.

Western Digital Corp., the biggest maker of computer disk drives, on Wednesday disclosed a $19 billion deal for memory-chip maker SanDisk Corp., a key supplier of memory devices for smartphones that is charging into Western Digital’s traditional business supplying computer makers. The deal would make Western Digital the broadest...