An apprentice asks a fair question: if fine-pitch QFPs already work and are far easier to inspect and rework, why did the industry move processors onto ball grid arrays at all? What is the section's answer?

Select one answer.

• Cost — spheres attach faster than leads form, and the package price drove the transition more than any electrical need.
• Arithmetic: a perimeter package's pin count grows with its edge — four sides, one row — while silicon's appetite for connections grew much faster: hundreds of power and ground pins for clean delivery, wide buses, radio and display lanes. The area array scales with the square of the package size and carries what no affordable perimeter could.
• Thermals — the ball field conducts die heat into the board's copper far better than gull-wing leads ever could, and processor power density forced the change, which is why the packages with the hottest silicon converted first and the cool peripheral chips kept their leads for another decade — the thermal-first migration pattern that tracks exactly which silicon converted when.
• Automation — area arrays self-center at reflow while leaded packages need vision alignment, and the assembly-line yield gap decided the packaging war.