The Case for a 1.1mm BGA/CGA PACKAGE

摘要

Most electronics engineers know there is no 1.1mm BGA or CGA package. Because we are forced to use a lmm pitch package, we live with tradeoffs. A slight increase in the pitch size, however, could satisfy the needs for today's high I/O pin count designs. This conclusion comes from my observations of building Class 3 and aerospace lmm pitch products, and the challenges, setbacks, redesigns, returned product, and field failures we all endure. Ideally, we would have the following allowances in a design for performance, layout, compliance and yield: 1.The ability to double tract conductors between via lands. 2.Conductors not less than 0.004". 3.Spacing between conductors not less than 0.004". 4.Drill-to-copper distance of 0.010". 5.Drill diameters of 0.010" and aspect ratios less than 12:1. 6.Annular ring that meets Class 3. (Design should have a land 0.014" over the drill size.) 7.Meets copper plating in the hole 0.001" minimum (IPC-6012 Class 3). 8.If via-in-pad, epoxy fill that meets IPC-6012. 9.A design that passes OM reflow (IPC-TM-650, method 2.6.8) and thermal shock (IPC-TM-650, method 2.6.27B) testing approaching 100%.