BGA Substrate Design

Very often IC package design requires designing a BGA substrate. Substrate design and layout is very similar to any other PCB design. The difference is that the substrate size is much smaller than most of the PCBs you have seen. In this post we do something a bit unusual and recommend a Free EDA tool (FREE!).

The substrate is a small PCB located inside the BGA package. Substrate design consists of layout of all signals from the package balls to the wirebond pads (in case of Wire Bond) or to the bump pads (in case of Flip-Chip).

Whether the BGA substrate design is done by the assembly house or by an external company specializing in substrate layout, you will need a tool to review the work as part of the development and sign off process.

Cadence has a free tool, called Allegro, which is very helpful for this task.

Allegro

The Cadence® Allegro® FREE Physical Viewer allows you to view and plot databases from Allegro PCB Editor, Allegro Package Designer, and Allegro PCB SI technology.

Download here: http://www.cadence.com/products/pcb/Pages/downloads.aspx

We are very happy with the tool.  It’s easy to use and offers all the required features to review the substrate design.

You can consider the Allegro as an MCM file viewer.

What is an MCM File

As the EDA market evolved and created various file extensions, the IC package design guys got the MCM extension — it the IC Package Design File format . The MCM file describes the package outline, the substrate layout and the pads.

It’s basically the same format as a .brd file which is used for PCB designers, but intended for IC packages. Currently, MCM file is a de-facto standard for package design database and the majority of the package/assembly houses will send out MCM files for review.