An Independent Journal Dedicated to the Advancement of Chip - Scale Electronics July - August 2000 Email the editor

Chip-scale package manufacturing supports different IC devices in similar process steps. For efficiency, different devices are processed using common frames or strips. The common device sites in a strip allow for common die attach and singulation programs at the cost of fewer device sites per strip. For highest manufacturing efficiency, however, device-specific characteristics such as die size, number of I/Os and bond-pad location require device specific programs on the equipment.

By Jerry Secrest Contributing Editor

Device specific programs may be needed at:

• Die attach
• Lead bond
• Ball/bump placement
• Singulation

A process line dedicated to one product allows the process programs to be resident on the equipment.

Each lot coming through the line would have the same program, and no equipment set-up is required. Alternately, a CSP process line supporting a number of devices will need quick changeovers between products to maintain high equipment efficiency.

Quick Changeover

The quick changeover can be accomplished by automatically selecting the program based on reading the magazine, strip, frame or reel ID.

Another requirement is to improve process yield and quality.

Detecting equipment errors on-line is one method. Automation of the process line allows detection of equipment errors by collecting and processing equipment alarms on-line.

As soon as a specific alarm condition is detected on equipment, a line computer can send a command to the equipment to stop processing.

This "stop" command minimizes the number of parts that may be lost to scrap and keeps defective parts from contaminating the lot.

The level of automation I'm writing about can be achieved without inventing any automation methods.

Software Standards

Process program control, equipment monitoring, remote equipment control and alarm messages are available from the SEMI SECS (SEMI equipment communications standards) and GEM (generic equipment model) software standards.

SEMI's SECS offers a library of messages useful in CSP manufacturing automation. GEM supplies the guidelines for implementing the messages to support automated factories.

Other useful messages for automation are the mapping of strips and frames.

Figure1 Automation hook-up Mapping enables testing the devices in the frame, transferring the test result frame map to the part marker, and then to the picking machine after singulation. The frame maps can be considered to be small wafer maps. Mapping messages are also available in SECS. Mapping messages between the equipment and a line computer are useful in the assembly of stacked CSP packages. Speed-tested die mapped on the wafer can be matched to speed-tested die from another speed-tested and mapped wafer. This process achieves higher packaged part yields through assuring the devices in the package are the same speed.

Not all CSP process lines will need automation. SECS assists specifically in implementing automation where automation will provide a benefit.