BACKGROUND• Performance inconsistencies occur due to operation complexity of the processes.

• A rotation of die of less than 1◦ is required, but less than 3◦ is achieved.

• Using FMEA and fault tree a hybrid approach is proposed to improve quality of the bonding process.

CURRENT CONDITIONS• Stage I: PR recognizes the die and collet moves towards the wafer table. When the collet is close enough,

the vacuum created in the collet as well as the impact push from the ejector cam move the die from wafer table to collet. (Part misalignment causing rotation)

• Stage II: The bond arm rotates from the PR system to the lead frame where the die has to be attached. (die slipping)

• Stage III: The die is positioned on the lead frame in the required position. (Problems similar to stage I)

GOALSThe goal is to reduce the orientation error of the bonded die from less than 3◦ to less than 1◦ with maximum failure rate of 5% for light emitting diode (LED).

ROOT CAUSE ANALYSIS

Metric Target Actual

Orientation Angle 1◦ 3◦

Failure Rate 5% 5%

Root Cause Countermeasures

Stage 1 die rotation detection error New improved PR algorithm

Rotational bond arm movement error

Linear movement of bond arm would reduce impact of stage 2 move errors

Wafer table not controlled satisfactorily

Replace current stepper motor with DC servo motor to control position with the closed loop system

Wafer table position error Redesign wafer table to have a floating structure

Irregular shape die Work with current supplier or find a new supplier to improve quality associated with die shape and size

ANALYSIS• Part misalignment is identified as the main cause problem to cause the rotation in stage I.• The die rotation movement can cause die slipping around the collet if the holding force is not strong enough.• For stage III as well part misalignment causes the die to move in the horizontal plane.

RECOMMENDATIONS• An early event is more important than a later event• A repeated event is more important than a one-off event• More critical events should be given higher priority• The die rotation error was reduced from 3◦ to 2◦ ,but the target is to make it less than 1◦

• There was 30% reduction in die rotation and also by simplification of fault tree the process can be improved

Reduce the Orientation error In Die Bonding process using hybrid approach Presented by : Aditya Kamble & Rohan Naik