West Bond Model 7476E-79 Wedge Wire Bonder STANDAR OPERATING PROCEDURE Version: 1.0 March 2014

Transcription

1 West Bond Model 7476E-79 Wedge Wire Bonder STANDAR OPERATING PROCEDURE Version: 1.0 March 2014 UNIVERSITY OF TEXAS AT ARLINGTON Nanotechnology Research Center (NRC)

2 TABLE OF CONTENTS 1. Introduction Scope of Work Description Safety Hardware Requirements Training System Restrictions Operating Procedures System Pre-Checks West Bond Model 7476E Wedge Bonder operation WestBond 7476E Aluminum (Gold) wire path for 45 Feed. 17 2

3 1.0 INTRODUCTION 1.1 Scope These procedures apply to the West Bond Model 7476E Wedge Wire Bonder. All maintenance should follow the procedures set forth in the manufacturer s maintenance and operations manuals. This document is for reference only. User s must also receive training and be authorized by trained Nanofab staff before operating this equipment 1.2 Description The West Bond Model 7476E Wedge Wire Bonder is an advanced bench-top microprocessor controlled ultrasonic /thermosonic wedge wedge wire bonder designed to manually interconnect wire leads to semiconductor, hybrid or microwave devices. The machine bonds aluminum or gold wire ranging from 0.7 mil to 2 mil (1mil =0.001 ~ 25µm) diameter. Bonds are made by wedge-wedge technique using ultrasonic energy to attach Al wire at room temperature or adding work piece heat for Au wire bonding. Wire is threaded and clamped diagonally using a 45 wire feed assembly to guide the wire under the bonding wedge allowing independent feeding action but requiring front-to-back bonding direction. The three-axis micromanipulator is arrayed above the work plane with range of motion of vertically and in the horizontal direction. The forward pivot tool assembly is built around K-Sine transducer operated at 63KHz and 8Vrms maximum. Thirty separate buffers of bond setting and machine configurations are programmable at the machine front panel and are displayed by a 40 character LCD screen 45 wire feed assembly Programmable bonding parameters displayed by a 40 character LCD screen 3

4 1.3 Safety This tool is connected to HIGH VOLTAGE. The West Bond Model 7476E must be connected to the Main Power source through surge protector power strip. Never perform any maintenance functions while the 7476E is in operation. Always power down the system first and remove the AC plug from the power strip as well. The Back Safety Cover should only be opened after powering down the machine. The safety panels should not be remove or bypassed or there is a risk of electrocution! Read carefully all warnings given in the Maintenance Manual before beginning any maintenance work. If you encounter any electrical malfunctions contact staff immediately Never operate the Bonder with any safety panels or covers removed Always keep your hands out of the Working Area while the Bonding Head is in operation Never touch the Heated Workholders (Au wire bonding ONLY) with your hands or any material with low melting point. The maximum temperature of the Heated Workholder is limited to 250 C. Wait until the heated Workholders are less than 50 C before removing your sample Never touch the Heated tool tip (Au wire bonding ONLY). The maximum temperature of the Heated tool tip is 125 C Beware of touching tools such as tweezers, scissors, and screw drivers as they may have sharp edges. 4

5 2.0 Hardware 2.0 Al wire only (Au wire is not installed). Gold wire requires staff approval to install. Current wire diameter is 1 mil (~25 µm). Current wire feed is 45. Any other wire diameter or wire feed conversion ( 90 ) requires staff approval 2.1 Substrate bonding area up to 1 x 1 (25 mm x 25 mm ). 2.2 West Bond unique three-axis micromanipulator where the entire mechanism is arrayed above the work plane. Each of the X,Y and Z axes is straight-line and purely orthogonal. Range of motion of the tool by the manipulator control is vertically and in the horizontal direction with an 8/1 ratio mechanical advantage. 2.3 Control of motor motions, Ultrasonic energy and machine logic is programmed and executed by Motorola microprocessor an 256KB of nonvolatile RAM. 2.4 Ultrasonic Transducer built around K-Sine US power supply operating at 63kHz transducer and 8Vrms maximum voltage and 4.5 watts. Bonding Force Calibration knob : gr. Set at 28 grams for 45 wire feed. Bonding Time : ms 2.5 Adjustable work height platform with electro less Nickel plating for ESD protection. 2.6 Heated Workholder with temperature control up to 250 C ±0.5 C. (Au wire bonding ONLY). 2.7 Heated Tool Tip with temperature control up to 125 C ±0.5 C. (Au wire bonding ONLY). 2.9 Thirty separate buffers (programs) of bond settings for a wire type can be entered and selected during bonding be a selector switch Microscope and eyepiece for zoom and focusing, platform illuminator and ccd camera. 5

6 3.0 Requirements 3.1 Training All users must be trained and authorized on the West Bond Model 7476E to use this system. Training is supplied by a Nanofab staff member please contact the tool owner to schedule training. 3.2 System Restrictions Users are not allowed to perform any maintenance functions, calibrations, machine adjustments, bonding tool tip or wire diameter changes. Contact staff for any process or maintenance issues that arise Before running the bonding tool attach your device (chip) to a suitable electronic package or a larger size chip carrier using high temperature adhesives. The maximum bonding area is up to 1 x 1 (25 mm x 25 mm ) Use only NanoFab approved tool tips from WestBond or DeWeyl Tool, Inc Note : The choice of bonding tool configuration/styles will depend on the particular applications such wire diameter, pad size, bond length, deep access wire feed or 45 wire feed applications. The 7476E requires the shank diameter of the tool be 1/16 and length be for 45 wire feed and a shorter (0.625 ) or longer (0.828 ) for deep access wire feed applications. The M45A-C /4-CM T=015 BR=001 is a standard 45º tool

7 3.2.4 Do not use the Workholder or Tool Tip heater for Aluminum wire wedge bonding. The use of heat will oxidize Al wire at the surface of the pads. OK to use the heaters only when Gold wire is installed After powering ON the machine wait at least 30 minutes until the machine electronics and Workholder warms up (Au wire bonding ONLY) For Al wire bonding to gold pads or aluminum pads use the WestBond suggested parameter values as a starting point or refer to the clean room logbook for other successful bonding parameters. Suggested parameters 7

8 3.2.7 Do not adjust the bonding force calibration knob above 28 grams. The knobs are set at 28 grams for 45 wire feed The WestBond three-axis micromanipulator motion is Front to Back Only! (Not left to right). Front to Back Only! This requires a NanoFab Management System reservation before using Read any posted NanoFAB Engineering Change Notices (ECN) for any hardware, process or safety changes before running the tool. 8

9 4.0 OPERATING PROCEDURES 4.1. System Pre-Checks Check to ensure all Safety Panels and Covers are installed Check to ensure the Workholder is cool, if not let it cool 30 minutes before setting Workholder height or mounting a device Check to ensure the N2 pressure regulator at the rear of machine is between psi Check to ensure the DeWeyl tool tip and Al wire are installed and threaded If any System Pre-Checks are not in specification call Nanofab staff to check. 9

10 MM DOCUMENT: West Bond Model 7476E Wedge Wire Bonder Standard Operating Procedure Version: West Bond 7476E Manual Aluminum (Gold) Wedge-Wedge Bonding Operation: Workholder Height Adjustment / Programming Bond and Machine Settings/ Performing Wire Bonding/ Heater Operations If you have not completed the System Pre-Checks in steps then you must complete those before proceeding Turn the front panel Main system power switch and microscope LED illuminator ON by moving the toggle switch to the UP position. Turn the ccd camera monitor ON by pressing the monitor power button as shown. Main System Power LED power switch CCD camera monitor Allow the system electronics 30 minutes to warm up and have thermal equilibrium. Check to ensure that the Buffer is set for 45 feed. Check to ensure the Buffer is set for 45 feed Mount your chip holder/device on the Workholder by pressing the mechanical clamp thumb button in and placing the sample between clamp and adjustable backstop. After placing the sample on the chuck release the button to secure the chip from moving. To mount larger packages use the appropriate size allen wrench to adjust the mounting backstop. Samples or chip carriers up to 1.0 X 1.0 can be mounted onto the Workholder. Note : For Gold Wire bonding make sure there is good thermal contact between the Workholder surface and your device package Clamp Button Sample placed between clamp and backstop, adjust if necessary 10

11 Carefully place the Workholder on the work height platform under the bonding tool Looking into the eyepiece adjust the Microscope s FOCUS and ZOOM knobs to view the bonding pads under the wedge of the tool tip. Move the Workholder to obtain a good bonding area field of view. Both die pads and tool tip should be in focus. FOCUS KNOB ZOOM KNOB Adjust the CDD camera s LED illuminator focus by rotating the lens until the image on the monitor is in focus Check for proper work platform height which is critical for quality wire bonding. To check the proper height compare the height of bonding surface to the position of the bonding tool wedge while holding the micromanipulator in its maximum down position. The bonding surface should be approximately mils( um) above the tip of bonding tool. If the work platform height adjustment is required turn the adjustment knob on the work platform as required. 11

12 Looking into the eyepiece re-adjust the Microscope s FOCUS and ZOOM knobs to view the bonding pads under the wedge of the tool tip. Move the Workholder to obtain a good bonding area field of view. Both die pads and tool tip should be in focus For Aluminum wire bonding to gold or aluminum pads check to ensure the Workholder is set to room temperature (20 C to 24 C) and tool tip heater potentiometer is set to 0 as shown. The use of heat will oxidize Al wire at the surface of the pads. Aluminum wire Set to room temperature (20 C to 24 C) Set to For gold wire bonding to Aluminum or gold device pads refer to section for heater operations and thermosonic process information using the substrate and/or wedge tool heaters up to 150 C then continue to section Programing the Machine settings and Bond settings. The 7476E has two programmable sections, one section is MACHINE SETTINGS and the other is BOND BUFFER SETTINGS. The Machine settings are used for initial machine setup and are infrequently changed. The Bond settings are commonly used by the operator and have factory suggested values available. Machine Settings : Bond Settings : : Wire Pull o Bonds per Wire Wire Tail o Ultrasonic Power DualForce/Calibrate o Ultrasonic Time (High/Low) o Force (High/Low) Beep on Contact o Loop Height Bond Counter o Drop Before Clamp(45 Only) UltrasonicPower during Feed Self Thread Model/Software Revision Level 12

13 The Bond settings are accessible by pressing the EDIT switch from the Main screen. The other bond settings are accessed be pressing the PREV / NEXT switch. Adjustments to the ultrasonic power and time settings are used to accomplish visually correct wire bonds or based on pull-tests results. NOTE: o o For thermocompression bonds the ultrasonic power is set to zero. The bonds are more responsive to a power level increase than to a time increase. A change in time is a gentler way to affect the bond At the Machine Setup / Calibrate Force page use the gram gauge to verify the force is grams as shown. DO not adjust the bonding force calibration knob. The knobs are set at 28 grams for 45 wire feed The last screen for Machine and Bond setting adjustments will display [ END OF BOND & MACHINE SETTINGS ]. Press EDIT to escape. 13

14 The hand controls on the 7476E are designed for minimal exertion of the hands and fingers. During operation the operator should rest his/her hand, wrist and forearm on the tabletop so that the thumb, index and middle fingers gently grip the manipulator knob. With the work piece centered in the microscope, and the tool centered to the optics the movement of the manipulator is normally within +/- ½ inch To produce the produce the first wire bonds use the micromanipulator to lower the bonding tool to the first bond location and gently touch the tip of the tool to the bond surface. An audible beep will be heard while the bond is being made. After completing the first bond gently lift the micromanipulator and move the bonding tool through the looping path (Front to Back only). When the tool has moved to the program height another beep will be heard. Continue to move down to the second bond site and gently touch the tip of the bond tool to the surface. An audible beep will be heard when the second bond is made. Repeat steps (Re-adjust the Microscope s ZOOM and FOCUS knobs) and steps to for each bond pair When you have finished your wire bonding move Workholder completely to the side so that no part of it remains under the bond tool and remove your device from the Workholder by pressing the mechanical clamp thumb button IN and removing the device that is between clamp and adjustable backstop. (For gold wire bonding if the heater was used allow the heater and device 30 minutes to cool down before removing you device). 14

15 Turn OFF the microscope illuminator, CCD monitor the system power. LED power switch CCD camera monitor Main System Power Enter required information in the logbook For Gold Wire Wedge Bonding turn the K~1200D Workholder temperature controller ON by moving the toggle switch to the up to the ON position as shown. Note : For Gold Wire bonding make sure there is good thermal contact between the Workholder surface and your device package Check that all indicator lights and segments are illuminated for several seconds; once the start-up sequence is completed the K~1200D will return to the normal operating mode. After power up the display will show the actual Workholder temperature. To change the set point temperature push and hold the SELECT key,use the INCREASE /DECREASE arrow keys to select the desired operating temperature. WARNING: Do not depress the program button labeled p unless you intend to change the operating program of the K~1200D. 15

16 The 7476E is equipped with a radiant heater for the wedge bonding tool temperature control. The bonding tool temperature is adjusted by the potentiometer located on the right side of the front panel marked Tool Heat CW direction Use the following chart to set the bonding tool temperature. Typically 80C to 150C will produce good Au on Au bonds After you have set the temperatures allow enough time for your pads to reach thermal equilibrium the proceed to section to continue the bonding procedures When you are done with the gold wire bonding turn the K~1200D temperature controller back to room temperature and turn power switch to OFF position. Turn the TOOL HEAT OFF by turning potentiometer CCW to

17 4.3. WestBond 7476E Aluminum (Gold) wire path Before continuing with this procedure go back a read Section 1.3 Safety Check to ensure the Al or Au wire is properly threaded through the 45 feed as shown. This can be done by using the microscope s ZOOM and FOCUS knobs and CCD camera monitor. If the wire is not threaded properly proceed to next step. 17

18 4.3.3 Using tweezers, scissors and careful eye hand coordination re-thread the wire as follows. The wire 1 st de-spool over the top of the spool, the routes through the guide tube, through the back of the 45 clamp and over the clamp shelf located on the front side of the 45 clamp; finally through the tool tip. To open the clamp press the FEED/OPEN switch UP once, to close the clamp press the FEED/OPEN switch DOWN once If you have difficulties threading the wire call staff to assist. 18