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The wirebonder is located in Pallavi Dhagat's lab. Once trained, users need to schedule with Pallavi at least 24 hours in advance before using the wire bonder.

The system is a West Bond 7476E and is set up in wedge bonding mode. As of now (2025) the wire bonder is using aluminum wire to bond.

The wirebonder manual:{{7476E Manual.pdf}}

As of January 2026, West Bond is no longer operating. Matt Ritchie (who did a service visit Dec '25) started a company and is doing service work on the tools: [[https://www.norcaltechsales.com/|NorCal Technical Sales]].

====== Introduction to Wirebonding ======

This video give a good introduction:

https://www.youtube.com/watch?v=mvZ1dJuvenw

====== Wedge bonding Theory ======

Wedge bonding relies on the application of ultrasonic power and force to bond the wire (bonding wire) to a metal pad (bonding pad). The careful application of both force and ultrasonic power deform the wire and diffuse the wire metal into the pad without weakening the wire too much. The strength of the wire after bonding is shown below as a function of deformation from ultrasonic energy and force applied.

{{wirebonding_optimization.png?700}}

Outside the optimal range, 
Foot lift: the bond pulls off the pad, meaning the metals didn't have intimate contact.

{{wirebonding_foot_lift.png?400}}

Weak bond: the wire was deformed too much by the bond tool.

{{wirebonding_weak_bond.png?400}}

The surface quality is also important. While the deformation needs to be managed, clean and properly adhered bond pads are important to successful bonding.


==== Threading ====

There are two key locations the wire must thread through. 
1. The shelf
2. The wedge tool

To get the wire through the shelf, you can open the clamps manually.

((pic here))

When properly through the shelf, the wire will not pull out of the clamp when the clamp is open.

((pic of wire hanging down))

To get the wire through the wedge, get a sharp piece of wire by clipping it with two tweezers, and fish through the eyelet. It gets easier with practice.

===== Making Bonds =====


Setting sample height: Pull the bond tool all the way to the bottom of its travel and raise the sample so it is almost in contact. Then, raise the stage half a turn. This should allow you to control with just your fingers and wrist.

Bonds should be made by moving in straight lines like a helicopter: Touch down briefly to make first bond, raise straight up, move to next bond site, and touch straight down to make second bond. Bonds are always made from the pad closer to you, to the pad farther from you.

((diagram))






====== Maintenance and calibration ======



===== Tuning Deformation With Ultrasonic Energy, and Force =====


The wire should be deformed about 150% of the original width. See below:

{{wirebonding_deformation.jpg?400}}

To tune this, do the following:
The force is set by the wire diameter. 25 mil gets 30 g of force as measured by the dynamometer. 

Start with a low ultrasonic energy, 150, and increased until the wire bonds consistently. If you get to the maximum, your issues may be related to the surface quality.


==== Measuring the force ====
((Include a picture showing where this is adjusted and how to measure.))

For 25 mil wire, 30 g of force is recommended.

===== Testing the ultrasonics =====


There are a handful of electrical tests for the tool. When Matt Ritchie, the engineer from West Bond, was here, he did three. 
- Test the oscillator frequency
- Test the output voltage, V_rms, (See 4.12)
- Test the transducer frequency. This one is important as it relates to the life of the tool.

These are on pg. 26 of the manual

===== Aligning the clamps =====

Realignment should be done with the tool threaded. The 

To change the separation of the clamp and wedge, open the motor settings by holding down edit while powering on. During the site visit, 46 was a good known setting. This relaxes the constraints on how aligned the tool needs to be in order to get good feed of the wire. If this is set too high,  the wire will not come in at the right angle.

The wire should come out of the bond tool straight towards you when everything is aligned.

====== Chip Packages ======
For chips going into the Cryostat in 308, they must be wirebonded to a [[https://www.spectrum-semi.com/products/sidebraze|Dual In-Line Package (DIP)]]. There are a few steps to prepare:
  - Cut the chip to size. You can use a razorblade as a shield for the sensitive part of the device while you scribe your substrate.
  - Clean your package if it was previously used. Cleaning silver paint is a pain, so it can be beneficial to but new packages if we can afford it.
  - Tack your chip (and maybe a filler chip, see below) to the package using silver paint. The back of a wooden Q-tip is great as it will leave just enough paint to hold the chip, but not make a mess. 

Once dried, you can wirebond.
==== Filler chips ====
If you want to focus a laser on your chip while in the cryostat, you'll need to ensure it is tall enough that it can sit in the focal plane of the objective you're using. To help, you can raise your chip up by tacking a "filler chip" in and then tacking your "device" chip on top of that.


====== Misc. ======

  * The wedge tools can build up with Al. Used 5% Sodium Hydroxide bath to dissolve the Al, then alcohol clean up.
  * Industry standard is to replace Al wire every 12 months.
  * The drop before clamp parameter is better left off. When on, when lowering the tool after the first bond, the clamp will engage. This tension can be problematic.
  * The loop height parameter only changes when the tool beeps when raising the bond head. It has no mechanical impact on the bond.