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July 2006

Wire Bonding Tools & Questions

 

Q: A purchase for a Palomar 2460-V is in the works. Is the programmable lighting option worth the additional expense? What’s your recommendation after working with systems with and without the option?

A: Cognex gray scale pattern recognition has made programmable lighting a solution without a problem. It would be absolutely necessary with the prior extremely light sensitive View Engineering pattern recognition systems on the 2460-II and 2460-III. Not so with the 2460-V! You can virtually turn the lighting off and Cognex will still locate the programmed point precisely.

Q: When we press the ‘SPEC FTNS’ key on our Palomar 2460-V to focus the system on a die, we never seem to get the same height as when the capillary touches down on the pad to determine height. Is this normal?

A: I’ve never had the numbers match yet. I always determine the part height by having the capillary touch the part on a non-used pad or a part of the die that does not contain active circuitry. Never depend on the information Cognex displays, Cognex focus and exact part height for bonding are two different things.

Q: Our gold ball wire bonder came with a de-spooler. What is its function? It’s driving our operators nuts. Can we remove it without destroying the machine’s bonding capability?

A: A de-spooler is usually an advantage when bonding with a wedge bonder using aluminum wire. Aluminum wire can retain a significant spool memory and the de-spooler reels the wire off the way it was spooled on and avoids the memory problem. It is an absolute requirement when using ribbon wire for the same reason. Feel free to remove the de-spooler but keep in mind you will need a wire spool cover and may need a new trumpet wire feed glass tube designed for use without a de-spooler. If the wire hangs up excessively, contact me for the standard wire feed guide.

Q: What is the proper use of the Hughes Adaptive Bonding System (ABS)?

A: The ABS system provides a current and voltage mode. Since the transducer is current driven, the current mode electronic feedback loop attempts to increase the current to the generator to maintain the programmed transducer excursions until the maximum power output of the generator is reached. The current mode was originally designed to be used on thick film and difficult to bond surfaces. Usually only the stitch will terminate on this type of surface.

In the voltage mode, the feedback mode is not active and the transducer excursions will stall out naturally, in theory, after a perfect bond is made. The voltage mode was intended to be used on easily bonded surfaces such as die pads and thin film. Usually, a ball is placed on these surfaces.

If you are bonding to a die and cratering with the current mode, I would recommend trying the voltage mode. It is not as robust and is less likely to cause cratering. Many, if not most of the companies I work with, use the current mode on pads, thick film, pins - virtually everything. Understanding the ABS modes and applying them wisely in your application is instrumental in wire bonding performance. Most of the manuals provide diagrams and a much more comprehensive explanation of the modes than is possible here.

Q: We get a large number of stitch bonds with a torn wire sticking up directly in the center of the stitch crescent. What’s happening?

A: The adhesion between the deformed wire and the surface gold in the stitch bond is greater than the breaking strength of the wire. This is a variation of stitch lifting, but usually when the stitch lifts, the adhesion is lower than the breaking strength of the wire and a long lifted wire results. The solution is the same; increase the force and ultrasonics incrementally. When the wire breaks above the stitch rather than at it, the stretched broken wire in the center of the crescent occurs. The other possibility is low clamping force causing the wire to slip before it is broken. Try increasing the force and ultrasonics before making any clamp tension adjustments.

Q: We recently had problems with booting our Palomar 2460-V. It would stall when initializing the axes. After moving the Z-axis S2C to the X-axis position, we determined it was the X-axis S2C since now the Z-axis failed to initialize. We exchanged a S2C from our 2470-V and received the error ‘incorrect software version’. What‘s going on?

A: You must exchange the EPROMs in the 2470-V S2C with the EPROMs in the 2460-V and perhaps any other differently labeled chips before trying to initialize the bonder. I cannot emphasize enough the ESD sensitivity of these chips and boards. The machines include an ESD wrist strap; make sure you use it. Always use the strap and place the boards on a suitable grounded surface when making chip changes. Transport the boards in ESD-safe containers. They are the most ESD sensitive boards with which I have worked and extremely expensive.

Q: Our Palomar 2460-V will not boot. It hangs up after the 128 Kb of cache is displayed. It just sits there, we assume, forever. What can we do?

A: I would guess the software on the hard drive has been corrupted. It’s also possible the hard drive crashed and is no longer functional. Let’s work on the basis that the hard drive is functional and just needs new software. You will shed fewer tears. Use the floppy disks provided with the system. You did keep them right? One set consists of 2 disks marked something like: SWWD15909-011-7 Rev. A. This will be install disk 1 of 2. The other disk, marked similarly, will be named ‘build disk’. It will also indicate on the build disk all setup and calibration data will be lost when the disk is used and to use it only if the system is inoperative. I have not contacted Palomar to determine their definition of inoperative. To me when the machine locks up, it’s inoperative, unless of course, it gives me some sign of a hardware problem such as ‘incorrect software version’.

Also, remember, MSDOS 6.2 (6.22 on newer systems) is the operating system used by the 2460-V. It’s my understanding MSDOS 6.2 must be on the hard drive when you install disk 1 and 2 or rebuild the system. So, if the hard drive has coughed up its last byte or it is totally corrupted and has to be rebuilt, just grab your copy of MSDOS 6.2 and go to it. OK, like all of us, you have long ago trashed your personal copy of DOS 6.2. This is the time to consider making friends with the office pack rat and hope he has a copy. If not, it may be possible to purchase a copy on the Internet.

If you follow the information on the disk(s) to the letter and the system is still down, it’s probably the hard drive. Contact Palomar for a new hard drive, hopefully with the software preinstalled. If no such hard drive exists, and sooner or later it will happen, it may be possible to purchase both DOS 6.2 and the hard drive on the Internet. Good luck.