Wire Bonders' Speak

Improving Wire Bond Strength and Reliability

Since the early days of wire bonding, engineers have been looking for ways improve the strength of the wire bond interconnect and improve its reliability. This is espcially important for industries with high realibility requirements: aerospace and defense, implantable medical device manufacturers, automotive, commercial optolectronics and telecommunications (RF/Wireless). For example, a heart pacemaker can't go "bad", a weapons system must hit its intended target...more industries with strict wire bond requirements are popping up all the time. Which brings us back to the point: making strong wire bonds can be the difference between success or failure, profits or loss, and even life or death. This may seem dramatic, but it is not - this is the reality of packaging microelectronics in high reliability environments.

The Security Bump and Stand-off-Stitch

The Security Wire was, for many years, the only way to achieve a stong wire bond. Now with the demand for smaller package size plus even further bond strength, new methods have been discovered. One such method is the Security Bump - it requires a smaller second bond termination site. 

Stand-Off-Stitch (SOS), which is Stitch on Bump, and defined as 1) placement of a ball bump at one end of the wire interconnect, 2) then placing a wire with another ball at the other end of the interconnect, and 3) stitching off the wire on the previous placed ball bump. SOS has many benefits that can be incorporated into a variety of applications such as circuit design. Here one can accomplish, with Stand-off-Stitch, better wire strength, fewer interconnects (die to die bonding) and lower loops. Reverse bonding is another use of SOS (reversed bonding defined as stitch bond on bump on die bond pad). This often results in a lower loop profile than standard forward wire loop. Also, the loop is much stronger because the wire hasn't been annealed above the ball, in the Heat Affected Zone.

Why the need for Auxiliary Wires?

This paper was inspired by the many customers Palomar has served over the years and the common problems/challenges faced when presented with wire bond application needs. Using Palomar's Versatile 8000 Wire Bonder/Ball (Stud) Bumper, these methods discussed have been developed, tested and proved. Some of these problems/challenges include poorly bondable materials, non-flat bonding surfaces, odd or uncommon packaging situations or just the need for higher reliability.

Motivation for Improving Wire Bonds

1. Increase Pull Strength of Stitch Bond
2. Improve Failure Mode from Destructive Pull Tests (more Mid-Span and Neck breaks than Tail Breaks even with Poor Materials)
3. Improve Bond Strength after High Temp Burn In 

Auxiliary Wires, Security Bumps and Stand-off-Stitch were developed to overcome these challenges and provide customers with rock solid packages that can withstand even the harshest environments. 

See in Action

Contact us with any questions on High Reliability Wire Bonding. If you are interested seeing Mr. Rasmussen's entire presentation on this topic, register to attend SEMICON West in associated with IMAPS Workshops "Wire Bonding Workshop", held at the San Francisco Marriot on July 14-15. 

This is the second blog in my "Guide to Buying a Wire and Die Bonder". It is vital to KNOW YOUR OPTIONS. Knowing your options will better help you maximize your return on investment over the long run by choosing the best bonder to meet your application needs. 

The New Bonder: much like a new car, the new bonder includes a full factory warranty and has been driven only a few gentle miles during acceptance testing. It has the new car smell, you will park it up front where everyone can see it - you especially can show it off to customers and senior staff. You will feel like a King (or Queen) - the entire capital equipment manufacturing team, of from whom you bought the bonder, is at your disposal - for it is their primary objective to satisfy you!

Although bonder manufacturers do their best to make lead times as short as possible, lead times for new machines can be longer if a) there is signifcant process development, and b) if customized material handling or tooling is required (and this can be said for all the choices)

The Demo Bonder: demostration or "demo" equipment is used at the manufacturer's site to demostrate capability and perform application for customers who are interesting purchasing equipment for their own facility. Demo systems can be a good option for customers looking for "new" equipment at a slightly reduced price; the demo system also benefits from having been "hardened" at the factory under the close supervision of the technical staff who built them. Although demo bonders have not changed title, they have seen a few application miles and been trotted around on the dog and pony show more than once. Typically, bonder manufacturing firms rotate demo machines in order to keep them fresh, and in doing so will usually only sell a few a year. Manufacturers don't rush to sell demo systems as they must backfill that demo system with a shiny new one. Because of this, demo equipment's discounts are usually modest. With this said, if you are interested in a demo system, it is best to contact the bonder manufacturer as early as possible - like anything, it is first come, first serve. Depending on your applicaiton, a demo system may require you to be flexible in your timing, accesories, tooling and material handling. These additional items are sold at "new" prices, as they were not originally part of the demo bonder.   

The Refurbished Bonder: a good microelectronics packaging system manufacturer will offer refurbished systems to its customers. A refurbished wire or die bonder is a good option for those seeking performance at a bargain price. Generally speaking, refurbished systems come from buy-backs from good customers - good meaning these customers have taken great care of the machine and kept it in good working condition. Also, these machines are almost always covered by the manufacturers service contract and warranty. Refurbished means to return the system to its near-original-condition. If neccesary, it is cosmetically repaired. The computer systems and software are updated and/or replaced and the machine is mechnically repaired and brought up to pass the same "acceptance test procedure" (ATP) - the same test procedure that is done will all new machines. A warranty is included as well. Unlike the demo and new system, refurbished machines are not scheduled and like the demo, are on a first come, first serve basis. 

The Used Bonder: reputable bonder manufacturers NEVER sell used equipment...I repeat...reputable bonder manufactuers NEVER sell used equipment!  Wire bonder, die bonder, and microelctronic packaging machines are highly complex products that require significant expertise and training to run effectively. A good bonder, will in effect "print money" for you. It's safe to say that a used bonder won't do anything for you except take up floor space and collect dust. Those who go down the road of buying a used bonder will find themselves searching for manuals, picking through spare parts, gathering odds and ends from PC boards, coming up with obsolete hardware,  software and componets. Generally, buying a used bonder elimates support all together. Additionally, the software to operate the machine is under license by the manufacturer and you will eventually have to pay a fee to use it, legally. In a lot of cases, used bonder are cannibalized for valuable spare parts or bastardized to meet the specific needs of the past owner.  The only one responsible for the used wire or die bonder plan together is you - I can promise that you would find this task somewhere between duanting and near impossible, or better said, a complete waste of your time. No matter how many cans of new car smell you spray on it, it will always smell like a burned FR4 with a hint of an overheated transformer! 

QUESTIONS?

Contact a Palomar expert to discuss how we can meet you application needs. System purchase or contract manufacturing services together or separately are ideal firms with complex, high reliability applications. 

-Steve Buerki

People new the die bonder and wire bonder world often do not know where to begin looking for a bonding machine. And when they find a few bonders that seem "right", what does one need look for in a bonder?  This is a very important question and one that must be throughly researched and understood. High-end, high quality bonders can cost as much as a single family home in California. Just the same, the lower-end, lower quality bonders will cost signifcantly less.

Choosing the right bonder (could) depend on the following:

1. application
2. precision and accuracy requirements
3. yield requirements 
4. factory size (floor space)
5. reliabilty requirements
6. support and training needs
7. budget and price requirements
8. timeline or time to market needs

The Basics of Bonding Purchasing

BUY RIGHT - get it right the first time; spend time comparing bonder manufacturing firm data sheets, speak directly with knowledgable sales people who can clearly explain the benefits, features and the invetible "give and take" that comes with any advanced packaging system. For example, if you are looking for speed, you will sacrafice precision and accuracy. The qualified salesperson will be able to help you gain a clear scope of your requirements. Using our example, if precision and accuracy is neccesary for your application, you have just narrowed down your selection to a few bonder providers. 

REDUCE RISK - looking at specs on a data sheet is not enough. Following the lead of your sales point person, you must spend time engaging with each company's scientists, engineers and program managers. These people live and breath wire bonding and die attach challenges and solutions. During this process you will get a feel for each company's work ethic, quality of support and technical expertise. 

PROVING BEFORE BUYING - the best wire and die attach manufacturers will often do a sample application to prove that the work can be done. You can choose to visit the companies in person or have the sample application mailed to you. The benefit of this is two-fold: 1) if your application is very specific, it will give each company a chance to see if they "can acutally do it" (good companies won't make a claim they can't provide) and 2) you can take the sample application directly to your boss and colleagues; under a microscope, everyone can see what they are getting.

KNOW YOUR OPTIONS - wire bonder and die attach machines come in three general categories:

New: much like a new car, the bonder includes a full factory warranty and has been driven only a few gentle miles during acceptance testing aka Applications Test Procedure (ATP). It has the new car smell, you will park it up front where everyone can see it - you especially can show it off to customers and senior staff. You will feel like a King (or Queen) - the entire capital equipment manufacturing team, of whom you bought the bonder from, is at your disposal for it is their primary objective to satisfy you! 

Although bonder manufacturers do their best to make lead times as short as possible, lead times for new machines can be longer if a) there is signifcant process development, and b) if customized material handling or tooling is required (and this can be said for all the choices).

Demo: demostration or "demo" equipment is used at the manufacturer's site to demostrate capability and perform application for customers who are interested in purchasing equipment for their own facility. Demo systems can be a good option for customers looking for "new" equipment at a slightly reduced price; the demo system also benefits from having been "hardened" at the factory under the close supervision of the technical staff who built them. Although demo bonders have not changed title, they have seen a few application miles and been trotted around on the dog and pony show more than once. Typically, bonder manufacturing firms rotate demo machines in order to keep them fresh, and in doing so will usually only sell a few a year. Manufacturers don't rush to sell demo systems as they must backfill that demo system with a shiny new one. Because of this, demo equipment's discounts are usually modest. With this said, if you are interested in a demo system, it is best to contact the bonder manufacturer as early as possible - like anything, it is first come, first serve. Depending on your applicaiton, a demo system may require you to be flexible in your timing, accesories, tooling and material handling. These additional items are sold at "new" prices, as they were not originally part of the demo bonder.  

 *6500 die bonder demo system - looking top down

Refurbished: a good microelectronics packaging system manufacturer will offer refurbished systems to its customers. A refurbished wire or die bonder is a good option for those seeking performance at a bargain price. Generally speaking, refurbished systems come from buy-backs from good customers - good meaning these customers have taken great care of the machine and have kept it in good working condition. Also, these machines are almost always covered by the manufacturers service contract and warranty. Refurbished means to return the system to its near-original-condition. If neccesary, it is cosmetically repaired. During refurbishment, the computer systems and software are updated and/or replaced and the machine is mechnically repaired and brought up to pass "acceptance test procedure" (ATP) - the same test procedure that is done with all new machines. A warranty is included as well. Unlike the demo and new system, refurbished machines are not scheduled and like the demo, are on a first come, first serve basis. 

below: a wedge bonder in the Palomar warehouse being refurbished

Used: reputable bonder manufacturers NEVER sell used equipment...I repeat...reputable bonder manufactuers NEVER sell used equipment!  Wire bonder, die bonder, and microelctronic packaging machines are highly complex products that require significant expertise to run effectively. A good bonder, will in effect "print money" for you. It's safe to say that a used bonder won't do anything for you except take up floor space and collect dust. Those who go down the road of buying a used bonder will find themselves searching for manuals and picking through spare parts. In short, buying used is not worth it. Buying a used bonder will likely cost you much more over time. 

In Conclusion

Maximize your investment by doing your homework. If you have any questions about the bonder buying process or need help in determining what your application requires, please feel free to contact us. If our capabilities don't fit your requirements, we are happy to help steer you in the direction to find a solution that meets your needs. 

-Steve Buerki

Here is a quick refresher on Epoxy Die Attach and Anisotropic Conductive Paste (ACP). Using a flexible die bonder with 3 channels of fluid dispense and a daub pot, you will be able to perform a highly accurate and realiable bond. 

How ACP Works

ACP works by trapping conductive particles between the corresponding conductive pads on the IC (integrated circuit) and the substrate. ACP consists of a very stable matrix of 3 micron to 5 micron ploymer spheres. Each of these are nickle-gold plated and then coated with a final insulating layer that protects them against shorting through contact with a neighboring particle. The insulated particles are distributed in such a way that their incidental contacts in the X and Y axes are low.

Pre-Bonding

During the bonding process, the insulation in the Z-axis where the balls are trapped is pushed away. This allows the Ni-Au layer on the particle to conduct electricity between the IC and the substrate while not shorting in the X and Y directions. The epoxy then cures, locking the particles in this compressed state.

Maintaining Electrical Connection

The elasticity of the compressed trapped particles causes them to constantly press outward on both contact points. This helps to maintain electrical connections through a wide range of environmental conditions. Improvements in particle uniformity, dispersion, and particle coating technologies have allowed ACP now match or exceed the reliability of older solder technologies. 

Post-Bonding

The final process subjects the ACP to high heat and temperature, permanently curing the epoxy and attaching the IC to the substrate. Although vast improvements have been made, an example of bonding profile would be 150-210'C and 40-300 grams/bump for 5-20 seconds. 

Highlights of Advanced Micro-Optoelectronic Interconnection Technology Seminar in Shanghai, China

Here are the highlights for those that weren't able to attend.

1) Fundamentals of Microelectronic and Optoelectronics Packaging, including:

• Packaging Formats and Thermal Design 
• Materials Used and their Properties
• Die to Package Interconnect Methods  

2) New advances in Assembly Tools: 

• Automated Precision Dispensers 
• Automated Ultra High Accuracy Die Bonders and Component Placement Systems (for such things as pick and place)
• Automated Die Bonders with super Flexible Work Areas (including Pulse Heat and Steady State for Eutectic Die Attach)
• Bond Testers, Die Sorters, Wire Pull Testers

3) A Survey of the Latest Trends on Microelectronic and Optoelectronic Packaging worldwide:

• Wafer Scale or Wafer Level Packaging
• 3D Packaging 
• TSV Die Stacking
• Embedded Dice in PCB  

Special emphasis was given to the interconnection process, especially hard solder eutectic chip attach. Nearly 150 top engineers and scientists from China were in attendance.  

Palomar Technologies and Beijing Yake held the full day seminar in Shanghai, on March 15th. Timing was appropo, as it took place days before Semicon China kicked off. Palomar CEO Bruce W. Hueners and Palomar Sr. Scientist Daniel D. Evans, Jr. were the key speakers of the event.  

For more information on Eutectic Die Attach, download Palomar Sr. Application Engineer, Zeger Bok's, Automated Eutectic Die Attach article.  

To speak with Palomar Asia about Palomar's award winning automated wire and die bonders or precision assembly services, please Contact Us.  

Its that time of year again in China. Semicon China (held in Shanghai this year) is one the largest and most important trade shows for the semiconductor industry. Semicon China is a good barometer of industry economics, future trends, and areas of growth (or otherwise). Case in point, China has the highest growth rate in the microelectronics industry and is expected to be the first to recover from the global recession. This year's show expects upwards 100,000 professional visitors, 1,000 exhibitors, 2,000 booths and 57,000 square feet of exhibit space. . This year's three theme pavilions will be 1) Reuse IC Fab Line Market and Ecosystem, 2) IC Applications of China Market, and 3) LED Manufacturing. New to the show is Semicon China's co-locations with SOLARCON China and FPD China. 

Palomar Technologies will be exhibiting with AST China in Booth #3559. Palomar will be doing two LIVE wire bonding and die bonding demonstrations.

Palomar's ultra flexible Model 3500-III Die Bonder and Automated Component Placement System with be performing:

• Flip Chip
• Component Handling
• Dot, Line, Pattern Epoxy Auger Dispensing
• Dot, Line, Pattern Time Pressure Epoxy Dispensing
• Eutectic Die Attach of Gold Tin (AuSn) with Pulse Heat Stage  - as part of this demonstration, Palomar's will showcase it's computer controlled Pulse Heat System including heat ramp and cool down graph "on-screen" along with the Pulse Heat Gauges that include cover gas, vacuum pressure, heating and cooling 
• Epoxy Daubing 

Palomar Technologies will also be doing a live wire bonding demonstration with its versatile, deep access Model 8000 Wire Bonder and Ball (Stud) Bumper. Palomar engineers will be displaying the wire bonder's capability in doing a flat ball bump and the the latest trend in Ball Bonding doing a short loop, called "stitch-stitch". The significance of "stitch-stitch" is that it the bonder creates a "bond" without setting down a "ball". This is very similar to wedge bonding, for it creates the same desired result (see image below). 

A manual system for die bond and wire bond will also be on display, in addition to a versatile wire pull, twist and die shear system.

The wire bonding and die attach applications are designed for atypical or odd form factor, complex microelectronic and optoelectronic packages. These packages are commonly used in military, aerospace, medical, telecommunications and consumer high technology industries. 

Palomar also offers precision contract assembly services through Palomar Microelectronics. These services are include supply chain management, prototyping, process development,  test, advanced packaging (wire bonding, die attach, eutectic and epoxy attach, LED packaging, RF Power Modules, complex hybrids, solar concentrators, LASERS,  and much more). All services are performed at Palomar's facility in Carlsbad, CA, USA with a full time, dedicated engineering staff and a vast high reliability equipment portfolio. Many non-US customers find Palomar's services a great value due to the high quality of work, managerial control on-site, its computerized paperless manufacturing laboratory, more for their money (due to decreased value of the dollar compared to other currencies), and protection of Intellectual Property. 

From the floor of Productronica in Munich, Germany. Traffic was much the same as it was at IMAPS 2009 in San Jose. From Tuesday thru Thursday, we saw medium traffic in the morning to afternoon. On Friday, the volume was noticeably lower. Nonetheless, it was a a successful show. 

Palomar's highly versatile 8000 Wire Bonder/Ball Bumper was center stage at the booth, wire bonding on a 10"x8" stage! Palomar's 6500 Ultra High Accuracy Die Bonder got considerable interest from many visitors, especially from those in the LED manufacturing business.

One can always get a good feel for the pulse of the business by looking at the number of exhibitors. In the case of Productronica, there were certainly fewer exhibitors. But I must say that the show's management did a great job in laying out the booths in proportion to the number of booth attendees: case it point, 50% of the trade show area was full AND yet it did not feel empty. The standard of booths felt higher than Semicon West. It was plain to see that exhibitors/companies were focused more on quality than quantity. 

The most significant thing we saw at this show was an influx of business from Eastern Europe, specifically Russia, Romania and the Czech Republic. Countries who once weren't considered real business opportunities in the advanced high tech market are suddenly viable. LED manufacturers represented the bulk of Eastern European companies. 

I was asked to contribute to the Palomar Technologies’ blog after a recent visit to their factory. This came about by way of meeting an employee of Palomar who was part of an executive education program that I am participating in at USD.  He shared with me a little about Palomar: their advanced microelectronic packaging systems manufacturing business, their contract assembly division (Palomar Microelectronics), the growth that they were seeing across all lines of the business and their goals for the future. Being a supply chain professional I was very interested in learning more about the supply chain behind Palomar, hence I graciously accepted the invitation to visit.

Upon entering the facility, I was received with a warm reception.  Here are some brief thoughts from what proved to be a fascinating and insightful visit:

Supply Chain Defined: 

In short, a company’s supply chain represents the flow of value from raw materials to the end customer.  Or, “a supply chain is the system of organizations, people, technology, activities, information and resources involved in moving a product or service”.

The term “supply chain” is admittedly a loose metaphor.  I prefer the term “Value Network” (see depiction below) as a network is more indicative of how most companies interact with competitors, customers, suppliers, regulators, etc.  Advanced value networks have a lot of characteristics, some of which include: systems of trust, collaborative innovation, lean processes, and advanced relationship management techniques. 

It was exciting to see elements of Value Network Management in practice at Palomar.  For example...

Innovation: 

My new friend shared with me how Palomar works with its customers to solve their large, unmet needs (needless to say, I was thrilled to hear this). It was evident that the company has carved out a nice niche in that it has (and is) consciously chosen not to be in the market of mass production;rather its focus is on high mix/low volume, high quality production – this enables them to be very attentive to solving unique customer problems.  An example given was the work they did with a military and defense contractor based in Europe. This customer had been turned away by other suppliers because their packaging challenge necessitated a customized solution and required only a few systems – these other suppliers could not meet the customer’s need even if they wanted to – they were entirely in the mass production mindset (these suppliers were in the business of selling 50-100 systems at a time, Palomar is in the business of customizing and selling1, 2, or 10 systems).  Palomar was able to win the customer’s order having proved able to meet their challenge and provide a custom solution (this included service and support, something the other suppliers were incapable of providing).  Result:  a satisfied customer who invariably will be a net promoter vs. detractor.

“Lean”: 

Supply chain professionals like me have been indoctrinated over the years on TPS (Toyota Production System)thinking.  Many companies havetried to replicate TPS with mixed results.  Toyota even invites potential competitors into its factoriesto see TPS at work.  Why would they do this?  Because they know a lot of what’s behind TPS “is in the walls” meaning you can sense it and feel it but it’s very hard for an outsider to replicate. 

The Intangibles: 

While walking the “supply chain” at Palomar, I got the sense that something special was “in the walls”.  You know it when you see it: professionalism, cleanliness, pride of work, order…it’s all there.  Having worked for a Fortune 50 company and gained a sense for world-class operations, I must say what I witnessed at Palomar appeared to be as good or better than what we had going at a multi-billion dollar company. 

I’ll pose a few questions to close on:

1.  Is your Supply Chain and Procurement organization looked to as source of competitive advantage for your company?  What characteristics have you seen with these organizations?

2.  In a fast moving, rapidly changing world the most sustainable source of competitive advantage is….? 

Visit Cask Technologies to see how CEO’s answered the last question in a recent survey.

-Jim Goodall

Jim Goodall is a Supply Chain/Value Network expert with Cask Technologies and can be reached at jim.goodall@casktechnologies.com.For more information, you can visit www.casktechnologies.com

Contract assembly services are invauable for start-ups and cash strapped companies who need packaging and assembly production but don't have (or want) the resources needed for out-right capital equipment purchases.

It is rare for die bonding and wire bonding equipment manufacturers to offer contract assembly services. Microelectronic packaging equipment manufacturers are often in the best position to understand and perform assembly and packaging services. This is because of the following:

1) they have intimate knowledge and understanding of their packaging and assembly systems and how to use them

2) they know how to reconfigure the packaging and assembly systems for many unique applications

3) they have experienced engineers dedicated to fine-tuning customers' processes and products on the packaging and assembly systems

4) the packaging and assembly systems are already is in place at their showrooms, testing facilities and laboratories 

For a designer and manufacturer of automated high-precision wire bonders, die bonders and component placement systems,  providing scalable production of complex microelectronic devices at its own facilities, is a natural progression.

Because the hybrid microelectronics packaging is a niche business, and volume of system sales are low in comparision to its semiconductor sibling, the machines are built on order (usually). A glaring benefit to using contract assembly with a packaging and assembly system manufacturer is the ability to set up a (customer's) process and move into production, while that customer's systems are being built. One the system is built, then shipped, the process and production are seamlessly integrated at customer's facilities. 

If you have a contract assembly need, contact us with your challenge and we will present a solution for free. 

Shrinking electronic package geometries are driving continuous improvements in interconnect technologies. Wire Bonding is a mature technology that continues to meet challenges of finer geometric capability: loop shape, bond pitch, ball size, and stitch size control.  

*The below rendering is a simplified representation of a wire interconnection showing the loop and change in ball and stitch geometries which occur during the ultrasonic bonding process.  

Palomar engineers developed a method called "Adaptive Bond Deformation" (ABD) method to enable the user to better improve cost-effectiveness of their wire bonding and ball bumping system (side note: unique ball bump applications where material, process and tool variations adversely affected yields due to occasional shorting of adjacent bumps were part of the motivation in developing ABD). 

The essence of ABD is to improve bond geometry; to control the geometry of both ball and stitch according to process parameter inputs supplied by the user; the technique adapts to normal variations in bond surface, bond tool coupling, part fixture, and other difficult to measure influences. Using Adaptive Bond Deformation the user is able to produce bonded ball bumps, and stitches with significant improvement in geometry consistency with similar or better results for ball shear and pul strength when compared to non-adaptive bonding. 

Adaptive Bond Deformation was developed to meet the challenges of the packaging industry. These challenges require a common set of improvements as geometries continue to shrink:

1) Uniformity of ball bump heigh and/or bump diameter to allow...

a. Reduced bond pitch for wires

b. Reduced bond pitch for bumps

c. Better bump co-planarity 

 2) Uniformity of stitch impressions to...

a. Minimize adverse impacts to sensitive materials for stitch

3) Process...

a. Reduced process develop time

b. Reduce sensitivity to material, environment, and setup variation 

c. Real-time capture/qualification of production data

d. Data trending analysis of production data