Posted by Rich Hueners on Thu, Jan 21, 2010 @ 06:54 PM
Taking from our last post, we determined that the playing field of contract assembly in complex microelectronics, in regards to cost has been leveled. A primary reason for this "leveling" has been that U.S. manufacturers have proven able to realize the advantages of Designing, Developing a Prototype, Creating a Process, and Manufacturing a Complex Product on-shore and doing it at High-Volume in a cost-effective manner.
What are North America's Advantages?
Let's unpack what some of the advantages of doing contract assembly for mircoelectronic and optoelectronic products on-shore (North America) are:
1) High skill set available for microelectronics design, prototyping, and packaging
2) Intellectual Property (IP) protection
3) Ease of communication between managers, engineers, and technicians - the factory and office are often in the same building and always close by
4) Time shortened between prototype and high volume production - freeing up valuable engineering sources sooner and resulting in a quicker time-to-market
5) Allows Managers and Sr. Engineering staff to react to changes or problems much more effectively
6) With the above-stated advantages, the contract assembly firm's ability to perform consistent complex applications and processes is strengthened
7) Close to many end users - again reducing time-to-market and enabling greater flexibility to make quick changes if needed to match market needs
Automation in Microelectronic Manufacturing
Time is money; automation cuts time down dramatically; automation is more cost-effective. When automating a complex process, setting up the process correctly the first time becomes imperative aspect in determining whether or not you will reach your time-to-market goals. A glaring benefit of automation is that an operator or technician can run a complex process (an operator or technician is cheaper than an engineer, obviously). But as with anything in life or business, things can go wrong, even in automation and even with a picture-perfect set up process by a skilled engineer. Having that skilled engineer/expert close by guarantees that any down time will be short; the operator is back to work quickly running the automated production.
below: operator on an automated die attach machine in the Palomar Microelectronics lab
Automation also is often the ONLY way complex packaging can be performed. For example, Multi-Chip Modules (MCMs) in excess of 20 components per part and 100 wires per module are typically automated. Operators can usually handle die sizes larger that 1mm, while automated equipment can handle die sizes below 250 microns. Automated wire bonders can usually attach more than 5 wires per second whereas manual bonders typically process one interconnect every 5 seconds. Even so, for most complex microelectronics, manual adhesive dispense is not an option.
The Lab Considerations
In the Palomar Microelectronic's Contract Assembly lab, the following considerations are taken into account to keep the process rolling along rapidly and accurately:
• Equipment/material certifications performed daily
• Packages or Substrates presented in boats or trays that hold lots of parts
• Piece part presented in ways that reduce work stoppage and yield loss
• Good communication between the process owner and the operator
• Process documentation that is easily accessible
High Accuracy Packaging - Where the Time Goes...
In performing high accuracy packaging, there is often more time spent on engineering: developing processes and defining daily equipment certification requirements and part presentation methods. Looking back to our automation discussion, the time spent on engineering is vital to ensuring as little intervention as possible, by the engineers, once the production begins. The engineers spend much time creating a process that can be supported with little intervention. Our operator and technician can then run production on several machines at the same time. This is high point of efficiency in complex micro-optoelectronic packaging.
Next week
Our next entry will look at a Case Study: an U.S. hybrid microelectronic packaging firm lost its Asian high volume assembly partner, and had to search for a new high volume partner. The search ended in pleasant surprise - a location that was in extraordinarily close proximity to the U.S. firm.
- Don Beck, General Manager, Palomar Microelectronics
Posted by Rich Hueners on Tue, Jan 05, 2010 @ 02:38 PM
This is the first of a multi-part blog series about North America having become a true competitor in the world of complex microelectronic contract assembly (including wire bonding and die bonding), from prototype to full production. With the declining dollar, a sophisticated high-tech infrastructure and a deep engineering talent pool, North America is poised to become a destination for micro-optoelectronic supply chains everywhere.
Competing with Off-Shore Manufacturers
Quite the contrary to what one may imagine at first thought, the U.S. microelectronic manufacturer is now more competitive with their off-shore counterparts. In fact, it could be said that the "playing field has been leveled" in this respect. Countries that were once emerging economies 10 and 20 years ago are now developed countries with governments vying for a legitimate place on the world stage. These countries that were once the "inexpensive off-shore" manufacturers are now industrialized societies with all the codes and regulations that come with any developed nation. The good news is that this translates into better working conditions for its people and for the environment as a whole. But it is a double-edged sword - the same compromises that every developed country has had to face: rules and regulations bring with it increased cost, even more so in the case of complex microelectronic assembly.
above: Palomar Microelectronics Contract Assembly lab, located in Carlsbad, California
A Brief History of Microelectronic Manufacturing
In the last 20 years it was fairly common practice for U.S./North American microelectronic manufacturers to design and manufacture their complex modules through prototype at their facilities in North America, and then launch the product in high volume at an off-shore location. This was done primarily because the risk/reward was too great to prototype a complex package off-shore, far from the design and manufacturing engineers in North America. Management at the North American firms were willing to incur additional costs to get it right the first or second time. Simply stated, there was an almost absent level of comfort in prototyping off-shore. Once the prototyping was completed, the manufacturer would launch the production in full-tilt at a dramatically less expensive (in comparison to the prototyping cost) price tag off-shore.
Who Wins?
However, this practice has changed as recently as 24 months ago. The off-shore advantage of cost has all but disappeared for the reasons stated above. The playing field in now leveled. We are truly in a global economy for microelectronic manufacturing. At the end of the day, customers around the world, especially in the pricier European countries, will win.
Next week we will be discussing microelectronic manufacturing advantages that North America possess, keeping in mind that cost is competitive with its off-shore counterparts.
- Don Beck, General Manager, Palomar Microelectronics
Posted by Rich Hueners on Tue, Nov 17, 2009 @ 05:37 PM
IMAPS 2009 in San Jose was, as expected, slow due to current economic conditions. It was evident that reduced travel budgets and last minute exhibitor cancellations left several booths empty, amplifying the lack of normal show noise in exhibit hall! However, the old saying rings true in this context: "when times are bad, traffic is slow...but the important people always show up".
Quality over Quantity
With the above-stated aside, IMAPS 2009 was no different from any other year. At the Palomar Technologies booth, we experienced slower than usual foot traffic but exceptionally high quality prospects. One could argue that this year IMAPS show was better than most because the decision makers came out. The desired result of any trade show exhibitor, if given the choice, is quality over quantity. Its probably safe to say that the exhibitors who showed up could say the same about their traffic.
Scientific Papers and Presentations
A highlight of the show were the technological papers given. Palomar's Sr. Scientist Daniel D. Evans Jr. presented a paper titled "Micron Level Placement Accuracy for Wafer Scale Packaging of P-Side Down Lasers in Optoelectronic Products" (I will have the paper posted on this link next week; or for an advanced copy contact us and we'll make sure you get it). This paper focused on applications requiring ultra high placement accuracies of 1um to 3 um. We knew Dan's paper was a success when several attendees stopped in at the Palomar booth to say how impressed they were; these complements garnered further interest in Palomar's Model 6500 Ultra High Accuracy Die Bonder and its capabilities.
Myself, Steve Buerki from Palomar, partnered with Amanda Hartnett from Indium Corporation in presenting "Process Reliability Advantages of AuSn Eutectic Die Attach". This paper focused on applications for high-power semiconductor devices mounted using Gold Tin (AuSn) eutectic solder. Gold Tin solder is a robust die-attach material that can handle the temperature fluctuations generated by the microchip (die) and mechanical stresses due to CTE mismatches between the die material, and the substrate it is mounted to. This presentation was also well received and was by a long shot the largest attended presentation of the show.
- Steve Buerki
Posted by Rich Hueners on Tue, Nov 03, 2009 @ 06:41 PM
New HB LED applications require maximum thermal transfer to achieve ever higher and higher performance requirements. With that said, Eutectic Soldering provides the user high-quality, low-risk performance.
System Setup
For the purposes of this discussion, we will use Palomar's Automated Bonding Systems as examples of necessary system setups. The user will require an automated die attach (die bonding) machine with a Pulse Heat System (to perform the heat ramp and cool down that eutectic die attach die requires). Secondly, the user will require an automated wire bonder and ball bonder (Palomar's 8000 Hybrid Wire Bonder is recommended). Third, an Epoxy Dispenser will be required for "encapsulation". Currently, the Palomar MicroElectronics lab uses GPD Global's precision dispensing system for much of their encapsulation work. It is a terrific machine and not only a beauty to watch at work, but also aesthetically and acoustically pleasing.
Die Bonding details
The user will benefit greatly from a large work area combined with great accuracy (+/- 5 micron with Pulse Heat Eutectic processing). Additionally, the flexibility of the bonder will be an important factor. Flexibility can be defined as a wide range of options (pulse heat, steady state, handlers, etc), 8 tools available on-the-fly via turret and WIP and different tooling.
Palomar's 3500 Die Bonder has a 710 square inch work area with a Pulse Heat Stage/Profiling that includes:
- Temp up to 500'C
- Temp accuracy +/- 2'C
- Fast ramp, up to 100'C (no overshoot)
What is the Pulse Heat System? Very simply, it is a system to provide a heated platform for hard solder eutectic bonding (Au/Sn, Si, Ge). It "pulses heat" which means it raises temperature of heated area via HOT BAR; and it does this following a user-defined eutectic heat profile.
Palomar's Pulse Heat System gives a better eutectic attach, for this reason - improved performance through reduction in the following error:
You can see the "overshoot" in this graph. When performing HB LED attach, this error is very likely to damage the device. Having tight control over the Pulse Heat process is imperative!! The opportunity cost of getting it right the first time and making it repeatable pays for itself many times over. You get what you pay for in this context!
Here is Palomar's Pulse Heat Profile for contrast:
As you can see there is very tight control over the process. An excellent and consistent eutectic attach is the outcome with this Pulse Heat system/process.
The Die Bond Process performed in the Palomar MicroElectronics lab use advanced LED array programming tools and process experience. Here are some examples:
The Ball Bonder details
Much like the die bonder, large work area for the ball bonder is important and necessary: it gives the user the best possible access in HB LED die array applications. Palomar's automated 8000 Ball Bonder is both a wire bonder and ball bonder (and stud bumper). It can be argued that this is the industry's most advanced hardware and software tools for yield enhancement - the "smart" bonder. This ball bonder has a dual axis bond head. It's Zl and Zr optimize delivery of force and ultrasonics, enabling repeatable ball deformation and improved shear strength and looping control.
The wire bond process achieves high speed automated ball bonds that strings LED arrays and provide excellent looping. Here are some examples:
Testing
Test is accomplished through lighting up completed assemblies! This is a quick and easy test procedure.
Posted by Rich Hueners on Fri, Oct 23, 2009 @ 06:55 PM
This is Part 3 of the Eutectic Die Bonding 101 series. In the previous 2 blogs, we discussed what "eutectic" means, the variables and parameters surrounding the process and the importance of automated temperature control with a Pulse Heat Stage. Anyone performing eutectic die attach wants a "void free eutectic die attach". We discussed the real meaning of "void free" and the financial paybacks that come through using Pulse Heat Profiling (via the Pulse Heat Stage).
Force/Scrub Attach
Scrub, in the eutectic context, can be defined as "application of force in X and/or Y direction". This is typical done over steady state heat.
The Scrub motion performs three actions: 1) breaks the oxide layer, 2) drives out voids, and 3) forces solder into die. The platform options that exist are a Hotrail conveyor (low mix, high volume) and a Pulse Heat system.
Let us discuss for a moment a common application: Gold Tin Solder. Scrub works well for Gold Tin Solder especially well because scrub and heat create a "gold rich" mixture, dramatically raising the liquidous temperature of the solder (as seen in the graph below).
Benefits of Scrub Attach
First off, it is a simple, reliable system. There are two glaring benefits of scrub attach: 1) low cost entry for eutectic attach, and 2) easily reconfigured design.
Secondly, it gives the user "void free" bonding which results in high yield. Any time one combines low cost with high yield in application, the benefit most certainly will be seem in the company's bottom line.
Scrub Attach's Payback
Just as we did with looking at the payback of the Pulse Heat Stage/Profiling in the previous blog, we will look at how Scrub pays you back!
Lets start with some assumptions about Scrub attach:
- 10 seconds saved per attachment vs. Pulse Heat
- 4 attachments/module
- 2 shifts/day
- $50/module (low end RFSOE part), 50% margin
With these assumptions, the user gets 4x throughput (20 sec vs. 60 sec) which is equal to $9,000 per day! Now that is quite significant.
It is important though to look at a few of the drawbacks with Scrub Attach:
1) Materials are brittle; they may be cracked or broken by scrub motion
2) Edge collets are required to grip the die and this may not be an option with restricted geometries and "no-touch" areas. Also, mechanical tolerances may affect accuracy.
3) Post-placement "swim" sometimes occurs - this may be an issue for post-placement accuracies better than 10 microns.
Hard Solder Comparisons
Making the hard solder comparison is important. 80Au20Sn melting temperature of 278C is more thermally stable than SnAgCu at 220C and SnPb at 183C. Now, why are these temperatures important?
Temperature is important for several reasons:
- When the bonding represents the sealing frame for a vacuum cavity, where a "getter" is needed to obtain the required vacuum. Such getters may require activation at high temperature (for instance, 350 oC).
- When chips are to be stacked and bonded in the successive proccesses, as in 3D integration.
- If interconnections and sealing rings are being bonded in different proccess steps.
Conclusions
When it is all said and done, if you can Scrub, then SCRUB! It provides constant temperature stability. It creates a robust bond (friction breaks oxide and passivation layers). And, the HOTRAIL option maximizes throughput.
We hope you have gleaned some valuable information from this blog series. If you have any questions or comments regarding eutectic die attach, please contact us and one of our die bonding experts are ready to speak with you.
Posted by Rich Hueners on Wed, Oct 14, 2009 @ 06:32 PM
This is Part 2 of "Eutectic Die Bonding 101". There are 10 process variables that exist, 4 of which Palomar is in the business of controlling (Temperature, Time, Force/Scrub, Gas Environment). The result is a successful void free eutectic die attach.
Before moving forward, I ought to make clear what "void free" means. Only true void free attach can occur in a vacuum - with that said, when working in reality, that is in-situ bonding, the industry accepts less than 5% total voiding and 1% to 2% single voiding.
Below is a great diagram showing the factors influencing voiding under die when eutectic bonding.
Temperature Effects
As discussed in Part 1, Eutectic means "easily melted". With that said, temperature is at the core of controlling and thereby implementing the eutectic process. Because the eutectic process is a delicate one and voiding is a frequent problem, very tight controls over temperature are imperative. To illustrate the importance of temperature control, here are a few examples: 1) excessive bonding temperature will blister a laser facet coating (rendering the laser useless), 2) solder reaction rates are affected by temperature because the rates increase exponentially with temperature, 3) oxide and passivation layers form rapidly under high temperature (again, creating defects), and 4) "leaching" occurs; creating very susceptible thin film deposits.
Controlling Temperature - Pulse Heat Profiling
Now that we know temperature can negate your entire process, how then is temperature controlled? It must be controlled to get a void free eutectic attach! The way temperature is controlled is with "Pulse Heat Profiling" via a "Pulse Heat Stage" (affixed to the bonder).
The figure shown the left is a screen shot of a Pulse Heat Profile. The temperature is ramped up quickly, then a short plateau, then a cool-down period where the attach is solidified
The benefits of Pulse Heat Profiling are many. First off, it provides closed-loop feedback thereby minimizing overshoot. Referring to item "1" above, this prevents laser facet blistering and gives the user higher yield through process repeatability. Secondly, it reduces cycle time (and enhances UPH) with its rapid heating rates. Thirdly, the user is enabled full control of profile through GUI. The benefit is seen in ensuring sufficient bonding time for solder to spread and wick - in short, you get a better joint. Forth, Scrub is not required. This is most important for users of III-V semiconductors, for they are then not in danger of being damaged.
Pulse Heat Payback
The Pulse Heat system is very cost-effective and provides tremendous value in both the short and long term.
Taking a few assumptions, we can see how Pulse Heat improves yield and pays back:
- $5 per part (cheapest known laser)
- 120 UPH (slow)
- 2 shifts/day
- 1% increase in Yield
In plain terms, it means that using Pulse Heat, the user/customer gets the following financial benefit:
$100 saved per day which accounts to = > $24,000 year
Next up, I will be discussing Force/Scrub attach and why Scrub works for Gold-Tin (AuSn) Solder.
For more information on Automated Eutectic Die Attach, please download Palomar's Sr. Applications Engineer's article on the subject.
Posted by Rich Hueners on Tue, Oct 06, 2009 @ 02:47 PM
Last week our President, Bruce Hueners, traveled to Asia to give several presentations (and attend Semicon Taiwan). One of these presentations was on Eutectic Die Bonding. It was one of the finest and simplest explanations of how this complicated process works that I've seen.
So, here we go...Part 1 of Eutectic Die Bonding 101:
Eutectic Bonding - Why is it Necessary?
This Eutectic Bond is 1) The Electrical Contact, 2) The Primary Heat Interface and 3) The Mechanical Support
Quick SCIENCE LESSON: The Law of Thermodymanics
1) Energy can neither be created nor destroyed (you can't win!)
2) Energy flows from a higher energy state to a lower energy state (hot or cold)
**in the event of a tie, mother nature wins!
Eutectic Bonding - What Does It Prevent?
Catastrophic Optical Damage (COD): damage to the mirror coating reflects energy back in to the laser and overheats over time
Reduced Device Longevity: poor thermal interface will require higher current input for desired light output
"Noise" Feedback: adhesive bonds provide noisy feedback at data rates > 40 Gps
Eutectic definition: Easily Melted
*Point "E" is the mixture point where heating the solder results in pure solid to pure liquid transition
How to Join with Solder: 2 Things Needed
HEAT and WETTING
1) Need sufficient heat to melt and reflow the solder
2) Don't want excessive heat that will damage the components OR the surrounding components
Wetting Vs. Non-Wetting
Solder droplet contact angle "0" affects wetting
It's important to keep in mind some of the process variables with Eutectic Bonding. Palomar Technologies' eutectic process can control the following:
Temperature, Time, Force Scrub, Gas Environment
Other variables, not controlled with Palomar's process:
Die material, Solder Material, Solder Size, Solder Presentation Method, Substrate/Bond Pad Material, Cleaning Methods
This is a large subject matter, so for the sake of time and space, I will be posting several additional blogs further explaining the eutectic bonding process. I will be covering Temperature Effects, How to Control Temperature (with Pulse Heat Profiling), Force Scrub Attach, Using Scrub for AuSn Solder and benefits of Eutectic Scrub Attach.
For more information on Eutectic Die Attach, please download Palomar's Sr. Application Engineer, Zeger Bok's "Automated Eutectic Die Attach" white paper.
Posted by Rich Hueners on Mon, Sep 28, 2009 @ 01:59 PM
For today's MEMS manufacturer, low volume and high complexity are no longer subject to only manual packaging processes. Automation is here, alive and working everyday throughout the world. Many MEMS device providers have configured automation into the design of their components. What we see today is that full-automation is not necessarily a requirement in MEMS production; but configuring the MEMS component design for automation is certainly worth its weight in gold as it reduces costs overall and positions a device manufacturer to handle the increasing demand of MEMS devices. 
Designing MEMS devices for automation means ensuring they possess the precise physical features and tight manufacturing tolerances needed for an automated assembly process. Generally the machine (automated die bonder and component placement system) can place parts only to the accuracy allowed by the quality of the components its placing. For example, in the telecommunications industry where opitical MEMS devices are used in switching arrays, the MEMS must be placed with a high degree of accuracy, on the order of 1.5 to 2 microns in the X, Y and Z axes, and 0.2 milliradians in Theta axis. This and other similar applications require the components to be of the highest quality, hence the need for excellent component design.
Physical features, such as metallization traces or fiducials, are used by the automated die bonder and component placement system's automated vision system to recognize the component's location and orientation. Oftentimes the required placement accuracy of a MEMS device is with respect to its microstructure. Therefore, MEMS manufacturers should ensure that the fiducials or metallization patterns are benchmarked to that structure. It should be noted that if the variance between the fiducial and the structure is greater than the acceptable placement accuracy, the required accuracy will never be met.
It is worth stating again that good MEMS design with an eye towards automated process production is ideal when looking to improve profit margins.
Posted by Rich Hueners on Wed, Sep 16, 2009 @ 08:25 PM
The Micro-Electro-Mechanical Systems (MEMS), which once existed only in the university laboratory, are common in many commercial products today. MEMS are found in such products as the automotive airbag deployment accelerometers and telecommunication optical switches. On the chip-level, MEMs are being used for many different applications in the aerospace and defense, information technology and medical device (especially implantable medical devices) industries. With demand increasing in each of these industries for MEMS applications combined with a need to reduce production costs (as it is a costly manufacturing process), automation becomes key to MEMS packaging success. 
By automating the MEMS packaging process, component providers are better positioned to take advantage of economies of scale, reduce yield losses by eliminating the need for human touch (via manual packaging), and increase package reliability and performance through repetitive and accurate component placement and attachment.
The semiconductor packaging industry has forged the path for automated component assembly, providing today's MEMS manufacturers with lessons that are directly transferable to MEMS packaging. Even with this foundation, automating a MEMS packaging process presents some unique challenges. The good news is that by understanding these challenges and addressing their solutions, component manufacturers will have the knowledge they need to successfully automate their MEMS packaging process.
Posted by Bruce W. Hueners on Sun, Sep 06, 2009 @ 09:27 PM
Palomar Technologies (S.E. Asia, Pte Ltd) will exhibit at this year's Semicon Taiwan, held at the World Trade Center Taipei, Taiwan. It's counterpart, Semicon West, held in San Francisco in July, proved "quietly encouraging" for the semiconductor market. We expect Semicon Taiwan to be much the same overall. The real challenge will be for individual companies to rise above and find success amid an evolving and crowded marketplace.
One Man's Opinion
As the semiconductor industry continues to mature, and along with the supporting infrastructure, namely the semiconductor capital equipment industry (for example: wire bonders and die bonders), finding new opportunities and uncovering unserved needs in this marketplace are increasingly difficult. In a mature industry, differentiation between products and assembly technologies that competing companies offer are exceeding thin. With several competing products available to the end consumer, all capable of performing the required task at high yield, the only means of differentiation is price, delivery, and terms...the definition of a commodity-like market!
In this type of "commodity-like" market, although volume high, margins suffer and are squeezed. Realistically, only two or perhaps three companies can survive, absent the protection of national and cultural boundaries.
So, what is left for the companies that supply capital equipment for the manufacturing sector of the semiconductor industry? The answer is specialization, focus of niche markets, selling to emerging technology and early adopters - 'less is more', and less is a means of survival and even prosperity if managed well.
The Show
Semicon Taiwan's press release for the the show states "Taiwan is one of the strongest performing regions in all sectors of the microelectronics industry...forecasts show that the materials market will grow to the $7.5B to $8.5B range in 2009"....also describing the show as a "can't miss destination".
If you plan to be at the show, please stop in at the Palomar Technologies booth at TWTC Hall 1, Booth 1141. Palomar's advanced packaging experts will be on hand to discuss ways to overcome your packaging challenges. Also, feel free to contact us to set up a time to meet with a Palomar specialist. We look forward to seeing you there!