We recently spoke with Antti Peltonen, Sales Manager at Primoceler, about his company's fiber laser bonding process. In this detailed interview, Antti compares fiber laser bonding to traditional approaches such as anodic, fusion, and adhesive bonding techniques. He also provides pros and cons for Primoceler's approach, as well as the best applications and uses cases which they've encountered so far.
MEMS Journal: How do you create the bond?
Antti Peltonen: The process is based on a fiber laser. In our process the lid remains undamaged and we only melt the two materials at the interface.
MEMS Journal: Isn't this a linear process that takes more time? In other words, what the throughput compared to other bonding methods?
Antti Peltonen: With anodic or fusion bonding the wafers need to be heated slowly and afterwards slowly cooled down again. That is time consuming even in batch processing. We can bond several wafers in an hour. You are correct that the process is linear and the speed depends on how many devices are on a wafer. The effective speed however is higher than with the traditional processes.
MEMS Journal: Have you compared the costs of your approach compared to other bonding methods?
Antti Peltonen: There is no consumables so the bonding process is cheap. A bigger factor is the speed and saved floor space as this is a single-step process and does not require preheating or similar steps.
MEMS Journal: What are the pros and cons with your approach? What's the main downside?
Antti Peltonen: The good advantages are: no heat, hermetic and permanent bond, fast process, and high precision. The weaknesses are that it requires good surface quality (which is not suitable for PV, for example), it is sensitive for particles, and it requires TGVs in certain applications. Our process is still new and fairly unknown solution which is often not considered during the design phase. Also, the bonded materials need to have similar (or close) CTE values. The bond is rigid and so there is no flexibility (as there would be with adhesive bonding, for example). This limits us from working with certain applications.
MEMS Journal: Why is TGV required in certain applications? Can you please expand on this point?
Antti Peltonen: If the customer requires high level hermeticity such as in aerospace or medical applicaitons, the throughputs need to be TGVs. Any planar coating between the wafers will not be hermetic.
MEMS Journal: Based on your experience, what are the best applications for your technology? With which applications do you currently have the most traction?
Antti Peltonen: Currently our biggest projects are in micro-optics. We started with medical implants, then moved to space applications, and now work with several consumer electronic projects.
MEMS Journal: Why is micro-optics the best fit? Can you give some specific reasons? Are all of the applications mentioned above (e.g. medical implants), focused on micro-optics?
Antti Peltonen: While the optical components are getting smaller, there is also growing requirements for the performance. Adhesives can cause problems to both aspects -- out-gassing and tilt (even a small one will affect the performance), and precision is not as high when the adhesive is applied. For the fusion and anodic bonding, the new UTG materials are challenging, since 250-400C is simply too much.
The benefits are different with different industries. For medical the big benefit is glass. Glass is neutral and highly biocompatible. It's also transparent for RF signals and so reprogramming and recharging inside glass encapsulation is possible. Titanium blocks that option. With space applications the huge plus is the fact that the bonding does not lose its qualities over time. It's extremely challenging to fix a optical sensor in a satellite after a launch. With both industries the demand for smaller packages and thinner materials is of course a factor as well.
MEMS Journal: Do you sell your equipment or services, or both?
Antti Peltonen: Both. Our welding tool costs approximately $1 million.
MEMS Journal: How do sell the tool? What's the ROI? Why do customers buy it? What types of services do you provide and how are these priced?
Antti Peltonen: The machines are sold through R&D projects. We work together with our clients to make sure that their design can be manufactured using our tool, and that the design is taking advantage of what we can offer. Most of our projects are with products that wouldn't have been possible in the past.
The ROI is impossible to calculate since our machine can be used to produce wide range of products. So the question is really about the price level (and profit margin) of the end product. Since there are no consumables, the usage of the machine is cheap and with WLP capabilities the throughput is high. We also provide R&D and small-scale manufacturing and after-sale maintenance.
MEMS Journal: How much work do you with MEMS companies? How many of your MEMS foundries are your customers?
Antti Peltonen: We do. Not as much as we would like to, as I mentioned earlier, since the technology is still new and so the demand has to come from the end customers for the foundries to Upgrade their equipment. During the past 6 months or so we have been presenting, as invited speakers, at the IMAPS shows in Orlando and Arizona, as well as Photonics West. These activities got us many new customers here in the US.
MEMS Journal: Are your typical cusromers upgrading and replacing their current bonders with your tools? Or are they usually just adding your equipment to the other bonders that they have?
Antti Peltonen: The "upgrade" would be getting rid of their anodic and fusion bonder, as well as their other machinery such as adhesive bonders. It's much more likely that the customer only approaches us when they are planning to launch a new product and look for more modern solutions and manufacturing methods.
MEMS Journal: Aside from micro-optics, which other applications do you think will be a good fit for your process? Why?
Antti Peltonen: Microfluidics is growing industry for us as well -- our bonding method provides much more reliable results due to the precision and repeatable processing. Obviously in some cases the customer wishes to use plastics (due to the costs), but in other cases glass is already widely being used and providing superior bonding method is of high demand.
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