Strengthening the Joint with a Revolutionary New Low-Temp Solder Paste

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I-Connect007 Editor Patty Goldman interviews one of Alpha Assembly Solution’s solder process experts, Traian Cucu, who is based at Alpha’s R&D center in New Jersey. Traian, along with Morgana Ribas, have played key roles in the development of Alpha’s innovation new low-temperature solder paste process.

Patty Goldman: Traian, please tell us a little bit about yourself and your career.

Traian Cucu: I have been working in the electronics assembly industry for nearly 20 years and spent several years as a research consultant in Romania. My work has centered on the implementation of lead-free solders and optimizing processes. Currently, I lead the Global Applications Technology expert team at Alpha, focusing on applications knowledge, identifying next generation assembly techniques, and overseeing testing of all new product technologies.

Goldman: Let’s talk about what is being called a ‘revolutionary’ new material that Alpha has developed as a low-temp solder paste solution.

Cucu: I like to call this a new process, more than a new material. It's really about the process, a new low-temperature assembly process that brings various benefits into the market. It includes a low-temperature solder paste with a new generation of low-temp alloys, which gives us excellent mechanical performance of the solder joint—much better than other low-temp solders that one can find on the market. This product solves many of the defects issues that one would see on a SAC assembly process. For example, the mechanical properties such as drop shock and thermal cycling performance is on par with the performance of drop shock and thermal cycling of a pure SAC solder joint.

Goldman: And you have test data to illustrate the performance. I am sure that’s music to engineers’ ears.

Cucu: Yes. As an engineer, we like numbers and graphs and to be backed up by data. Data always appeals to engineers.

Goldman: Now, one of the things about paste printing that I have learned, and this isn’t really my background, is this whole endeavor to make pastes with smaller and smaller particles so that you can print increasingly smaller areas. Does that affect your new paste?

Cucu: Yes. I’m glad that you asked that because it is a new chemistry platform for solder paste, and this new chemistry platform, being the latest generation, can print very small apertures using regular standard Type 4 solder paste, or we can use Type 5 as well. So it's a very robust chemistry platform. We can go into smaller powder as well, which will allow us to print even smaller features. Type 5 and Type 4 refer to the size of the particles. The smaller the particle, the higher the number; the smaller the number, the smaller the aperture that you can print, with finer features.

Goldman: And I take it that becomes more important as we go along.

Cucu: Well, look at our phones today and our laptops. Everything is shrinking—smaller, lighter and faster. And that's the other big benefit of this product; by cramming more and more stuff into the components, they are getting bigger. Then, in the regular SAC 305 process, we have this issue with warpage. It's called the high warp of signature components, mainly microprocessors but not exclusively, and that's where the innovation comes in with this new material.

In the industry today, everybody's looking to solve this problem by modifying the chemistry platform that's using the conventional SAC solder pastes like 305, 405 and all the combinations in between. Alpha’s new approach on this is to drop the assembly temperature—drop the peak, drop the whole thermal energy that goes into the process, so that we don't warp the components anymore.

The result is significantly less warpage and therefore, less defects; we get the same mechanical performance of a chip without warping the chip. Not only do we reduce defects, but we put less thermal stress on the component, which enhances the component performance and extends the life of the final assembly.

Goldman:  If the components are getting larger, then the mechanical performance becomes even more important.

Cucu: Exactly. Because it's not only that they become larger at the surface so more things can be crammed into them; at the same time, they become thinner because everybody wants a thinner phone and laptop.

Goldman: And they want it to survive at all sorts of temperatures and they want to be able to drop it or step on it or drop it in the toilet, all without worry.

Cucu: Don't even mention that (laughs).

Goldman: That's the next thing, to make it totally waterproof.

Cucu: It is, and with this chemistry, we have done preliminary testing for that as well. Because basically we are looking to the compatibility of our chemical platforms, not only for this material but in general for solder paste, for all the underfill material and glob-topping and for all the conformal coating types of materials.

Goldman: Yes, of course. You aren't the only material on that board.

Cucu: Exactly. We have to play nice with everything else on the board. We look at the compatibility with the other materials on the board; on top of that, we try to come up with a complete solution. When we say a complete low-temp process we are also referring to the combinations with the solder wire and the repair materials and everything else that comes in contact with the board. We pretty much try to see the whole picture and not only have one material and say, "Okay, our job is done.”

Goldman: You're right, you can’t operate independently. I talked earlier with Morgana Ribas; is this the same product or is this a different product?

Cucu: Yes, Morgana is the mother and the father of the alloy itself. She's the one that came up with the HLR1 alloy, and I'm specifically talking about the solder paste made from that alloy. Since the alloy itself is the one that gives you the performance, we need to put that alloy on the board and create a joint. To do that we have the solder paste, which is a powder plus the flux gel. The flux is the chemistry platform I was talking about. It's the carrier for the alloy. It gets the alloy on the pad and then the component, and then finally during the reflow process the solder joint is formed.

Goldman: Today, don’t most people use solder paste in the SMT process?

Cucu: Yes, more or less. Though, believe it or not, there are still people out there who are using wave soldering. This material will allow those people who are reluctant to transition from wave soldering to SMT to do so in small steps while using a low-temp process. This will allow them to use their boards and their components in an SMT low-temp process and make the assessment of the new process while using their own components.

Goldman: There's so often a reluctance to try something new.

Cucu: If it's not broken, why change it?

Goldman: Except that things change.

Cucu: Things change. And I am a curious engineer so I always like to try new stuff, and I'm at the right place now with Alpha. At some point in time, people need to look at the benefits and the added value. The world is moving.

Goldman: Speaking of the world, Alpha has quite a global presence, is that correct?

Cucu: Yes, we have an R&D center in New Jersey where we do a lot of scale-up for solder paste. We also have an R&D center in Japan and another in India. We are truly a global team, working together; the more minds, the higher probability there is of coming up with something new.

Goldman: It helps tremendously to be global, especially from a service point of view.

Cucu: We also have European production facilities in Hungary, Holland, and some capabilities in France as well. Then we have warehouses and general partners across Europe. So, yes, global in every way.

Goldman: Traian, thank you so much for your time.

Cucu: Thank you very much. It was a pleasure.

Visit I-007eBooks to download your copy of Alpha's micro eBook today:
The Printed Circuit Assembler’s Guide to… Low-Temperature Soldering



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