In addition to sophisticated new material solutions, Heraeus offers engineering services to customers to help bring next-generation products to market faster and increase the overall module reliability.
When it comes to making the most efficient EVs possible, materials matter. Nobody knows that better than Heraeus, a German-based technology group that has a stake in global industries including health, environment, electronics, mobility and industrial applications.
One area of focus for Heraeus is developing new materials and technologies for insulated-gate bipolar transistor (IGBT) modules. In the course of this effort, Heraeus has started to offer engineering services to a range of customers in the EV supply chain, right up to the top.
“We are working with the whole supply chain up to the OEMs,” Peter Dietrich, Head of Engineering Services for Materials Solutions at Heraeus, told Charged. “And we, as the material experts, are at the beginning of the supply chain.”
Heraeus’s advantage, Mr. Dietrich explains, is exactly that: the company’s deep experience with material science. He admits that while OEMs and suppliers are often comfortable with simulation and design, none are as well-versed as Heraeus in their knowledge of materials.
“We can offer simulation and design services,” Dietrich says. “In simulation, we do not believe that we are on the same level as our customers. They’ve been doing simulations of their model for several decades. But material science-based knowledge can benefit with our experience and give FEM [Finite Element Model] simulation a small advantage in how the material behaves.”
Heraeus’s engineering services
With respect to the IGBT modules used in electric and hybrid vehicles, one of the main services Heraeus offers is to help customers transition from soldering to sintering techniques. These are techniques used to join electronic components, such as a die (or chip), to a substrate.
In soldering, solder material is heated to become liquid, and then cools to join components together. This can be achieved by hand, using a soldering iron, or with a larger piece of equipment known as a reflow oven. Sintering, in contrast, is a diffusion process that uses heat or mechanical pressure to join the die to a power substrate, with no liquification required. According to Mr. Dietrich, using sintering techniques instead of soldering can result in much higher reliability of IGBT modules.
“Sintering is a diffusion process, and it’s very stiff,” he said. “And we can achieve much higher cycle capability with sintering than with a material compound like a solder. With solder you have fatigue cracking, crack propagation. And sinter is much, much more reliable.” With these features, the sintering technology enables customers to solve new challenges in the power electronics market.
However, despite the advantages of sintering, many companies Heraeus works with have trouble justifying a switch. One reason is cost: customers will ask for samples of sinter material to run trials, but won’t spend a lavish amount of money on the proper equipment, settling for the minimum toggle press and heat plate. At the end of the trial, even though the customers are happy with the material strength, the improvement is too modest to proceed with sintering.
This is where Heraeus steps in, offering customers the use of its state-of-the-art equipment so that customers can see the true advantages of the sintering process.
“We have a PINK SIN200+ and a Boschman Sinterstar in our laboratory in the clean room, which at the moment is the latest state-of-the-art equipment,” Dietrich said. “We spent a lot of money, more than 1 million euros, to have the latest equipment. This cannot be spent by customers just for testing. And then we can use this equipment and our know-how to proceed in a professional way with good results and provide prototypes to our customers.” Another reason why customers are reluctant to introduce sintering technology is the missing experience. With more than 10 years of experience in sintering, Heraeus is the leading manufacturer for sinter paste, and supports its customers to introduce the sinter technology for future products. By offering a Sinter Seminar in October 2018, Heraeus helped customers to become familiar with the advantages of sintering.
In addition to offering the use of its professional equipment, Heraeus helps its customers develop familiarity with materials and processes. In doing so, Dietrich explains, Heraeus is also able to determine where it can offer the most innovative solutions.
“We can do all tests in-house besides the mechanical tests, and we are offering training and coaching to our customers to familiarize them with our materials. For us, this is a strategic element to position Heraeus Electronics as a solution provider. We want to have closer partnerships with our customers and also to feed back to our own R&D and product management. By going out of the comfort zone and seeing what the customers need, we can create new solutions. If we feel the same pain as our customers, we believe we can make ourselves more innovative for the right solutions.”
Heraeus’s material products
One of Heraeus’s differentiators, according to Dietrich, is the number of power electronic products it can offer. “Normally our competitors have only one or two, and we have four, five, or six of these products available,” he said. “Our products are used for the assembly and packaging of electronic modules. Our substrates are the materials where you put the die on: die attach materials, soldering or sintering, and the die top connection, which is a bonding wire. And in the case of copper wires and aluminum wires, we also have a metallization technique which is called a Die Top System.”
Heraeus offers bonding wires in the form of aluminum, copper, or hybrid, which consists of a copper core and aluminum cladding. As Mr. Dietrich explains, copper wire requires a copper surface, and most of the die surface isn’t made of copper. “If the die has no copper on top we also offer a die top system, which is a copper sheet pre-applied with sinter paste. And then you can sinter this copper sheet on the top of a die, when the die has nickel gold on top, which is very common. And then you can bond with copper. And the combination of sintering die top system and copper wires enlarges your ability a lot. We made one single test and could achieve 55 times more cyclic capability at one specific temperature point in comparison to the standard aluminum and soldering techniques.”
Heraeus also provides products and services for LED modules, which Mr. Dietrich says have comparable requirements to power electronics. Though the LED market is bigger, power electronic suppliers tend to place a higher value on quality material. “We are providing added services here to help our customers,” said Dietrich. “We are doing prototyping, design, and assembly. We are also doing the qualification and testing, as well as the process optimization. We are very, very strong in material analysis and material simulation.”
This article originally appeared in Charged Issue 38 – July/August 2018 – Subscribe now.