How the right solder preform helps power module manufacturers balance performance, cost and manufacturing efficiency
As power electronics continue to evolve, manufacturers face growing pressure to reduce costs while maintaining the reliability required for demanding applications such as electric vehicles, renewable energy systems and industrial drives.
One area with significant optimization potential is the connection between the power module and the heatsink. While this interface is often overlooked, the material selected for module attach has a major impact on thermal performance, manufacturing robustness and long-term reliability.
Silver prices remain volatile. At the same time, power modules are expected to deliver higher power density, greater reliability and longer service life - all while keeping manufacturing costs under control. For engineers and procurement managers, selecting the right module attach material has become a balancing act between technical performance, process efficiency and total cost of ownership.
Choosing the right material for module attach
Transfer molded power modules (TMMs) have become a widely used packaging technology because of their compact design and high performance. However, attaching these modules reliably to the heatsink presents unique challenges.
The attachment material must:
- withstand thousands of thermal cycles
- efficiently transfer heat away from the module
- avoid damage during assembly
- support cost-efficient manufacturing
While silver sintering delivers exceptional performance, it is not always the most economical choice for every application. Large-area soldering with solder preforms offers an excellent alternative, combining reliable thermal performance with efficient processing and attractive overall costs.
Why solder alloy selection matters
Not every solder alloy is equally suited for module attach applications.
Transfer molded modules contain epoxy mold compounds that are sensitive to excessive process temperatures. If soldering temperatures become too high, mechanical stress within the package increases, potentially affecting long-term reliability.
For this reason, low-melting solder alloys are preferred. They reduce thermal stress during assembly while still providing the mechanical strength required throughout the lifetime of the power module.
At the same time, engineers must balance another important factor: material cost.
With silver prices remaining volatile, reducing precious metal content has become an increasingly important consideration for procurement and manufacturing teams alike.
Lower silver content. Proven reliability
To address these challenges, Heraeus Electronics developed Microbond® Innolot® 2.0 solder preforms, combining significantly lower silver content with the high reliability expected from the Innolot alloy family.
Compared to conventional high-silver alloys, Innolot® 2.0 contains only around 1.5 wt% silver, helping manufacturers reduce precious metal costs without sacrificing reliability.
For customers, this translates into several practical benefits:
- Lower material costs
- Reduced dependency on silver price fluctuations
- Reliable large-area solder joints
- Compatibility with temperature-sensitive transfer molded modules
- Straightforward integration into existing manufacturing processes
Reliability starts with material science
Reducing silver content only creates value if reliability remains uncompromised.
Extensive material characterization, lifetime simulations and thermal shock testing show that the optimized alloy maintains excellent creep resistance - a key property that determines how solder joints perform under repeated thermal cycling.
Lower creep deformation means lower mechanical stress throughout the service life of the module, particularly in demanding automotive and industrial environments where power modules experience continuous temperature changes. The evaluation presented in the underlying study demonstrated that the Innolot alloy family generated lower thermomechanical strain than commonly used alternatives, resulting in reduced delamination after thermal cycling tests.
Beyond the alloy: Benefits of Solder Preforms for Power Module Attach
The alloy itself is only one part of achieving a robust module attach process.
Microbond® solder preforms provide a precisely defined amount of solder exactly where it is needed. This enables highly repeatable solder joints, minimizes material waste and supports automated manufacturing.
Combined with optimized vacuum soldering processes, solder preforms help create nearly void-free joints that deliver excellent thermal conductivity and consistent quality.
For manufacturers, this means:
- High process stability
- Excellent joint consistency
- Improved production efficiency
- Reduced material waste
- Reliable thermal management
A balanced solution for engineering and purchasing teams
Selecting the right module attach material is no longer only an engineering decision. It also directly affects manufacturing costs, supply chain resilience and long-term product competitiveness.
Microbond® Innolot® 2.0 solder preforms help bridge these priorities by combining:
- high reliability under thermal cycling
- reduced silver content
- low process temperatures
- efficient large-area soldering
- attractive total cost of ownership
The result is a practical solution for manufacturers looking to optimize both performance and cost without compromising product quality.
Soldering or sintering? Find the right solution for your application
There is no one-size-fits-all solution for module attach. While silver sintering offers outstanding thermal performance for the most demanding applications, solder preforms provide an excellent balance of reliability, manufacturing efficiency and cost for many power module designs. The best choice depends on your thermal requirements, production strategy and total cost of ownership.
To help you evaluate the trade-offs, download our free whitepaper,
"Soldering vs. Sintering for EV Power Modules: Alleviate the Power Struggle."
It compares both technologies, explains their strengths and limitations, and provides practical guidance for selecting the right attachment method for your application.
Looking ahead
As power densities continue to increase and pressure on manufacturing costs grows, advanced interconnect materials will play an even greater role in power module design.
By combining decades of materials expertise with application know-how, Heraeus Electronics continues to develop solder preforms that help customers build reliable, cost-efficient power modules for the next generation of electric mobility, renewable energy and industrial power electronics.
