QPAC Binders in Semiconductor and AlN Thermal Processing

insights from industryPeter FerraroDirector of Business DevelopmentEmpower Materials

 AZoM speaks to Peter Ferraro from Empower Materials to find out the A-Z of QPAC polymer binders in semiconductor and AlN fabrication.

To start, could you give an overview of Empower Materials and where QPAC fits within your portfolio of materials for the semiconductor industry?

Empower Materials is the largest manufacturer of polyalkylene carbonate polymers, producing a portfolio sold under the QPAC trade name. Among these, QPAC 40 polypropylene carbonate is the most widely used. Customers worldwide rely on it for a range of binder applications, where it serves as the polymer “glue” that holds particles together. As a result, it plays a critical role in forming shapes and components across various industries, including semiconductor fabrication.

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QPAC is often described as an enabling binder for advanced ceramic and semiconductor processing. At a high level, what differentiates QPAC from conventional binders used in semiconductor manufacturing?

QPAC polymers are excellent binders because it provides strong adhesive properties and excellent mechanical properties to the “green” part prior to sintering. However, its signature strength is its thermal decomposition properties. QPAC binder burns out evenly and easily at low temperature in all types of furnace environments. It also leaves extremely low levels of ash and contaminants after the burnout step compared with other conventional binders.

These properties are critical in semiconductor applications because the final product’s electronic or ionic conductivity is affected by any residual contamination. Many materials in semiconductor fabrication are also detrimentally affected by high temperatures needed for the debind step. QPAC can be removed at lower temperatures to prevent any adverse reactions to the materials being bound together.

When you look specifically at semiconductor components for data centers, what are the key performance or reliability challenges that QPAC is helping to address?

Data centers use high amounts of semiconductors and generate high amounts of heat. These semiconductor components are made from high-purity materials, such as silicon, geranium, aluminium nitride, and silver powders, for example. The function of these materials could be to control the flow of electrons, help with heat management and perform other functions. For electroconductivity, specific additives are added to the pure semiconductor materials to control the conductive or insulating nature of the system.

The ability to adjust the rate of electrical conductivity or thermal conductivity are critical and can be affected by any unwanted materials. Other conventional binders may leave behind carbon or other contaminants that can alter the electical conductivity or thermal conductivity. The cleanliness upon debind of the QPAC results in a part that contains practically no contaminants that will interfere with performance.

Aluminum nitride (AlN) is becoming increasingly important for high-power, high-frequency devices. Can you walk us through how QPAC is used in AlN fabrication and what advantages it provides in that process?

AlN is used extensively in semiconductor applications for its outstanding thermal conductivity. In semiconductor devices, high amounts of heat are generated. AlN helps dissipate heat and improve device reliability. Parts formed from AlN ceramic include substrates for power electronic modules, heat sinks and thermal spreaders, chip carriers, and electronic housing. The binder is needed to hold the ceramic together and form the part through pressing or tape casting operations. Tapes and pressed parts formed using QPAC with AlN powders have excellent green strength and flexibility due to the polymer’s inherent properties and Tg. 

Thermal management is critical in AI data centers. How does the combination of AlN substrates and QPAC-enabled processing translate into better thermal performance or device efficiency at the system level?

The fabrication of parts from AlN benefits from QPAC’s decomposition properties. This is a high-growth area for QPAC binder. Fabricators know they can make high-reliability thermal components using QPAC. The removal of the binder from AlN parts requires thermal debind in an inert environment. QPAC will be completely removed in an inert environment, such as vacuum or nitrogen, while other binders will not be fully removed.

This advantage is critical to fabricate highly reliable thermal management parts for the semiconductor industry. Also, the release of gases during the debind step can cause fractures or imperfections in the parts structure. QPAC debinds in a way that leaves a consistent and fine microporous structure. This allows for improved control of thermal conductivity.

From a manufacturing standpoint, what impact does QPAC have on yield, process cleanliness, and defect reduction compared to more traditional binder systems in ceramic and semiconductor workflows?

Semiconductor manufacturing requires extremely high standards of purity, consistency, and dimensional precision. The choice of the right powder type is critical. The choice of the right binder is also critical. The binder is considered an inactive component of the semiconductor part. However, it critically determines cohesiveness, interfacial stability, electrochemical, and thermal stability.

The failure rate due to interference from binder contaminants increases as foreign particles remain. With QPAC, the final product contains only the ceramic and other additives intended. As a result, the structure integrity is maintained, and there is no detrimental contribution to both the electical and/or thermal conductivity.

Environmental and contamination concerns are huge in semiconductor fabs. How do the decomposition profile and byproducts of QPAC influence contamination control, outgassing, and overall fab cleanliness?

QPAC has excellent debind properties and decomposition components are also clean. In atmospheric furnaces, only water and CO₂ are released as byproducts of decomposition. In inert environments, propylene carbonate vapor is released. This harmless vapor is easily removed from the furnace. This allows for a cleaner fabrication environment overall and higher furnace throughput due to no carbon buildup in the equipment.

Looking ahead, what new applications or device types in the AI and high-performance computing space do you think will benefit most from QPAC-enabled AlN and other advanced ceramic technologies?

Low-temperature sintering silver paste formulations is one area that will benefit from QPAC-enabled AIN. This includes the die attach process for semiconductor fabrication and silver termination packaging pastes. The die attach process involves attaching a silicon chip to the substrate or die pad of the support structure. This integrity of the process is critical in the fabrication of semiconductors to ensure high quality of the final packaging. For this process, a paste comprising monometallic particles and a resin is printed onto the substrate in patterns corresponding to the location and shape of the die. The die is then mounted on top of the substrate. Heat is applied to evaporate the resin and additives. Pressure is then applied. The sintering process then takes place, which may be performed in an inert environment to prevent oxidation.

The binder is a critical component in the process because it is needed to promote adhesion of the integrated circuit/die to its substrate. It also must debind effectively to prevent large voids in the final connection and failures of the semiconductor device. Additionally, there is a trend to use fine or nano silver powder with a low sintering temperature as it offers additional electrical performance properties. These finer silver particles are sintered at temperatures of approximately 200 °C.

QPAC^® 40 polypropylene carbonate can meet these demanding challenges of the low-sintering silver adhesive. It can decompose at temperatures as low as 150-200 °C when applied with the metal. This will allow complete decomposition of the binder before the sintering process. Additionally, the debind process of QPAC^® 40 produces only CO₂ and water, allowing for very fine pore structure in the final part. QPAC^® 40 can also decompose cleanly with little to no residue in inert and vacuum debind environments. Therefore, QPAC^® is an excellent choice for this application. As such, it is gaining increasing attention and evaluation in the low-temperature nano silver Die Attach process.

Other applications that could benefit from QPAC include:

1. Packaging, such as temporary place holders for chips on substrates
2. MEMS packaging and creating channels for microfluids
3. Air gaps for interconnects

For engineers and materials scientists who may not yet be familiar with QPAC, what key considerations or best practices would you highlight for successfully integrating it into existing semiconductor or AlN fabrication lines?

As with any new material in a formulation, there will be modifications based on the polymer's functionality. Adjustments will most likely be needed in the formulation to account for these differences. This may include changes to the solvent system or other additives, such as dispersants and plasticizers. QPAC 40 comes in a range of different molecular weights to offer flexibility in formulation control in parameters, such as viscosity.

Empower Materials has expertise in providing assistance in formulation optimization in key semiconductor applications. We work closely with our potential customers to incorporate QPAC into their product so that they can benefit from all the advantages QPAC has to offer.

This information has been sourced, reviewed and adapted from materials provided by Empower Materials.

For more information on this source, please visit Empower Materials