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Solutions for Electronic Cooling
Thermal interface materials (TIM) represent an increasingly important role in electronics manufacturing, performance and reliability. The single most frequent failure mode of electronic devices is heat. Thermal interface materials are designed to minimize the impact of heat in electronic systems even as the power and heat generation increases. Below are the typical forms TIM materials are produced in.
Saint-Gobain boron nitride can play an important role in these TIM materials by controlling key properties of BN powder to meet the thermal, electrical and rheological demands of the application.
Electronics Cooling
By controlling key characteristics like particle size and distribution, density, particle shape and purity, Saint-Gobain is able to customize solutions for individual applications to maximize the inherent material properties of boron nitride that make it valuable to the TIM market like high thermal conductivity and excellent dielectric properties. Saint-Gobain is able to showcase our ability to customize boron nitride powder solutions within our wide range of agglomerated boron nitride powders.
Size and Size Distribution:
Different agglomerate sizes and size distributions, from 60 to 400 microns, offer customers the ability to optimize the packing of BN in the matrix. Larger agglomerates provide improved flowability and typically improve thermal conductivity by providing larger contact area for heat flow.Key process parameters that can help determine the optimal size and particle morphology are (1.) bond line thickness, extrusion size or coating thickness and (2.) intensity of mixing forces. Due to the nature of particle-to-particle bonding, BN agglomerates best retain their morphology in low-medium shear forces.
Density:
Density is an important factor when working with BN agglomerates as it affects not just the product performance, but also the final cost of the resulting product.
Higher density improves the thermal performance by increasing the number of contact points within the agglomerate, providing an efficient heat transfer path. Higher density also yields stronger agglomerates, improving the energy tolerance of BN agglomerates in maintaining their morphology. Benefits of high-density agglomerate powder must be balanced with its relatively high cost compared to low density agglomerates.
Shape:
Saint-Gobain offers a selection of shapes utilizing its expertise in manufacturing BN. Crushed agglomerates have a more irregular and random shape, whereas Spherical agglomerates offer uniquely tight particle size distributions, and therefore better packing density and particle to particle interactions to achieve optimum thermal conductivity.
Our current product range includes agglomerates from 120 to 300 microns with the ability to produce both finer and coarser agglomerates for custom solutions.
Purity:
Saint-Gobain can tune the purity and composition of BN agglomerated products to meet customer demands. Our standard suite of agglomerated powders offers over 99.5% purity which allows for the highest dielectric properties for increased breakdown voltage and signal strength in the final products.In certain applications, we can offer composite agglomerated powder to meet application demands and balance both performance and cost to bring value.
By utilizing our unique synthesis processes and expertise, we can offer precise value without over engineering the solution.
Dispensable gap filler has been growing in popularity due to the push for more and more automation in the manufacturing industry. Application of a thermal interface material (TIM) to an electronic package has been done historically through pads, films and greases. These systems can be effective, but a dispensable system offers the most benefit in an automated process.
Boron nitride (BN) offers a unique solution for this system with its combination of high thermal conductivity, dielectric properties and low coefficient of friction.
- The low coefficient of friction and low wear property of BN lends itself to the dispensable gap filler market because of the need for high precision on the nozzle tip to precisely control the amount and placement of the gap filler in the electronic. This, along with the other characteristics of BN, makes it an effective and unique choice for this application.
- To further enhance the performance of BN in this application, Saint-Gobain offers a series of spherical agglomerates to maximize the thermal conductivity of the filler and enhance the processability by providing an extremely flowable powder to incorporate into the gap filler matrix.
- Saint-Gobain products--CTS3M, CTS7M and CTS25M--offer premium performance and enhanced processability in this demanding application.
Glass fiber/epoxy laminates have been the foundational structural substrate in printed circuit boards for decades. A PCB substrate can be made from paper, glass fiber in woven or nonwoven form, or a composite of paper and glass fiber. These materials can be impregnated with a variety of resins, but epoxy is the most common. This mix is called a prepreg and is where thermally conductive fillers can also be added to the composition. The need for enhanced thermal performance of the prepreg material which is laminated with copper foil has increased as the industry has progressed from single sided PCBs to multilayer PCBs where several layers of prepreg are laminated with copper foil to become a laminate. It is common for 8 to 16 layer boards to be manufactured.
Due to the concentration of energy in these multilayer boards and ever increasing power requirements in electronic components, thermal demands have increased and boron nitride is an excellent option for heat management within the PCB.
- A key for laminate production is the bonding strength between the copper foil and the laminate which is typically measured via a peel strength test. Standard boron nitride platelets are a very inert and generally have difficulty maintaining good peel strength in the different prepreg compositions.
- Saint-Gobain boron nitride has shown the ability to optimize this situation in different resin systems with tight control of the platelet size, morphology, chemistry and surface properties.
- Utilization of an agglomerated boron nitride material can also improve peel strength while having the added benefit of improved thermal performance. Saint-Gobain offers fine agglomerates that allow for these improved performance characteristics while still allowing for the targeted thickness of each layer.
An added benefit to boron nitride in the PCB vs other thermal materials such as alumina is that in multilayer PCBs there are holes drilled to connect the layers electrically. This is a very critical and precise operation where having a BN filler improves tool life and ease of drilling accurate and repeatable holes in the PCB.