Thermal Conductive Adhesive Research Articles

Diamond-Reinforced Al(H2PO4)3@Epoxy Hybrid Thermal Adhesive With Ultra-High Thermal Conductivity and Bonding Strength.

The miniaturization, integration, and increased power of electronic devices have exacerbated serious heat dissipation issues. Thermally conductive adhesives, which effectively transfer heat and firmly bond components, are critical for addressing these challenges. This paper innovatively proposed a composite comprising inorganic phosphate/alumina as a matrix and diamond as filler. The composite achieved an isotropic thermal conductivity (TC) of up to 18.96Wm-1K-1, significantly surpassing existing reports while maintaining electrical insulation. First-principles calculations and experimental tests confirmed that the high TC of phosphate and excellent interface contact ensured efficient heat transfer. To optimize bonding performance, a modified-diamond/Al(H2PO4)3@epoxy hybrid composite is subsequently developed using an organic modification method. The unique hybrid structure, combining inorganic thermal pathways and an organic adhesive network, enabled the hybrid composite to simultaneously possess a high TC (3.23Wm-1K-1) and strong adhesion (14.35MPa). Compared to previous reports, the comprehensive performance of this hybrid thermally conductive adhesive is exceptionally remarkable. The superior heat dissipation capability of the hybrid thermal adhesive is demonstrated in chip cooling scenarios. This organic/inorganic hybrid approach offered a new direction for obtaining advanced thermal interface materials, demonstrating significant application potential in chip soldering, packaging, and heat dissipation.

Ultrahigh Thermal Conductivity of Epoxy/Ag Flakes/MXene@Ag Composites Achieved by In Situ Sintering of Silver Nanoparticles.

The growing use of high-power and integrated electronic devices has created a need for thermal conductive adhesives (TCAs) with high thermal conductivity (TC) to manage heat dissipation at the interface. However, TCAs are often limited by contact thermal resistance at the interface between materials. In this study, we synthesized MXene@Ag composites through a direct in situ reduction process. The Ag nanoparticles (Ag NPs) generated by the reduction of the MXene interlayer and surface formed effective thermally conductive pathways with Ag flakes within an epoxy resin matrix. Various characterization analyses revealed that adding MXene@Ag composites at a concentration of 3 wt % resulted in a remarkable TC of 40.80 W/(m·K). This value is 8.77 times higher than that achieved with Ag flakes and 7.9 times higher than with MXene filler alone. The improved TC is attributed to the sintering of the in situ reduced Ag NPs during the curing process, which formed a connection between MXene (a highly conductive material) and the Ag flakes, thereby reducing contact thermal resistance. This reduction in contact thermal resistance significantly enhanced the TC of the thermal interface materials (TIMs). This study presents a novel approach for developing materials with exceptionally high TC, opening new possibilities for the design and fabrication of advanced thermal management systems.

An in situ strategy to produce high-performance composite thermal adhesives with excellent bonding, thermal transfer and adjustable electrical performance based on a designer hyperbranched epoxy copolymer

Thermally conductive adhesives (TCAs) have attracted considerable attentions in recent years as they can simultaneously promote interfacial bonding and thermal transfer. So far, a lot of strategies have been explored for producing them. Among them, modifying adhesive resins with thermally conductive nanofillers is one of the most frequently reported methodologies, which often involves complicated process and tedious procedures. We herein report a facile strategy for producing TCAs via an in situ process with the assistance of a designer hyperbranched epoxy copolymer, HBPE@PGMA. This copolymer consists of a hyperbranched polyethylene (HBPE) core and multiple poly (glycidyl methacrylate) (PGMA) side chains, which can be synthesized under mild conditions by a two-step polymerization process. As a stabilizer, this copolymer is found to effectively promote the exfoliation of hexagonal boron nitride (h-BN), natural graphite or multi-walled carbon nanotubes (MWCNTs) in chloroform under sonication, rendering boron nitride nanosheets (BNNS), graphene and individually dispersed MWCNT, respectively. Meanwhile, some of the copolymer can be irreversibly adsorbed on the resultant nanofiller surface based on the noncovalent CH-π interactions. This makes them well dispersible in chloroform and allows us to obtain high-performance TCAs from their dispersions via in situ process directly using the copolymer as matrix. The resultant TCAs simultaneously exhibit excellent interfacial bonding, thermal transfer and adjustable electrical performance. This strategy paves a way for producing high-performance TCAs through in situ process with relatively simple process.

Preparation of environmental-benign castor oil-derived polyurethane thermal conductive structural adhesives with superior strength

Thermal conductive structural adhesives offer a robust solution for injection into the battery core of power battery packs in new energy vehicles, effectively providing filling, protecting, and facilitating timely heat dissipation. In this work, a series of castor oil (CO)-based polyurethane prepolymers with different isocyanate (NCO) contents were synthesized by a solvent-free method, which designated as Component B (curing agent) for the CO-based polyurethane (CIPU) adhesives. Polyaspartic acid ester (PAE) resin compounded with poly (tetramethylene ether glycol) (PTMG) of different molecular weights, constituted Component A of the CIPU adhesives. The effect of mass ratio of PAE to PTMG (M value) on mechanical performance of the CIPU adhesives under different curing agent conditions was investigated. The results indicated optimal overall performance for the CIPU adhesive with an M value of 3, exhibiting a tensile strength of 10.25 MPa, an elongation at break of 107.14%, and a steel-steel tensile shear strength of 4.7 MPa. Subsequently, a series of CIPU thermal conductive structural adhesives were prepared by introducing thermal conductive fillers into the optimized CIPU adhesive formula. The introduction of a 35% Boron nitride content yielded a CIPU thermal conductive structural adhesive with a thermal conductivity of 0.64 W/m·K, and a steel-steel tensile shear strength of 6.97 MPa. These innovative CIPU thermal conductive structural adhesives prepared herein are expected to be applied in the new energy automotive and electronics industries.

Effect of the alumina micro-particle sizes on the thermal conductivity and dynamic mechanical property of epoxy resin.

Epoxy thermal conductive adhesives with high thermal conductivity and dynamic mechanical properties are important thermally conductive materials for fabricating highly integrated electronic devices. In this paper, micro-Al2O3 is used as a thermally conductive filler for the epoxy resin composite and investigated the effect of micron-sized alumina particle size on the thermal conductivity and dynamic mechanical property of epoxy resin by the transient planar hot plate method and DMA (Dynamic mechanical analysis). The experimental results show that with the same amount of alumina filling, the thermal conductivity and Tg (glass transition temperature) of epoxy/Al2O3 composite material decrease with the increase of alumina particle size. The maximum thermal conductivity of the composite material is 0.679 (W/mK), while the energy storage modulus of epoxy/Al2O3 composite material increases with the increase of alumina particle size, and the maximum energy storage modulus of the composite material is 160MPa. Compared with pure epoxy resin, the thermal conductivity and energy storage modulus have increased by 2.7 and 3.2 times, respectively. The epoxy/Al2O3 composite was applied to the COB (Chips On Board) type LED package, and the substrate temperature of the LED dropped to the lowest after 1.5 hours of operation using EP-A5 composite, and the temperature was stabilized at 38.2°C, indicating that the addition of 5-micron alumina composite has the best heat dissipation in the COB type LED package. These results are critical for the implementation of particulate-filled polymer composites in practical applications because relaxed material specifications and handling procedures can be incorporated in production environments to improve efficiency.

Near-Theoretical Thermal Conductivity Silver Nanoflakes as Reinforcements in Gap-Filling Adhesives.

The rapid development of highly integrated microelectronic devices causes urgent demands for advanced thermally conductive adhesives (TCAs) to solve the interfacial heat-transfer issue. Due to their natural 2D structure and isotropic thermal conductivity, metal nanoflakes are promising fillers blended with polymer to develop high-performance TCAs. However, achieving corresponding TCAs with thermal conductivity over 10W m-1 K-1 at filler content below 30 vol% remains challenging so far. This longstanding bottleneck is mainly attributed to the fact that most current metal nanoflakes are prepared by "bottom-up" processes (e.g., solution-based chemical synthesis) and inevitably contain lattice defects or impurities, resulting in lower intrinsic thermal conductivities, only 20-65% of the theoretical value. Here, a "top-down" strategy by splitting highly purified Ag foil with nanoscale thickness is adopted to prepare 2D Ag nanoflakes with an intrinsic thermal conductivity of 398.2W m-1 K-1 , reaching 93% of the theoretical value. After directly blending with epoxy, the resultant Ag/epoxy exhibits a thermal conductivity of 15.1W m-1 K-1 at low filler content of 18.6 vol%. Additionally, in practical microelectronic cooling performance evaluations, the interfacial heat-transfer efficiency of the Ag/epoxy achieves ≈1.4 times that of the state-of-the-art commercial TCA.

Performance Study of Diamond Powder-Filled Sodium Silicate-Based Thermal Conductive Adhesives.

With the development of miniaturized, highly integrated, and multifunctional electronic devices, the heat flow per unit area has increased dramatically, making heat dissipation a bottleneck in the development of the electronics industry. The purpose of this study is to develop a new inorganic thermal conductive adhesive to overcome the contradiction between the thermal conductivity and mechanical properties of organic thermal conductive adhesives. In this study, an inorganic matrix material, sodium silicate, was used, and diamond powder was modified to become a thermal conductive filler. The influence of the content of diamond powder on the thermal conductive adhesive properties was studied through systematic characterization and testing. In the experiment, diamond powder modified by 3-aminopropyltriethoxysilane coupling agent was selected as the thermal conductive filler and filled into a sodium silicate matrix with a mass fraction of 34% to prepare a series of inorganic thermal conductive adhesives. The thermal conductivity of the diamond powder and its content on the thermal conductivity of the adhesive were studied by testing the thermal conductivity and taking SEM photos. In addition, X-ray diffraction, infrared spectroscopy, and EDS testing were used to analyze the composition of the modified diamond powder surface. Through the study of diamond content, it was found that as the diamond content gradually increases, the adhesive performance of the thermal conductive adhesive first increases and then decreases. The best adhesive performance was achieved when the diamond mass fraction was 60%, with a tensile shear strength of 1.83 MPa. As the diamond content increased, the thermal conductivity of the thermal conductive adhesive first increased and then decreased. The best thermal conductivity was achieved when the diamond mass fraction was 50%, with a thermal conductivity coefficient of 10.32 W/(m·K). The best adhesive performance and thermal conductivity were achieved when the diamond mass fraction was between 50% and 60%. The inorganic thermal conductive adhesive system based on sodium silicate and diamond proposed in this study has outstanding comprehensive performance and is a promising new thermal conductive material that can replace organic thermal conductive adhesives. The results of this study provide new ideas and methods for the development of inorganic thermal conductive adhesives and are expected to promote the application and development of inorganic thermal conductive materials.

Synthesis of multitask star‐shaped oligoaniline: Introducing a novel, efficient epoxy hardener

AbstractMultitask star‐shaped oligoaniline (S‐TAH) was synthesized using microwave irradiation in three steps: preparation of phthalic acid‐ capped tetra‐aniline (as the arm), synthesis of a tetrafunctional biobased core, and subsequently, coupling arms to the core, using a divergent approach. A biobased core was synthesized through a direct condensation reaction of pentaerythritol, with l‐lactic acid. The chemical structures were extensively characterized using Fourier‐transform infrared and proton nuclear magnetic resonance spectroscopy. The performance of S‐TAH, as a multitask hardener for bisphenol A‐based epoxy resin (EP), was evaluated using differential scanning calorimetry, thermal gravimetric analysis, dynamic thermomechanical analyses (DMTA), and four‐prob conductometry. Peaks of cure exotherms for S‐TAH/EP (1:1) systems appear at 135°C with a tail‐like peak around 175°C. Compared to conventional amine‐cured EP, the thermal stability of the S‐TAH/EP cured was significantly higher, that is, ~ 40°C enhancement in half weight loss temperature (T50). A three‐fold improvement in char yield was observed. From DMTA, the material cured with S‐TAH displays representative storage moduli in glassy (9.4 GPa) and rubbery (5.2 GPa) states reflecting a uniform network and viscoelastic behavior. The electrical conductivities (σ) of the pure S‐TAH and the epoxy systems cured with S‐TAH/EP are 4.3 × 10−4, and 2.65 × 10−4, respectively. T star‐shaped oligoaniline is a promising multitask hardener—functioning as hardener, thermal stabilizer, electrically conductive and toughening agents—which can be versatilely applied in thermal resistance anticorrosive coatings and conductive adhesives.

Thermal conductivity and shear strength characterisation of hybrid GNPs and silane functionalised BN as thermal conductive adhesive

ABSTRACT The demand for high thermal conductivities and improved adhesion of thermal conductive adhesives has heighten the need for hybrid fillers with extraordinary properties, such as boron nitride (BN) and graphene nanoplatelets (GNP) especially at lower filler contents (<20 wt.%), particularly with silane-functionalised BN (fBN) and adhesion using the single lap joints approach. Thus, this study was conducted to measure the thermal conductivity and shear strength of hybrid GNP with BN or fBN at different filler sizes, GNP ratios, and silane coupling agents (KK550 and KH560). We observed that the hybrid GNP/fBN_KH560 composite at a ratio of 0.75 exhibited the highest thermal conductivity and shear strength with enhancements of 198.42% and 81.82%, respectively, attributed by the high compatibility between fBN_KH560 and the polymer matrix, proven by the lowest measured contact angle and Hansen solubility parameter difference. Despite the thermal conductivity value not surpassing that of the single-filled GNP composite, the hybrid composite at lower filler content was considered a success as it exhibited a synergetic effect when compared with single-filled BN or fBN; with the difference of 0.111. Besides, crack deflection, particle debonding and pull-out mechanism improved the shear strength and promoted cohesive failure in the hybrid composite.

Heat Dissipation Analysis of Thermal Conductive Adhesive Based on Liquid Cooled Battery Pack

In view of the serious heating problem of the automotive power battery, different thermal conductive adhesive cooling structures of the liquid cooled battery pack were designed. Based on a battery cell for an electric vehicle, five battery pack models in series are used to measure the discharge internal resistance data under constant normal temperature and high temperature conditions respectively. The influence of thermal conductive adhesive structure on temperature field is analyzed through Fluent. The results showed that the thermal conductive adhesive structure between the monomers had a significant effect on reducing the maximum temperature of the battery pack and improving the temperature field balance.

Thermal conductivity and dielectric properties of high thermal conductive adhesives in the large generator insulation materials

Thermal conductivity and dielectric properties of high thermal conductive adhesives in the large generator insulation materials

Fabrication of Thermal Conductive Adhesive Using Ni Graphite Core-shell and Application to LED Lighting

Fabrication of Thermal Conductive Adhesive Using Ni Graphite Core-shell and Application to LED Lighting

Mechanical and thermal properties of graphene and carbon nanotube reinforced epoxy/boron nitride adhesives

Outstanding mechanical properties and high thermal conductivity epoxy composites are being developed and are becoming urgent in the electronic and aerospace industries. Boron nitride nanosheet (BN), a nanomaterial with high thermal conductivity, and its epoxy composite adhesive have high thermal conductivity. However, due to its characteristics, the mechanical properties of BN/epoxy will decrease when more BN is added. Therefore, this study graphene platelet and carbon nanotube are selected and packed epoxy/BN composite adhesives to develop adhesives with excellent mechanical properties and thermal conductivity at the same time. In this study, an enhancement effect between a graphene platelet (GnP) and a carbon nanotube (CNT) within an epoxy/BN composite is reported. In the three-phase composite adhesive, the 2 D graphene platelets and 1D carbon nanotubes form a global bearing force network, and the boron nitride nanosheets provide high heat conduction inside the epoxy. They both complement each other in developing thermal conductive and high mechanical energy epoxy composite adhesives. At filler ranging from 0 to 1.0 wt%, epoxy/BN-CNT can improve the fracture toughness (K 1c ), critical stress-energy release rate (G 1c ) and Young's modulus of pure epoxy, are 89, 484, and 67% compared to 52, 286, and 42% in epoxy/BN-GnP composites, respectively. When adding 5.0 wt% of BN-CNT, the epoxy composites' thermal conductivity is up to 0.8 W/m%K, 400% higher than pure epoxy. This article also tested the electrical conductivity of epoxy/BN-CNT and epoxy/BN-GnP composites and found that the electrical conductivity was increased by 12 and 10 orders of magnitude, respectively, and it could be used as an antistatic material. Investigating the enhanced mechanism of epoxy/BN/CNT and epoxy/BN/GnP composites by scanning electron microscopy analysis. Lap shear strength tests on epoxy composite adhesives confirm the reinforcement effect of GnP and CNT of epoxy/BN composites.

Extreme Low Interfacial Thermal Resistance Heat Conductive Sheet Design

High thermal conductive adhesive is important to cool power devices. Recently thermal conductivity reaches more than 10W/mK by efficient addition of thermal conductive filler(1). However, high loading of filler makes the thermal conductive sheet poor adhesion. In order to have high thermal conductivity and good adhesion, we tried to use AlN whisker developed by Nagoya university(2) to orient Z-direction. One volume percent of the AlN whisker improved the thermal conductivity drastically (3). Furthermore, we focused on reducing an interfacial heat resistance between high thermal conductive sheet composed of resin and heat conductive filler and metal such as Cu or Al. The interfacial heat resistance was determined by dispersion of high heat conductive filler and interfacial residual stress. The good dispersed sheet shows lower interfacial resistance than poor dispersed sheet, The interfacial residual stress causes an poor contact to metal to make void in the interface. To consider the effect of those facts, we successfully developed the high thermal conductive sheet with extremely low interfacial resistance. Bulk heat conductivity of the sheet is higher than 13W/mK. The interface heat resistance is below 0,009W/C.

Finely balanced high heat conductivity, peel strength and breakdown voltage in polymer composites with binary hybrid inorganic fillers

Nowadays, the demand of polymer based composites with high thermal conductance is rapidly increasing. Thermal conductive acrylate pressure sensitive adhesives are widely studied due to their excellent ageing resistance, light resistance, water resistance, oil resistance and broad application field. In this work, thermal conductive pressure sensitive adhesives with excellent comprehensive performances have been prepared from acrylate pressure-sensitive adhesive (matrix) and aluminum oxide/aluminum nitride particles (fillers). The influences of the class, loading content and grain size of fillers on heat conductivity, electric insulation and mechanical features of composites were deeply researched. High dispersion of fillers in matrix could be obtained by surface modification of fillers using silane coupling agent and polymethyl methacrylate. Heat conductivity of composites was improved with increasing of filler content and sharply elevated at a critical filler content. As filler content was increased, electric insulation trait was reduced but still kept at a relatively high level. High filler content was harmful to mechanical property. Fortunately, the composites with hybrid fillers of varied grain sizes were found to have significantly promoted thermal conducting, electric insulating and mechanical performances in comparison with single filler of one size. That might be ascribed to synergistic effect of both fillers with varied grain sizes. Finely balanced comprehensive features were achieved at a weight ratio of 3:7 (small size filler/large one). High heat conductivity (∼0.83 W m−1K−1), breakdown voltage (∼1.9 kV) and 180° peel strength (∼8.3 kN m−1) were obtained. This work might open the door to the large-scale fabrication of high-performance thermal conductive acrylic pressure sensitive adhesives based on size effect of hybrid fillers.

Forensic smartphone analysis using adhesives: Transplantation of Package on Package components

Investigators routinely recover data from mobile devices. In many cases the target device is severely damaged. Events such as airplane crashes, accidents, terrorism or long submersion may bend or crack the device's main board and hence prevent using standard forensic tools. This paper shows how to salvage forensic information when NAND memory, SoC or cryptographic chips are still intact. We do not make any assumptions on the state of the other components. In usual forensic investigations, damaged phone components are analysed using a process called “forensic transplantation”. This procedure consists of unsoldering (or lapping) chips, re-soldering them on a functionnal donor board and rebooting.Package on Package (PoP) component packaging is a new technique allowing manufacturers to stack two silicon chips, e.g. memory, CPU or cryptographic processors. Currently, PoP is widely used by most device manufacturers and in particular by leading brands such as Apple, BlackBerry, Samsung, HTC and Huawei. Unfortunately, forensic transplantation destroys PoP components.This work overcomes this difficulty by introducing a new chip-off analysis method based on High Temperature Thixotropic Thermal Conductive Adhesive (HTTTCA) for gluing the PoP packages to prevent misalignment during the transplantation process. The HTTTCA process allows the investigator to safely unsolder PoP components, which is a crucial step for transplantation. To demonstrate feasibility, we describe in detail an experimental forensic transplantation of a secure mobile phone PoP CPU.

Joining of carbon fibre reinforced polymer to Al-Si alloy for space applications

The joining of hypereutectic Al-Si alloy heat pipes to CRFP skins has been studied for radiator panel applications. Three different epoxy adhesives (two thermal conductive adhesives and one high-strength structural one) were used and mechanically characterised before and after thermal cycling. Two adhesives gave the most promising results, in terms of mechanical strength (apparent shear ~ 25MPa for 100µm thick lap joints). Thermal cycling (10 cycles between −30°C and +90°C) did not significantly affect the mechanical properties of the joints or the failure propagation mode. The use of the thermal conductive adhesive could also guarantee good thermal conductivity of the designed panel.

Electrically conductive adhesives, thermally conductive adhesives and UV adhesives in data extraction forensics

Recent publications underline the interest of using polymers in microelectronics (Li and Wong, 2006a; Cui et al., 2014). Polymers are the ideal interconnect alternative to solder materials containing lead. Electrically Conductive Adhesives [ECAs] (Li and Wong, 2006b), Thermally Conductive Adhesives (TCAs) (Felba et al., 2011) and UV Adhesives (UVAs) (Asif et al., 2005) mainly consist of a polymeric resin (epoxy, silicon, polyurethane or polyimide) that provides physical and mechanical properties such as adhesion, mechanical strength while containing metal fillers (silver, gold, nickel or copper) that conduct electricity (Luo et al., 2016). Currently it is possible to find really cheap polymeric resin. Using these resins for digital forensic purposes is the focus of this paper, that we demonstrate in a hardware reverse engineering prototype case study.When considering new mobile devices, such as secure phones, it is often necessary to spy communication and perform numerous tests on the memory (e.g. by changing some bytes) to understand or modify the implemented security mechanisms (manipulate system time, locate password hashes, observe artefacts of implemented security algorithms, etc.). Traditional techniques use either laser attacks/probing (chip on) or soldering/read/re-soldering (chip off/on) (Heckmann et al., 2016, Jongh, 2014). These two techniques are unsuitable for repeated operations requiring many readings/changes/injections. This paper describes a concrete case study using adhesive properties complementary to chip on and chip off methods.We present the steps using different properties of adhesives (ECA, TCA, UVA) that we will lead to the realisation of a prototype particularly suitable for the repeating of the read phases/changes/injections necessary for reverse engineering secure mobile devices.

Thermal conductivity of epoxy adhesive enhanced by hybrid graphene oxide/AlN particles

This study aims to improve the heat dispersion of electronic equipment by utilization of thermal conductive adhesive composed of epoxy matrix and filler. AlN particles with different size, graphite, graphene oxide (GO) were used alone or in a synergistic manner to prepare thermal conductive adhesives. The structure of prepared GO was characterized by XRD, FT-IR, Raman spectra and AFM. The analysis indicates that most of prepared GO is in single layer structure. The thermal conductivity and viscosity of adhesive were measured by thermal constants analyzer and rotational viscometer respectively. The results show adhesives filled with larger AIN particles possess higher thermal conductivity than that filled with smaller particles at the given filling content. GO is better than graphite as the filler to improve the thermal conductivity of the epoxy resin. When 8wt% GO or 70wt% 5μm-AlN particles was added, the thermal conductivities of adhesives were about 6.42 times and 11.8 times that of pure epoxy respectively. To further improve the thermal conductivity, 50wt% 5μm-AlN particles and 6wt% GO hybrid filler were proposed, and the final thermal conductivity reached up to 2.77W/mk, that was 14.6 times of that of neat epoxy. In addition, Agari equation as a systematic theoretical modelling was cited to analyze the effect of each filler on improvement of thermal conductivity of adhesive.

Thermal analysis of chip-on-flexible LED packages with Cu heat sinks by SnBi soldering

Purpose – The purpose of this paper is to discuss the possibility of using soldering process for the bonding of chip-on-flexible (COF) light-emitting diode (LED) packages to heat sinks. The common bonding materials are thermal conductive adhesives. For thermal performance and reliability concerns, Tin-Bismuth (SnBi) lead-free solder paste was used for the connection of the COF packages and the Cu heat sinks by a soldering process in this study. Meanwhile, the geometrical effect of the SnBi solder layer on the thermal performance was also investigated. Design/methodology/approach – The effects of the bonding materials and the area of the solder layers on the thermal performance of the LED modules were investigated by finite element simulation and experimental tests. Findings – The SnBi soldered modules show much lower thermal resistance at the bonding layers than the adhesive-bonded LED module. Vertical heat transfer from the LED chips to the heat sinks is the primary heat dissipation mode for the SnBi soldered modules. Thus, the LED module with local solder layer shows similar LED thermal performance with the full-area soldered module. Meanwhile, the local soldering process decreases the possibility to form randomly distributed defects such as the large area voids and residue flux in the solder layers. Research limitations/implications – The research is still in progress. Further studies mainly focus on the reliability of the samples with different bonding materials. Practical implications – COF package is a new structure for LED packages. This study provides a comparison between SnBi solder and adhesive material on the thermal performance of the LED. Meanwhile, the authors optimized the geometrical design for the solder layer. The study provides a feasible bonding process for COF packages onto heat sinks. Originality/value – This study provides a soldering process for the COF LED packages. The thermal performance of the LED light source was improved significantly by the new process.