Bulk Resistance Evaluation of Anisotropic Conductive Adhesive Particles Considering the Current Bending Effect

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
X. C. Chen ◽  
Bo Tao ◽  
Z. P. Yin
Keyword(s):  
Particle Diameter ◽  
Conductive Adhesive ◽  
Bulk Resistance ◽  
Deformation Degree ◽  
Bonding Force ◽  
Anisotropic Conductive Adhesive ◽  
Bending Effect ◽  
Current Flows ◽  
And Control ◽  
High Density Packaging

Because it is difficult to accurately estimate the electric resistance of anisotropic conductive adhesive (ACA) joints, the ACA’s applications in high density packaging field have been greatly limited. The bulk resistance of particles is an essential part of the resistance of ACA joints. For the ACA using solid nickel (Ni) particles, because current flows along the spherical profile of the particles, the bulk resistance of these particles will be underestimated if the current bending effect is neglected. Here we propose a new method, which considers this current bending effect, to accurately evaluate the bulk resistance of Ni particles. First, a mathematical model to calculate the resistance of an arbitrary shaped resistor is deduced on the basis of electromagnetic theory. Second, a numerical model is introduced to calculate the potential distribution in the particles. Finally, the bulk resistance calculated by the new model is compared with the conventional methods. It is shown that the value obtained from this model is much higher than those calculated by other methods. Furthermore, the correlation studies between the bulk resistance and the particle’s diameter, the deformation degree, and the bonding force are carried out. And the results show that these three parameters influence significantly on the bulk resistance. In conclusion, to obtain accurate bulk resistance of ACA particles and make them stable and reliable, it is important to take the current bending effect into consideration and control the particle diameter and the bonding force properly.

scholarly journals Design Guidelines for Anisotropic Conductive Adhesive Assemblies in Microelectronics Packaging

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Melida Chin ◽  
S. Jack Hu ◽  
James R. Barber
Keyword(s):  
Contact Resistance ◽  
Adhesion Strength ◽  
Modulus Of Elasticity ◽  
Elastic Recovery ◽  
Electrical Contact ◽  
Design Guidelines ◽  
Conductive Adhesive ◽  
Bonding Force ◽  
Anisotropic Conductive Adhesive ◽  
Number Of Particles

Multiple parameters are involved in the design of anisotropic conductive adhesive assemblies, and the overlapping influences that they have on the final electrical contact resistance represent a difficult challenge for the designers. The most important parameters include initial bonding force F, number of particles N, the adhesion strength GA, and modulus of elasticity E of the cured resin. It is well known that as the bonding force increases, the contact resistance decreases. However, when the bonding force reaches a certain maximum value, the contact between conductive particle and conductive track is disrupted due to delamination of the cured resin during the elastic recovery. The authors have shown in previous studies that the delamination is caused by high residual stresses and that it largely depends on the adhesion strength of the assembly and on the modulus of elasticity of the cured resin. Additionally, the authors have provided a methodology to quantify the maximum threshold value of the bonding force for different numbers of particles trapped between mating conductive tracks. In this paper, the relationships between contact resistance R and each one of these parameters are systematically investigated to create diagrams that give regions of robust design. Given the number of particles and their size, adhesion strength, and modulus of elasticity of the resin, the required bonding force can be found in order to achieve a desired range in contact resistance.

scholarly journals Design Guidelines for Anisotropic Conductive Adhesive Assemblies in Microelectronics Packaging

2005 ◽  
Author(s):  
M. Chin ◽  
S. J. Hu ◽  
J. R. Barber
Keyword(s):  
Contact Resistance ◽  
Adhesion Strength ◽  
Modulus Of Elasticity ◽  
Elastic Recovery ◽  
Electrical Contact ◽  
Design Guidelines ◽  
Conductive Adhesive ◽  
Electrical Contact Resistance ◽  
Bonding Force ◽  
Anisotropic Conductive Adhesive

The multiple parameters that are involved in the design of anisotropic conductive adhesive (ACA) assemblies, and the overlapping influences that they have on the final electrical contact resistance, represent a difficult challenge for the designers. The most conflicting parameters include initial bonding force F, number of particles N, adhesion strength GA, and modulus of elasticity E of the cured resin. It is well known that as the bonding force increases, the contact resistance decreases. However, when the bonding force reaches a certain maximum value, the contact between conductive particle and conductive track is disrupted due to delamination of the cured resin during the elastic recovery. The authors have shown in previous studies that the delamination is caused by high residual stresses and that it depends largely on the adhesion strength of the assembly and on the modulus of elasticity of the cured resin. Additionally, the authors have provided a methodology to quantify the maximum threshold value of the bonding force for different numbers of particles trapped between mating conductive tracks. In this paper, the relationships between contact resistance R and each one of these conflicting parameters are systematically combined to create design diagrams that give regions of robust design. It is found, for example, that for particles of radius 5μm, E = 0.9 GPa, GA = 50 J/m2, and 2 ≤ N ≤ 5, the required bonding force to achieve contact resistance within the range 7 < R < 40 mω, is 2.5 < F < 20mN.

scholarly journals Morphology and Degradation of Multicompartment Microparticles Based on Semi-Crystalline Polystyrene-block-Polybutadiene-block-Poly(L-lactide) Triblock Terpolymers

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4358
Author(s):  
Nicole Janoszka ◽  
Suna Azhdari ◽  
Christian Hils ◽  
Deniz Coban ◽  
Holger Schmalz ◽  
...  
Keyword(s):  
Cross Sections ◽  
Ring Opening ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Selective Degradation ◽  
The Core ◽  
Transmission Electron ◽  
And Control ◽  
Triblock Terpolymers

The confinement assembly of block copolymers shows great potential regarding the formation of functional microparticles with compartmentalized structure. Although a large variety of block chemistries have already been used, less is known about microdomain degradation, which could lead to mesoporous microparticles with particularly complex morphologies for ABC triblock terpolymers. Here, we report on the formation of triblock terpolymer-based, multicompartment microparticles (MMs) and the selective degradation of domains into mesoporous microparticles. A series of polystyrene-block-polybutadiene-block-poly(L-lactide) (PS-b-PB-b-PLLA, SBL) triblock terpolymers was synthesized by a combination of anionic vinyl and ring-opening polymerization, which were transformed into microparticles through evaporation-induced confinement assembly. Despite different block compositions and the presence of a crystallizable PLLA block, we mainly identified hexagonally packed cylinders with a PLLA core and PB shell embedded in a PS matrix. Emulsions were prepared with Shirasu Porous Glass (SPG) membranes leading to a narrow size distribution of the microparticles and control of the average particle diameter, d ≈ 0.4 µm–1.8 µm. The core–shell cylinders lie parallel to the surface for particle diameters d < 0.5 µm and progressively more perpendicular for larger particles d > 0.8 µm as verified with scanning and transmission electron microscopy and particle cross-sections. Finally, the selective degradation of the PLLA cylinders under basic conditions resulted in mesoporous microparticles with a pronounced surface roughness.

Electrical and mechanical characterization of an anisotropic conductive adhesive with a low melting point solder

2008 ◽  
Vol 85 (11) ◽  
pp. 2202-2206 ◽  
Author(s):  
Yong-Sung Eom ◽  
Keonsoo Jang ◽  
Jong-Tae Moon ◽  
Jae-Do Nam ◽  
Jong-Min Kim
Keyword(s):  
Melting Point ◽  
Mechanical Characterization ◽  
Conductive Adhesive ◽  
Anisotropic Conductive Adhesive

Issues in Assembly Process of Fine Pitch Chip-on-Flex Packages for LCD Applications

2004 ◽  
Author(s):  
Changsoo Jang ◽  
Seongyoung Han ◽  
Jay Ryu ◽  
Hangyu Kim
Keyword(s):  
Bonding Process ◽  
Conductive Adhesive ◽  
Assembly Process ◽  
Anisotropic Conductive Adhesive ◽  
Advantages And Disadvantages ◽  
Fine Pitch ◽  
Laser Bonding ◽  
Material Process ◽  
Process Combination ◽  
Underfill Material

Some of the current assembly issues of fine pitch chip-on-flex (COF) packages for LCD applications are reviewed. Traditional underfill material, anisotropic conductive adhesive (ACA) and non-conductive adhesive (NCA) are considered in conjunction with two applicable bonding methods including thermal and laser bonding. Advantages and disadvantages of each material/process combination are identified. Their applicability is further investigated to identify a process most suitable to the fine pitch packages (less than 40 μm). Numerical results and subsequent testing results indicate that NCA/laser bonding process produces most reliable joint for the fine pitch packages.

A Novel Anisotropic Conductive Adhesive for Lead-Free Surface Mount Electronics Packaging

2005 ◽  
Author(s):  
S. Manian Ramkumar ◽  
Krishnaswami Srihari
Keyword(s):  
Surface Area ◽  
Electronics Packaging ◽  
Conductive Adhesive ◽  
Lead Free ◽  
The Novel ◽  
Small Surface ◽  
Surface Mount ◽  
Anisotropic Conductive Adhesive ◽  
Fine Pitch ◽  
Very High

The electronics industry, in recent years, has been focusing primarily on product miniaturization and lead-free assembly. The need for product miniaturization is due to the continuous demand for portable electronic products that are multifunctional, yet smaller, faster, cheaper, and lighter. This is forcing the industry to design and assemble products with miniature passive and active devices. These devices typically have fine pitch footprints that provide a very small surface area for attachment. The solder attach technique relies primarily on the formation of intermetallics between the mating metallic surfaces. With a reduction in the surface area of the pads, the ratio of intermetallic to solder is very high once the solder joint is formed. This could result in unreliable solder joints, due to the brittle nature of intermetallics. In addition, the need to eliminate lead-based materials as a means of interconnection has renewed the industry’s interest in exploring other means of assembling surface mount devices reliably. This paper discusses the performance characteristics and preliminary research findings pertaining to a novel Anisotropic Conductive Adhesive (ACA) for electronics packaging applications, utilizing the Z Bond™ technology from Nexaura Systems, LLC. Typically, ACAs require the application of pressure during the curing process, to establish the electrical connection. The novel ACA uses a magnetic field to align the particles in the Z-axis direction and eliminates the need for pressure during curing. The formation of conductive columns within the polymer matrix provides a very high insulation resistance between adjacent conductors. The novel ACA also enables mass curing of the adhesive, eliminating the need for sequential assembly. The novel ACA’s I-V characteristics and performance under thermal and temperature-humidity aging are discussed in detail.

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