Industrial adhesives play a crucial role in the electronics manufacturing industry. These adhesives are used variedly in the electronics industry, including bonding, sealing, encapsulating, and protecting electronic components. In addition, electronic adhesives also offer properties such as electrical conductivity, thermal conductivity, low outgassing, and moisture resistance.
In the electronic manufacturing industry, a wide variety of adhesives are available, each suited for specific applications and requirements. We understand that finding the correct adhesive for electronic and electrical applications that work for your needs can be a bit challenging. Thus, we will help you with the electronic adhesive selection process in this blog. However, before we get to that, let’s take a look at the various types of adhesives used for bonding electronic components.
A] Types Of Adhesives And Application Process Used To Bond Electronic Components
1. Conformal Coatings
Conformal coating serves as a thin polymer layer applied to a printed circuit board (PCB) to safeguard it against various elements such as dust, moisture, chemicals, stress, shock, and vibrations. This protective coating is carefully applied to cover the PCB, shielding its solder joints and other components. When it comes to adhesives for printed circuit boards (PCBs), it is crucial for them to cure rapidly and exhibit high-temperature resistance capabilities.
2. Die Attach
Electronic adhesives play a vital role in bonding semiconductor chips, commonly referred to as die, to their microelectronic semiconductor packages. This crucial process is widely known as die attach. In addition to its bonding role, electronic adhesive is vital in minimising stress levels during the system’s operation. The die attach epoxy adhesives must have good electrical conductivity and thermal resistance, with low ionic impurities, to ensure the desired result. Die attach is generally done using a jetting or stamping method.
Sealants are crucial for protecting electrical components from external moisture, water, and corrosive substances. On the other hand, they also work as electrical insulators in case of any problem with the circuitry.
3. Glob Top
Glob top refers to any protective encapsulation on semiconductors that protects the sensitive dies and wire bonds. They offer protection from moisture, physical damage, temperature fluctuations and other contaminants. Glob top is generally used in chip-on-board (COB) applications with the help of a dam-and-fill mechanism or applied directly. The thermal as well as electrical properties of adhesive systems should also be considered for glob top applications.
4. Surface Mounting
Surface mounting is the process of bonding the electrical components to the printed circuit board (PCB). The surface mount adhesive (SMA) can be used as an alternative to soldering the components. SMA can also be used to hold the components in place before soldering. Surface mount adhesives are applied via the dot method and cured using heat.
5. Underfilling
The underfill is used to coat and encapsulate the flip-chip, chip scale packaging (CSP) and ball grid array (BGA) devices. Underfills provide mechanical stability and reinforcement to the semiconductors by filling gaps between them. Low coefficients of thermal expansion, low ionic content and excellent shock resistance are some of the factors for selecting electronic adhesives that you should consider.
6. EMI / RFI Shielding
EMI/RFI shielding creates a protective layer over the circuits that protect the circuit from external electromagnetic interference. EMI/RFI shielding adhesives prevent electromagnetic or radio frequencies from entering or exiting the circuit. The adhesive used for EMI/RFI shielding should have the right degree of electrical conductivity and also provide structural bonding.
7. PCB & Semiconductor Manufacturing & Packaging
Adhesives are used extensively in PCB & semiconductor manufacturing and packaging industry. They are used for bonding components, encapsulating PCB, wire tacking and holding components in place for soldering. For high-quality performance, the adhesives must have thermal and electrical conductivity, high purity and low CTE.
B] Factors To Consider When Choosing The Right Adhesives For Electronic Components
1. Thermal Conductivity
Thermal conductivity is the physical property of a material to transfer heat. Electronic adhesives with good thermal conductivity can avoid overheating by dispensing heat, keeping the equipment safe. Usually, heat sinks are used to direct the heat away from the components.
Thermal conductivity helps to maintain an optimal working temperature of the component, protecting it from premature failure due to overheating. Hence, You should always test for thermal conductivity while choosing adhesives for electronic applications, as most electronic components produce high thermal energy. One component epoxy systems are an excellent choice for adhesives with thermal conductivity.
2. Electrical conductivity
Adhesives with electrical conductivity are designed to facilitate the free flow of electrical energy. As many electrical components require the free flow of electrical currents, electrical conductivity is crucial for an electrical adhesive. Electrically Conductive adhesives for electronics are essential for facilitating the proper functioning of various components, including the PCBs and their packages.
Adhesives with good electrical conductivity are usually made with silver, nickel or graphite. The silver-filled adhesive offers the best conductivity; however, it is also the most expensive one. Meanwhile, graphite-filled adhesive offers the most economical solution with relatively good electrical conductivity.
3. Adhesive Material
Adhesive materials can vastly affect the properties of the adhesive. Adhesives for electrical uses require certain chemical and mechanical properties, which are possible through certain selective materials. The choice of adhesive materials is based on the properties the adhesive is required to have.
Epoxy-based adhesives provide excellent bonding strength, thermal stability, and electrical insulation. Silicon-based adhesives are known for their flexibility, high-temperature resistance, and excellent electrical insulation. Similarly, Polyurethane adhesives offer a balance of mechanical strength, flexibility, and electrical insulation properties.
4. Moisture Resistance
Environmental considerations play a critical role in the selection of electronic adhesives, as moisture can have detrimental effects on PCBs and other electrical components. These effects include the risk of short circuits, corrosion, and current leakage. Moisture-resistant adhesives can be used in multiple ways to protect the PCB and smaller components from damage. Potting and encapsulation, conformal coatings, and underfilling are some of the ways to stop moisture from entering the components.
It is important to select moisture-resistant adhesives for electronic manufacturing to ensure the component’s longevity and optimal performance. Electronic adhesives seal the circuits, making them impervious to environmental moisture, thus making them compatible to use in various situations.
5. Chemical Resistance
An electronic device might be exposed to various chemicals during manufacturing, installation and maintenance. An adhesive with poor chemical resistance will degrade over time, reducing its performance. This could potentially cause problems with the device as well. Without the layer of protective adhesive coating, chemicals can hamper the electronic device and even cause short circuits.
Hence, chemical resistance should be one of your adhesive selection criteria for electronics. Chemical-resistant adhesives can endure frequent contact with chemicals without losing their bonding properties, keeping the device safe.
6. Heat Resistance
Electronic components are frequently subjected to high temperatures during the manufacturing process, as well as daily operations. Processes like soldering during manufacturing and electrical resistance during the equipment’s work life can cause the device to overheat. Adhesives without high-temperature resistance will either melt or lose their bonding strength, damaging the components of the electronics.
One-part and two-part epoxies, sodium silicate, and silicone-based adhesives are best suited for high-temperature adhesives for electronics. Adhesives specifically designed to withstand high temperatures will increase the device’s longevity and be safer and more cost-effective in the long run.
Conclusion
The adhesive used for bonding, coating and encapsulating electronic components plays an essential part in electronic devices’ performance, reliability, and longevity. Selecting the correct adhesive is crucial for the electronics industry. Consider the above points as a checklist for your electrical adhesives requirements. There are specific questions to analyse while selecting an adhesive, which will help you choose the adhesive with the right properties for your needs.
Choosing the correct adhesive will provide mechanical and chemical stability to the device in addition to reliable safety. It will also ensure product longevity and minimise device failure, boosting customer satisfaction.
If you are in the market for high-performance adhesives for electronics, Kohesi Bond is the right choice for you. Kohesi Bond provides high-quality, bespoke electrical adhesives with various mechanical and chemical properties for your industry needs. Contact us today for a detailed discussion!
