Terpineol based SOLVENTS
FOR ORGANIC CARRIERS OF ELECTRONIC PASTES
SUPPLY CHAIN
The organic carrier is the base material of electronic pastes. Carriers are classified as volatile or non‑volatile. Volatility strongly influences paste rheology and initial tack.
Typical carrier systems include ethyl cellulose (EC), nitrated cellulose (NC), PVA, PAA, polyurethane emulsion (PUE), PVB and PAM. Binders commonly employ pine oil, turpentine, EC–terpineol and acrylic resins; among these, EC–terpineol is the principal stabiliser–solvent system (Shiyong Luo, 2007). Paste viscosity is governed by the mass fraction of EC; in testing, formulations with approximately 5% EC performed well.
FEATURE
In stabiliser–solvent systems, solvent volatility is a primary design variable. Pure‑solvent blends can volatilise too rapidly, leading to unstable paste behaviour.
Excessive volatilisation increases viscosity, narrows the rheology window and promotes screen blocking. Volatilisation that is too slow delays printing and drying, raising reject rates. If evaporation is concentrated within a narrow temperature band, the film may crack and pinhole after sintering (Shiyong Luo, 2006).
Selecting the right solvent package is therefore critical to the performance of electronic pastes.
Electronic pastes comprise a conductive phase of metal particles dispersed in an organic binder. Conductivity is influenced by the binder resin type, the particle size distribution and the metal loading (Dandan Wu, 2008). Terpineol is a primary solvent used to dissolve tackifiers and other organic components.
Paste formulations must meet customer requirements. Different manufacturers specify targets for adhesive strength and film toughness. Adhesion performance depends on the binder resin and the interfacial stresses at the contact surface. Excessive internal stress can cause thermal‑expansion mismatch that is unacceptable in semiconductor devices.
Research indicates that the organic‑carrier content affects the measured cut force or shear strength of the sintered film (Weiping Gan, 2007). As carrier content increases, shrinkage increases and the cut force of the sintered film tends to decrease; improving the shrinkage ratio enhances film compatibility. Conversely, if the carrier content is too low, the paste is prone to screen blocking.
Performance
Volatilisation losses are higher with neat‑solvent formulations than with blended systems. Owing to differing boiling points, neat solvents tend to strip the carrier; using solvent blends allows control of evaporation by adjusting the proportions of volatile components such as turpentine, terpineol, diethylene glycol monobutyl ether acetate (DBAC) or dibutyl phthalate (DBP). The organic carriers exhibit pseudoplastic behaviour, which helps reduce volatilisation loss.
In the EC–terpineol stabiliser–solvent system, volatility can be tuned by adding turpentine, terpineol, DBAC or DBP; a reference blend is 28.5% DBAC, 57% terpineol, 9.5% DBP and 5% ethyl cellulose (Shiyong Luo, 2006).
The mass loss of ethyl cellulose was 91.66% at 325–375°C. The carrier volatilised between 150 and 200°C, with a mass loss of 93.88%.
INNOVATION & MARKET FORECAST
Global E-inks market value was USD 1.6 billion in 2014. The CAGR is forecast 2.2%, grown to USD 2.3 billion in 2023. ( Source: IDTechEx)
The 2014 market value of printed electronics in China was USD 1.15 billion, it is forecast to USD 16.7 billion, CAGR by 58%. ( Source: n-tech Research)
The main photovoltaic pastes are back Ag paste, silverback paste, and front silver paste. According to the forecast for photovoltaic installation in 2015, the market volume of Ag paste was 30k tons, the Silver paste was 160k tons. The total volume of the Chinese market in the world by 36%. (Source: xincailiao.com)
- Reduce manufacture cost, use BME replace NME.
- Improve performance.
- Eco-friendly, limited to use BBP, DBP, and unleaded formulas will are the industry standard.
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