Brief Introduction to Anti-static Workbenches
Anti-static workbenches are workbenches designed to limit electrostatic potential, suitable for electrostatic protection operations. Workbenches come in many styles, but structurally they basically consist of an anti-static work surface, support structure, and accessories.
Work surface: An anti-static work surface is a flat surface with sufficient strength and flatness, suitable for electrostatic protection operations, designed to limit electrostatic potential.
The work surface is the key component of an anti-static workbench. Since the work surface comes into direct contact with electronic components, it must effectively limit electrostatic potential and quickly discharge static charge. In addition, the work surface must provide a flat operating surface, be wear-resistant, scratch-resistant, impact-resistant, and stain-resistant to facilitate various operations.
Currently, most work surfaces are made of a composite material of anti-static melamine high-pressure decorative laminate (commonly known as anti-static fireproof board, hereinafter referred to as anti-static fireproof board) as the surface material and wood. The wood material is generally particleboard, with conductive elements such as steel columns embedded to achieve conductivity. The surface resistance and system resistance of a typical anti-static work surface are both around 10⁸ Ω.
The current problems with general anti-static worktops are twofold: firstly, their anti-static performance is not very stable, and their resistance is relatively high, making it difficult to quickly and effectively release static charge; secondly, their overall physical and chemical properties are relatively low, making them unable to effectively adapt to different work intensities and environments. For worktops that directly contact various electronic components, the ideal surface and system resistance should be between 10⁶ and 10⁸ Ω, while the initial voltage should be below 100V. Simultaneously, the worktop should possess comprehensive physical and chemical properties, including wear resistance, scratch resistance, impact resistance, stain resistance, aging resistance, and environmental friendliness. As is well known, advanced manufacturing has very high requirements for the production environment, demanding cleanliness and zero pollution. Anti-static worktops are made of anti-static fireproof boards combined with other materials, typically particleboard, requiring the use of adhesives. Both adhesives and particleboard release harmful substances such as formaldehyde, so formaldehyde emission levels must also be considered for anti-static worktops. Formaldehyde emission should be below 0.5 mg/L (equivalent to the European E1 standard), abrasion resistance should be greater than 1000 revolutions, and scratch resistance, impact resistance, stain resistance, and aging resistance should meet the requirements of GB/T 7911-1999 "High-Pressure Decorative Laminates (HPL) for Thermosetting Resin Impregnated Paper".
The above problems are mainly due to the fact that the performance of the antistatic fireproof board directly restricts the performance of the antistatic workbench. The quality of antistatic fireproof boards is discussed in other articles and will not be elaborated upon here. It is recommended to use imported antistatic fireproof boards, such as the Pride antistatic fireproof board from the Italian company Abete, which meets all the requirements for antistatic workbenches. At the same time, the composite substrate should be changed to an antistatic inorganic material, which is more environmentally friendly and safer. There is currently an antistatic inorganic material with a volume resistivity of approximately 104 Ω, a formaldehyde emission of less than 0.1 mg/L, and impact resistance superior to particleboard. It can stably control the system resistance value and voltage, making it an ideal substrate.
Supports refer to components used to support workbenches, and are classified by material into steel supports and composite wood supports. Steel supports are made of steel pipes no less than 1.5mm thick, coated with anti-static powder coating, and are further divided into C-type and H-type according to their structure (see Figures 2 and 3). Composite wood supports are made of double-layered anti-static and fireproof board composite wood substrate (see Figure 4).
H-type steel supports are mainly used for heavy-duty workbenches, while composite wood supports are mainly used for simple workbenches. C-type steel supports are increasingly accepted by users and have become the mainstream product for anti-static workbenches due to their aesthetic appearance, grounding function, adjustable height, and customizable accessories.
C-type steel supports consist of adjustable height support legs and a support surface. The support legs are formed by stamping steel in one piece, and the support surface is generally welded from steel pipes. Considering load-bearing requirements, the steel thickness is generally required to be no less than 1.5mm, and the surface must be covered with anti-static powder coating. The surface of the steel support must be smooth and glossy, free from peeling, blistering, dents, indentations, scratches, pitting, and sharp edges. Cuttings, drilling, and chamfering must be deburred.
The surface of the steel support must be covered with powder coating, primarily to increase the steel's corrosion resistance and enhance its appearance. Powder coating mainly consists of epoxy resin or polyester, an insulating material. It is charged by high-voltage electrostatic spraying and then evenly adsorbed onto the surface of the workpiece. Upon heating, the accumulated solid particles melt and solidify into a uniform, continuous, smooth, and even coating. Generally, electrostatic spraying refers to powder coating using the above processing method. The "electrostatic" aspect describes the processing method, not the actual antistatic properties. Because electrostatic spraying requires the powder coating to be charged, adding any antistatic materials would inevitably affect the powder's chargeability, making antistatic powder coatings difficult to process. There have been introductions to such products in Japan, but I have not seen any products on the market, nor have I heard of them being sold in China.
Is it always necessary for the steel support of an antistatic workbench to be antistatic? I believe it depends. The steel support area is generally small and doesn't directly contact the product. Furthermore, the film thickness of typical powder coatings is around 50-70 μm, which is easily broken down by 500V. Tests show that for steel supports with a film thickness of 50 μm, using the testing instruments specified in ASTM F150-1998, "Test Method for the Resistance of Conductive and Dissipative Resilient Floors," under the same testing conditions, resistance cannot be measured at 10V and 100V. However, when the voltage exceeds 500V, a surface resistance of 106Ω can be measured, and the surface resistance decreases as the voltage increases. Therefore, I believe that for general environments, a common powder coating is sufficient for the steel support of an antistatic workbench. However, for workbenches requiring specific antistatic properties, antistatic powder coatings must be used, but it is recommended that the testing voltage be less than 100V.
Appendices: Appendices are various non-essential components for extended applications. There are many types of accessories available, which can be flexibly adjusted according to user needs. They are mainly divided into wooden and steel types. The system resistance value should also meet the user's requirements.