In PCB (Printed Circuit Board) manufacturing, drilling is a crucial step that requires precise control to maintain the quality of the final product. One important aspect of this process is the use of upper and lower backing pads. These pads are essential for preventing the surface and bottom of the PCB from blooming or producing burrs during drilling. By using these auxiliary materials, the drilling surface remains smooth, which directly improves the overall quality of the PCB and increases its yield rate. Although these backing pads add some cost to the manufacturing process, their benefits—such as significantly enhancing the qualification rate of the product and reducing defects—justify the expense.
The upper backing plate for PCB drilling serves several important functions. First, it must provide sufficient hardness to prevent burr formation on the surface of the PCB during drilling. However, it is critical that the backing plate is not too hard, as excessive hardness could result in increased wear on the drill bit. The resin composition of both the upper and lower backing plates must also be carefully balanced. If the resin content is too high, molten resin can form and adhere to the hole walls during drilling, causing further issues.
In addition to hardness and resin composition, thermal conductivity is another key factor to consider. The backing pads should have high thermal conductivity to quickly dissipate the heat generated during drilling. This helps to lower the temperature of the drill bit, preventing it from overheating and reducing the risk of drill bit annealing. Moreover, the backing pads must have a certain level of rigidity to prevent excessive movement of the PCB when the drill bit is lifted. At the same time, they should exhibit sufficient elasticity, allowing the pads to deform slightly when the drill bit makes contact. This ensures precise alignment of the drill with the desired drilling position, ultimately improving the accuracy and reliability of the drilling process.
In summary, the use of upper and lower backing pads in PCB drilling is essential for improving product quality and manufacturing efficiency. These pads not only prevent defects such as burrs and blooming but also contribute to better thermal management and precise drilling. While they add to the cost, their positive impact on product yield and overall quality makes them a worthwhile investment in the PCB manufacturing process.
The material used for PCB drilling backing boards must have consistent uniformity to ensure smooth and precise drilling. Any irregularities, such as nodes caused by impurities, which result in uneven softness and hardness, can lead to drill bit breakage. Furthermore, if the surface of the upper backing board is hard and slippery, smaller drill bits may slip, deviating from the intended hole and potentially creating an angled elliptical hole on the PCB.
In China, the common materials for upper backing boards include phenolic paper rubber sheets, epoxy glass cloth sheets, and aluminum foils like LF2Y2 (No. 2 anti-rust aluminum, semi-cold hardened) and LF21Y (No. 21 anti-rust aluminum, cold work-hardened), typically with thicknesses ranging from 0.2 to 0.5mm. These materials are well-suited for use in double-sided drilling operations, offering good hardness that prevents burrs from forming on the upper surface of the drilled hole. The aluminum foil, in particular, provides rigidity, elasticity, and excellent thermal conductivity, which aids in dissipating heat from the drill bit. This significantly reduces the likelihood of drill breakage and minimizes the occurrence of partial holes, making aluminum foil more reliable than phenolic paper, which is prone to impurity-related issues.
Aluminum foil’s good heat dissipation capabilities help maintain optimal drilling temperatures and make it an environmentally friendly option. Furthermore, compared to oxygen plates, aluminum foil ensures that the resin does not contaminate the holes during drilling. The most common thicknesses for aluminum foil used in practice are 0.15mm, 0.20mm, and 0.30mm. Although 0.15mm offers the best contact with the PCB surface, it is difficult to handle during cutting, transportation, and usage. The 0.30mm foil, while higher in price, is less commonly used due to its cost, and 0.20mm (typically around 0.18mm in practice) is often selected as a balanced option.
Internationally, composite upper backing boards are also available. These boards feature 0.06mm aluminum alloy foil on the upper and lower layers, with a pure fiber core in the middle, totaling a thickness of 0.35mm. This design is tailored to meet the needs of high-quality multilayer PCB drilling. The advantages of this structure over traditional aluminum foil are clear: it offers superior drilling quality, precise hole positioning, longer drill bit life due to reduced wear, and greater resilience as the board returns to its original shape after external pressure. Additionally, composite backing boards are significantly lighter than aluminum foil, making them ideal for small hole drilling applications.
As for underlay boards, common options in China include phenolic paper boards, cardboard, and wood chip boards. Cardboard is soft and prone to burr formation, though it offers a uniform texture that prevents drill bit breakage and bit biting. Its low cost makes it suitable for thin copper foil or single-sided boards. However, it is less effective for drilling thicker copper foils. Wood chip boards, though harder than cardboard, suffer from poor texture uniformity, and burrs may appear when drilling copper foils thicker than 35 microns. For example, attempts to drill double-sided boards with 70-micron copper foil using wood chip board resulted in failures. Phenolic paper boards provide the best hardness uniformity among these options, offering the most reliable drilling results, though they are more expensive and not environmentally friendly.
In international markets, composite underlay boards are also available, with the same structure of 0.06mm aluminum alloy foil on the upper and lower layers and a pure fiber core in the middle, but with a greater total thickness of 1.50mm. These boards offer exceptional performance, particularly for drilling multilayer boards or small-diameter holes, and are more environmentally friendly than phenolic paper boards. However, the primary drawback is their higher cost.
In summary, selecting the right backing material for PCB drilling depends on balancing performance, cost, and environmental factors. For high-quality, multi-layer PCB applications, composite backing materials offer superior results, while more traditional options like phenolic paper and aluminum foil remain cost-effective choices for less demanding tasks.
The upper backing plate for PCB drilling serves several important functions. First, it must provide sufficient hardness to prevent burr formation on the surface of the PCB during drilling. However, it is critical that the backing plate is not too hard, as excessive hardness could result in increased wear on the drill bit. The resin composition of both the upper and lower backing plates must also be carefully balanced. If the resin content is too high, molten resin can form and adhere to the hole walls during drilling, causing further issues.
In addition to hardness and resin composition, thermal conductivity is another key factor to consider. The backing pads should have high thermal conductivity to quickly dissipate the heat generated during drilling. This helps to lower the temperature of the drill bit, preventing it from overheating and reducing the risk of drill bit annealing. Moreover, the backing pads must have a certain level of rigidity to prevent excessive movement of the PCB when the drill bit is lifted. At the same time, they should exhibit sufficient elasticity, allowing the pads to deform slightly when the drill bit makes contact. This ensures precise alignment of the drill with the desired drilling position, ultimately improving the accuracy and reliability of the drilling process.
In summary, the use of upper and lower backing pads in PCB drilling is essential for improving product quality and manufacturing efficiency. These pads not only prevent defects such as burrs and blooming but also contribute to better thermal management and precise drilling. While they add to the cost, their positive impact on product yield and overall quality makes them a worthwhile investment in the PCB manufacturing process.
The material used for PCB drilling backing boards must have consistent uniformity to ensure smooth and precise drilling. Any irregularities, such as nodes caused by impurities, which result in uneven softness and hardness, can lead to drill bit breakage. Furthermore, if the surface of the upper backing board is hard and slippery, smaller drill bits may slip, deviating from the intended hole and potentially creating an angled elliptical hole on the PCB.
In China, the common materials for upper backing boards include phenolic paper rubber sheets, epoxy glass cloth sheets, and aluminum foils like LF2Y2 (No. 2 anti-rust aluminum, semi-cold hardened) and LF21Y (No. 21 anti-rust aluminum, cold work-hardened), typically with thicknesses ranging from 0.2 to 0.5mm. These materials are well-suited for use in double-sided drilling operations, offering good hardness that prevents burrs from forming on the upper surface of the drilled hole. The aluminum foil, in particular, provides rigidity, elasticity, and excellent thermal conductivity, which aids in dissipating heat from the drill bit. This significantly reduces the likelihood of drill breakage and minimizes the occurrence of partial holes, making aluminum foil more reliable than phenolic paper, which is prone to impurity-related issues.
Aluminum foil’s good heat dissipation capabilities help maintain optimal drilling temperatures and make it an environmentally friendly option. Furthermore, compared to oxygen plates, aluminum foil ensures that the resin does not contaminate the holes during drilling. The most common thicknesses for aluminum foil used in practice are 0.15mm, 0.20mm, and 0.30mm. Although 0.15mm offers the best contact with the PCB surface, it is difficult to handle during cutting, transportation, and usage. The 0.30mm foil, while higher in price, is less commonly used due to its cost, and 0.20mm (typically around 0.18mm in practice) is often selected as a balanced option.
Internationally, composite upper backing boards are also available. These boards feature 0.06mm aluminum alloy foil on the upper and lower layers, with a pure fiber core in the middle, totaling a thickness of 0.35mm. This design is tailored to meet the needs of high-quality multilayer PCB drilling. The advantages of this structure over traditional aluminum foil are clear: it offers superior drilling quality, precise hole positioning, longer drill bit life due to reduced wear, and greater resilience as the board returns to its original shape after external pressure. Additionally, composite backing boards are significantly lighter than aluminum foil, making them ideal for small hole drilling applications.
As for underlay boards, common options in China include phenolic paper boards, cardboard, and wood chip boards. Cardboard is soft and prone to burr formation, though it offers a uniform texture that prevents drill bit breakage and bit biting. Its low cost makes it suitable for thin copper foil or single-sided boards. However, it is less effective for drilling thicker copper foils. Wood chip boards, though harder than cardboard, suffer from poor texture uniformity, and burrs may appear when drilling copper foils thicker than 35 microns. For example, attempts to drill double-sided boards with 70-micron copper foil using wood chip board resulted in failures. Phenolic paper boards provide the best hardness uniformity among these options, offering the most reliable drilling results, though they are more expensive and not environmentally friendly.
In international markets, composite underlay boards are also available, with the same structure of 0.06mm aluminum alloy foil on the upper and lower layers and a pure fiber core in the middle, but with a greater total thickness of 1.50mm. These boards offer exceptional performance, particularly for drilling multilayer boards or small-diameter holes, and are more environmentally friendly than phenolic paper boards. However, the primary drawback is their higher cost.
In summary, selecting the right backing material for PCB drilling depends on balancing performance, cost, and environmental factors. For high-quality, multi-layer PCB applications, composite backing materials offer superior results, while more traditional options like phenolic paper and aluminum foil remain cost-effective choices for less demanding tasks.
