1. The term “FR-4” we frequently encounter is not a specific material name.
“FR-4,” commonly mentioned by circuit board manufacturers, refers to a classification for flame-retardant materials. It denotes a material specification indicating that the resin must self-extinguish once ignited. Rather than a specific material, it represents a material grade, leading to a variety of FR-4 grade materials utilized in standard circuit boards. Most of these are derived from a specific type of epoxy resin combined with fillers and glass fiber to create a composite material.
For instance, the water-green and black fiberglass boards produced by our company exhibit properties such as high temperature resistance, insulation, and flame retardancy. When selecting materials, it’s crucial to determine the specific characteristics required. This ensures you acquire the appropriate products.
Flexible printed circuit boards (FPCs), also known as flexible printed circuits, are crafted using a flexible substrate through a printing process.
There are primarily two categories of printed circuit board substrates: organic and inorganic materials, with organic substrates being the most commonly used. Different layers of PCBs also utilize varying substrates. For example, prefabricated composite materials are typically used for 3- to 4-layer boards, while glass-epoxy materials are predominantly found in double-sided boards.
2. Considering the Impact of SMT When Selecting a Sheet
During lead-free electronic assembly, as temperatures rise, the bending of the printed circuit board increases. This necessitates the use of boards with minimal bending, such as those made from FR-4 substrates. The expansion and contraction stress on the substrate from heating can adversely affect components, potentially causing electrode detachment and decreasing reliability. Therefore, it’s essential to pay attention to the material’s coefficient of thermal expansion, especially when dealing with components larger than 3.2 x 1.6 mm.
PCBs employed in surface mount technology must exhibit high thermal conductivity, excellent heat resistance (up to 150°C for 60 minutes), and solderability (up to 260°C for 10 seconds). They should also have strong copper foil adhesion (at least 1.5 x 10^4 Pa) and bending strength (around 25 x 10^4 Pa), as well as high conductivity, a low dielectric constant, and good punchability (precision of ±0.02 mm). Compatibility with cleaning agents is also important, and the surface must be smooth and flat, free from warping, cracks, scars, and rust spots.
3. PCB Thickness Selection
1. The thicknesses of printed circuit boards include 0.5mm, 0.7mm, 0.8mm, 1mm, 1.5mm, 1.6mm, (1.8mm), 2.7mm, (3.0mm), 3.2mm, 4.0mm, and 6.4mm. Notably, PCBs with thicknesses of 0.7mm and 1.5mm are commonly utilized for designing double-sided boards with gold fingers, while 1.8mm and 3.0mm are considered non-standard sizes.
2. From a production standpoint, the dimensions of a printed circuit board should not be smaller than 250mm x 200mm, with an ideal size typically ranging from (250mm to 350mm) by (200mm to 250mm). For PCBs where the long side is less than 125mm or the short side is under 100mm, a jigsaw method is recommended.
3. Surface mount technology specifies that the allowable warpage for a substrate with a thickness of 1.6mm is as follows: upper warpage must be ≤0.5mm and lower warpage must be ≤1.2mm. Generally, the permissible bending rate should remain below 0.065%. Metal materials can be categorized into three types, as illustrated in typical PCBs, and structural softness and hardness can also be classified into three categories.
4. Electronic plug-ins are evolving towards higher pin counts, miniaturization, SMD, and increased complexity. These plug-ins are mounted on the circuit board via pins, which are then soldered on the opposite side. This method is known as THT (Through Hole Technology) plug-in technology. Each pin requires a drilled hole in the PCB, exemplifying a typical PCB application.
5. Drilling is essential. With the rapid advancement of SMT chip technology, multilayer circuit boards require interconnections, achieved through electroplating post-drilling, necessitating various drilling equipment. To fulfill these demands, a range of PCB CNC drilling equipment with diverse capabilities is currently available both domestically and internationally.
6. The production process for printed circuit boards is intricate and encompasses a broad spectrum of techniques, primarily involving photochemistry, electrochemistry, and thermochemistry. The PCB production process includes multiple steps, and using rigid multilayer circuit boards as an example, the processing procedures can be illustrated effectively.
“FR-4,” commonly mentioned by circuit board manufacturers, refers to a classification for flame-retardant materials. It denotes a material specification indicating that the resin must self-extinguish once ignited. Rather than a specific material, it represents a material grade, leading to a variety of FR-4 grade materials utilized in standard circuit boards. Most of these are derived from a specific type of epoxy resin combined with fillers and glass fiber to create a composite material.
For instance, the water-green and black fiberglass boards produced by our company exhibit properties such as high temperature resistance, insulation, and flame retardancy. When selecting materials, it’s crucial to determine the specific characteristics required. This ensures you acquire the appropriate products.
Flexible printed circuit boards (FPCs), also known as flexible printed circuits, are crafted using a flexible substrate through a printing process.
There are primarily two categories of printed circuit board substrates: organic and inorganic materials, with organic substrates being the most commonly used. Different layers of PCBs also utilize varying substrates. For example, prefabricated composite materials are typically used for 3- to 4-layer boards, while glass-epoxy materials are predominantly found in double-sided boards.
2. Considering the Impact of SMT When Selecting a Sheet
During lead-free electronic assembly, as temperatures rise, the bending of the printed circuit board increases. This necessitates the use of boards with minimal bending, such as those made from FR-4 substrates. The expansion and contraction stress on the substrate from heating can adversely affect components, potentially causing electrode detachment and decreasing reliability. Therefore, it’s essential to pay attention to the material’s coefficient of thermal expansion, especially when dealing with components larger than 3.2 x 1.6 mm.
PCBs employed in surface mount technology must exhibit high thermal conductivity, excellent heat resistance (up to 150°C for 60 minutes), and solderability (up to 260°C for 10 seconds). They should also have strong copper foil adhesion (at least 1.5 x 10^4 Pa) and bending strength (around 25 x 10^4 Pa), as well as high conductivity, a low dielectric constant, and good punchability (precision of ±0.02 mm). Compatibility with cleaning agents is also important, and the surface must be smooth and flat, free from warping, cracks, scars, and rust spots.
3. PCB Thickness Selection
1. The thicknesses of printed circuit boards include 0.5mm, 0.7mm, 0.8mm, 1mm, 1.5mm, 1.6mm, (1.8mm), 2.7mm, (3.0mm), 3.2mm, 4.0mm, and 6.4mm. Notably, PCBs with thicknesses of 0.7mm and 1.5mm are commonly utilized for designing double-sided boards with gold fingers, while 1.8mm and 3.0mm are considered non-standard sizes.
2. From a production standpoint, the dimensions of a printed circuit board should not be smaller than 250mm x 200mm, with an ideal size typically ranging from (250mm to 350mm) by (200mm to 250mm). For PCBs where the long side is less than 125mm or the short side is under 100mm, a jigsaw method is recommended.
3. Surface mount technology specifies that the allowable warpage for a substrate with a thickness of 1.6mm is as follows: upper warpage must be ≤0.5mm and lower warpage must be ≤1.2mm. Generally, the permissible bending rate should remain below 0.065%. Metal materials can be categorized into three types, as illustrated in typical PCBs, and structural softness and hardness can also be classified into three categories.
4. Electronic plug-ins are evolving towards higher pin counts, miniaturization, SMD, and increased complexity. These plug-ins are mounted on the circuit board via pins, which are then soldered on the opposite side. This method is known as THT (Through Hole Technology) plug-in technology. Each pin requires a drilled hole in the PCB, exemplifying a typical PCB application.
5. Drilling is essential. With the rapid advancement of SMT chip technology, multilayer circuit boards require interconnections, achieved through electroplating post-drilling, necessitating various drilling equipment. To fulfill these demands, a range of PCB CNC drilling equipment with diverse capabilities is currently available both domestically and internationally.
6. The production process for printed circuit boards is intricate and encompasses a broad spectrum of techniques, primarily involving photochemistry, electrochemistry, and thermochemistry. The PCB production process includes multiple steps, and using rigid multilayer circuit boards as an example, the processing procedures can be illustrated effectively.
