Keyword: pcb board, PCB, circuit board, printed circuit boards
A phenolic substrate Phenolic Phenolic resin substrate , the resin ester from benzene and formaldehyde in a solvent, pcb board the reaction product formed by dehydration condensation reaction . Phenolic resin reinforced paper filler , and then pressed to the substrate foil , therefore , they are also referred to as " paper phenolic laminate ." The first intoxicated based substrate may wake pcb board steep tree is known as phenolic cloth . With cloth and phenolic resin, the resin with a suitable solvent to form a solution which can be used to melt impregnated fabric . Then , diffuse stains resin cloth is cut into pieces, stacked piles and placed two system board used pcb board in the process of heating the middle of the plate . The combined effect of temperature and pressure and the flow of the resin melt to form a whole. Thus, after the last cycle of the system board link, a very hard, rigid substrates on the system better. In essence, phenolic cloth has now been replaced by phenolic paper . In accordance with the National Electrical Manufacturers Association (NEMA) standards, the level of the substrate is divided into X, XX and XXX, which means that the phenolic pcb board resin content of about 35% , respectively , 45% , or 55% , the rest is filler paper and other and additives . For these substrates is , X and XX level of performance is poor , and therefore rarely used. XXX level is the result of further improvement of the material can be divided into XXP and XXXPC level , where P is the resistance can be washed , PC is a cold drawing process . Their properties are summarized as follows : 1.XX levels: paper phenolic resin , having an average electrical properties, good mechanical properties , pcb board is not suitable for punching, less wear on the drilling machine . 2.XXP levels: the XX level similar, but at a high temperature (200 - 250 F) can be punched under . 3. XXX grade : resin content than XX grade , and has good electrical and mechanical properties, suitable for use in RF applications in the field . 4.XXXP levels: the level XXP same, but contain pcb board more resins suitable for the intended use of the most common . 5.XXXPC levels: as the XXXP level , but can be cold- punching (70 - 120 F), has a high insulation resistance , low water absorption , it is suitable for applications in high humidity areas . Phenolic resin substrate with good punching resistance, ease of processing . Their prices are also relatively inexpensive, so get the widest range of commercial applications. Phenolic paper substrate, a drawback is their poor arc resistance and water absorption higher than the epoxy substrate pcb board.
Epoxy substrate Substrate is used as the epoxy resin and glass fiber filler or reinforced fiber paper , and then pressing the top foil to obtain CCL . Accordingly , depending on the type of filler which is called " epoxy glass cloth laminate " or " epoxy laminate paper pcb board." In the process of the system board , by heating, pressing and adding the epoxy resin curing catalyst . The final product is neither dissolved nor reversible thermosetting resins, which can withstand all but the acid descaling chemicals , except at high temperatures , almost no damage pcb board. Some special properties of epoxy resins are: 1.during the curing shrinkage rate is low ; 2.hard material ; 3.has excellent posts Relay ; 4.exhibit high mechanical strength ; 5.has a high alkali resistance and pcb board excellent acid and solvent capacity ; 6.a wide range of temperature and frequency conditions, shows a good electrical properties , which are excellent insulating material with a high dielectric strength ; 7. excellent moisture resistance and low water absorption. Epoxy resin is usually reinforced with a high -quality materials such as glass fiber cloth, pcb board composite materials and other combinations , showing extremely high mechanical strength and excellent electrical properties. glass cloth board For the production of glass cloth reinforced epoxy glass cloth boards. G-10, G-11, FR -4 and FR-5 , etc. are some of the glass cloth board is now available types . The diameter of the glass fibers or filaments is typically 9.6m (0.38mil). In knittings , bunching together they are , after New Jiaocheng line, and woven into a glass fiber cloth . Their line is different, the glass fiber cloth fabric lines per inch line indicates the number pcb board. 1. 6mm thick layer of a substrate comprising glass fiber cloth 8 , if the drilled hole with a diameter of 1mm , will cut off about 10,000 filaments . The hole in the wall of the glass fiber will be of 20,000 terminals. Spiak and Valiquette (1994) describes the system board industry to seek better quality, pcb board more rapid production of material trend. Printed circuit boards of the most "pan and industry standard base is a strong Tg epoxy glass fiber cloth or a value of 135 'C for FR-4. Its relative dielectric constant of about 4.4 , the propagation delay is approximately 178ps / in, one or more layers of these substrates using epoxy resin impregnated glass fiber woven cloth . FR-4 because its performance is suitable for most applications in the field of electrical and mechanical performance requirements and become the most widely used materials they exhibit high mechanical strength and workability , allowing drilling resistance, thermal stability and flame retardancy level reaches Vo . of single-and double-sided design , they are flexible with the processing , and the finished product board performance and suitable for many surface mount technology applications. However, the following higher pcb board performance to (Guiles, 1998) the development of new materials has become necessary : 1.board to meet the special requirements of the heat , that is, in a small space to handle highly concentrated energy ; 2. the number of large or high-level board manufacturing complexity requirements , including the need for accurate alignment of the etching pattern of the complex ; 3. Due to the special assembly technology ( flip chip , chip on board technology) or increase the reliability pcb board requirements , the board needs to have a controlled thermal expansion ; 4.a plate requires special or harsh electrical properties , particularly to ensure that low propagation delay , low crosstalk and high clock speeds and requires a low dielectric constant , in order to ensure low attenuation , an Good signal integrity , higher clock speed required low dissipation factor and the portable electronic device in the low power requirements. Substrate important physical properties of a z-axis direction pcb board is the total expansion of the expansion occurred in the circuit board assembly of the production and subsequent use, the first offset caused by a series of soldering temperature , then the operating temperature due to the environment of use offsets. z- direction dimension of the harmful effects of the pillars expansion body ( plated through holes) hardening . lower z-axis expansion , structural hardening and lower overall life of electronic assemblies is derived from a larger base pcb board of development (Lucas, 1993).
Ehrler (2002) tested a variety of epoxy pcb board materials and reinforcement properties , they improve the electrical printed circuit boards and thermodynamic properties , represents the direction of development of new materials . As shown in Figure 611 , the low point of the high soldering temperature Tg of this expanded range of the z-axis direction has a lower expansion , thereby improving the reliability of the through hole . This is usually accomplished by increasing the cross-linking material . Achieved . FR-4 material having a high pcb board Tg point (I80 "C), reducing the z-axis expansion , and thus its space , better stability, this complex circuit board is very important because the core do not like the conventional the FR-4 as many heated to a temperature above the Tg point , while enhancing the substrate defects for stress resistance , improved product life pcb board expectancy. this high-performance FR-4 substrate and the standard category "E" glass reinforced materials, it has a low dielectric constant and 168ps/in to 3.9 propagation delay . However, some high Tg point of FR-4 resin, thermal stability and conventional FR-4 does not match , and their copper foil peel strength is low. Lin (2003) describes a series of material properties NPLD with desirable high Tg point (200 ), low dielectric constant ( 3.5 -3.9 ) and dissipation factor ( 0.038 -0.01 ) . These materials provide improved thermal resistance, dielectric properties and moisture resistance pcb board, they are best suited in the GHz frequency range applications.
