Experience of producing halogen free PCB From China factory
Experience of producing halogen free PCB
1 introduction 1.1 what is halogen-free substrate According to jpa-es-01-2003 standard, copper clad plate with chlorine (C1) and bromine (Br) content less than 0.09% Wt(weight ratio) is defined as halogen-free copper clad plate.(meanwhile, CI+Br quantity ≤ 0.15% [1500PPM]) 1.2 why do we ban halogen Halogen refers to the halogen group of elements in the periodic table of chemical elements, including fluorine (F), chlorine (CL), bromine (Br), and iodine (1).At present, the flame retardant substrate, FR4, cem-3, etc., flame retardants are mostly brominated epoxy resin.Brominated epoxy resin, tetrabromobisphenol A, polybrominated biphenyl, polybrominated diphenyl ether, polybrominated diphenyl ether is the main resistance fuel of copper clad plate, its cost is low, compatible with epoxy resin.But research shows that institutional containing halogen flame retardant materials (polymerization polybrominated biphenyl PBB: polymerization polybrominated diphenyl ether PBDE), waste burning, emit two well English (dioxin dioxin TCDD), benzene furan (Benzfuran), such as large amount of smoke, smelled, highly toxic gas, carcinogenic, unable to discharge after intake, not environmental protection, affect human body health.Therefore, the European Union initiated a ban on the use of PBB and PBDE as flame retardants in electronic information products.The same document from the ministry of information industry of China requires that electronic information products put on the market by July 1, 2006, must not contain substances such as lead, mercury, hexavalent chromium, polymerized polybrominated biphenyls or polymerized polybrominated biphenylene ether. The eu law prohibits the use of PBB and PBDE and other six substances, it is known that PBB and PBDE in the copper coated plate industry has been basically not in use, more use is in addition to PBB and PBDE bromine flame retardant materials, such as tetrabromobisphenol A, dibromophenol, etc., the chemical formula is CISHIZOBr4.There are no laws and regulations on this kind of brominated flame retardant copper clad plate, but this kind of brominated copper clad plate, when burning or electrical fire, will release a large number of toxic gas (brominated type), the amount of smoke;When PCB is welded with hot air and even components, the plate is subjected to high temperature (>200) impact, will also release trace of hydrogen bromide;Whether dioxins are also produced is still being assessed.Therefore, FR4 plates containing tetrabromobisphenol A flame retardants are not currently prohibited by law and can still be used, but cannot be called halogen free plates. This paper discusses the processing characteristics and experiences of halogen-free PCB. 1.3 principle of halogen-free substrate At present, most of the halogen-free materials are mainly phosphorous and phosphorous nitrogen systems.Phosphorous resin in the combustion, thermal decomposition to produce polyphosphoric acid, extremely strong dehydrating, the surface of the polymer resin to form a carbonized film, isolation of the resin burning surface and air contact, so that fire extinguishing, flame retardant effect.The polymer resin containing phosphorus and nitrogen compounds produces non-combustible gas when burning, which helps the resin system flame retardant. 2 characteristics of halogen-free plate 2.1 insulation of materials Since P or N are used to replace halogen atoms, the polarity of molecular bond segment of epoxy resin is reduced to a certain extent, thereby improving the insulation resistance and resistance to penetration. 2.2 water absorption of the material As the N and P fox in N and P deoxidizing resins of nitrogen and phosphorus series have fewer electrons than halogens, the probability of forming hydrogen bond with hydrogen atoms in water is lower than that of halogen materials, so the absorbency of the materials is lower than that of conventional halogen flame retardant materials.For the plate, the low water absorption has a certain effect on improving the reliability and stability of the material. 2.3 thermal stability of materials The content of nitrogen and phosphorus in the halogen-free plate is higher than that of the halogen in the ordinary halogen material, so the monomer molecular weight and Tg value are increased.Under the condition of being heated, its molecular motility will be lower than that of conventional epoxy resin, so the thermal expansion coefficient of halogen-free materials is relatively small. 3. Experience in producing halogen-free PCB Halogen free panel supplier Currently, a large number of panel suppliers have developed or are developing halogen-free copper clad sheets and corresponding semi-cured sheets, such as Polyclad pcl-fr-226/240, Isola DEl04TS, S1155 / S0455, South Asia, hongren ga-hf and panasonic electrician GX series. In 2002, our company has started to use Polyclad pcl-fr-226/240 panels in batch for the production of mobile phone panels. This year, we have developed shengyis S1155 substrate and the production of multi-layer panels. Besides, the halogen-free panels in South Asia are also on trial.At present, the use of halogen-free plate has accounted for 20% of our total plate consumption. Laminated 3.1: Lamination parameters may vary from company to company.In the case of the above mentioned shengyi substrate and PP as a multi-layer board, in order to ensure the full flow of resin, so that the bonding force is good, the requirements of a low rate of plate material temperature (1.0-1.5℃ / min) and multi-stage pressure coordination, in addition to the high temperature stage requires a long time, 180℃ to maintain more than 50 minutes.The following is a recommended set of pressing procedures and the actual plate temperature.The bonding force between copper foil and substrate was 1.ON/mm for the pressed plate, and no stratification or bubble appeared after six thermal shocks. 3.2 drilling machinability: The drilling condition is an important parameter, which directly affects the quality of the hole wall in the process of PCB processing.Due to the use of P and N series functional groups, the molecular weight of halogen-free copper clad plate is increased and the rigidity of the molecular bond is enhanced, so the rigidity of the material is also enhanced. Meanwhile, the Tg point of halogen-free material is generally higher than that of ordinary copper clad plate, so the drilling parameters of ordinary fr-4 are adopted for drilling, which is generally not ideal.When drilling halogen-free plate, some adjustment should be made under normal drilling conditions. For example, our company adopts shengyi S1155 / S0455 core plate and PP four-layer plate, the drilling parameters are not the same as the normal drilling parameters.When drilling halogen-free plate, the rotation speed should be increased by 5-10% faster than the normal parameters, while the speed of inlet and discharge is reduced by 10-15% compared with the normal parameters. In this way, the roughness of the drilled hole is small. 3.3 alkali resistance In general, halogen-free plates are less alkaline than ordinary fr-4. Therefore, special attention should be paid to the etching process and the rework process after resistance welding. The soaking time in alkaline film solution should not be too long to prevent the appearance of substrate white spots.In the actual production, our company had eaten kui: finished resistance welding and curing of halogen free board, because of some problems need to return to wash, but according to the ordinary FR - 4 while returning to wash back to wash, the temperature of 75 ℃, soaked in 10% NaoH concentration for 40 minutes, the wash out all of the base material white spot, shorten the soaking time for after 15 to 20 minutes, this problem no longer exists.Therefore, for the halogen-free plate rework resistance welding, it is best to do the first plate, in order to get the best parameters, and then batch rework. 3.4 halogen-free resistance welding production At present, there are many kinds of halogen-free resistance welding inks introduced in the world, and its performance and ordinary liquid photosensitive ink is not very different from the basic operation and ordinary ink is almost the same. 4 conclusion Due to its low water absorption and environmental protection requirements, halogen-free PCB board can also meet the quality requirements of PCB board in other properties. Therefore, the demand for halogen-free PCB board has been increasing.In addition, the major plate suppliers have also invested more funds in the research and development of halogen-free substrates and halogen-free PP. It is believed that in the near future, the low price halogen-free sheet structure will be put into the market immediately.Therefore, all PCB manufacturers should put the trial and use of halogen-free board on the agenda, make a detailed plan, gradually expand the possession of halogen-free board in our factory, so that they go ahead in the market demand.
Tracy
Tracy