Electronic cigarette self start? In-depth analysis of the importance of microphone protection and comparison of solutions
During the use of electronic cigarettes by users, it is inevitable to produce droplets such as water vapor and smoke oil condensate. Without effective protection, smoke oil or water vapor entering the gap of the capacitor diaphragm can reduce the performance of the switch, and even cause dry burning or self ignition of the electronic cigarette when the failure is severe, and even cause the electronic cigarette to explode. Therefore, doing a good job in oil and anti-seepage work on important components of electronic cigarette sets is crucial for improving the product quality, service life, safety, and user experience of electronic cigarette sets.
电子烟在用户使用过程中难免会产生水汽、烟油冷凝液等液滴，如缺乏有效的防护，烟油或水汽进入电容膜片间隙造成开关性能降低，甚至失效严重时会引起电子烟的干烧或自燃，甚至引发电子烟爆炸。因此，在电子烟具的重要器件上做好防油防渗工作，对电子烟具的产品品质、使用寿命、安全性、用户体验有关键提升。
一、电子烟具防护方案
新国标对电子烟具的品质及各项器件标准已有严格把控，出现故障的概率也逐渐降低，但在电子烟具本身的设计和工作原理要求下，若在防水、防油、防渗技术上稍有欠缺，仍然有出现各类故障（自吸、自启动、延迟、爆炸等）的可能。
电子烟具的防护手段主要有以下四类方案：结构防水、传统涂层、派瑞林、纳米涂层。
（1） 结构防水：结构防水主要是针对外观、外壳结构做的防水，这类防水方式能够阻挡液体的进入，但很难防止水汽侵入内部。在电子烟领域，烟具整体可以采用结构防水，因为电子烟必须有气道传输，在此基础上仍然需要针对PCBA板和咪头等重点部件做针对性的防水方案。
（结构防水需要投入很多成本：研发成本、物料成本、组装难度成本，同时大口数电子烟在运输、储存、抽吸时，不可避免会出现自吸问题。由于电子烟自身结构问题，电子烟上做结构防水，没办法达到最好的防护手段）
（2） 传统涂层：传统的三防漆或其他化学物质涂层在电子烟具的PCBA板上能够起到防护作用，但涂层返工难度大或不可返工、影响PCBA板散热，同时施工效率较低、性价比较低，影响了传统涂层在电子烟具工业生产中的应用。
此外，在进行传统涂层涂覆时，需在生产过程中进行遮蔽以避开焊盘、测试触点等部位，也影响其量产效率。（传统的三防漆涂层，类似于灌胶，把PCBA上的电子元器件包裹防护，油滴在PCBA表面，对电子元器件也没有影响。缺点：加工慢，只能板子处理，咪头没办法处理）
（3） 派瑞林：派瑞林涂层在电子产品防护上具有性能较优的显著特点，但聚对二甲苯二聚体的价格相当昂贵（每磅价格在2000至10,000美元之间）使派瑞林涂层的价格高昂，同时由于处理时长较长、日产能相对较低，导致派瑞林涂层的性价比较低。与传统涂层相同，派瑞林在处理时也需进行遮蔽，同样影响了派瑞林在量产过程中的应用。
（4） 纳米镀膜：纳米镀膜采用等离子体化学气相沉积技术，具有“无孔不入”的显著优势，膜层的形成过程犹如在基材表面“生长”出一层薄膜，与基材紧密贴合，膜层有疏水性能，提供绝佳的防护性能。纳米镀膜防护技术具备生产效率高、价格适中的优点，性价比较高。
（最大亮点：咪头要达到泡油7天，只能通过真空纳米镀膜工艺，在咪头上镀一层纳米级聚合膜。不仅防护咪头防尘网，还防护pcb透气孔、压合缝隙。）
综合结果:纳米镀膜综合解决电子烟防护问题，生产效率高，性价比高。电子烟组装过程中，结构、储油棉、冷凝液、掉进水里、注油过满等，导致电子烟的滋滋滋作响的自吸问题，结构防水与三防漆都没有办法完全解决这类问题，但是真空纳米镀膜可实现解决。
镀膜后电子烟咪头和PCBA板能够承受168h及以上的泡油测试，中途不异常亮灯、闪烁，测试结束后各项功能正常。
二、电子烟咪头的防护和测试原理
在各类解决方案中，针对电子烟咪头的防护设计和测试是重中之重。众所周知，通用电子烟的工作流程为：当有气流(吸气或呼气) 穿过咪头，咪头即产生模拟信号。唛头的模拟信号到达一定程度引起中断，唤醒MCU，随即驱动 PMOS，加热发热丝喷放烟雾，并且点亮LED。
当 MCU 监测到模拟信号减弱或者消失，停止驱动PMOS 和 LED，然后监测电池电压，如无到达最低值则睡眠，到达最低值则闪烁LED 进行低电压提醒。
在各类防油测试方案设计中，借用灯闪工作原理。在测试防水防油性能过程中，电子烟具的各类指示灯异常亮起则标志着防护性能不达标。主流咪头影响防水性能的主要构成：防尘网、膜片、芯片、pcb透气孔。
1、 Electronic Cigarette Protection Plan
The new national standard has strict control over the quality and various device standards of electronic cigarette sets, and the probability of failure has gradually decreased. However, under the design and working principle requirements of electronic cigarette sets themselves, if there is a slight lack of waterproof, oil proof, and anti-seepage technology, there is still the possibility of various faults (self suction, self start, delay, explosion, etc.).
There are four main types of protective measures for electronic cigarette sets: structural waterproofing, traditional coating, Perrin, and nano coating.
(1) Structural waterproofing: Structural waterproofing is mainly aimed at waterproofing the appearance and shell structure. This type of waterproofing method can block the entry of liquids, but it is difficult to prevent water vapor from entering the interior. In the field of electronic cigarettes, cigarette sets can be structurally waterproof as a whole, as electronic cigarettes must have airway transmission. On this basis, targeted waterproof solutions still need to be made for key components such as PCBA boards and microphone heads.
(Structural waterproofing requires a lot of investment: research and development costs, material costs, assembly difficulty costs, and the inevitable occurrence of self priming problems during transportation, storage, and suction of large mouth electronic cigarettes. Due to the structural problems of electronic cigarettes themselves, structural waterproofing on electronic cigarettes cannot achieve the best protective measures.)
(2) Traditional coating: Traditional three proofing paint or other chemical coatings can play a protective role on the PCBA board of electronic cigarette sets, but the difficulty or non rework of the coating affects the heat dissipation of the PCBA board. At the same time, the construction efficiency is low and the cost-effectiveness is low, which affects the application of traditional coatings in the production of electronic cigarette sets industry.
In addition, when traditional coating is applied, shielding is required during the production process to avoid solder pads, test contacts, and other areas, which also affects its mass production efficiency. (Traditional three proof paint coating, similar to adhesive coating, wraps electronic components on PCBA for protection. Oil droplets on the surface of PCBA have no impact on electronic components. Disadvantages: slow processing, can only be processed on the board, and the microphone cannot be processed.)
(3) Pyrelin: Pyrelin coatings have significant performance advantages in electronic product protection, but the price of polyxylene dimer is quite expensive (between $2000 and $10000 per pound), making the price of Pyrelin coatings high. At the same time, due to the long processing time and relatively low daily production capacity, the cost-effectiveness of Pyrelin coatings is low. Like traditional coatings, Perrin also requires masking during processing, which also affects its application in mass production.
(4) Nano coating: The nano coating adopts plasma chemical vapor deposition technology, which has a significant advantage of "no holes, no penetration". The formation process of the film layer is like "growing" a thin film on the surface of the substrate, closely fitting with the substrate. The film layer has hydrophobic properties, providing excellent protective performance. Nano coating protection technology has the advantages of high production efficiency, moderate price, and high cost-effectiveness.
(The biggest highlight: In order for the microphone to soak in oil for 7 days, it can only be coated with a layer of nanoscale polymer film through the vacuum nano coating process. This not only protects the microphone's dust screen, but also protects the PCB's air holes and pressure gaps.)
Comprehensive results: Nano coating comprehensively solves the problem of electronic cigarette protection, with high production efficiency and high cost-effectiveness. During the assembly process of e-cigarettes, the structure, Oil storage cotton, condensate, falling into water, overfilling, and other factors can lead to the self priming problem of the e-cigarette's sizzling sound. Structural waterproofing and three proofing paint cannot completely solve this type of problem, but vacuum nano coating can solve it.
After coating, the electronic cigarette head and PCBA board can withstand a soaking test of 168 hours or more, without abnormal lighting or flashing during the process. After the test is completed, all functions are normal.
2、 Protection and Testing Principles of Electronic Cigarette Emitters
Among various solutions, the protection design and testing of electronic cigarette heads are of utmost importance. As is well known, the workflow of a universal electronic cigarette is: when there is airflow (inhalation or exhalation) passing through the microphone, the microphone generates an analog signal. The analog signal of the mark reaches a certain level, causing interruption, waking up the MCU, and then driving the PMOS to heat the heating wire and spray smoke, and lighting the LED.
When the MCU detects that the analog signal weakens or disappears, it stops driving the PMOS and LED, and then monitors the battery voltage. If it does not reach the minimum value, it will sleep. If it reaches the minimum value, it will flash the LED for a low voltage reminder.
In the design of various oil proof testing schemes, the principle of flashing light is borrowed. During the testing of waterproof and oil resistant performance, abnormal lighting of various indicator lights on electronic cigarette sets indicates that the protective performance is not up to standard. The main components that affect the waterproof performance of mainstream microphones include dust screens, membranes, chips, and PCB air vents.
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