PCB knowledge

印刷电路板 (PCB) 是印刷电路板的简称。 通常以绝缘材料，按预定设计，制成印制电路、印制元件或两者结合的导电图形称为印制电路。 设置在绝缘基板上的元件之间电气连接的导电图称为印刷电路。 这样，成品板的印制电路或印制线路就称为印制电路板，也称为印制板或印制电路板。

PCB is indispensable for almost all electronic equipment we can see, from electronic watches, calculators and general computers to computers, communication electronic equipment and military weapon systems. As long as there are no electronic components such as integrated circuits, PCB is used for the electrical interconnection between them. It provides mechanical support for fixed assembly of various electronic components such as integrated circuits, realizes wiring and electrical connection or electrical insulation between various electronic components such as integrated circuits, and provides required electrical characteristics, such as characteristic impedance, etc. At the same time to provide automatic solder blocking graph; Provide identification characters and graphics for component installation, inspection and maintenance.

How are PCBS made? When we open the thumb drive of a general-purpose computer, we can see a soft film (flexible insulating substrate) printed with silver-white (silver paste) conductive graphics and potential graphics. Because of the universal screen printing method to get this graph, so we call this printed circuit board flexible silver paste printed circuit board. Different from the motherboards, graphics cards, network cards, modems, sound cards and printed circuit boards on home appliances we see in Computer City. The base material used is made of paper base (usually used for single side) or glass cloth base (often used for double-sided and multi-layer), pre-impregnated phenolic or epoxy resin, one or both sides of the surface glued with copper book and then laminated curing. This kind of circuit board covers copper book board, we call it rigid board. Then we make a printed circuit board, we call it a rigid printed circuit board. A printed circuit board with printed circuit graphics on one side is called a single-sided printed circuit board, and a printed circuit board with printed circuit graphics on both sides is interconnected on both sides through the metallization of holes, and we call it a double-panel. If using a double lining, two one-way for outer layer or two double lining, two blocks of single outer layer of the printed circuit board, through the positioning system and alternate insulation adhesive materials and conductive graphics interconnection according to design requirement of printed circuit board becomes four, six layer printed circuit board, also known as multilayer printed circuit board. There are now more than 100 layers of practical printed circuit boards.

The production process of PCB is relatively complex, which involves a wide range of processes, from simple mechanical processing to complex mechanical processing, including common chemical reactions, photochemistry, electrochemistry, thermochemistry and other processes, computer-aided design (CAM) and other knowledge. And in the process of production process problems and will always meet new problems and some problems in didn’t find out the reason disappears, because its production process is a kind of continuous line form, any link wrong would caused production across the board or the consequences of a large number of scrap, printed circuit board if there is no recycling scrap, Process engineers can be stressful, so many engineers leave the industry to work in sales and technical services for PCB equipment or materials companies.

为了进一步了解PCB，有必要了解通常单面、双面印刷电路板和普通多层板的生产工艺，以加深对它的了解。

单面硬质印制板：——单面覆铜——下料擦洗、干燥）、钻孔或冲孔——>丝印线路蚀刻图案或使用干膜抗固化检查固定板、铜蚀刻和干抗印刷材料，以擦洗、烘干、丝印电阻焊图形（常用绿油）、UV固化到字符打标图形丝印、UV固化、预热、打孔、定型——电开短路试验——擦洗、干燥→预涂焊接抗氧化剂（干）或喷锡热风整平→检验包装→成品出厂。

双面刚性印制板：——双面覆铜板——下料——层压——nc钻导孔——检查、去毛刺擦洗——化学电镀（引导孔金属化）——薄铜镀层（全板）——检查擦洗——>丝印负电路图形、固化（干膜/湿膜、曝光显影）——检查和修复版材——线图电镀和电镀锡（耐镍/金）——>印刷材料（涂层）——蚀刻铜–（退火锡）擦洗干净，常用图形丝印电阻焊接热固化绿油（感光干膜或湿膜，曝光，显影和热固化，常热固化感光绿油）和干洗，以丝印标记字符图形、固化、（锡或有机保护焊膜）成型加工、清洗、干燥到电气通断测试、包装和成品。
通孔金属化方法制造多层工艺流程到内层覆铜双面切割、擦洗钻定位孔、粘在干涂层或涂层上以抵抗曝光、显影和蚀刻和薄膜——内部粗化和氧化– 内检 –（单面覆铜板外线生产，B – 粘合片，板粘合片检查，钻定位孔）到层压，几个控制钻孔-> 处理和化学镀铜前的孔和检查-全板和薄铜镀层检查——坚持耐干膜镀或镀膜剂镀底曝光、显影和固定板——线图电镀——或镀镍/金和电镀锡铅合金成膜和蚀刻——检查——丝印电阻焊图形或光致电阻焊图形——印刷字符图形——（热风整平或有机屏蔽焊膜）和数控清洗成型→清洗、干燥→电气连接检测→成品检验→包装出厂。

从工艺流程图可以看出，多层工艺是由双面金属化工艺发展而来的。 除了双面工艺，它还有几个独特的内容：金属化孔内互连、钻孔和环氧树脂去污、定位系统、层压和特殊材料。

我们常见的电脑板卡基本都是环氧玻璃布双面印刷电路板，一面是插元件，另一面是元件脚焊接面，可以看到焊点很规整，元件脚离散焊接这些焊点的表面我们称之为焊盘。 为什么其他铜线上面没有锡？ 因为除了焊锡板等需要焊接的部分外，其余表面都有一层波阻焊膜。 其表面焊锡膜多为绿色，少数采用黄色、黑色、蓝色等，因此PCB行业常将焊锡油称为绿油。 其作用是防止波峰焊桥现象，提高焊接质量，节省焊锡等。 它也是印制板的永久性保护层，可以起到防潮、防腐、防霉和机械磨损的作用。 从外面看，表面是光滑亮绿色的阻挡膜，对膜版感光，热固化绿油。 不仅外观要好，重要的是焊盘精度要高，这样才能提高焊点的可靠性。

从电脑板我们可以看出，组件的安装方式有三种。 一种将电子元件插入印刷电路板上的通孔中进行传输的插入式安装工艺。 不难看出，双面印制电路板通孔如下：一个是简单的元件插入孔； 二是元件插入和双面互连通孔； 三是简单的双面通孔； 四是底板安装定位孔。 另外两种安装方式是表面安装和芯片直接安装。 实际上，芯片直接贴装技术可以认为是表面贴装技术的一个分支，它是将芯片直接粘在印制板上，然后通过线焊法或带装法、倒装法、梁式引线连接到印制板上方法和其他封装技术。 焊接面在元件表面。

表面贴装技术具有以下优点：

1）由于印制板在很大程度上取消了大通孔或埋孔互连技术，提高了印制板上的布线密度，减少了印制板面积（一般为插装式安装的三分之一），还可以减少数量印制板的设计层数和成本。

2）减轻重量，提高抗震性能，采用胶体焊料和新型焊接技术，提高产品质量和可靠性。

3）由于布线密度的增加和引线长度的缩短，寄生电容和寄生电感减小，更有利于改善印制板的电气参数。

4）比插件安装更容易实现自动化，提高安装速度和劳动生产率，相应降低装配成本。

As can be seen from the above surface safety technology, the improvement of circuit board technology is improved with the improvement of chip packaging technology and surface mounting technology. The computer board that we see now card its surface stick installs rate to rise ceaselessly. In fact, this kind of circuit board reuse transmission screen printing line graphics is unable to meet the technical requirements. Therefore, the ordinary high precision circuit board, its line graphics and welding graphics are basically sensitive circuit and sensitive green oil 生产过程。

随着高密度电路板的发展趋势，对电路板的生产要求越来越高。 越来越多的新技术应用于线路板的生产，如激光技术、光敏树脂等。 以上只是表面的一些粗浅的介绍，线路板的制作由于空间的限制还有很多东西，比如盲孔、绕线板、铁氟龙板、光刻等等。 如果你想深入学习，你需要努力工作。