从面包板上的原型电路到设计我们自己的电路 印刷电路板 (PCBS), it was like getting off the training wheels. There’s a lot to learn about this process, so let’s get started. PCB 设计是在电气工程 (EE) 过程中进行的。 EE 创建了设备工作方式的“大脑”。 Without electronics, you’re left with little more than a pile of metal and plastic.

Things to know before starting PCB design: 1. PCB size – this depends on your product size (or case size). 产品尺寸是在电子工程设计过程中定义的。 You can watch a video about it here. 2. PCB 层数——层数越多，PCB 的制造就越复杂。 （注意：即使是单层 PCB 也可能是复杂的 PCB，但这里我们谈论的是制作 PCB 的复杂性。 PCB 的层数越多，制造成本就越高。）

Layer 2 is usually used for simple toy products

物联网相关产品通常有4层

Typically used for floors 6 to 8 of a smartphone or smartwatch.

3. Your PCB manufacturer’s requirements. Be sure to read the guidelines for rhythm, trace size, power isolation, and file naming before you start designing.

您需要提供给PCB制造商的信息：

Number of layers (e.g. 2, 4, 6, etc.)

材料（FR-2（酚醛棉纸）、FR-3（棉纸和环氧树脂）、FR-4（玻璃纤维和环氧树脂…… 等）

厚度（0.5 毫米、1.0 毫米… 等）

Color (red, black, green… 等）

表面处理（ENIG（化学镍/金浸）、DIG（直接浸金）、OSP（有机可焊防腐剂等）

铜重量（1 盎司（35 微米）、2 盎司（70 微米）、0.5 盎司（18 微米）…… 等）

Gerber文件

PCB design process:

电路设计

For this step, you need to create the schematic. This is a document, like a blueprint, that describes how components relate to each other and work together. To create the schematic file, you will need a software tool. 我们喜欢 Quadcept，因为它针对制造用 PCBS 的设计进行了优化（例如，您可以直接从工具导出物料清单 (BoM)）并且基于云，因此可以轻松地在任何地方使用。 (They also offer a free community version of the tool for manufacturers and students.)

There are many other options you can choose from:

Altium的

快递PCB

变频装置

KiCad的

Cadence allegro

垫

计算机辅助设计

浸渍跟踪

After you install the selected tools, you need to obtain the component specifications for each selected component. 它们通常可以在供应商的网站上找到。 模型文件将帮助您绘制原理图。 This component becomes available in the database when you upload the model to the software tool. Then, all you have to do is follow the data manual and connect the wire to each pin in the component. （注意：设计过程的细节将取决于所选择的软件工具）。

Each schematic symbol needs to have an associated PCB space area to define the physical dimensions of the component and the location of the through holes on the brazing pad or PCB. You should have selected the components (or are now selecting them), and we describe this process in the EE Design Process video (see video).

Example diagram

A good schematic is really important, as it will be used as a reference document during debugging and is a good communication tool with other engineers. 此外，制造商可以通过本文档中的测试点对设备进行测试。

PCB layout + Gerber file

To design the PCB layout and create Gerber files, you can use the same software tools we mentioned in circuit design. 与原理图不同，PCB 布局将实际组件分配到 PCB 上的确切位置，并显示将每个组件在 PCB 层之间连接在一起的轨迹。 As mentioned at the beginning of this article, the more layers, the more complex the manufacturing required, and the higher the cost.

Divide the PCB into logical parts based on functions (e.g. power supply, audio output, etc.). Then, be sure to group the components of each section into the same area. 通过这种方式，您可以保持导电走线较短，并减少噪声和干扰。

The user interface (UI) also needs to be kept in mind when designing a PCB. 需要调整音频插孔、连接器、LED 等组件以实现最佳用户体验。

Once the layout is designed, a Gerber file is generated. 您的 PCBA 制造商将使用此文件。 There are many companies that offer these services, and from HWTrek’s expert library we recommend Kingbrother, NexPCB, and HQPCB.

Sample Gerber files

元件在 PCB 上的放置非常重要。 Some components can interfere with each other and cause unexpected behavior. 例如，如果您同时拥有蓝牙和 Wi-Fi 模块，则它们具有相同的 2.4GHz 带宽，并且如果放置不当可能会相互干扰。

印刷电路板生产

When you send the Gerber file to the PCB manufacturer, they can print the board. 这将是进一步为向 PCB 添加组件和制造 PCBA（印刷电路板组件）奠定基础的基础。

Unassembled PCBS

PCBA (Assembly)

材料准备

在您的 EE 设计中，此时您应该已经选择了组件。 You can ask the PCBA manufacturer to order the required components for you, or do it yourself if you choose a supplier. 注意事项：

Lead time: As these components come from different suppliers, keep the lead time in mind. For some components, it can take up to 8-16 weeks.

Packaging: Order components from reels that are automatically picked up by SMT machines instead of packaging them individually.

最小订货量：检查组件的最小订货量。 如果您购买的数量少于最低数量，请确保所选组件有库存。 For small batches (up to 50), you can order online from DigiKey or Mouser. 如需更多数量，请咨询您的制造商。

Loss: Order 10% more to cover loss (not for expensive components)

Install components on the PCB

There are two main ways to place components on a PCB surface:

Through-holes (through-holes) are manual methods of assembling assemblies with wires into holes on the surface of a PCB. It is also commonly known as DIP or dual in-line packaging process. (See SMT in progress in this video)

SMT（表面贴装技术）是批量生产中使用最广泛的方法。 It is done by fast, accurate SMT machines that save you time, money and avoid human error.

要记住的事情

Your component type number must not exceed the number of reels that the manufacturer’s SMT machine can support.

Optimize and consolidate your components so that only one SMT runs.

Check manufacturer supported footprint pad sizes. Otherwise, the SMT machine will not install components correctly.

Some larger components cannot be installed by machine and still require manual through-hole work. Therefore, both technologies can be used on the same board.

Any components you need to manually add via the through-hole method add to the manufacturing cost.

Reflow soldering

Reflow soldering is the process of making components “stick” to the PCB. The PCBA heats the circuit board through a reflow furnace or an infrared lamp until the solder melts, thereby permanently attaching the component to the circuit board.

这里最棘手的部分不是过热或损坏组件，因为每个封装的热特性是不同的。 可靠的 PCBA 制造商将负责此过程，您所需要做的就是向他们提供组件规格。

回流过程。

Other welding methods:

波峰焊主要用于通过通孔方法手动添加元件。 在这种情况下，您的PCBA将首先通过回流焊炉，然后在通过波峰焊机后手动添加其他组件。

铁焊可用于特定情况，但不能用于批量生产。

测试和质量检验

在这一步中，对PCBA样品进行测试以确保质量。 常见错误有：断开的元件短路、未对准的元件和不应连接的电路部分。 最常见的测试：

ICT（在线测试）。 When designing a PCB, some test points are usually reserved for debugging, programming, and other purposes. ICT 机器将使用这些测试点进行开路/短路测试，并检查无源元件（电阻器、电感器、电容器）的值是否在规格范围内。

AOI（自动光学检测）。 Manufacturers use a “gold sample” (reference PCBA) to compare with other samples. 对于此测试，硬件创建者需要向制造商提供规格和容差以设置参数。

X 射线。 The PCBA manufacturer will use X-rays to check the welding conditions of the BGA (ball Grid Array) components. 观看此视频中的 X 射线测试。