01 What happens
- Screen or inkjet prints reference designators, polarity and logos on mask.
- Ink must stay off pads and usually off the RF keep-out.
- White on green is readable; tiny 0.6 mm text is not, even if the EDA allowed it.
PCB / Legend / silkscreen
Bare board · 08
Legend / silkscreen
Ink that tells a human which way the part goes. It does not carry current, but it saves first-article hours.
02 On an ESP32 board
- ESP32 module pin-1, USB connector, and electrolytic polarity should be obvious without the CAD.
- Antenna keep-out outlined on silk helps the assembler not park a shield screw there.
- Version and date codes on silk beat a sticker that falls off in temperature test.
03 What usually fails
- Ink on pads, unreadable refdes, mirrored bottom silk.
- Polarity mark on the wrong end of a diode or tantalum.
- Silk over a test pad you needed for bring-up.
04 What we check
- We keep pin-1, USB and power polarity, and a board rev on silk.
- We clip silk off pads and off the antenna area before Gerber goes out.
中文
PCB工艺 / 丝印
光板 · 08
丝印
给人看装哪一面、哪一脚。不导电，但能省掉首件几小时。
01 这一步做什么
- 网印或喷印位号、极性和 logo。
- 油墨不能上焊盘，射频净空一般也不要印。
- 绿底白字好认；0.6 mm 字软件能过，人认不得。
02 落到 ESP32 板上
- ESP32 模组 1 脚、USB、电解电容极性离开 CAD 也要能看懂。
- 天线净空用丝印框一下，避免螺丝打在净空里。
- 版本和日期印在板上，好过高低温一测就掉的贴纸。
03 常见失败
- 油上盘、位号糊、底层丝印镜像。
- 二极管或钽电容极性画反。
- 测试点被丝印盖住，点亮没地方下表笔。
04 我们查什么
- 1 脚、USB、电源极性、板号要在。
- 出 Gerber 前把焊盘和天线区上的丝印裁掉。