PCB / Outer pattern and etch

Bare board · 06

Outer pattern and etch

Outer copper is imaged and etched to the tracks you drew. Fine pitch ESP32 modules live or die on remaining copper.

01 What happens

  • Outer dry film is exposed to the outer artwork. Pattern plate may add copper on traces and holes before etch.
  • Etch defines final trace width. Compensation in CAM tries to hit the drawing after etch undercut.
  • Outer AOI looks for nicks, shorts and pad size before mask.

02 On an ESP32 board

  • 0.4 mm pitch module pads need a fab that can hold annular ring after etch, not only on the gerber.
  • Antenna traces are geometry. Over-etch changes impedance and match.
  • Crystal and RF keep-out must stay empty — no accidental copper slivers.

03 What usually fails

  • Mouse-bites on fine traces, shorts between module pins.
  • Pads too small for the stencil after undercut.
  • Unetched copper in keep-out.

04 What we check

  • We match min space to the fab capability they quoted, not to an EDA default.
  • For ESP32-S3 / module boards we look at pitch vs their 4/4 mil vs 5/5 mil line.

← Previous step: PTH and copper plateNext step: Solder mask →

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PCB工艺 / 外层图形与蚀刻

光板 · 06

外层图形与蚀刻

外层按你画的线蚀出来。细间距 ESP32 模组看的是蚀完还剩多少铜。

01 这一步做什么

  • 外层干膜曝光。图形镀可能先给线和孔加铜再蚀。
  • 蚀刻决定成品线宽。CAM 补偿是为了对付侧蚀。
  • 阻焊前外层 AOI 查缺口、短路和盘大小。

02 落到 ESP32 板上

  • 0.4 mm 间距模组盘，要看蚀完环宽还在不在，不是只看 Gerber。
  • 天线走线是几何。蚀过了阻抗和匹配都变。
  • 晶振和射频净空不能留铜丝。

03 常见失败

  • 细线咬边，模组脚之间短路。
  • 侧蚀后焊盘比钢网还小。
  • 净空区蚀不干净。

04 我们查什么

  • 最小间距按工厂报价能力，不按软件默认。
  • S3 或模组板要对一下脚距和他们 4/4 还是 5/5 mil。

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