PCB / Solder mask

Bare board · 07

Solder mask

Mask keeps solder on the pads. Dams between ESP32 pins are a process, not a colour choice.

01 What happens

  • LPI mask is coated, exposed and developed. Vias may be tented, opened or plugged.
  • Mask expansion vs copper is a CAM setting. Too tight and mask on pad; too loose and solder bridges.
  • Colour is cosmetic. Thickness and registration are not.

02 On an ESP32 board

  • Fine-pitch module pins need a mask dam the fab can actually print.
  • Via tenting under a can or battery avoids wicking; via-in-pad still needs plug.
  • USB connector and ESP32 RF can need defined mask openings, not a flood that covers a pad.

03 What usually fails

  • Mask on pad (solderability), or no dam (bridges on 0.4 mm).
  • Peeling after reflow, especially on ENIG if cure was wrong.
  • Vias leaking flux onto the RF keep-out.

04 What we check

  • We look at mask expansion and dam width vs pin pitch.
  • We specify tented vs plugged vias on purpose, not ‘whatever the fab does’.

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中文

PCB工艺 / 阻焊

光板 · 07

阻焊

阻焊把锡留在焊盘上。ESP32 脚之间的阻焊桥是工艺，不是选颜色。

01 这一步做什么

  • 感光阻焊涂覆、曝光、显影。过孔可盖油、开窗或塞孔。
  • 阻焊开窗相对铜皮是 CAM 参数。太紧油上盘，太松桥连。
  • 颜色是外观。厚度和对位才是工艺。

02 落到 ESP32 板上

  • 细间距模组脚需要工厂印得出的阻焊桥。
  • 屏蔽罩或电池下面的过孔宜盖油，避免吃锡；盘中孔仍要塞。
  • USB 和射频开口要明确，不能把盘盖住。

03 常见失败

  • 油上盘（上锡差），或没桥（0.4 mm 连锡）。
  • 回流后起皮，ENIG 上固化不好更常见。
  • 过孔漏助焊剂到射频净空。

04 我们查什么

  • 看开窗和桥宽对不对脚距。
  • 盖孔还是塞孔要写死，不能「工厂看着办」。

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