PCB / PTH and copper plate

Bare board · 05

PTH and copper plate

The hole wall gets copper so layers connect. This is the difference between a via and a decorative hole.

01 What happens

  • Desmear cleans resin smear after drill. Electroless copper seeds the hole, then electrolytic plate grows the barrel.
  • Panel plate or pattern plate is chosen by the fab; both must hit copper thickness in the hole.
  • Cross-section coupons prove barrel thickness; a quote without coupons is a hope.

02 On an ESP32 board

  • GND vias under an ESP32 thermal pad must actually connect inner GND, not look connected on the silkscreen.
  • USB and RF reference vias need reliable barrels; a thin plate shows up as flaky high-speed, not a pretty open.
  • Press-fit or thick-pin headers need enough copper and a specified finished hole.

03 What usually fails

  • Voids, cracks, or thin copper in the barrel — intermittent after thermal cycles.
  • Hole too tight after plate for the connector pin.
  • Pink-ring or poor desmear on inner connection.

04 What we check

  • We want finished hole sizes on the drawing, not only drill sizes.
  • For a first article we ask whether the fab does microsection on the lot.

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PCB工艺 / 沉铜与电镀

光板 · 05

沉铜与电镀

孔壁上铜，层间才导通。这是过孔和装饰孔的差别。

01 这一步做什么

  • 去钻污清树脂，化学沉铜打底，再电镀加厚孔壁。
  • 全板镀或图形镀由工厂选，孔铜厚度都要达标。
  • 切片证明孔铜；报价里没有切片，只是希望。

02 落到 ESP32 板上

  • ESP32 散热垫下的地孔必须接到内层地，不能只是丝印看起来通。
  • USB、射频参考过孔要孔铜够；镀薄了是高速发飘，不是明显开路。
  • 压接或粗针排针要写成品孔径和孔铜。

03 常见失败

  • 孔壁空洞、裂纹、铜薄，冷热循环后断续。
  • 镀完孔太紧，插件插不进。
  • 去钻污不好，内层结合差（粉红圈一类）。

04 我们查什么

  • 图纸写成品孔径，不要只写钻嘴。
  • 首件会问这批有没有做切片。

← 上一步: 钻孔下一步: 外层图形与蚀刻 →