PCB / SPI, AOI and X-ray

Assembly · 15

SPI, AOI and X-ray

Machines look at paste, parts and hidden joints. They do not replace a UART log on first bring-up.

01 What happens

  • SPI measures paste. AOI checks presence, polarity, offset and some solder fillets.
  • X-ray looks under QFN, BGA and big module pads for voids and bridges.
  • Programs are only as good as the golden board. A wrong polarity in CAD becomes a wrong pass.

02 On an ESP32 board

  • ESP32 modules hide most pins; AOI sees the shield, X-ray sees the pads.
  • USB-C and fine connectors need side-view or a human after AOI.
  • LED polarity is an AOI classic — and still wrong if the courtyard was mirrored.

03 What usually fails

  • No X-ray on a QFN power rail that is open in the middle of the pad.
  • AOI skipped on a ‘simple LED board’ that still has a 0.4 mm module.
  • False passes because the golden sample was already rotated 180°.

04 What we check

  • Fine-pitch ESP32 first articles should include AOI; QFN power should include X-ray if we cannot probe.
  • We still power the board. Optical pass is not ‘Wi-Fi joined’.

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PCB工艺 / SPI、AOI 与 X-ray

组装 · 15

SPI、AOI 与 X-ray

机器看锡、看件、看隐藏焊点。代替不了第一次点亮的串口日志。

01 这一步做什么

  • SPI 测锡量。AOI 看有没有件、极性、偏移和部分焊脚。
  • X-ray 看 QFN、BGA、模组大焊盘的空洞和桥连。
  • 程序取决于金板。CAD 极性错了，AOI 也会当对的放过。

02 落到 ESP32 板上

  • ESP32 模组脚大多被罩住，AOI 看外壳，X-ray 看焊盘。
  • USB-C 和细连接器往往还要侧看或人工。
  • LED 极性是 AOI 经典题——封装镜像了照样错。

03 常见失败

  • QFN 电源盘中间开焊却没拍 X-ray。
  • 「简单灯板」跳过 AOI，上面其实有 0.4 mm 模组。
  • 金板已经转了 180°，假通过。

04 我们查什么

  • 细间距 ESP32 首件要 AOI；探不到的 QFN 电源要 X-ray。
  • 仍然要上电。光学过了不是 Wi-Fi 连上了。

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