01 What happens
- HASL (lead-free) is cheap and rugged; pads are not flat.
- ENIG is flat and suits fine pitch, edge connectors and modest shelf life.
- OSP is flat and cheap for fast SMT; it does not like long storage or multiple reflows as much as ENIG.
PCB / Surface finish
Bare board · 09
Surface finish
ENIG, HASL or OSP on the pads. For ESP32 RF and fine pitch, the finish is a design choice, not a cheaper checkbox.
02 On an ESP32 board
- 0.4 mm ESP32 modules and QFN prefer ENIG or a well-controlled OSP, not uneven HASL.
- Castellated module edges often specify ENIG.
- Gold fingers or pogo test pads need a finish that survives the fixture.
03 What usually fails
- HASL lumps on fine pitch — tombstones and opens.
- OSP past shelf life, or black pad on bad ENIG.
- Mixed finish on one panel when the drawing did not say so.
04 What we check
- First ESP32 articles we usually call ENIG unless cost forces OSP with a short path to SMT.
- We write shelf-life and number of reflow cycles on the assembly note.
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中文
PCB工艺 / 表面处理
光板 · 09
表面处理
焊盘做沉金、喷锡或 OSP。ESP32 射频和细间距这是设计选择，不是勾最便宜那一项。
01 这一步做什么
- 无铅喷锡便宜耐用，焊盘不平。
- 沉金平，适合细间距、金手指、短中期存放。
- OSP 平、便宜、适合很快贴；不如沉金耐放、耐多次回流。
02 落到 ESP32 板上
- 0.4 mm ESP32 模组和 QFN 优先沉金或控得好的 OSP，不要高低不平的喷锡。
- 铸孔模组边常用沉金。
- 金手指或探针测试盘要能扛夹具。
03 常见失败
- 喷锡鼓包，细间距立碑、开焊。
- OSP 过期，或沉金黑盘。
- 图纸没写，一块拼板上混了几种表面处理。
04 我们查什么
- ESP32 首件一般点沉金，除非成本逼着用 OSP 并且马上贴。
- 组装说明写存放期和回流次数。