From 923d8002723233ba14f48f6ab2c3d870b5debf49 Mon Sep 17 00:00:00 2001 From: Frederick Yin Date: Wed, 5 Apr 2023 19:36:57 +0800 Subject: projects/reflow-workshop: 2023-04-05 update --- .../img/reflow-workshop/bolted_stencil.jpg | Bin 0 -> 268766 bytes .../reflow-workshop/partial_test_run_hotplate.jpg | Bin 0 -> 232887 bytes .../reflow-workshop/partial_test_run_joints.jpg | Bin 0 -> 319944 bytes .../img/reflow-workshop/partial_test_run_paste.jpg | Bin 0 -> 246124 bytes docs/projects/reflow-workshop.md | 67 +++++++++++++++++++++ 5 files changed, 67 insertions(+) create mode 100644 docs/projects/img/reflow-workshop/bolted_stencil.jpg create mode 100644 docs/projects/img/reflow-workshop/partial_test_run_hotplate.jpg create mode 100644 docs/projects/img/reflow-workshop/partial_test_run_joints.jpg create mode 100644 docs/projects/img/reflow-workshop/partial_test_run_paste.jpg diff --git a/docs/projects/img/reflow-workshop/bolted_stencil.jpg b/docs/projects/img/reflow-workshop/bolted_stencil.jpg new file mode 100644 index 0000000..2bfa684 Binary files /dev/null and b/docs/projects/img/reflow-workshop/bolted_stencil.jpg differ diff --git a/docs/projects/img/reflow-workshop/partial_test_run_hotplate.jpg b/docs/projects/img/reflow-workshop/partial_test_run_hotplate.jpg new file mode 100644 index 0000000..62fdfea Binary files /dev/null and b/docs/projects/img/reflow-workshop/partial_test_run_hotplate.jpg differ diff --git a/docs/projects/img/reflow-workshop/partial_test_run_joints.jpg b/docs/projects/img/reflow-workshop/partial_test_run_joints.jpg new file mode 100644 index 0000000..b8f4cbc Binary files /dev/null and b/docs/projects/img/reflow-workshop/partial_test_run_joints.jpg differ diff --git a/docs/projects/img/reflow-workshop/partial_test_run_paste.jpg b/docs/projects/img/reflow-workshop/partial_test_run_paste.jpg new file mode 100644 index 0000000..d516df6 Binary files /dev/null and b/docs/projects/img/reflow-workshop/partial_test_run_paste.jpg differ diff --git a/docs/projects/reflow-workshop.md b/docs/projects/reflow-workshop.md index 1396bc1..a0c293f 100644 --- a/docs/projects/reflow-workshop.md +++ b/docs/projects/reflow-workshop.md @@ -213,3 +213,70 @@ The tweezers are here. ## 2023-03-30, Thursday So are the LEDs. + +## 2023-04-01, Saturday + +I ordered 10 tin scrapers. Fun fact: in German they're called +["Japanspachtel"](https://de.wikipedia.org/wiki/Japanspachtel) (der +Japanspachtel, plural is die Japanspachtel) to distinguish from regular +[Spachtel](https://de.wikipedia.org/wiki/Spachtel_(Werkzeug)). + +Also, I almost ended up buying the wrong kind of chemical. What I need is +isopropyl alcohol, but "industrial alcohol" on the marketplace refers to +methanol. The customer service kindly suggests I look for "industrial +ethanol". I ordered 500 mL. + +## 2023-04-03, Monday + +The Japanspachtel are here. I headed to the hackerspace and did a partial +test run. I attached the stencil and, with the most sloppy skills +possible, literally smeared solder paste wherever there are holes. + +![Stencil and PCB held together with bolts and +nuts](img/reflow-workshop/bolted_stencil.jpg) + +▲ Before applying the paste. + +Upon removal, there were quite a lot of shorts, but easily fixable with +the sharp edge of the Japanspachtel. + +![Grey gooey solder paste over +pads](img/reflow-workshop/partial_test_run_paste.jpg) + +▲ Most of the tiny displacements will fix themselves once heated. + +Then I placed all the capacitors, resistor packs and LEDs with tweezers. +Finally it's time to heat it. I cranked up the hotplate, but _boy_ how +does it get hot _so_ fast. A minute and it's already 250 C. Way too high +than needed. I cooled it down to ~180 C and shoved down the PCB. + +![PCB on the hotplate](img/reflow-workshop/partial_test_run_hotplate.jpg) + +▲ I forgot to place D3. Whoops. + +I forgot to bring this up, but the solder paste I bought is not the +regular kind. Instead, it's Sn42Bi58 (42% tin and 58% bismuth), the same +kind Kliment used for his workshop. The bismuth makes the melting point +really low, as low as 138 C. + +It only took moments for the fume to come out, and here we have our solder +joints. + +![Silver solder joints on pads connecting parts to PCB. A QFN32 footprint +is left unpopulated](img/reflow-workshop/partial_test_run_joints.jpg) + +▲ These joints look solid, or so I hope? At least they don't jiggle. + +I'm surprised it went so well. I mean, not up to my finest standard, but +it's really more than I expected from so little effort. + +In the evening, I received the ethanol. + +## 2023-04-04, Tuesday + +With the ethanol I got yesterday I wiped the stencil and Japanspachtel +I was using. Good as new. + +## 2023-04-05, Wednesday + +Apparently my ATtiny's arrived in Shenzhen yesterday! Any day now… -- cgit v1.2.3