projects/reflow-workshop: 2023-04-05 update

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@@ -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…