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diff --git a/docs/projects/reflow-workshop.md b/docs/projects/reflow-workshop.md new file mode 100644 index 0000000..7cb9ed1 --- /dev/null +++ b/docs/projects/reflow-workshop.md @@ -0,0 +1,792 @@ +# Reflow Workshop: A Journal + +Status: updating + +## 2023-03-15, Wednesday + +Today I took a group interview for assistants of a new hackerspace. Five +students were present, in a room with Mr. Xiao, the manager. + +My prior work experience bought me some credibility, and I shared with +Xiao my frustration not being able to properly do electronic engineering +for lack of resources. + +We then took a walk in the empty hackerspace. The proper name is actually +Tang Junyuan Student Innovation and Entrepreneurship Center, but I prefer +hackerspace. + + + +▲ This is only half of the hackerspace. + +We had a heck of a time discussing what this space is potential of. +Four-wheelers. LaTeX and vim workshop up the stairs. And of course +— reflow soldering. + +Reflow soldering is on my [list of life goals](../random/life_goals.md), but +it's in my dream since 2019. At that time I was a nobody in high school. +All I could solder was through-holes. Kliment, my IRC friend (though we've +met IRL once) kindly mailed me one of his works: [an electronic +kitten](https://github.com/kliment/catws). It is 5cm×5cm. + + + +▲ It purrs when you stroke it right; otherwise, it hisses. + +## 2023-03-16, Thursday + +So I revealed my plans to Kliment, who was very supportive as usual. He +forwarded me an email listing the things I need. + +One crucial thing is that I have to program the <abbr +title="microcontroller unit">MCU</abbr> before soldering, so I need +a <abbr title="Quad-Flat No-leads with 32 pads">QFN32</abbr> test socket. +Kliment estimated it to cost 800 RMB, but in China it seems to only be +~200. I bought one for 180. + +## 2023-03-17, Friday + +Just ordered the two parts from LCSC with specific numbers: Murata +PKMCS0909E4000-R1 and Meihua MHS110FRGBCT. LCSC gave me a 20 RMB coupon. + +After that I went to look for the MCUs (ATtiny88-MU) and found them in +a random Taobao store that sells them at 7 RMB apiece. I think I might +need other chips later, so I also added some ATtiny48 and ATmega328PB to +my shopping cart. I asked customer service if they got any in stock. They +said I could just place my order, so I did. + +Then I went to hunt for the PCB and stencils. Kliment forewarned me that +factories use only one stencil per assembly line, so my use case is +extremely rare. I will have to consult the manufacturer for a quote. + +## 2023-03-19, Sunday + +Talked to the sales rep of JDBPCB, they were confused for a good minute, +then realized what I was asking for. They told me to just place my order. +They claim they had seen this kind of thing before. Kliment suggests it +might have been [Honza Mrazek](https://honzamrazek.cz/). + +Sent <abbr title="basically a zip file of everything the factory needs to +produce PCBs and stencils">Gerbers</abbr> to them, along with my requests +in the notes. They PCBs are approved. + +## 2023-03-20, Monday + +I received the piezo speaker and RGB LEDs from LCSC today. + +To my surprise JDB approved my stencil request, and priced it at an +unexpectedly low 80 RMB. + +Later the customer service approached me to confirm once again that +I wanted 10 copies of the same stencil. Upon hearing yes, they revealed +that the 80 RMB was actually the price for *one* stencil, but for me they +could do 216 RMB for 10, tax included, with the implication that I do not +do this kind of shit to them again. They fear me. + +Kliment helped shave off 46 RMB off my budget. I was looking for +a hotplate which he said will not cost more than 80 RMB. When I told him +best I could find is 135, he said I was looking for the wrong thing; what +I need is not a hotplate advertised for solder work, but a consumer grade +for heating food and beakers. I changed the keyword and found one at 89. + +## 2023-03-21, Tuesday + +Cell batteries, holders, and the QFN32 socket have arrived. + + + +▲ \*Kneels on floor\* \*Unlids socket\* \*Presents brand new ATtiny88-MU\* +Will you marry me? + +The socket is a delicate piece of hardware. You would place the MCU in +a 5mm×5mm slot where two adjacent pins are 0.5 mm apart, and access them +from a <abbr title="Dual In-line Package">DIP</abbr> interface where that +distance (also known as the lead pitch) is 2.54 mm. + +The microcontrollers on the other hand haven't even begun shipping yet. +I asked them what's wrong, and their answer was: "we don't have them." + +…Then don't sell them? + +I then asked when they will be back on stock. They read my messages but +remained silent. Chances are they will never ship, says Kliment. This is +just a scam on a chain of fake distributors. The evening they finally gave +in, offering a refund. + +At the same time I'm looking for more trustworthy vendors. Kliment +referred me to Winsource. Although a Shenzhen company, they don't seem to +ship to China under that brand. So I reverse engineered a bit to find that +its Chinese trademark is 聚源鑫. Small company, not super well-known, not +even a store on Taobao. I'll talk to them in working hours tomorrow. + +I am currently inside an episode of self-doubt. What if I fail to learn +reflow myself? Even if I can barely manage, what qualification do I have +to teach other people? Perhaps I should have picked my battles and went +for a simple SMD hand soldering workshop instead. That's much much easier, +and I have done this three times. + +## 2023-03-22, Wednesday + +As I rose from bed I realize I could have ordered 5 stencils, and +organized two or more sessions in series. But I guess 10 is ok. Especially +when imbursement is possible. + +Was busy most of the day, and I forgot to contact that shady vendor. + +After dinner I moved what I have got so far to the hackerspace with my +bicycle. + + + +▲ It was a 2.5 km ride. + +In the empty hackerspace I unboxed the hotplate: + + + +▲ They sent along a *physical* invoice, a rare item these days + +## 2023-03-23, Thursday + +I rang 聚源鑫 to ask about the availability of ATtiny48-MU, the cheaper +alternative to 88. They don't have any. + +Now that the hope of getting chips from shady sources has vanished, +I returned to LCSC to check out their offers. They are able to act as +a broker between me and Mouser, charging 12.87 RMB apiece. Sounds good. +I ordered 20. + +## 2023-03-24, Friday + +The much awaited stencils are here! They were sandwiched between two +pieces of pretty rigid cardboard. The PCBs are in the same box. + + + +▲ For scale, each stencil is 5cm×5cm + +## 2023-03-25, Saturday + +The major chunk of my BOM is taken care of. Now we shall focus on the +nitty bitty discrete parts, such as capacitors and resistor packs. As +always they are extremely cheap. + +Last time I forgot to give LCSC the invoice info eligible for +reimbursement, so this time I ordered 20 more piezo speakers with the +info. Totally necessary and not abusing the hackerspace funding. + +## 2023-03-26, Sunday + +The discrete parts have arrived. + +Also I brought all the tools I have from home: multimeter, soldering iron, +solder, flux, etc. + +## 2023-03-27, Monday + +Mouser seems to have shipped the MCUs. + +In other news, I found this beautiful graphic that would make a great +poster background: + + + +▲ Credits: [Shapo on pixiv](https://www.pixiv.net/en/artworks/91199411) + +I made a mistake. On Saturday I thought a friend had spare LEDs from +a keyboard workshop last year so I didn't order any. But turns out I got +the size (monumentally) wrong, they're actually 3528 instead of the 0603 +I want. (Makes sense though; we soldered them for backlight and 0603's +would be barely visible.) So I ordered 100 along with 10 pairs of +tweezers. + +## 2023-03-29, Wednesday + +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. + +## 2023-04-02, Sunday + +Today I made what I consider one of my best designs with Inkscape. + + + +▲ The font is Orbitron. + +## 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. + + + +▲ Before applying the paste. + +Upon removal, there were quite a lot of shorts, but easily fixable with +the sharp edge of the Japanspachtel. + + + +▲ 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. + + + +▲ 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. + + + +▲ 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… + +## 2023-04-08, Saturday + +They're here! Sadly I don't have time to play with them, I need to go to +a barbecue… + +## 2023-04-09, Sunday + +Guess whose dream four years ago came true today! + +I can hardly contain my excitement, but I'll try my best to describe what +I did just now: + +### 20:00 + +I arrived at the hackerspace and set everything up. I was alone so there's +no pressure. I think I might be able to finish this by ten. + +### 20:10 + +I carefully picked up one (1) ATtiny48-MU chip and placed it inside the +QFN socket. It looks like this: + + + +▲ Finally, I can propose to my cyberfiancé(e) + +I closed the lid and taped it shut. I don't want to lose it! + +### 20:25 + +The chip must be programmed before going onto the PCB. For this I'm using +a [USBasp](https://www.fischl.de/usbasp/). + + + +▲ Actually there are mistakes in this photo. Three consecutive pins are +off-by-one. + +After that, I connected the USBasp to my computer and attempted to +communicate with the chip, but failed. By continuous trial-and-error, +I found and fixed three problems: + +- the MOSI, MISO and SCK pins are off-by-one +- I didn't pull `~RESET` low +- The baud rate is too high + + + +▲ Finally, we have established diplomatic relationship with the Silicon +World. + +I then set the fuses so that it runs at 8 MHz. And… it's done I guess? + +### 21:10 + +Then comes the exciting part. I need to repeat what I did on +[2023-04-03](#2023-04-03-monday), but now we're going full throttle. I now +have a chance to capture photos I forgot by then. + + + + + +### 21:30 + +Doing the QFN32 is harder than I thought. There's always too much paste. +At first I thought it was my recklessness, so I kept reworking with +increasing care. It took me three tries to realize it is not. Actually, it +was the tiny displacements of the stencil as I scraped the other parts. + + + +▲ All the pads make one single blob. Not ideal. + +So, instead of scraping the QFN32 footprint first, in my fourth run +I scraped it _last_. But upon removal there was too little. Time was +running out, so in a risky move I re-attached the stencil and scraped +a little more paste. + + + +▲ It worked! + +So after manually separating a few shorts on the discrete components, it's +time to pick & place! + +### 22:00 + + + +▲ Didn't lose D3 this time + +Onto the hotplate! + +### 22:10 + +Watch C2 fall in place as the solder heats up. + +<video controls> + <source src="../img/reflow-workshop/cap_reflow.mp4" type="video/mp4"> +</video> + +▲ MP4, 4.1 MiB, no sound + +The only problem was two shorted leads, which are easily fixed with flux +and the soldering iron. + + + +### 22:20 + +BEHOLD + +THE FIRST PROTOTYPE + + + +▲ Everything works as intended + + + +▲ Kliment's electronic kitten on the left, mine on the right + +I spent another ~20 min cleaning up the workbench, then left. + +## 2023-04-10, Monday + +Now that the prototype turns out a success, I can finally tell JDB to +produce more PCBs. Interestingly, the first batch of five cost 90 RMB, but +the second batch of 20 cost only 111. The more boards you order, the +cheaper each one is. + +I then ordered a box of Kimtech lint-free wipes. They are much cheaper +than I thought. + +## 2023-04-11, Tuesday + +I ordered 5 magnifying glasses and 5 spray bottles. + +## 2023-04-12, Wednesday + +Both the magnifying glasses and spray bottles are here. + +## 2023-04-15, Saturday + +I got the 20 PCBs and the invoice for everything I ordered from JDB. + +## 2023-04-26, Wednesday + +After a week of final exams, I took a few days off to relax, before +rediscovering the existence of reflow workshop. + +It's spring break right now and I'm at home. At this point everything +seemed ready, but an inventory check reported a lack of cell batteries and +holders. So I ordered a bunch more. + +## 2023-04-28, Friday + +I went back to uni to pick up the package. I also went to two concerts +where I caught a guitar pick. + +## 2023-05-06, Saturday + +I discussed workshop arrangements with my colleagues at TechJI. It will be +held twice on both evenings this weekend. + +## 2023-05-07, Sunday + +Behold, the final poster design: + + + +▲ Despite the visual effect, most of the graphics is not my own. + +## 2023-05-08, Monday + +I drafted the promotional article to be published on WeChat. + +## 2023-05-10, Wednesday + +### Afternoon + +The article is published, but WeChat decided that hyperlinks are not +allowed. Among them is the survey we use to register participants. +Sabotaged by WeChat's pointless restrictions. + +I received messages asking for the link, but I can't edit the article +(thanks WeChat), nor can I post it in the comments without approval (many +fucking thanks WeChat). I ended up urgent pinging the admin, who +thankfully made it public real fast. + +The moment link went public applications blew up. In two hours we had 32 +applicants. We can seat at most 19, because we only have so many ATtiny's +left. This means I'll have to send rejection letters to so many people. +I've always hated rejection letters. Now I've become what I swore to +destroy. + +Conclusion: Tencent is a horrible asshole whose sole purpose is to destroy +the open internet. + +### Evening + +I made a horrible mistake. I made applicants fill in their cell number, +and stated that I will contact them via SMS or WeChat. HUGE mistake. I had +to manually copy the numbers to my phone. Should have asked for email +instead. + +## 2023-05-11, Thursday + +I went to print the poster on an A2 sheet of paper. It's pretty! + + + +▲ The exposure is _just_ long enough to blur the print head, which I think +makes the photo way more dynamic + +I cycled to the hackerspace to hang it up. It's much smaller than all the +other posters, but it's hands down the prettiest. + +After that we had an internal training session within TechJI. The purpose +is to familiarize ourselves (including me, because the last time I did +this was one month ago). We started with an overview, then we smeared +solder paste. Everyone had their own technique. The common trend is too +much paste, and/or going over one place too many times. Everyone had to +rework at least once, because that is essential knowledge for the +workshop. + +Who could apply paste the best? We have a winner! + + + +▲ This is a sign that they are better at it than I am + +Up next we had pick-and-place. Sadly we can't offer a complete kit to +everyone because we need to leave enough for the 19 people. Two of us were +actually among the 19, so we decided to make two prototypes. + +I demonstrated C1 and C2 (the two 0805 caps), and made a few comments on +the polarity of the diodes, pins of the QFN, and the 0402 region where you +make a recognizable pattern so you know which board is yours on the +hotplate. + +No one had any trouble. I inspected the result which is shockingly great, +then turned on the heat. + +One of them is observed to have two shorts on RN2, and the other is +flawless. However, when we put a battery in it, the RGB LED (D6) doesn't +turn on. Why not? It turns out D6 was upside down. It is indeed very +subtle, and even I failed to catch that before heating. Then I noticed the +same problem on the other board. With a soldering iron I manually fixed +them. + +It's time to test our products. Weirdly, one works, but the other is +really bad-tempered for some reason. Whenever you remove your finger from +the battery, it hisses nonstop. I would advise it to see a therapist. + +I asked Kliment what could be the reason, and he suggested it was either +a short on the MCU or the resistor packs, or a shoddy battery holder, +because the kitten hisses when reset. + +To my disappointment I only ordered 100 LEDs, which is _barely_ enough. +And to an electronic engineer _barely_ enough is not enough. We have to +keep a redundancy, so I ordered 200 more. + +## 2023-05-13, Saturday + +Just finished the first session and I am so fucking exhausted. Three +hours, working nonstop. I forgot where I left my bag so I couldn't even +show the slides I made. + +Long story short, we instructed 8 terrified beginners how to do reflow. +Out of all participants, one managed perfect paste on the first try; most +made it in three. + +Here's some of the jobs that made me go "hmm that's not bad": + + + +We began toastin' at exactly the two hour mark. + + + +▲ One core, two threads + + + +▲ Typical board right after heating + +I then spent like half an hour manually fixing shorts, reinforcing the +battery holder, etc. Everyone's electronic kitten purrs and hisses, but +not every LED turns on. It could be a fault in the touch sensing area, +MCU, resistor pack, or the LED itself. I did not have the time to diagonse +one by one. On one board this happened on the tail, which makes the kitten +immune to tail pats, and consequently really tame and hardly hisses. + +Everyone got their product at 21:something and I cleaned up the place and +wiped every tool until minutes to 22. It's a miracle we finished the whole +thing before 22:00, especially when the staff is made up of three +ex-terrified beginners, two of whom literally learned reflow 48 hours ago. + + + +▲ This is honestly how I feel + +Later, I found my bag in another room. + +## 2023-05-14, Sunday + +OK today I put my bag in the right place. And we have more tables to sit +around. This is good because I don't have to run around all the time. +I also got to use a giant LCD screen to project slides on. Overall +a significant improvement. + +Today we have 9 people coming. That's one more than yesterday, but we're +more prepared than ever. + +One person did a perfect paste job in one go; most did 2, 3, or 4. For +some reason the people today are really into reworking. One of them +reworked a near-perfect board only to end up with the same thing. But hey, +practice makes near-perfect. + +This trend of endless reworking brought us behind schedule. We expected to +move on to pick & place at 19:30, but didn't manage until 20:something. At +least they're having fun?? + +I really should have forbade reworking once it's good enough. + +Introducing today's contenders in the QFN arena: + + + +The first one is the one-go job. Pads 27-31 didn't seem to catch any +paste, but that's fine because we can fix that at the end. The +bottom-right is an outright expert. They somehow managed to separate +_every single pad_. + +This person's job overall is also impressive: + + + +▲ D6 and the 0402 region are _flawless_ + +Pick and place is easy. And since I have slides to help me today, it was +a piece of cake. Only one person had challenge understanding the +orientation of the RGB LED, and another misplaced the speaker by 90 +degrees. Other than that, no problem at all. + +And as always, now the job is almost done for everyone but me. We ran five +rounds on the hotplate. Twice I forgot to monitor temperature and let it +go too low, but luckily nothing went wrong. About 2 or 3 boards needed +manual fixups, like un-shorting resistor packs, but after that every +single one works. All the LEDs light up, too. + +One interesting problem: on one board the sound is intermittent. I pressed +down the MCU, which seems to solve the issue for once and for all. + +We ended at around 21:40, but then one person came back telling me their +battery holder broke. The positive contact snapped off. The only way is to +replace it, so that's what I did. + +One remarkable observation: despite the facts that + +- my uni is mostly boys +- my major is mostly boys +- TechJI is mostly boys + +this workshop has more girls. This is really nice, because I experienced +a level of diversity not present in a room of dudes. This is the future we +want. + +At the end we took out more trash than we ever imagined: + + + +## 2023-05-15, Monday + +This morning I moved the tables and chairs back where they belong, and put +away every tool that I used. It's been exactly two months since this +journal began, and it's finally coming to an end. I believe it's time for +some reflections like I always do post-workshop. + +### What did I do right? + +- I began early (or, in other words, I prepared for way too long) +- I bought most things with redundancy in mind +- I designed a poster +- I did it myself and proved it was possible +- I showed my friends how to do it and now they can help me +- I felt confident throughout the workshop + +### Who should I be thankful for? + +- Whoever funded this hackerspace and the ones who run it +- My friends at TechJI for the help +- My parents for their money +- Kliment for the idea, design files, and help +- Every delivery person who sent my packages + +### How did this workshop help me mature? + +- I fulfilled a dream since 2019 +- I learned to communicate with corporate sales, and to be shameless + around them +- I even made one (1) phone call, even though it didn't help +- I have killed my fear of reflow soldering + +### What can be improved? + +- When I said I ordered things with redundancy in mind, that does not + include the LEDs +- I FORGOR MY BAG 💀 +- Sunday session went overtime due to ORS (Obsessive Reworking Syndrome) +- Should have used email to organize a bunch of people I don't know +- Should not have trusted WeChat for any purpose + +People have expressed wishes for more sessions in the future. Indeed, if +I were rejected by someone else, I'd be sad. Sadly this is not likely, +because (1) we've run out of chips, and (2) it is an extremely +time-consuming workshop (only next to keyboards). More people = more +inspections = more hotplate runs = more manual fixes. I would very much +like to take a break from workshops. + +## 2023-05-16, Tuesday + +Today I took care of the accounting required for reimbursement. The sum +worked out to be 1380.80 RMB (but I definitely spent more than that since +I didn't ask for an invoice for everything). + +3 invoices are on paper, 8 are electronic. One vendor sent me an invoice +in .ofd format (which is some kind of Chinese alternative for PDF, namely +GB/T 33190-2016). The format is poorly supported except for a handful of +commercial readers. It took me ages to find an online service and convert +it to PDF. + +I sent all of them to the supervisor and I hope he gets back to me soon. + +My old keychain (which is a keyring on a green binder clip) was lost +today, but just at the right time: introducing the Kitten PCB keychain! + + + +(Fun fact: in the workshop I told everyone "even if you fail, your failed +PCB could make a nice keychain." Glad it never happened.) + +## 2023-05-22, Monday + +Supervisor says he "lost" one of the invoices due to the "gust of wind" +that blew it away while he was away from office. And I was like …OK? + +Not that I'm mad. I cannot reject the null hypothesis that he is right. +I'm just upset that it's the one that carries the most value. 417 RMB out +of 1380 is 30%. + +So I asked JDB and they said they can't just print another one. Instead, +all they can do is make a photocopy from their archive, then stamp it. + +I'll wait. + +## 2023-06-01, Thursday + +After weeks of waiting, I ask JDB what they've been up to, only to find +that the sales rep I talked to has resigned and now I'm talking to another +person. They gave me another number, who agreed to mail me the thing. + +## 2023-06-06, Tuesday + +The invoice copy is here. I'm gonna hand it to the supervisor tomorrow. + +## 2023-06-07, Wednesday + +Supervisor now has the invoice. + +Later he sent me a spreadsheet because the accounting office needs me to +fill in an inventory of what I bought/used, how many, and when. I, being +the sole accountant of the workshop, had no trouble doing it. But I don't +like the attitude of theirs at the accounting office. This is a great way +to ensure I won't hold a workshop here again. + +To get revenge, I did a passive-aggressive, highly accurate inventory that +ended up 45 rows long, detailing every single purchase and consumption +(even only one) on the invoices. I also left this note, in white font, on +Sheet 2: + +> do you know how much work i put into this? of course you don’t. and now +> you try to challenge me to count my consumables? well let me tell you +> something. i HOSTED the workshop. of course i know how many batteries +> i used. OF COURSE i know when i ordered them, when i received them, and +> when i unboxed them. stop trying to refuse me my money. i am invincible. |