 Welcome to Lady Aida. Hey everybody and welcome to my desk. It's me Lady Aida at my desk with me Mr. Lady Aida on camera control. Baby Aida sleeping soundly. We got a bunch of stuff going on this weekend. Any news or updates? I think we're not shipping. So tomorrow is Martin Luther King Jr. Day. It is a paid holiday data fruit also a day of service. We do paid days off for charity in addition to Martin Luther King Jr. Day. Check out our website and more for details. Shipments will be going out on Tuesday. This week, Wednesday, JP will be doing a show and tell. There will be no Ask an Engineer but we might be publishing a video that we're pre-recording. Raspberry Pi folks are in town. We're going to be talking with them. We'll see if we could do a live show but we'll put something up on the website. And then we have our full week of shows. Lady Aida what is on your desk this week? Well let's go to the overhead because I have a bunch of designs that I worked on this week. A bunch of prototypes I put together. First up, we were doing... There's a lot of dust on this table. We were doing some QT Pi BFF designs. At least autofocus lock. So folks know you know these cute little dev boards that we have with the SAMD 21 or RP 2040, ESP32, etc. I've been making a lot of little like add-on boards. So this week I put together prototypes for this Neo key. So it's a tactile switch, not tactile, sorry, an MX switch socket. And let's see if I don't... Yeah, when I press it you can see there's a little Neo pixel underneath a reverse mount Neo pixel. And this is a socket for a key. You can put any kind of pressy key and maybe like make a one key project. I don't know what it would be good for but I thought it was adorable that like the MX keys fit like almost exactly in the same outline. So I thought you know it's gonna be like a $2 board. I mean somebody might have some use for it. So why not? So that's the Neo key QT Pi breakout. And then I also did... Oh, the micro SD BFF which we talked about. I designed a couple of weeks ago on the show. So I actually made one mistake. I didn't reverse the design. Like this should be back to back with the QT Pi but it's actually front ways. So I'll show you what I did. I like to have the BFFs be on the back like this is how it's supposed to be. Sorry, the other way around. So that you can solder it to the back of the PCB even if it's flat. And then like you'd have a little storage file here. You have a SD card, micro SD card and you could slip it in and you can do like a little micro data log. I thought this would be really cute and pretty useful actually. You know especially if you want to do a little micro web server. You need more disk storage. You can put any size micro SD card. But I made a mistake again when I laid it out. I forgot to reverse it to be on the back so it's on the front. So I did test this design but it had to be yeah this way. I accidentally made it so it plugs in this way which is not as useful I think. I wanted to be so the SD cards on the back. But no big deal. I flipped it around to order the PCBs. Otherwise it works really well. Another thing I wasn't so sure about is I have these little solder jumpers to select the chip select pin right because for micro SD cards use the SPI port and the SPI pins are defined as over here as S-Clock. We need a chip select pin and so I picked I think TX by default. But you can also select RX or A0 or A1 or you know there's an old jumper you can put a wire if you want. And I wanted to make sure that it would even if you soldered the jumper you could still insert the micro SD card right because it slides very close to the edge of the PCB. You can see there's a little bit of a bump here where the solder is but it's still well below the height of the SD card which you see doesn't sit quite flush. There's like a little bit of height to it. So it doesn't I'm going to say it's not impeded by that solder bump which is good. So these are also ordered and will be in the shop quickly. These are really fast to put together because it's just the micro SD slot. I kind of just you know I kind of love these little add-on boards. I'll make a little you know a quad droopler or whatever of BFFs at some point. But I just love the idea of like you just solder like one of these to the back and you make a little project. It's a little bit of teeny circuits you know when we're filled they were at Maker Faire. They had like little you know little circuit boards and it was like each circuit board did one little thing you could plug them together. Yeah also it reminded me when I first saw this I'm like oh these are like micro machines for makers. I can't even have an old post from on Make where it was like you collect them you trade them they're really tiny they're compact and I also like the idea of single serving things where it's like this is what this does. Yeah just like a button in the epic so I kind of like it's like these are yeah add-on boards are very inexpensive like it's all very very cheap if long as you know you know you don't do something complicated a lot of people are like oh but what if I wanted to like add this this and I'm like well at some point you're talking about a feather or a metro like if you want a DC jack or you want uh lipo charging and you know data storage you want a longer feather but can you flip the direction of the insertion for the micro SD? No I wanted this way because I'll tell you why it's it's it's it's finger on purpose it's this way because a lot of um my BF my QDPIs have Wi-Fi and so the antenna would be over here I didn't want the shield to be over the antenna area and so like the only way that it would work is plugging in this way and then you know you'd be able to remove it from the outside. Next up can you do an OLED BFF using the 0.5 inch OLEDs? You know I I haven't yes they're kind of a pain solder and I have to find a good source for them um I'm not sure they would fit to be honest either but um I can take a look they're they're quite cute I have to you know I have to find one that's I squared C in particular maybe I found one source of like the 0.62 inch OLEDs but then like I had it it was like they were really pain the ass to solder so it's like yeah I don't know if it's worth it okay so this is the BFS so yeah there's more there's more coming always and then um the big project you know I I chat about is I'm revising the ESP32 as two feathers and S3 feathers they all were made with the LC709203 battery monitor which is you know it's a fine monitor um but uh I'll just get this stuff out of the way um it's a fine monitor but um it's discontinues end of line and the new version is like a fine point it's a fine pitch BGA and like like I think one of the pins you need is like it's a nine pin BGA and like one pins in the center and so I'd have to go like four four DRC to route it and I was like it's not worth it so um I'm updating them all to use the uh max 17 oh let's see if one of these has the text on it one moment anything no uh they don't have the text um later on I added the text so I'm updating them to use the max 17 048 which is a great maxim um battery monitor it's almost the same size too that's the battery monitor here that's the max and then this is the LC709 I mean it's almost the same size this is like a you know BGA and this is a uh TDFN uh so swapping them around and like revising but there's like seven feathers right there's like the S2 the S3 with that PS RAM the S3 with PS RAM the TFT S2 the TFT S3 the reverse mount TFT yeah it's like there's a lot so like going through all these and revising them and checking to make sure I don't you know like for some for a vision like this I still want to get a prototype so like putting all together the prototypes um but like for example this is the S3 uh we have D in this past today um and I got those nice big uh tactile buttons I talked about and showed off last week um so you're all being revised okay um a little bit nice to SBFF MIDI BFF is there a proto BFF already there's not I don't know I don't know how many I don't know how many of these BFFs I'm going to do but I want to do them eventually well I want to get to the cowbells as well BFF of the day cowbell of the day oh the cowbells yeah I'm a little behind on my cowbells I was kind of like oh I'll do a cowbell a week in 2023 and it's already been two weeks um usually than reading a book a week um all right so then getting into uh last thing before we get into um great search so one of the prototypes I got the S3 8 megabyte um I got these and they didn't enumerate um so one of the nice things about the S2 and S3 ESP is that they have built-in ROM bootloader which makes um testing whether you got the basics working really easy because you just hit the boot button you plug it in it pops up as a USB device and you're like great I can immediately start loading code you don't have to like like with the SAMD 21 and 51 you have to like haul out your swd programmer your your jlink or whatever uh your at malice and um so I thought it was you know what I really liked that there's built-in ROM bootloader I'm like instantly you know getting things going um however like I said these didn't enumerate and um I was a little bit like why would this not work because I had the prototype for the S2 um ordered and the S2 has the same um layout as the S3 so it's like why would the S2 prototype I just tested that worked the S3 didn't um and you know I whenever I make prototypes I always make more than I always recommend two for even the most basic boards three to four of complicated boards the reason is actually um I did pull off the module off of one of them because I was like I looked around like I probed and basically the reset line was pulled low and it looked like there was like the reset line was pulled low because I think it was actually the pull-up was powering back powering the module the three volt line wasn't powering um the module itself there's nothing on the debug line um the the module itself wasn't powered and the reset line was was pulled low because it was you know was trying to power through the the the input MOSFET so um so I pulled off um the module I do that by putting this on a hot plate give me some seeds a little bit uh brown I put on a hot plate get it to 240 degrees C and then I gently use tweezers and I pull this off and I pulled it off you'll know that there was solder paste deposition on all these like you see that there's a nice rounded uh paste let me see if I can uh oh I can you said I can pinch and zoom yes you can oh whoa too good work too pinchy too zoomy um so you can see that there's nice rounded paste on all these when you look at the module see how there's some gold here see these are silver that's good that means the paste melted and adhered to it's when I pulled it off right you pull off a little bit of paste is stuck on the PCB and a little bit of the melted solder gets on the um should get on the pads but look some of these pads are gold which means that they never had adherence of solder to them so there was a cold solder joint right so um what I did is I um took some solder paste on a syringe this is ancient this is like 2021 but it's fine by the way you know solder paste lasts a lot longer you if you only don't keep it hot I keep it kind of in a cool area away from sunlight and away from anything hot no no computer nearby no uh solder on nearby and the paste is okay for rework and um I put some paste on uh the pads and then not this one obviously this one's I just I pulled it off so I can show y'all what it looks like during the failure and then um I put a paste on it and then I use a solder um soldering iron to kind of melt the the paste and get the flux around um I do that instead of a using um wire solder because wire solder it doesn't it's it's harder to get it to the right temperature with solder paste you can be a little messy and then you'll just note that when you um melt it with the tip of a soldering iron you get you're more likely to get uh nice bubbles of solder on all the pads so basically kind of fluxed and we worked all these pads and then I read you know this was still hot but I just pulled the module off and then I replaced the module and um you know you kind of try to center it as best you can and then um you give it a couple taps just to uh you know with your um tweezers you can't give a couple taps it'll center itself and then let it cool and pull it off and uh you know I managed to fix one so this is the one I you know removed to show you these are two that I had tried to do that technique with and I didn't succeed I did uh pull off the covers you know after it failed the second time so I was like well is there something going on here but I think I just didn't you know it's it's hard to um get enough flux and get the solder so you know I I didn't want to keep we working the same two boards but the third board uh it did happen so that's why it's good to make multiple prototypes um when you're dealing with especially modules with pads on the bottom what could cause this um ironically I think in miss storage if there's if these are stored without you know not in a closed container without desiccant you'll get oxidation on the pads even though it's gold right you'll still get a little bit of oxidation and that oxidation could uh make adherence not work also if the picking place didn't push the module down enough that's I think less likely but usually it means you don't have maybe support from the underneath so those are two things that could cause this issue okay questions uh any plans to re-spin the nrf 52 840 feathers and then thoughts on a p ir bff with esp 32 variant for security it sounds like you you can actually design some of these and we want to launch the we need to do we need to do a bff contest I know but we should um I no plans for for that um these are all good ideas that yeah they're all good ideas I just don't know if I'm gonna get to them I'm just I just have so many things I gotta work on um the nr 52 840 feather the sense does need to be redesigned because it used all st sensors and all those sensors are now like triple the price and so um it needs to be redone in order to be affordable to use lead free solder for all your prototype stuff the prototypes are uh it depends actually um it depends on what I'm doing if I'm doing them at home and um I need to do some pretty serious rework I'll sometimes go for leaded just because I'm gonna have more success rate uh this in particular is lead free this is the lf uh 4300 it's a lead free um you know obviously anything that goes into the shop is going to be um lead free but if I'm working on a prototype at home and I know it's never going to you know get into other people's hands I'll use leaded solder to make it to make it faster if I need to have a better heat transfer you can zoom back out okay that's fun all right okay next up how would you better store the bga chips and how to get oxidation scale off if it does happen you can't get oxidation off other than you just um put flux on and and hope that it burns away some of that oxidation okay is there a amount of force like measure torque ratings for lots of under chip pads for example pad count increases um you would check the package documentation for what part you're placing they'll usually tell you you know but you want to like push it down a little bit okay that's a technical term all right what else you get going that's it it's time to go to the great search because people are like hey where can I get some of this oh yeah solder paste the great search brought to you by digikey and a deferred thanks digikey every single weekly data user power of engineering to help you yes you find the things that you need on digikey.com later what is the great search of this week this week's great search is solder paste uh I was showing on desk lady a to have to rework uh this board under the overhead I'll show real fast I was reworking this board which had a module with under pads the pads are on the bottom of the module and so you have to you can't solder this by hand you have to solder it with a hot air station or a hot plate in this case I was using a hot plate um and I was using a syringe with solder paste this is a go-to technique I mean this board is going to be tossed so I'll just show what it's like but you know if you need to put some paste down I find this syringe to be great let's see I'll use the zoom in feature again with the rework how are you sure the pins don't bridge with solder um very carefully yeah but you don't put too much uh you get used to it there you go maybe move it sorry yeah I know I'm just I'm getting used to whoa too much hold on let me see if I can I'm just that's best around that's not too bad okay um so yeah I mean you would put some paste down and you could uh you know hot air it to get it to bubble um and and cover the pads or use the tip of a soldering iron um either way uh you know or if I'm just even uh reworking chips that have pins on the outside a little bit of paste especially because the flux is already in it it's it's it's sitting in flux it's a great and easy way to do smt rework and um this is kind of one of the one of the tricks and secrets if you have um paste uh solder paste in a syringe you don't need to have very fine why it's sometimes very hard to heat up the wire solder especially if you have a very fine tip and very fine pitch parts um luckily you can get solder paste uh from digigane you can get overnighted if you want to keep it cold but personally you know at work we keep the solder paste in the fridge to keep it nice and cold at temperature at home you know from just messing around I keep it in a cool dark area and it lasts quite a while as long as it doesn't dry out so let's go to digikey okay so uh let's search for solder paste so you can get all sorts of different solder paste um it's going to be under solder so solder paste comes in basically two or three different uh containers so it comes in tubs is what you use on a um paste printer because you know you scoop it out and you put it down on the on the stencil and then the squeegee squeegees it down we have tons of videos that we show on our Wednesday show if you want to see what this looks like um the automation process and then of course you can get it like I said as a uh tube there's two sizes of tubes there's like mega tubes uh this is 600 grams so this is as much sorry this is more solders in this tub and these are actually the big ones are for automated uh stencil deposition machines usually like normally a human doesn't hold a half a kilogram more than half a kilogram of um take a sausage worth of solder paste uh usually I want to go with the smaller you know 35 gram this one uh that I've got here I think is 35 grams two yeah yeah 35 grams so 35 grams is in less is what I suggest a 35 gram um solder paste syringe can last you a very long time by the way like easily a year or two like this you know is from 2020 so they last quite a quite a long time so you get the smallest one you can get um so let's uh go to stacking let's start with it's only active and let's only get a syringe just the way we're looking for and then there's a couple different options um so there's leaded and there's lead free so this is the first kind of differentiator we want to make chances are if you're manufacturing in the industry you're all lead free anyway so of course you're going to select lead free if you're soldering at home um you can use leaded solder or there's some industries where leaded solder is acceptable um you know when I'm doing rework again if I'm doing prototypes at home and especially if I have something that is um you know very I need to be able to rework it very easily leaded solder is going to be easier to rework you know it doesn't go to a customer um I'll do that at home otherwise I use a lead free lead free needs a higher temperature of rework so you need um hot plates and hot air guns that can go up to that temperature like 240 degrees you know 250 or higher uh leaded needs a lower temperature um that said uh I think I'm going to just select lead free because um I'm going to assume that you guys need lead free so I'm going to uh not select 63 37 or 63 37 that's the lead pv is lead okay next up flux type no clean or water soluble this is sneaky a lot of people are like oh I want it with water soluble I want it to be like you know cleanable if you get flux that's water soluble you must clean it because it's actually more activated so unless you have a water washing system um that you're going to put your boards through you should select no clean there's nothing wrong with no clean I mean it leaves a little bit of residue um but that residue is non-conductive and it's not harmful for your electronics and it's protective it's like the the flux that covers it I personally always use no clean I've used no clean all of Aida for use is no clean there's no reason for us to wash if you have boards that you want to wash or you have a washer go with water soluble otherwise no okay next up mesh type 345 uh so I was actually like what is the difference I know at the Aida fruit for our stencil machine we actually use mesh four because we have 0.4 millimeter pitch uh parts that we use if you're using 0.4 millimeter pitch yes you'll want maybe mesh four if you're using you know oh two oh ones oh one oh five sorry oh one oh five you can use four or five I just googled really quickly and there's like you know some nice web pages that talk about um the the sizes of the um the solder balls in general though like pretty much everyone uses three um this paste that I have here is 25 to 40 this is actually oh funny this is no sorry yeah mine is type three so this is a type three I use type three for pretty much everything again other than uh 0.4 millimeter or smaller you know BGA components really fine apertures you'll want four or five otherwise three is perfectly fine and it's the most common okay so I only have four options left so now there's um so these are both from uh these are all four these are from chip quick uh she'll surprise me chip quick makes a lot of rework uh stuff especially home rework or small scale rework um they have two types of products here one is you'll see here the differences in the temperatures one has like 220 degree C melting point that's going to be your standard lead free solder and then they have this low temp 138 C so the 138 C stuff again that's really low temperature I mean that's low enough that a very hot component will desolder itself right which we probably don't want so um keep in mind what you're using it for 138 C is is not very warm um if you're doing I think rework where you're removing parts I think people tend to like that because it's easier to keep everything you know the board stays pretty hot on your hot plate you can remove and rework stuff very easily that said I I don't actually use the low temp stuff that much um the chip quick is famous for it try it out but for general purpose I tend to use you know your standard lead free you know um 10 96 silver 3 copper you know point you know 96.5 3.5 and then um finally they they have what's left and there's two versions one is a 35 gram and one is a 15 gram um same equipment you know same same material and everything just one is a little smaller it's five ccs not 10 ccs honestly I would just get like unless you really need a lot just get this you know it's about half the price 35 grams is a lot uh you unless you're really making a lot of boards um you know if you're just doing prototypes at home you do a couple prototypes a week I think this uh 15 gram syringe of lead free no clean solder paste will do great and another nice thing is um as you can see it comes with the plunger and um the tip also so the dispenser tip and you can get other dispenser tips from digikey we will cover that next week um I tend to use the the yellow tip whatever that size is but depending you know it doesn't really matter just depends on whether you'd like to be able to squeeze more in one squeezing but this is my pick and that's a great search okay here's a couple questions again why you're doing this uh first uh should you let the solder paste melt before after applying the parts for a bga um it depends on whether you're reworking or you're soldering for the first time if you're soldering for the first time you put the paste down you put the component on top and then you heat it and the the as the solder melts it'll pull the part into location if you're reworking um well first if you're going to bga you probably have to put like you know bga the balls back on um if the rest of the board is soldered and I'm trying to repair something um not necessarily bga but like qfn I'll put paste on the component and I'll melt it on to to create two uh you know solder covered areas and then I'll heat them together and they'll um squish together but it's really like there's no right or wrong way you kind of have to figure out depending on the component and your pcb what's going to work can you use solder paste like regular flux um or do you need a stencil uh you can hand deposit it it just takes longer I've absolutely made lots of PCBs just by hand depositing the paste but of course it's faster if you have a stencil because you just do it all at once and you can get um better print resolution less likely to have bridging too okay next up to use low melt lead free often I don't use low melt at all um the stuff from quick melt that the quick the chip quick stuff that's 130c I've actually never really used it I know it's good for reworking uh I just I just kind of always put stuff on a hot plate um but I've used leaded I don't use leaded solder paste anymore but I used to you know before lead okay isn't over 100 seem uh metal and beyond component spec except for military automotive I don't is it over I guess 100 Celsius your parts can get beyond I mean I wouldn't get that 138 is pretty it's it's pretty low says most parts operate to 125c yeah it's just it's getting close to that limit right um I wouldn't I would not use it for anything that is leaves the house except to silver help it melt I've been using 99.3 10 0.7 copper for regular soldering um this stuff's good I mean I don't know chip quick chip can know what they're doing I would I would assume that they're uh 96 305 it's it's pretty good okay and with that is disc of Lady Aida all right thank you everybody we'll see everyone throughout the week we have a lot of cool stuff we're posting up and more thanks for hanging out with us special thanks to our team our community our customers everyone who keeps this going and thanks to um our little kiddo who loves to just listen to Lady Aida talk about electronics uh why we do these shows so all right keep setting this bff idea I mean I'm not gonna be able to get to all of them but I think it wasn't the midi bff that was a good idea it could be chunky midi uh connector what else was there there was the PR yeah there was a bunch there was a bunch okay all right we'll get to that but we'll get a couple then all right good night everybody bye everybody