TSOP, TSSOP, VMFP. All kinds of quite cryptic acronyms that I am told refer to some sort of surface-mount device packaging. So, considering that I am going to need to work with these to do what I want, what does Wikipedia have to say to enlight me on the subject? There is one article on Small Outline Integrated Circuit (SOIC). Unfortunately, that Wikipedia article contains a dearth of information on the full variety of surface-mount device packaging types. For example, VMFP is nowhere to be seen.
20190101/https://en.wikipedia.org/wiki/Small_Outline_Integrated_Circuit
20190101/https://en.wikipedia.org/wiki/File:SEG_DVD_430_-_Hynix_HY29LV800BT-70-4279.jpg
Nevertheless, it still is a useful introduction to the variety of packaging types in the subject, and the difference between narrow SOIC (1.27 mm pin spacing) and small outline package (SOP, 0.65 mm pin spacing). Add a “T” in front for “thin” in TSOP, and an “S” for “shrink” in TSSOP. An Exposed Pad (EP) means that there is a large exposed pad purportedly on the bottom of the IC that acts as a heat sink.
Now, if you want some great background information on the current state of affairs, the 7400 series integrated circuit article is a great one.
20190101/https://en.wikipedia.org/wiki/7400-series_integrated_circuits
So, what are the important things we’ve learned? First of all, only the original 5 V 7400 series chip is available in a through hole mounting package. All of the additional variants, such as 3.3 V variants, are available in surface-mount device packages. Second, the variety of surface-mount device packaged chips address 3.3 V logic quite well. So, long story short, if you want 3.3 V logic chips, you’ve got to use surface-mount device packages, albeit being so small that they are difficult to solder. And, in the end, indeed this is what I want, as another thing that I didn’t like about needing to use additional chips with the Raspberry Pi is the size and bulk that they can add. Surface-mount device packaging aims to keep this to a minimum. The main disadvantage is that in the present day, these smaller form factors entail a higher design and engineering cost any way you put them. Robotic pick and place machines are the mainstay of mass production with these chips, but getting a custom job with these machines is unfortunately quite expensive. Therefore, most people will hand-solder these chips in the early design phases, although that also entails more cost it is difficult to learn how to do this due to their small physical size.
Worthy of note is that the 7400 series chip runs off of 4.5 V unregulated power from 3 AA batteries just fine.
Let’s continue searching for more information on the larger Internet.
20190101/DuckDuckGo socket surface mount integrated circuit
Ball grid array (BGA) and pin grid array (PGA) sockets are listed in here, but not the other surface-mount types.
20190101/https://www.futureelectronics.com/c/interconnect/ic-sockets
Basically the same story for sockets here too.
20190101/http://www.te.com/usa-en/products/connectors/card-socket-connectors/ic-sockets.html
Possibly there are the devices you are looking for on Ebay.
20190101/https://www.ebay.com/sch/i.html?LH_CAds=&_ex_kw=&_fpos=&_fspt=1&_mPrRngCbx=1&_nkw=surface+mount+socket&_sacat=&_sadis=&_sop=12&_udhi=&_udlo=&_fosrp=1
Sparkfun! That’s always a very informative site for beginning hobbyists like me. Indeed, this site has some useful information that was not found on the Wikipedia article. Notably, a very useful accelerometer/gyroscope module comes inside a quad-flat no-leads (QFN) package.
20190101/https://learn.sparkfun.com/tutorials/integrated-circuits/all
Okay, but I’m still looking for sockets for surface-mount devices. Sockets features for through-hole plastic leaded packages galore.
20190101/DuckDuckGo surface mount plcc ic socket smt smd base
20190101/https://www.electronics-notes.com/articles/electronic_components/surface-mount-technology-smd-smt/plastic-leaded-chip-carrier-plcc.php
Ah, finally! Getting to some useful links, through Electronics StackExchange of course. Here’s some listings for J-lead surface-mount devices.
20190101/https://electronics.stackexchange.com/questions/185655/soj-socket-to-pcb
20190101/http://www.morethanall.com/images/products/175496295148302c5ae8f40.jpg
broken/http://chufon.sell.curiousexpeditions.org/pz56f008a-plcc-socket-soj-socket-adapter-with-tin-plated-contact-and-84-pin-plcc-socket.html
20190101/http://www.shopsri.com/pdf/augat/soj.pdf
Okay, now that was quite a hard search, and only partially successful, I must reckon. Mainly, I was trying to prove that there are in fact surface-mount device sockets available on the market, and I’ve found at least one such example. But, upon further thoughts, maybe these sockets are more effort to use than they are worth. In any case, socket or no socket, I’m going to need to solder something down to my boards. Yes, I’ve already covered the hand soldering iron tricks. Those work well for surface-mount devices with protruding pins, but for quad-flat no-leads (QFN) packages with their pads sitting squarely underneath the bottom of their packages, soldering gets a bit tougher. Yeah, maybe you can use larger pads and conduct heat along the exposed pad to get a good solder joint. Maybe even this technique can be extended to ball grid array (BGA) packages. Reiterating the Sparkfun article, “[i]f you can hand-solder a BGA-packaged IC, consider yourself a master solderer.”
But, alas, if I can’t get hand soldering to work, I can look toward doing my own reflow soldering. Okay, so I’ve read that you can build your own reflow soldering ovens relatively easily and the process itself isn’t that difficult. Let’s review the subject here.
Oldies but goodies. The IEEE Spectrum article I first read to learn about this trick.
20190101/DuckDuckGo ieee spectrum build your own reflow soldering oven
20190101/https://spectrum.ieee.org/geek-life/hands-on/the-poor-mans-solder-reflow-oven
Wow, so here are some nifty tricks conveyed in this article. First of all, you can use an existing toaster oven with convect (to avoid hot spots) capability as a base upon which to build your reflow soldering oven. Some hobbyists stop there, with using only relatively crude temperature control and air cooling. Second, getting a PID ramp/soak controller is quite cheap at of 2012, only $75. So, if you are willing to do some electronics hacking on your toaster oven, you can get some very good results for a very good price.
Looking to the Internet for more information, I found this other article. This one, unlike the last article, details the overall process in more detail. First, you lay out the solder paste manually by hand onto the pads. Second, you place the components on top of the pads. Don’t worry if it’s a little messy, the reflow soldering process can straighten things out a little. Surface tension from the melted solder paste will cause the components to shift around so that their leads are in the center of the pads.
Here, this author used crude temperature control, square-wave style temperature setpoints and durations, but got quite good results. This author also noted that others have noted that you you can also simply heat the board up to the reflow temperature for four minutes and that will also give you just as good results. Additionally, the author notes that once you are done prototyping a design, you can prepare a solder paste stencil mask to make applying the solder paste much easier and faster.
20190101/DuckDuckGo reflow soldering oven at home
20190101/http://www.cupidcontrols.com/2013/12/home-reflow-soldering-on-a-budget/
20190101/http://www.cupidcontrols.com/wp-content/uploads/2013/12/recipelist.png
20190101/https://en.wikipedia.org/wiki/Toaster#Toaster_ovens
N.B.: A toaster oven is basically just a smaller form factor of an electric oven. That, of course, is preferable for making small job, single custom printed circuit boards as it is less energy to heat the smaller space. But, if you have a larger electric oven with convect capability, you can use that just as well for the crude temperature control techniques.
What is the temperature control curve for lead-free, RoHS solder paste? Naturally, it’’s a few degrees Celsius higher than that of leaded solder paste. Don’t worry, it’s not too much higher. Chances are that if you have an oven that can reflow leaded solder paste, it can do lead-free paste as well. I’ve also found some nice confirmation information on the temperatures to use for leaded reflow soldering too. Note that passive air cooling, by simply turning the oven off and letting it cool or letting the board cool in open air, works quite well at the end of the process for cool-down.
20190101/DuckDuckGo temperature curve rohs refow solder paste
20190101/nts/download_center_1/reach___rohs/Standard_Reflow_Wave_Solderprofil_LF.pdf
20190101/https://www.compuphase.com/electronics/reflowsolderprofiles.htm
Here’s another interesting idea. Rather than using soldering paste, you can make your own pads out of conventional solder on the printed circuit board. Then, you use adhesive tape to hold the components in place instead of soldering paste. You put the whole board in the reflow oven, then you observe the components adhere to the solder.
This SparkFun article is a great capstone on all my notes on reflow soldering thus far. It details the process that SparkFun uses for electronics assembly, from small hand-assembled batches to larger production batches. An important point that this SparkFun article brings up: solder paste has an expiration date and should be used up completely relatively quickly after its date of purchase. This has to do with the flux added to the metals for the paste consistency. Also, you have to be careful about another defect that can happen during reflow soldering. Sometimes for really small components, if one side adheres but the other doesn’t, the reflow causes the component to stand on one side, called “tombstoning.”
20190101/https://learn.sparkfun.com/tutorials/electronics-assembly
Also, your idea about taping components down? Indeed, in larger assembly runs, sometimes components are glued in place, rather than being held by solder alone.
Also, there’s another important step that they cover: washing. I thought this step to not be necessary in the simplest of soldering jobs, and maybe that is true. But, if there is any residual flux left on your parts, that can turn into a sticky residue over time, even become acidic, and make your solder joints brittle. Cleaning with hot distilled water in a cheap crockpot and a toothbrush is a good way to do this at home. If you only have a small number of connections to clean, a Q-tip with some isopropyl alcohol works quite well.
UPDATE 2019-01-06: Okay, so why did I never had to clean the flux from the solder before? I have a serial cable that I’ve soldered together quite a few years back, and it still works just fine. Well, it was nominally 60% tin 40% lead solder, and possibly Rosin-core. Maybe that since it came with a starter kit, it was formulated to make this be less of a problem.
UPDATE 2020-03-15: Indeed, this is the case. There is a such thing as “no clean flux” that is used in some kinds of solder, and it could be that is the kind of flux they used in that particular solder.
Alas, I must concede that the leaded versus lead-free solder paste situation makes me feel much the same as I do about black and white versus color film developing. Black-and-white film is easier to develop and more forgiving toward process variations, but it is not as featureful as color film. Hence color film was preferred for mass market film developing… until it was made obsolete by digital. Technically speaking, however, the situation is a bit different for solder paste. Black and white film developing can easily be environmentally friendly. Indeed, however, comparing lead-free hand soldering versus lead-free reflow soldering, running an oven hotter is easier than handling a hotter soldering iron.
Now, I’ve got an interesting idea. Is it possible to do all of your electronics projects with only solder paste? Now that I think about it, the answer is “no.” Typically, there will be wire connections to battery power terminals that you will, of course, prefer to solder down the wires rather than put on paste and put the whole in a reflow oven. So, although you can do an entire project using only conventional solder, you cannot do an entire project using only soldering paste.
UPDATE 2019-01-03
How do we know that reflow soldering in your home kitchen’s oven really works? Take this piece of vernacular knowledge. If your laptop is not working, put your laptop in the oven with a wet towel around it, and that will fix it. Indeed, that’s how we know it works. Although, it is more effective if you remove the circuit boards, and the wet towel probably isn’t necessary.
UPDATE 2019-11-05
However, please note that the lead-free reflow soldering temperature, about 260 degrees Celsius, is above the melting point of most plastics, about 200 degrees Celsius. This means that you cannot put an electronic in an oven whole to do a reflow solder. It would melt the plastic casing and it would be ruined. You must put only the circuit boards in the oven and remove all other external casing, batteries, SD memory cards, and so on.