As a millennial, it’s all about having the newest phones and gadgets, not to mention playing the newest games (Pokémon Go anyone?). But does newer always equal better? Personally, I’d rather stick with my bike than ride one of those hoverboards. Remember them? They were the hottest item of the 2015 holiday shopping season before people realized they had a slight issue with spontaneous combustion.
There are certain times in life where using a high-quality and reliable product or brand outweighs novelties and fads. A few things that come to mind: my car, my furniture and my grandmother’s peach cobbler recipe. Trust me. Nothing could ever improve upon that peach cobbler recipe.
Even the semiconductor world isn’t immune to trends and marketing hype. For example, in the world of direct current (DC)/DC regulator packaging, the focus is on creating the smallest package possible. However, semiconductor developers who focus solely on creating that smallest package possible seem to have forgotten one very important fact: there are tens of thousands of customers worldwide who still prefer traditional packages with pins or leaded packages, despite their larger size.
Don’t get me wrong: TI is also investing in cutting-edge package technologies. However, we haven’t forgotten our pin/leaded package-loving customers and so continue to release new products like the new SIMPLE SWITCHER® LMR23610/25/30 36VIN buck regulator family in trusted package technologies like small outline integrated circuit (SOIC)-8.
You may be curious as to why so many customers still like ancient packages like the 8-pin SOIC, or SOIC-8, when there are so many newer and smaller technologies available. Many customers prefer packages because they are easier to work with in the lab and the factory. The leads on SOIC-8 packages are very easy to hand-solder and work with on the bench. Designers can easily debug their circuits since the pins are exposed. In the factory, using a leaded package technology technology with pins enables designers to use visual inspection technology to confirm that the device has been soldered correctly and to screen out any faulty boards.
On the other hand, with a leadless package like a very thin small outline no-lead (WSON) or a quad flat no-lead (QFN), the pins are completely underneath the package, making it extremely difficult to solder or debug by hand. The location of the pins also makes visual inspection impossible, necessitating additional X-ray inspection equipment to confirm proper soldering connections. Watch a video “Engineer It: How to Simplify the Power Supply Prototyping and Manufacturing” for a soldering demonstration on an SOIC-8 package.
Additionally, the SOIC-8 on the LMR236xx family includes a single die attach pin (DAP) on the bottom to help extract the heat. This enables a lower junction-to-ambient thermal resistance (theta J/A) and better thermal performance than many QFN-style packages, like competitor A’s package in Figure 1.
Figure 1: Thermal images taken at VIN = 12V, VOUT = 5A at 3A, 2MHz
For many customers, the easy-to-use aspects of a package with pins outweigh the size advantages of a leadless package. Whether you prefer to stay on the cutting edge of package technology or want peace of mind from using a trusted and reliable package, the SIMPLE SWITCHER regulator family has an option for you. Check our website for more information about the SIMPLE SWITCHER LMR23610/25/35 family.
Nice article. Do you will post the peach cobbler recipe? I think I want it. Package size/type and other details plays a quite important role in the cost benefit ratio. This ratio is very different among specific niches/objectives, yet, dealing with applications/solutions of the same general type. Prototyping stage; evaluation; space constrains; final public; production scale, in the process as a whole a simple package 'what to pick' decision can have a great impact on project efficiency overall. 'The hype' type of stuff in detriment of logic, practicality and efficiency is a very serious discussion.
Another thing to consider is that leaded packages will be a bit more tolerant of flexing of the PCB due to
either mechanical stress (think vibration or flexing) or thermal stress due to exposure to high heat. A bit of the flex can be
absorbed by the pins, vs. QFN has NO give when the PCB flexes.
Great point Dave. Part of the reason we are still releasing new products in leaded packages is because they can be more robust than their QFN counterparts in harsh environments. The ability to withstand high temperatures and mechanical stress is very important.
Rodrigo - I'm afraid the peach cobbler recipe will have to stay a family secret :)
I see no reason for sticking with SOIC packages for prototyping. QFN and WSON are just as easy to work with, and the smaller footprint helps keeping PCB's small. The only requirement is a hot air soldering station that costs les than $100 and some practice (the first few times). I sometimes make double sided PCB's with QFN pitch 0.4mm and 0402 caps/res in my shop (using laserprinter, UV-box and etching) when time is limited. So, perhaps in the next article, you encourage and help "prototypers" finding a way to use the new wonderful smaller packages... size matters :) Cheers!
These pin-head sized legless wonders are great for production work, the assembly can be outsourced to a specialist, in the development lab however they are a source of utter frustration. In a small company with a limited budget prototyping is still done breadboard style using hook up wires, a soldering iron and whatever happens to be to hand as a pcb, the result is hours of grind and a pile of destroyed samples.
If only there were leaded versions of every new chip, just for try-out purposes, my job would be so much less stressful.
To those who still love the breadboard: (I love the SO8)
There are some, including myself, who still love those clunky long legged dip and SO8 style packages in particular for visual electrical testing - You know the "old school" hands on way of doing things. Sometimes you just need to play with a circuit, directly at its pins, to spark that needed imagination to take your concept to the next level or maybe you're just learning something new?
When a dip type package is not available for your circuit testing, taking more modern SMT packages to the breadboard has many advantages when ESR, ESI and impedance are not huge factors. Yes, you do have to consider frequency of operation on many breadboards yet even with their intrinsic high ESI, ESR and connection capacitance one can achieve 70MHz plus on data lanes on a breadboard you just need to consider the EMI rules of use for you region. Achieving high frequency on a breadboard is one method that contributes to making better high frequency SMT circuits designs from the very start which in turn can save a lot of time and costs down the road. Another benefit to high frequency design on a breadboard is in extreme temperature circuit designs (example: +232 degrees Celsius processor based system) where you learn how to deal with high impedance and high capacitance loads which increase as temperature increases. It is very cool to build a high temperature circuit which functions as expected the very first time! The final benefit to achieving higher frequency design on breadboards is that taking SMT to the breadboard becomes almost a trivial task as you know what to expect in terms of circuit performance by the way of implementing a matched impedance scheme in the SMT DUT.
One can argue that simulation software can replace most electrical testing and even circuit designing done at the breadboard level, yet, there is no substitute in getting that proverbial "green light" to go on when your circuit functions correctly for the first time. My thinking is that a more hands on approach is key to good circuit design since anyone can let software do the work for you, however, we all know how that can turn out when software drives a design exclusively. In my opinion, the breadboard has more to do with aligning the human mind to a more binary state which is needed in performing most of the complex circuit design tasks in SMT. The key benefit for doing things the old school way is that circuits can be built quickly, tested quickly, changed on the fly and it also helps to improve and helps to maintain one's electrical acuity. Whereas, changes to SMT circuits designs often require a new PCB be built which most likely involves new parts, arguably spending a lot more time, and let's not forget to mention those extra costs! There are trade offs to consider in whichever design approach one implements - personally I do both interactively. You don't have to build the whole house to see if the kitchen works for you or not unless you're really rich of course :)
One can make a dip package from most SMT flat pack types using a "generic package" sized PCB template with either surface mount or through hole header connectors as the pins and let's not forget those 402 or 805 sized bypass capacitors. The only major limitation when implementing SMT at the breadboard level is ESR and ESI becomes much larger, as such, impedance and circuit frequency are important considerations in circuit design.
Thank you for reading and have fun with your breadboard!
- Jamie Fisher
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