8-bit uC - is there even a point?

[Mechatrommer]

What is the thing with DIP? Are they still being used by any mass produced products?
The only DIP chips I can still think of are DIP4 optocouplers and DIP8 integrated flyback SMPS chips.

besides SMPS PSU you mentioned that alone can count in millions, DIP are in gazillions in home appliances such as heater shower, water heater, refrigerator, air conditioning, toaster everything but highly densed electronics/computing related stuffs.

[nctnico]

If you want to use a single sided SRBP PCB, as many whites goods makers still do, DIPs are the prefered package.

Just use an SOP as a DIP. Fan out the pins and it's virtually a DIP, without the high package material cost and manual part insertion cost.

DIPs can be placed automatically for decades.

[wraper]

Modern single layer PCBs usually consist of largish SMT parts glued on the bottom including ICs and through hole parts and jumpers on the top. Like electrolytic capacitors, power semiconductors, optocouplers. All of it is wave soldered, no reflow. If it's simple circuit, it may be through hole only as well.

[wraper]

DIPs can be placed automatically for decades.

Don't think that's true for China, or maybe I'm wrong.
In my mind, automatic THT placement is expensive and prone to failure, way more expensive than SMT.

Automated through hole placement is slow and easy to screw up. I don't think it 100% of parts are automated even at places with machine placement.

[wraper]

Like here at 4:30, they machine place TH capacitors but other stuff is placed by hand.

https://youtu.be/ylk6VMBLrvM

[langwadt]

Modern single layer PCBs usually consist of largish SMT parts glued on the bottom including ICs and through hole parts and jumpers on the top. Like electrolytic capacitors, power semiconductors, optocouplers. All of it is wave soldered, no reflow. If it's simple circuit, it may be through hole only as well.

if it has bunch of big connectors you might have to do wave solder any way so going all through hole might same a few steps

[wraper]

Modern single layer PCBs usually consist of largish SMT parts glued on the bottom including ICs and through hole parts and jumpers on the top. Like electrolytic capacitors, power semiconductors, optocouplers. All of it is wave soldered, no reflow. If it's simple circuit, it may be through hole only as well.

if it has bunch of big connectors you might have to do wave solder any way so going all through hole might same a few steps

Nobody does reflow soldering on single layer phenolic PCBs to begin with. There is additional assembly step but PCB goes through soldering only one time.

[nctnico]

DIPs can be placed automatically for decades.

Don't think that's true for China, or maybe I'm wrong.
In my mind, automatic THT placement is expensive and prone to failure, way more expensive than SMT.

Automated through hole placement is slow and easy to screw up. I don't think it 100% of parts are automated even at places with machine placement.

I visited a TV manufacturing plant from Nokia in Germany in the early 90's and even back then they placed all through-hole components automatically. The machines would even detect a failure, pull the part back out (bin it) and re-insert a new one. I'd say those through hole placement machines where more impressive than those newfangled SMT p&p machines 
The SMT parts where glued to the solder side and the whole PCB would then go through the wave soldering machine.

[wraper]

I visited a TV manufacturing plant from Nokia in Germany in the early 90's and even back then they placed all through-hole components automatically. The machines would even detect a failure, pull the part back out (bin it) and re-insert a new one. I'd say those through hole placement machines where more impressive than those newfangled SMT p&p machines 
The SMT parts where glued to the solder side and the whole PCB would then go through the wave soldering machine.

That's probably one of the reasons why Nokia TVs are not made since 1996.

[coppice]

DIPs can be placed automatically for decades.

Don't think that's true for China, or maybe I'm wrong.
In my mind, automatic THT placement is expensive and prone to failure, way more expensive than SMT.

There are many automated THT lines in China.

THT placement has been cheap and highly reliable since DIP devices first appeared. That is why the design of the DIP package has the legs splayed. That was specifically so the machines could flex them in and they would spring back enough to secure the device until it reached the wave soldering station. Its why resistors and capacitors come on taped reels. The placement machines clip them out of the reel, form the legs, and stuff them into the board. In most cases the legs are left long. After the wave soldering step a really brutal looking machine slashes off the excess length of all these overly long legs in one operation.

For many years THT placement was much more reliable than SMT placement, as SMT placement is prone to things getting shaken out of place. The industry went through several generations of glue spot/don't glue spot/glue spot and other techniques before settling down to modern practices.This kind of thing is rarely a problem with automated THT lines.

[westfw]

Absolutely smallest and cheapest won't have core-coupled RAMs, of course.

If you meant the "Tightly Coupled Memory" (TCM) feature provided by ARM, that's an OPTION in CM7, not available at all in CM0 through CM4.  (According to the wikipedia table.  OTOH, the SAMD51 claims to have TCM, and the WP table also claims that M0, M3, M4 don't have cache, either.  While several data sheets claim to have simple caches.  (I assume that this is the difference between implementing the cache in the vendor-provided memory system vs using the ARM-provided IP.  In which case I don't know what Atmel/Microchip means by "TCM"...)
So, a very small number of ARM chips have TCM.Many ARM have RAM that is faster than their flash, and you can put code there if you want faster execution.  But we were talking more about determinism than raw speed, I thought.  (and "just put your critical code in executable RAM" is right up there with "just use bank select of you need more than 64k of data" - possible, but a bit contradictory with the the "simple" claims.)

[ogden]

Absolutely smallest and cheapest won't have core-coupled RAMs, of course.

If you meant the "Tightly Coupled Memory" (TCM) feature provided by ARM, that's an OPTION in CM7, not available at all in CM0 through CM4.

Indeed he did mean Core Coupled Memory (CCM). CCM is additional small RAM segment with own bus interface. STM32 F3 series have 8KB CCM RAM. Don't know about other manufacturers/chips. Actually useful for busy MCU's - CPU can fetch instruction or do whatever it pleases with CCM RAM while (during same clock cycle) DMA is doing transfers using main RAM.

More info about stm32 CCM here

[richardman]

Well, this post certainly wanders all over the place ;-)

[KL27x]

What is the thing with DIP? .... For the sake of love, I've not used a DIP for years, literally years, besides student teaching projects.

I bet by the time you used your first SMD chip, other people had been using them for years, literally years.

The reason, as far as the manufacturers are concerned, is because of branding/marketing/education. If some n00b chooses TI over Maxim IC because it comes in DIP, he might end up buying hundreds of thousands of (SMD) TI parts in the future, just because that's what he is familiar with. 

PS. Also why TSSOP? They are harder to hand solder than DFN/QFN. The gull wing sucks and stores solder, so bridging happens all the time with short pad extension. With QFN, I can do 0.2mm extension per side and they still don't bridge.

At least one practical reason is that QFN are more culpable to cracked solder joints due to board flex and/or thermal expansion/cycling. The difference has been tested. And regarding deep thermal cycling, apparently gull wing chips can be more than an order of magnitude better in some of these tests.

[ogden]

Well, this post certainly wanders all over the place ;-)

If you think something is wrong in that particular post - then provide correct information.

[edit] If you have problems using internet search engines to check keywords I did provide, you are welcome to read this document.

[Siwastaja]

Absolutely smallest and cheapest won't have core-coupled RAMs, of course.

If you meant the "Tightly Coupled Memory" (TCM) feature provided by ARM, that's an OPTION in CM7, not available at all in CM0 through CM4.

I don't know what any table says, and I'm not always exactly correct. But, I have been happily using fast core-coupled RAMs for timing critical and deterministic interrupt stuff in MCUs with CM3 and CM4 cores, and being non-existing or imaginary, I have measured them working remarkably well!

STM32F334 being one such example I can remember*. Clearly, it's ST's addition, and not the "ARM's option". The name is "CCM" for core-coupled memory instead of "TCM". This terminology is similarly irrelevant as is the classical discussion on "who's fault the bug is". I buy real MCU's based on what they offer and how they perform. An actual $3 ARM MCU offering me way better performance than a $3 8-bitter (including real-world interrupt latency, measured on real-world terms; I use oscillosscope to measure from trigger to result) and way better peripherals offloading the CPU even further, is the fact of reality, and as I have stated earlier, it has quite little to do with ARM exactly. IMHO, ARM core is boring enough not to be fanboy'ed over.

*) I did something similar on STM32F205 on its another extra SRAM, but it shares the bus and hence, heavy DMA traffic can cause a few clock cycles of jitter on interrupt latency during stack push, which is guaranteed 50% of bus arbitration cycles. Whether this is important, when the actual interrupt processing latency at 120MHz is still likely to be faster than on almost any 8-bitter, is up to you decide.

But yeah, I have also put a single quickly-needed instruction on the AVR's interrupt table directly, avoiding the delay of the jump. At 20MHz, this is very fast as well, and indeed will outperform a cheap M0 stacking registers through a bus also used by DMA. But most of the time, the timing-critical interrupts are longer than that, and the important result happens later than at the first machine instruction.

I mostly use the very cheapest 8-bitters only, but I guess most share this viewpoint nowadays; the "large $5 AVRs" make even less sense today than they made a decade ago.

[Mr. Scram]

I bet by the time you used your first SMD chip, other people had been using them for years, literally years.

The reason, as far as the manufacturers are concerned, is because of branding/marketing/education. If some n00b chooses TI over Maxim IC because it comes in DIP, he might end up buying hundreds of thousands of (SMD) TI parts in the future, just because that's what he is familiar with. 

At least one practical reason is that QFN are more culpable to cracked solder joints due to board flex and/or thermal expansion/cycling. The difference has been tested. And regarding deep thermal cycling, apparently gull wing chips can be more than an order of magnitude better in some of these tests.

I understood that QFN is actually one of the most reliable packages from a mechanical point of view. I think I read about this in a paper somewhere, but I don't think I'd be able to find that again. I stand to be corrected.

[Rerouter]

QFN is reliable, so long as you have soldermask spacing, e.g. not pad flat to copper with no gap for the solder, this gives it some distance to keep forces inside the elastic zone of deformation. similar to BGA, if you didn't have the balls at the right height they just rip pads off either the chip of the board when flexed,

Though I still see the center pad of QFN's a right pain to get right every time, you have to generally get weird with your paste masks to get better than 99.9% yields, which generally leads me to fitting a dot when its needed, vs a full pad,

[coppice]

PS. Also why TSSOP? They are harder to hand solder than DFN/QFN. The gull wing sucks and stores solder, so bridging happens all the time with short pad extension. With QFN, I can do 0.2mm extension per side and they still don't bridge.

At least one practical reason is that QFN are more culpable to cracked solder joints due to board flex and/or thermal expansion/cycling. The difference has been tested. And regarding deep thermal cycling, apparently gull wing chips can be more than an order of magnitude better in some of these tests.

The reliability of QFN mounting is quite variable. If people take the thermal stress issues seriously during soldering, as people normally do with BGA packages, results can be very good. if you fail to get things evenly heated during the soldering process you can get very poor results. So, don't expect most hand soldered QFNs to achieve wonderful reliability. The thermal expansion of the QFN package material has been chosen to be close to that of FR4. If you tried to use any other PCB material you might find reliability problems with QFNs.

[Nauris]

I visited a TV manufacturing plant from Nokia in Germany in the early 90's and even back then they placed all through-hole components automatically. The machines would even detect a failure, pull the part back out (bin it) and re-insert a new one. I'd say those through hole placement machines where more impressive than those newfangled SMT p&p machines 
The SMT parts where glued to the solder side and the whole PCB would then go through the wave soldering machine.

Yes, they are truly impressive, like the Panasonic AV132 puts components in like good old chip-shooter places chips at 30000 per hour or thereabout. They just appear on the board faster than eye can see!


These days there is also very much interest and growing market in the odd-form flexible thru-hole placement machines capable of placing anything from axial resistor on tape&reel to loose connectors or big transformers.
Like the new one from Fuji:
http://smt.fuji.co.jp/e/datas/movie/smartfab/Insertion(2).mp4
Or the Cencorp (Chinese-owned company by the way):

[wraper]

I visited a TV manufacturing plant from Nokia in Germany in the early 90's and even back then they placed all through-hole components automatically. The machines would even detect a failure, pull the part back out (bin it) and re-insert a new one. I'd say those through hole placement machines where more impressive than those newfangled SMT p&p machines 
The SMT parts where glued to the solder side and the whole PCB would then go through the wave soldering machine.

Yes, they are truly impressive, like the Panasonic AV132 puts components in like good old chip-shooter places chips at 30000 per hour or thereabout. They just appear on the board faster than eye can see!

It's nowhere near to fully automated TH component placement. All it places are axial parts with 2 leads like resistors.

[Bassman59]

Though I still see the center pad of QFN's a right pain to get right every time, you have to generally get weird with your paste masks to get better than 99.9% yields, which generally leads me to fitting a dot when its needed, vs a full pad,

The data sheets for QFN-with-pad parts recommend a pattern of small square holes in the paste mask for the pad instead of filling the whole pad. For example, Silicon Labs' Si5344 data sheet says to use a 3x3 array of 1.25 mm square cut-outs on 1.8 mm pitch. The pad itself is 5.2 mm square.

[Nauris]

Yes, they are truly impressive, like the Panasonic AV132 puts components in like good old chip-shooter places chips at 30000 per hour or thereabout. They just appear on the board faster than eye can see!

It's nowhere near to fully automated TH component placement. All it places are axial parts with 2 leads like resistors.

It needs bit more explanation, it seems. Automated thru-hole line consist of three kinds of machines. Typically there is first the axial component inserting machine (ex. AV132), after that comes the radial inserting machine placing radial components, like small electrolytics, film caps and such. Then at last there is one or usually more odd-form machines placing rest of components, like connectors, transformers, big electrolytics and such. That kind of line you would be using, if you were making thru-hole only boards.

Of course that is rarely case today, you usually have also smd machines inline and often no axial or radial inserter, but only a few odd-form machines handling the thru-hole component placement.

[westfw]

Clearly, it's ST's addition, and not the "ARM's option". The name is "CCM" for core-coupled memory instead of "TCM".

Thanks for the clarification and example part.
I guess my point was that claiming 32bit CPUs are "easier to use" than 8-bit chips is a bit ... misleading, if you're going to end up using a relatively complex-to-use vendor-specific feature to get the job done.  On the other hand, writing timing-critical "needs every cycle" code for an 8bit chip isn't an easy task, either.  Just ... different.

[PCB.Wiz]

Really, entire world? Then why new parts still appear no the market?

Semiconductor MCU revenue market forecast –millions of dollars

Nice stats, which show that the 4 & 16 bitters are the ones that stagnate, but the 8b & 32b are growing at actually very similar CAGR