What is the acceptance of SMD chips in the community?

[graynomad]

What the title says, what is the acceptance of SMD chips in the community?

I see that all PICAXEs are now available in SMD packages, are people happy using these on a development board or are DIPs still preferred?

There is at least one obvious benefit to DIPs and that is you can easily replace the chip if you let the smoke out, but does this really happen much? Is it worth the extra PCB real estate for that?

 

[srnet]

I dont think we can answer that for you.

Whether you use SMD rather depends on the application, your soldering skills, and how much overall PCB size is important.

And DIPs are only 'easy' to replace if you use DIP sockets.

 

[TAMeyer]

On current projects everything is 1206, SO-23, SOIC8, etc, except the micro.

None of the three NA distributors SparkFun, Robotshop USA, PHAnderson....carry PicAxe in SMD.

Smoke aside, the lack of inventory over here is the sole reason I continue to use PicAxe DIP.

T

 

[westaust55]

It is something of a case of horses for courses.

As srnet suggests, SMD chips are warranted for final products where PCB space is limited.
However for typical bread boarding and used of many proto-boards, DIP chips are seen (by me at least) as the way to go.

There are many companies out there selling SMD to DIP adapter boards to enable users to work with a DIP outline for breadboards etc. Those adapters would be less available if there was little demand.

 

[srnet]

There are many companies out there selling SMD to DIP adapter boards to enable users to work with a DIP outline for breadboards etc. Those adapters would be less available if there was little demand.

With a fair few modern ICs, they are only available in SMD packages.

So if you want to breadboard a design you need adapters.

 

[BeanieBots]

Personally, not for me. Between the DTs and poor vison the chances of me soldering an SMD correctly are very remote!
Also, I use PICAXE mainly for rapid prototyping. The key word being rapid. I've usually knocked up the circuit on strip-board (using DIP) long before any PCB design has been drawn up.

 

[Grogster]

I used the 08M and 08M2 SMD, along with the 14M2 SMD chips.
I only used these, when space becomes an issue, preferring the standard DIL packages whenever I can make them fit.

Generally speaking, smoke is only a problem if you let it escape, as you pointed out.
When I was doing my training, my boss told me: "It's the smoke that makes them work. If it gets out, they stop, and it's impossible to get the smoke back in again."

 

[inglewoodpete]

I'd use them more if they were made bigger!! Most of my projects are developed on breadboard (0.1" / 2.54mm pitch) and most of them are one-offs, so I use stripboard/veroboard rather than design and make small runs of printed circuit boards.

I know there are adapter boards: I have a stock of many of them. Quite apart from soldering the fine pins, the issues often all revolve around the incompatibility of the pin spacing.

 

[manuka]

Smoke! What kind of talk is this- I've supervised & worked with perhaps 1000s of PICAXEs (mostly DIP but some SMD) over the last decade, and have not lost one yet! The little darlings are near bullet proof.

This contrasts with my experiences using the likes of discretes (1960s) and 1970s'-80s era 555s/Op Amps/Logic chips etc. The mid 90s BS-1 BASIC Stamp I recall as being especially touchy...

 

[Grogster]

To be fair, although I have killed a couple of PICAXE chips, they never smoked - figure of speech.

 

[JimPerry]

I'd find more of a use for the special SMD download socket - but it is not listed as available seperately

Edit: Sorry it is available - but at 10 times the cost of normal socket!

 

[inglewoodpete]

I'd find more of a use for the special SMD download socket - but it is not listed as available seperately

Edit: Sorry it is available - but at 10 times the cost of normal socket!

SMD sockets that offer a lot of leverage have their downfalls. My experience with this type of component has been that the tend to easily lift the copper traces off the PCB.

 

[graynomad]

Well, no surprises there I suppose , some like 'em, some don't.

Just to be clear(er) I'm talking about the processor only, all other components would be SMD, these days that's a no brainer I think.
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PCB real estate is at a premium, so that is an issue. That said there is room for a DIP but that will mean not having a proper 3.5mm programming jack. Is a 3-pin header acceptable? Apart from the 3.5mm jack is there a "standard" header for programming?

EDIT: Sorry graynomad -meant to quote and reply but managed to edit in error ;-(

 

[inglewoodpete]

Well, no surprises there I suppose , some like 'em, some don't.

Just to be clear(er) I'm talking about the processor only, all other components would be SMD, these days that's a no brainer I think.

OK, PICAXEs only.

A couple of years ago, I was caught out by an old (and incompatible) version of firmware on a 20X2. Waste of an otherwise good chip$. Discussed in this thread. Otherwise, the SMD versions save a lot of board space.

 

[SAborn]

Cant say i have ever used a programming jack yet over 100s-1000 of boards, i have always used the little white 3x header pins with the tab on the back for 1 way plug in when board space is limited, otherwise use the standard serial D9 socket for robust connections and it standard to 99% of the cheap USB to serial cables.

For the header pins i made a D9 to header socket adapter cable.

The programming jacks would cost me a fortune if i used them on every board, where the headers are 10c each and the D9 is cheaper than the stereo jacks as well.

 

[srnet]

Is a 3-pin header acceptable?

No need for a header really, 3 pads with wire loops will do.

Make up a adapter, 3.5mm line socket to 3 grab type test leads, good enough for me.

 

[srnet]

all other components would be SMD, these days that's a no brainer I think.

Why, unless space is at a premium, what the problem with using wired components ?

 

[graynomad]

white 3x header pins with the tab on the back

JST headers ?

OK, sounds like the 3.5mm jack is not required, that makes life easier.

unless space is at a premium, what the problem with using wired components ?

Space is an issue and being able to put components on both sides is very liberating

Also SMD components are just easier to work with in most ways, obviously they can be a bit small to handle (and don't drop them on the carpet) but they are easy to solder and WAY easier to unsolder than leaded components.

 

[manuka]

Re 3 wire PCB programming socket -a long standing skinflints approach involves simply trimming an IC DIP socket to suit. Long term contact is not brilliant, but it's quite adequate for the brief program transfer.

 

[JimPerry]

I've wired an inline socket to 3 coloured jumper leads with sockets which plug into a 3 pin header. The AXE27 just plugs into it

 

[hippy]

PCB real estate is at a premium, so that is an issue. That said there is room for a DIP but that will mean not having a proper 3.5mm programming jack. Is a 3-pin header acceptable? Apart from the 3.5mm jack is there a "standard" header for programming?

There's the 3-pin keyed header that was used with the AXE025 before the 3.5mm jack became the standard.

While it doesn't particularly matter technically what is used, the 3.5mm jack is now the standard, PICAXE users will often be expecting or desiring that, and will likely have cables to use it. Diverging from that may be advantageous for the board but could be disadvantageous to the user, and even to yourself in complicating support issues.

The issue of providing primarily for yourself or providing for the customer is always a fraught one. It depends perhaps on your target audience and what target audience is being sought.

 

[graynomad]

The issue of providing primarily for yourself or providing for the customer is always a fraught one. It depends perhaps on your target audience and what target audience is being sought.

I think this is a board for more advanced users, mostly because beginners don't need more than is currently available (for that matter advanced users may not either ).

It may come down to a 3.5mm jack and SMD chip, or 3-pin header and DIP chip. I'm fiddling with the layout as we speak.

 

[Jakob2803]

The only casualties my chips have sustained are a snapped pin on an 18M2 (after removing it from a socket in the wrong way too many times) and a 14M2 that will not do PWM on one of the PWM pins.

 

[srnet]

The only casualties my chips have sustained are a snapped pin on an 18M2 (after removing it from a socket in the wrong way too many times)

Stack them.

Mount the PICAXE on a socket, and plug that socket into the PCB DIL socket.

If you bend a pin all you need to replace is a cheap socket.

 

[westaust55]

Is a 3-pin header acceptable? Apart from the 3.5mm jack is there a "standard" header for programming?

See PICAXE manual 1 (V7.8) page 44 for both 3.5mm and "standard" header type connections.

 

[graynomad]

after removing it from a socket in the wrong way too many times

Now there's an argument for SMDs

I'm aware of the schematic for the download, but is that connector a standard? It looks like a JST but could be anything.

Also hippy basically said that the jack is the standard, and given that RevEd actively sell the jack and various compatible cables and as far as I can see do not sell any 3-pin headers I think if possible I should go for the jack.

I'm now thinking that as the 40X2 is the same price as the 28X2 I may as well use the larger chip, especially in light of my "more advanced users" comment. And as a DIP 40 won't fit on the PCB regardless of any other components it looks like it's SMD all the way.

Any reason NOT to use the 40X2? I notice that they are out of stock at MicroZed so that's not a good omen.

 

[eclectic]

Available here:
http://www.techsupplies.co.uk/epages/Store.sf/en_GB/?ObjectPath=/Shops/Store.TechSupplies/Products/AXE014X2SM

£4.99 compared to Au $13.40

e

 

[jedynakiewicz]

Following on from the idea of socketed chips, does anyone with heaps of experience have any recommendation regarding the use of turned-pin DIL sockets as opposed to the standard type? The turned pin sockets are significantly more expensive, but I am not clear regarding the advantages of using them. Any thoughts or opinions?

 

[eclectic]

Following on from the idea of socketed chips, does anyone with heaps of experience have any recommendation regarding the use of turned-pin DIL sockets as opposed to the standard type? The turned pin sockets are significantly more expensive, but I am not clear regarding the advantages of using them. Any thoughts or opinions?

1. They are much stronger.

2. They fit into breadboards, and then can be safely removed again.

All my breadboarding Picaxe chips "live" permanently in TP sockets.

e

 

[graynomad]

The turned-pin version are better quality and grip the chip much better. For that reason they are not so good for prototyping where you plan to insert and remove the chip many times. They are generally better for a permanent installation.

That said eclectic's idea of leaving the chip in a socket and using the combination for breadboarding is good because the socket and chip are not constantly being separated.

 

[graynomad]

The turned-pin version are better quality and grip the chip much better. For that reason they are not so good for prototyping where you plan to insert and remove the chip many times. They are generally better for a permanent installation.

That said eclectic's idea of leaving the chip in a socket and using the combination for breadboarding is good because the socket and chip are not constantly being separated.

 

[Haku]

Also SMD components are just easier to work with in most ways, obviously they can be a bit small to handle (and don't drop them on the carpet)

During replacement of the joystick on one of my iRiver mp3 players I accidentally desoldered a 0402 capacitor next to the joystick, and if that wasn't bad enough I accidentally dropped it on the carpet, and I didn't have a spare...

After carefully brushing the carpet into a dustpan and then using sellotape and a magnifying glass I found it and soldered it back in, the player still works years later

 

[srnet]

Following on from the idea of socketed chips, does anyone with heaps of experience have any recommendation regarding the use of turned-pin DIL sockets as opposed to the standard type?

For an application where you want long term reliability, but also retain the ability to remove the IC if necessary then they are ideal. More resistant to vibration and damp\corrosion. Yes they are not cheap, but compared to the overall cost of a product its not a lot extra.

Not so good for standard prototype PCB stuff, as the insertion force is higher, thus an increased chance of damage to the ICs pins.

 

[hippy]

The turned-pin version are better quality and grip the chip much better. For that reason they are not so good for prototyping where you plan to insert and remove the chip many times.

I'd disagree with that as in my experience turned pin sockets will usually withstand repeated insertion and removal far better than leaf contact sockets. There's nothing worse than a contact leaf coming out with a leg and having to replace the entire socket or a leaf no longer having enough spring in it to make a reliable contact. Stacked multi-sockets can help mitigate that but the sockets don't always grip the thin legs of leaf sockets well.

The downside is that chips can be harder to insert and remove, but a leg straightener and practised technique in sliding a thin screwdriver under the chip solves that. In fact, I'd say once the legs have been bent at right angles to the chip they are easier to insert.

The AXE091 has turned pin sockets and I often change PICAXE chips multiple times a day and haven't had any difficulties or damage, even when getting the 18-pin parts out of the middle with the 20-pin and 28-pin sockets above and below it populated - I moved the 100nF caps to beneath the board to make that easier to use my screwdriver technique rather than using an IC remover.

 

[graynomad]

contact leaf coming out with a leg and having to replace the entire socket

That sort of thing has happened to me a few times.

Anyway I think I'll use the 40X2 (TQFP version but I'm talking about the DIP here) so I started looking at it's pinouts and that of the PIC18F45K22 that I believe it's based on and I can't reconcile some of the pin functions.

The PIC18F45K22 has two hardware UARTs with IO on pins 25/26 and 29/30, the 40X2 has HSERIN/OUT on 26/25 so that makes sense, but it has no obvious serial connection on 29/20 unless that's what KBDATA/CLK are.

Is that the case?, and if so why would the second UART be unused and what are the the Serial In/Out pins (6/7)? Are they bit-banged?

Also the PIC18F45K22 has two MSSPs each of which is capable of SPI and I2C, it appears that they could be used independently on different pins however the 40X2 has both these interfaces on the same pins.

Is the above true or have I got the wrong end of the stick?

 

[nick12ab]

Anyway I think I'll use the 40X2 (TQFP version but I'm talking about the DIP here) so I started looking at it's pinouts and that of the PIC18F45K22 that I believe it's based on and I can't reconcile some of the pin functions.

The pinout is on page 40 of PICAXE Manual 1.

Is that the case?, and if so why would the second UART be unused and what are the the Serial In/Out pins (6/7)? Are they bit-banged?

The Serial In/Out pins are bit-banged like serin and serout.

Also the PIC18F45K22 has two MSSPs each of which is capable of SPI and I2C, it appears that they could be used independently on different pins however the 40X2 has both these interfaces on the same pins.

The pinout doesn't say that they're not on the same pins but if you want them on different pins you might have to poke some SFRs.

 

[srnet]

Is the above true or have I got the wrong end of the stick?

Taking the TQFP 18F45K22\40X2 as an example, pins ,25,26,27 are on 18F45K22 port E, not PICAXE port A. Not a problem unless you start poking the PIC registers directly.

The 18F25K22 and 18F45K22 have dual SPI\I2C ports also, that only one is implemented is just the way the PICAXE firmware runs.

 

[jedynakiewicz]

Wow, this thread seems to be going all over the place...
Back on the subject of DIL sockets, many thanks for the helpful comments. My problem is that the turned pin sockets seem so counter-intuitive; they are literally "a square pin in a round hole". The legs of the chips are oblong in cross-section being pressed from sheet metal, and it would seem logical that the leaf sockets, with the two laterally-aligned leaves pressing against the two flats of each pin, should form a superior contact. Deep within the turned pin sockets there appear to be four leaves that press inwards to grip the IC leg but these are not oriented in any particular direction, clearly in any socket they aligned quite randomly. Hence, my question about the relative merits against the increased cost. One advantage that I see is that the turned pin sockets are relatively immune to flux overrun etc or even the occasional excessive application of solder that can flood into the leaf sockets, but all that is just a question of working cleanly and neatly. @Hippy, your comments reflect my general experience, but again I simply have the difficulty in understanding how the square legs fit better in a round hole rather than a square one!

 

[AllyCat]

Hi,

Yes, I agree with hippy.

If you don't have a leg straightener, then rest one side of the legs on a table and "roll" the package until the legs are at right angles to the body. Then repeat for the other side, before you even try to insert the package into a turned pin socket.

IMHO the ring "springs" in TP sockets are far better than the leaf springs - see how little "spring" there is in the solder pin end of the contacts!

Cheers, Alan.

 

[BeanieBots]

After many decades and many thousands of socketed ICs, I too fully agree with Hippy even down to replacement of the decoupling caps. It has a lot to do with getting the IC pins straight by bending the main part of the pin NOT just the thing section.
After many insertions and extractions the chip can become a little loose but it is the chip and not the socket which yealds. Even so, I have never experienced any problems with turned pin sockets. I wish I could say the same about the other types!

I would never consider anything other than turned pin, be it for prototype work or product.
The wasted time, damage and cost that has resulted from other types far outways the extra cost.