Hi Guys,

As I'm starting the transition from my z80 project (and redesigning it in the process :-p) over to a 65c02s version I have on on numerous occasions been tempted to move to faster, cheaper and smaller packages that would make the design a lot easier. For instance, going with a TQFP package over a PLCC package or going with some surface mount, 10ns RAM over a bulky 70ns DIP case.

I've always wondered why, for the majority of my projects, I stick with through-hole. For me, the most important ones are:

- I can wire-wrap my designs which means I don't have to spend $$$ on PCB runs
- I can troubleshoot circuits a LOT easier when I'm not dealing with 0.5mm pins
- I can replace a dead part in seconds
- I can re-use all of my (socketed) components
- I can hand-solder everything once I do decide to make a PCB
- I can share my design and reach a bigger audience as most people have less of an issue with 0.100" spaced pins

While it's becoming harder and harder to source parts (thank God for eBay!) I hope manufactures will continue to crank out through-hole parts, especially now that my eyes are starting to age...

Yvo

Says who and to which parts are you referring? Although through-hole parts will steadily disappear from large-scale manufacturing, prototyping will continue to use them, precisely for the reasons you enumerate. Both Digi-Key and Mouser stock many TH parts, and depending on what your requirements are, other vendors (e.g., JAMECO) may be viable as well.

Incidentally, I have no trouble hand-soldering 50 mil parts, and neither my eyes or nerves are what they used to be.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Mainly 'fast' memory like 28hc256 and programmable logic that doesn't cost you an arm and a leg. For instance, Digikey charges $35 for an EPF10K10 which can be had on ebay for $10 or less.

YMMV with regards to soldering and what not. Maybe it's time for me to look into getting some glasses

Yvo

See the related topic, "Home computer construction with SMT parts and PLCCs".

Also, this whole thing is partly why I offer the 4Mx8 5V 10ns SRAM module with pins that go into soldertail or wire-wrapable sockets in standard perfboard:



Wire-wrap sockets are not cheap (in fact, sometimes the SMT-to-DIP adapters aren't either), but you can do WW without getting a custom PCB made.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I think the case is for durability.

My C-64 still works. The parts are larger and there is more to wear out. My laptop died after 5 years because it is made of surface mount parts, it gets hot fast because everything is close together and the parts are smaller. The USB stopped working and then the CD drive and then one day it wouldn't boot plus the battery went bad so it wasn't worth fixing.

If you want speeds faster than 50 MHZ, you should go with surface mount parts.
Amplifier parts sound better with through the hole parts.

The current thinking is buy a disposable computer, it gets updates, becomes obsolete and they get repeat sales because you buy a new one. The parts cost less because there is less material used in the parts so they are making a big profit off of less.

The bad part is that hobbyists have to pay money for cad drawing programs which charge for the number of holes you have and you have to pay for boards.

That's a pretty big leap to make... I agree that most laptops are not very durable, but not because they are built from surface-mount parts. Note that desktops are also mainly built with surface-mount chips these days.

The main reliability difference between SMT and thru-hole is in connectors or heavy parts whose forces can break SMT solder joints or rip the foils right off the board. Thru-hole has kind of a rivet effect. Europe's no-lead requirement has been bad too, as the no-lead solders are not as reliable (which is why they're not allowed in medical and military equipment). Obviously that will be more of a factor for SMT than for thru-hole. Our company has basically said the European market is not worth the trouble, and we use only leaded solder. I could say plenty more about the politics of the no-lead requirements, but I think I'll refrain.

Leaded ICs like PLCCs and SOICs offer some flex in the leads which harmlessly takes up any movement resulting from board flex or from differences in coefficients of thermal expansion, unlike BGAs, QFNs, and others that just have metalization the gets soldered down to the board directly with no leads.

I don't think the SMT-heat argument is valid, as so much (except sometimes the processor itself) is very low power today compared to something like the non-CMOS Apple II's which I remember having problems if you didn't hook a separate fan unit on the slots on the side.

I remember amplifier advertisements from decades ago (before SMT) touting .00005% distortion, which was really a bit ridiculous when good speakers could have well over 1% distortion. Marketing is a strange thing though. SMT capacitors, specifically MLCCs, have a lot of distortion if you don't keep the WVDC at least 5x as high as the highest voltage you expect your circuit to ever put on them.

Making a reliable SMT design requires knowledge of the assembly methods. When our company was getting into it, I got a book that was $300+ and told about all the ins and outs. I digested it thoroughly, then bent the rules to get higher density, and we have not had any reliability problems at all.

I do wish that anything that's not high-speed were available in thru-hole for prototyping and hobby use.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

In non-electrical usage, unleaded solders have proved problematic as well.

A friend who is a retired licensed plumber, and certified high pressure steam pipe fitter, mentioned some time back that the incidence of failed joints in copper potable water piping has significantly increased since the switch to lead-free solders. He also insists that the switch was pointless, as there is no scientific proof that the lead in the soldered joints was leaching into the water (I tried to find something to refute that and wasn't successful).

I'm well aware of the structural problems with no-lead soft solder, as I used type K copper pipe for the suction and return lines in my large-scale locomotive. I could not get joints soldered with the no-lead solder to hold up. The combination of expansion and contraction as the propulsion system heats up and cools down, along with the ever-present vibration when the unit is running, conspires to cause tiny cracks in the solder, and of course, leaks. I repaired joints several times, only to have them leak again. I finally redid all of the copper plumbing with 30/70 leaded acid-core solder (sold through industrial supply houses in the USA), which appears to have permanently solved the problem.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

I grew up in another country where all our water came to us in lead pipes. They weren't just soldered with lead-- the pipes themselves were lead. This was also true of the boarding school I went to there; and a very high percentage of the kids who went there became doctors and engineers; so I'd have to say that whatever small amount of lead that did get into our drinking water certainly did not hurt our brains any.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?