Are small SMD resistors factory-tested one by one?

I wonder if the accuracy is granted by the process itself,by testing samples,or automatic test one by one; the last would be amazing in case of very cheap and very small resistors(or other passive components).The same question could be extended to semiconductors,despite test on wafer is probably easier, by mechanical point of view,what about the sealed component? Thanks and forgive improper use of english language. Diego

Reply to
blisca
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Resistors are generally laser trimmed. Look at some under a microscope. Trimming requires that every resistor be measured.

We only buy 1% resistors, and they are probably all trimmed. Apparently some sloppier parts, like 10%, aren't trimmed. Heck, a resistor that fails one bin can just go into the next one.

But we never see bad resistors. Whatever the process, it sure works.

An automatic test machine could measure resistors as fast as they can be processed. A millisecond is plenty of time to measure resistance.

Youtube knows all.

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John Larkin         Highland Technology, Inc 

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Reply to
jlarkin

ples,or automatic test one by one;

(or other passive components).The same question could be extended to semico nductors,despite test on wafer is probably easier, by mechanical point of v iew,what about the sealed component?

I just got another 700+, 7" reels of resistors, capacitors and transisto rs. Most appear to be full reels. It is going to take a while to sort every thing out.

Reply to
Michael Terrell

I, and the rest of my engineers, have been forbidden from taking parts out of the stock room. We have to send an email, and one of the production people bring us the parts. I don't like to wait, so we've bought a lot of various R and C and L sample kits for engineering, and I have a private stock of ICs and discretes.

And there's always nights and weekends.

I have a career-long record of successfully burgling stockrooms.

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John Larkin         Highland Technology, Inc 

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Reply to
jlarkin

samples,or automatic test one by one;

ors(or other passive components).The same question could be extended to sem iconductors,despite test on wafer is probably easier, by mechanical point o f view,what about the sealed component?

ors. Most appear to be full reels. It is going to take a while to sort ever ything out.

Me, too. The first time was in the Army. They wouldn't give me what I neede d to keep a TV station on the air. In a three week period, I used 1400 line items, at a total of a little over 2100 parts. The station was still in go od shape almost two years later when it was decommissioned and dismantled. I've talked to people who were there after I left for home.

I have a room full of discretes. There were a lot of ROHS COG SMD capacitor s in the last purchase. Most are under 1000pF. A real boon for people who p lay with RF. I have a local electroncs store that sells components to the p ublic that I can trade parts with on a reel by reel basis. I also have doze ns of 'Taiyo Yuden SMD/SMT Capacitor Kits' in small footprints.

Reply to
Michael Terrell

I never worked for a company so big that I couldn't walk to the stockroom and production floor and machine shop. I've known engineers who worked in a "office building" where there they didn't even have a lab. And I know outfits that send everything, even prototypes, out to a contract manufacturer.

I could tell a funny story.

Reply to
John Larkin

eded to keep a TV station on the air. In a three week period, I used 1400 l ine items, at a total of a little over 2100 parts. The station was still in good shape almost two years later when it was decommissioned and dismantle d. I've talked to people who were there after I left for home.

tors in the last purchase. Most are under 1000pF. A real boon for people wh o play with RF. I have a local electroncs store that sells components to th e public that I can trade parts with on a reel by reel basis. I also have d ozens of 'Taiyo Yuden SMD/SMT Capacitor Kits' in small footprints.

Tell it.

I don't have a full machine shop, but I do have some nice tools for buildin g prototypes. I havee a Cameron precision drill press, a floor model drill press and a small milling machine. My latest addition was a small lathe. T hey are in my 1200 Sq foot detached garage.

Reply to
Michael Terrell

For the best quality you have to do both I believe. Testing each units rejects duds at the individual level, and statistical sampling to reject bias or errors in your trimming and measurement apparatus at the process level.

Reply to
bitrex

Statistical sampling can ensure whole batches are very close to perfect, like with prescription drug manufacturers. Testing pills is destructive, though, so obviously they don't test each one in that biz they do it statistically and set up the manufacturing process with hard limits so if it's going to be off it's going to be off-low.

To ensure there are exactly 0 out-of-spec resistors in a batch you have to test each one there's no way around it and for precision resistors that's what they do, they're easier to test as individuals than pills.

But I believe for the best quality they also do batch sampling because there can be errors in your overall process that just testing individuals may not detect. No "precision" manufacturing pr mechanical process stays precision forever, there's always some drift, and what happens if your manufacturing apparatus and test apparatus drift the same way, just sampling individuals won't detect that.

Reply to
bitrex

amples,or automatic test one by one;

rs(or other passive components).The same question could be extended to semi conductors,despite test on wafer is probably easier, by mechanical point of view,what about the sealed component?

It's next to impossible for a small company to reproduce the testing done b y today's electronic component manufacturers. The only reason to do so is t o sub-select parts for a tighter spec than the manufacturers.

Sealed lead-acid batteries are another story, however. I did not use these in my products, but I have consumed them in my aircraft. I do 100% incoming inspection and testing, and annual retesting to ensure performance. I have switched to LiFePO4 batteries where possible. Their quality is much higher , along with their cost.

Reply to
Flyguy

Just testing individuals, rather

Reply to
bitrex

Well, sorta funny. I was chief engineer of a big company. I was 25 and looked 15. I went into the machine shop and asked a guy to drill a hole in a piece of aluminum for me. He said "Who do you think you are?" and I said "I'm Larkin." He was shocked. All the big burly machinists surrounded me and pointed and said "That's Larkin!"

He drilled it for me. I wound up dirt bike riding with a bunch of them. They made their own pistons.

We have a nice little shop downstairs. My manufacturing manager is a superb machinist and mechanical designer too. That's really handy to have around.

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John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 
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Reply to
jlarkin

e:

needed to keep a TV station on the air. In a three week period, I used 140

0 line items, at a total of a little over 2100 parts. The station was still in good shape almost two years later when it was decommissioned and disman tled. I've talked to people who were there after I left for home.

acitors in the last purchase. Most are under 1000pF. A real boon for people who play with RF. I have a local electroncs store that sells components to the public that I can trade parts with on a reel by reel basis. I also hav e dozens of 'Taiyo Yuden SMD/SMT Capacitor Kits' in small footprints.

ding prototypes. I have a Cameron precision drill press, a floor model dril l press and a small milling machine. My latest addition was a small lathe. They are in my 1200 Sq foot detached

I had only worked at Microdyne for a couple weeks when some guy walked up a nd starts asking me a bunch of questions. He didn't introduce himself, and some of the questions were things that no one outside of the company should be asking. I looked up from the bench and said, "Excuse me, but I have wor k to do." He came back five minutes later with my boss who was furious!. Th e man was the head of production, but he had not been introduced to me. He told my boss that I had done the right thing by not just sit there talking to a stranger.

I learned to run a lathe in high school, and a friend owned a nice machine shop in Ohio. He manufactured replacement parts for Model T and Model A For ds. Most were made on original Ford dies. He was one of the first companies allowed to use the Ford logo on his boxes. He made replica ignition coils with he Ford logo embossed on the steel can. He bought the raw coils from E chlin, and put them in the cans that he stamped. He made the Model T fender s with a heavy steel wire rolled into the edge, on original tooling and mac hines from Ford. I could use any machine that wasn't in use. He started thi s part time, while working as a tool and die maker in the Aerospace industr y. That company developed the honeycomb steel heat shields for the early sp ace program. He went full time during a layoff, and never went back.

Reply to
Michael Terrell

I like worker-guys - plumbers, farmers, electricians, machinists, construction guys with giant pickup trucks.

At the place I mentioned, we had a huge Whitney n/c punch press. It would punch 4" holes in 1/8" steel plate about 1 per second, and the building shook at every hit. It was programmed from paper tape in an atrocious format, so I wrote a language compiler for our PDP11 timeshare system, loosely based on Quickpoint syntax. It was fairly basic, but it did have a PATn command to punch a pattern and remember it for reuse, and OFS Xddddd Yddddd and OFS DXcccccc DYnnnnn to offset the origin absolutely and incrementally. We turned that loose on the machinists and discovered that they were soon writing elegant and efficient programs with just a few control tools.

I also implemented a BHC (bolt hole circle) command which they adapted to scallop really big holes using a smaller punch. It was awesome to watch it punch out their programs on a big steel console panel.

The Westinghouse n/c controller was all discrete-transistor logic cards. It read a paper tape and could do smooth vector moves into big servo motors with encoders, using what we'd think of as a DDS algorithm, all in BCD.

One thing I've noticed about those worker-guys is that they tend to be mystified by and afraid of electricity. They think I wear robes and pointy hats because I can wire a ceiling fan.

All kids should learn some basic machining and welding and electrical/electronics skills. Some really high-end private high schools do that.

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John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 
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Reply to
jlarkin

:

rote:

t I needed to keep a TV station on the air. In a three week period, I used

1400 line items, at a total of a little over 2100 parts. The station was st ill in good shape almost two years later when it was decommissioned and dis mantled. I've talked to people who were there after I left for home.

capacitors in the last purchase. Most are under 1000pF. A real boon for peo ple who play with RF. I have a local electroncs store that sells components to the public that I can trade parts with on a reel by reel basis. I also have dozens of 'Taiyo Yuden SMD/SMT Capacitor Kits' in small footprints.

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to

uilding prototypes. I have a Cameron precision drill press, a floor model d rill press and a small milling machine. My latest addition was a small lath e. They are in my 1200 Sq foot detached

p and starts asking me a bunch of questions. He didn't introduce himself, a nd some of the questions were things that no one outside of the company sho uld be asking. I looked up from the bench and said, "Excuse me, but I have work to do." He came back five minutes later with my boss who was furious!. The man was the head of production, but he had not been introduced to me. He told my boss that I had done the right thing by not just sit there talki ng to a stranger.

ne shop in Ohio. He manufactured replacement parts for Model T and Model A Fords. Most were made on original Ford dies. He was one of the first compan ies allowed to use the Ford logo on his boxes. He made replica ignition coi ls with he Ford logo embossed on the steel can. He bought the raw coils fro m Echlin, and put them in the cans that he stamped. He made the Model T fen ders with a heavy steel wire rolled into the edge, on original tooling and machines from Ford. I could use any machine that wasn't in use. He started this part time, while working as a tool and die maker in the Aerospace indu stry. That company developed the honeycomb steel heat shields for the early space program. He went full time during a layoff, and never went back.

They need to put shop classes back into public schools. It was a huge mista ke to remove them. I took every shop class that I could, along with the Col lege prep track that I was on. I got sick of being told that I should go in to medicine or law, because of my IQ. I also got sick of being told that I needed to see the numbers. I never did look at whatever was in the envelop that they slid across the table to me. I just pushed it back. I was but on thee College Prep track in thee seventh grade. I often got the highest scor es on the aptitude tests of anyone in my school system, but it didn't matte r to me. I wanted to learn, for the sake of learning, not to impress people . I had a good laugh after one test on mechanics. There were two perfect sc ores in the entire school system. Me and a girl. The boys who claimed to be mechanical geniuses scored very low. They couldn't figure out what directi on the output shaft would turn in a gearbox, yet it was obvious at a glance .

I learned to weld. I learned to wire a house when I was 10. I have a portab le Oxyacetylene torch that can be carried to places that you can't take the big bottles. Those were handy as a Broadcast Engineer. You could cut up ol d crap too remove it, or make temporary repairs until a tower crew could re place a tower. They were also handy to solder 2" and larger copper pipe i t he transmitter cooling systems. People thought that I was nuts, because I p re-tinned the pipe and the cast brass fittings, but my work never leaked. O ld systems that I had to take apart often had only a thin ring of flowed so lder that would crack from vibration. One idiot had brazed the copper pie t o the brass fittings. Those took a lot of work to reuse. They were custom d esigned by RCA, and there hadn't been spares for at least a decade. I had t o use Oxyacetylene on an area that wasn't brazed, and drive a thin punch in to the seam to dimlpe the copper pipe. Then I had to file the brazing off f rom the sloppy repairs. After that, a large pair of needle nose pliers were used to twist it loose while the solder was molten. I salvaged and reused every one of them. It was the worst use of 50/50 solder that I had ever see n. I replaced it with a very high tin content solder that flowed properly. It had 0.5% Antimony and may have been 99.5% tin. I still have the rest of the five pound spool somewhere.

I had a bunch of those large, bright orange Burroughs plasma displays for e arly CNC machines. They were from industrial terminals wit cast aluminum ca binets. The displays ran so hot that they needed it to cool the displays. I think they were in a warehouse that I lost in 2001 when I ended up bedrid den for two years.

Reply to
Michael Terrell

Probably on company time. ;)

When our ship comes in, we're going to get a bigger lab with a room dedicated to mechanical work and test jigs. We couldn't fit even a Sherline into our current space because of all the other stuff. ;)

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

Several of us had Yamaha 250 dirt bikes. I was used to mine. I tried one of the machinist's bikes, cranked the throttle as usual, and it wheelied and flung me into the air. They found that to be amusing.

We'd ride in the bonnet carre spillway (which was illegal) and play motorcycle tag in a big bowl-shaped gravel pit. Crashed a lot.

We have a Tormach, which is fabulous. But I still like our ancient manual Bridgeport; you can *feel* it cutting metal. When they refurbed it, I wanted them to paint it purple but they stuck with grey.

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Reply to
John Larkin

I learnt how not to wire a house when I was 10.

Reply to
Tabby

Did you burn it down?

Reply to
Michael Terrell

no :P

Reply to
Tabby

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