Hackaday Trims Its Own Resistors | Hackaday

Sometimes you may need an odd value resistor. Without spending money to buy a 3,140Ω resistor in the store, you can bring a good ohmmeter and be willing to solder in series and parallel. But when you want one

Resistance value, and you need many resistance values, then repeatedly combining many Frankenstein resistors together is a bad solution.

Like 8-bit

For example, 17 two-value resistors are required, and the accuracy is better than 0.4%. This is just something I don't have on hand, and the serial/parallel approach will quickly become boring.

A long time ago i read

, But suppose this is the realm of lunatics. On the other hand, this is Hackaday; I have some time and documents. Can I adjust and match the resistance to within 0.5%? Please read carefully to find out.

Your ordinary through-hole resistor is

It is made by depositing a thin layer of metal on a non-conductive ceramic cylinder. The metal film is cut into a spiral shape, and the length, width and thickness of the resulting metal coil determine the resistance. Since the deposited metal is so thin, between 50 nm and 250 nm, you might think it would be picky to trim it by hand.

Jump directly to the key point. When I try to change the resistance by a small amount (maybe less than 5%), it is very easy to accurately drop the point to the exact expected value. I have bags with 1kΩ and 2kΩ 1% resistance, and I think I will make a lot of mistakes while studying.

The reality is that I exceeded the target once in seventeen attempts and only completed one ohm. I can measure the remaining resistance and fine-tune it-down to a single ohm. (My meter and probe have an offset of 0.3Ω, but there is nothing I can do.) I made a tip for the "bad" probe, made another one, and had a perfect setup in a short time.

This is the whole process. I put the resistor in some insulating clips and fixed the ohmmeter at both ends. I used a small round file and went. The first few strokes allow you to pass through relatively thick coatings, but once you see metal or spot a spot on the ohmmeter, it is usually a light touch with a file. As you approach, you may blow off some metal dust between the brush strokes, but I didn't notice a big difference. Seven or eight taps were performed on the small, lightweight file, bringing the resistance down to ten points.

Indeed, because it was too easy at first, I found that the ideal candidate resistance was 1,990Ω. Many of my 1kΩ resistors are introduced with 999Ω resistance, which makes it difficult to pass through the case without exceeding the mark. I may have just left them. The good news is that most 1% resistors will have a resistance of more than a few ohms in both directions, otherwise they will be sold at 0.1% resistance. Of course, you need to choose a source resistance with a lower resistance than the target resistance-you are not

Metal and documents.

Therefore, only one resistance value is needed in the kit, right? Absolutely not. It is troublesome to create a 1.2kΩ resistor with a 1kΩ original resistor. I made it work several times by restarting the archiving process in another location instead of simply going deep into a hole, down to one ohm again, but I don't recommend this, I don't know when you need it. Just connect a 200Ω resistor in series and adjust it. Remember, you are starting to thin out metal spirals with a thickness of only 100 nm. easy.

It is much easier to set the through-hole resistor to the value accurately than I expected, so I decided to take more difficult measures. I nailed a 1206 2.1kΩ resistor on a peeling board. Don't you know, it reads 2,100Ω accurately, so 2,105Ω becomes the target. That's not good at all. I ended up with a 2,722Ω resistor that was faster than expected.

The second 1206 started at 2,103Ω, and I just tested it without a target. By operating very carefully, I got resistance

To 2,009Ω, then jump to 2,600Ω or even higher. There is no point in reducing resistance at all. Maybe I dragged some solder into the gap and effectively thickened the metal layer? I have been looking for information, but there is no deeper understanding of the structure than Vishay's data sheet: "Metal glaze for high-quality ceramics" is not much inspired.

After two more attempts, I couldn't adjust the SMT resistor at all. The deposited metal layer is too thin. And, anyway, I'm not sure how useful this will be-the 17 ideas of soldering and desoldering are not very attractive.

Trimming through-hole resistors is awesome. I made a complete set of matched resistors better than 0.05% (!) for an 8-bit DAC in half an hour, with only a file and an ohmmeter. And in my first attempt. You can easily make a 10-bit DAC in this way. The result was an order of magnitude better than I had hoped, and it was not difficult at all. amazing. There is nothing cooler than a handmade handmade DAC. (For odd-numbered cool.)

On the other hand, my attempt to trim surface mount resistors completely failed. Does anyone care to guess why? Is it just the clumsiness of cutting ultra-thin film? Anyone who owns a precision laser cutting machine wants to go

?

Usually, you don't need an exact value, but a constant value, so you need an expensive resistor with a very low temperature coefficient.

I want to know PTC and NTC in parallel or series. Do you think that if you find a good match, you can do it?

Resistors sold in the form of PTC or NTC generally have a large temperature coefficient and are generally not linear. If you want to minimize the effect of temperature, it is best to choose a conventional (precision) resistor and find two resistors with opposite temperature coefficients.

The temperature coefficient has almost no effect on the DAC, because the resistance ratio is calculated. As long as you install them close to the heat source, it does not help at all.

I know it doesn't matter for DACs, but this is not the only application for precision resistors. I mainly use them for Pt100 measurements, so accurate values ​​are not as important as stability over time and temperature (I can use precision benchmarks for calibration).

So: quickly dip in epoxy to reseal them, and then install them in contact with each other?

Allen: That's what I want to say. Before IC operational amplifiers, there was an old trick that was common when constructing differential amplifiers: Wrap the transistor pairs with an aluminum tape to keep the same temperature at the same temperature. Yes, maybe something similar-apply the entire R-2R ladder to a strip of aluminum.

@ [BrightBlueJim]

You can buy two transistors in one die and the same 6-pin package. It even has its own TO-xxx number. Not sure, but I think this is an NPN PNP pair.

Yes, I have seen these, but they are usually much more expensive than two transistors.

You just described a 5.6 volt Zener diode. In any case, Zener/op amp or comparator will always provide a better reference.

This is why the internal ADC reference voltage on the microcontroller is not very accurate or stable. You can use the IO pin for a voltage doubler/charge pump, so you can have a 5.6 volt Zener, and use a resistor to divide it back below Vcc. If you use an active crystal oscillator, you can use unused passive crystal oscillator pins instead of IO, but because of the higher frequency, the design is a bit tricky.

For almost the same reason, you can use a normal diode (forward biased) as a temperature sensor. Their voltage range is very small, but you can use two diodes as ADC reference voltages in the same thermal environment and can provide a ratio that can be calibrated based on temperature. Two diodes will provide about 1.2 volts-sounds familiar?

Zener voltage is sensitive to temperature and current.

1,2V may sound "familiar", but usually they come from a circuit called a "bandgap reference" that uses some physical parameters of silicon that are (or at least not closely) related to a forward voltage (Or not closely) related. Two) Silicon PN junction.

As a temperature sensor, you can still use a transistor to amplify the diode voltage drop. Yes, transistors also depend on temperature, but temperature sensors are needed anyway. If the operation is correct, the extra diode can be omitted.

In fact, I read Bob Widlar's description of the bandgap reference circuit some time ago, so I can’t be 100% sure, but in my opinion, he said that the circuit will be forward biased. The voltage drop across the selection resistor increases the voltage drop across the selection resistor to eliminate the temperature coefficient. The band gap is the reason why the PN junction has a voltage drop of 0.6V.

From

Zener reverse breakdown is due to electron quantum tunneling caused by a high-intensity electric field. However, many diodes described as "Zener" diodes rely on avalanche breakdown instead. Both types of breakdown are used in Zener diodes. The Zener effect prevails below 5.6V, while in the above avalanche breakdown. "

"In silicon diodes up to about 5.6 volts, the Zener effect is the main effect and exhibits a clear negative temperature coefficient. Above 5.6 volts, the avalanche effect will dominate and exhibit a positive temperature coefficient. In the V diode, these two effects occur simultaneously, and their temperature coefficients almost cancel each other out, so the 5.6 V diode is very useful in temperature-sensitive applications."

Another way to consider film removal could be to use a laser. Once the focus is determined, it should provide you with more precise control over how much material you remove. This is also a method used in the industry.

"...The method used by the industry." Not many of us have powerful pulsed lasers at home. If you try to use any laser, let the resistance cool to room temperature after each shot, and then take the measurement. Micro-blasting is also used to trim the resistors.

"After each measurement, let the resistance cool to room temperature before measuring again"

Lasers used for laser trimming of commercial parts are not as powerful. I use a 10 mW YaG laser at my work place, but that is the resistance on the chip, not the high-power 1/8 W thin-film resistor. We need about 5 seconds to test and trim each part, so there must be no waiting time for cooling, but the test after trimming never showed any problems. The heating is very localized.

Yes, I can try it myself-after exposing the resistance element, I want to know how oxidation affects it.

Maybe some transparent nail polish or something similar to seal it?

Oxidation will almost certainly cause this value to rise. If you can prevent any moisture from staying under it, resealing it with varnish or varnish may help.

Made from 100% pure snake oil!

Epoxy glue?

I used this technique to fine-tune the resistance of the 555 timer circuit in the late 1980s. Equipping with a 4-wire ohmmeter will help. I didn't try it at that time, but wondered if applying a varnish or enamel coating would help.

In my opinion, if you are looking for accuracy, you need a calibrated 4-wire DMM, otherwise the lead length of your meter will still exist and the connection will add or subtract resistance.

Specifications of Fluke Model 12 ± (0.9% + 1)

And how long ago was the last calibration...

Or measure the wire resistance and subtract it.

…Then calibrate the resistance of the probe wire.

If you are only worried about the ratio, the resistance of the ohmmeter leads is the same. A 4-wire ohmmeter actually only works when you have a lot of numbers, such as HP3456 in ohm mode, or more commonly, when you are reading very low values ​​and the wire resistance will be an important part of the reading.

In the past, I have used a low-value trimmer in series with 1% R, but this may not have the best long-term stability. I have selected cherry resistors with closely matched values ​​and paralleled a higher value with a lower value to adjust the part.

The strange thing is that one of the devices I make that requires the closest component matching is a device that can quickly help select resistors.

Artenz: "Or measure the wire resistance and subtract it." We have a winner, or at least someone has read this article. :)

I mentioned that my probe has a 0.3 ohm setting. However, in thousand kilometers mode, it is lower than the least significant number, so I can't really subtract it. Or we can all pretend that I did this because it will not make any changes with the reported accuracy. Fourth line personnel-your answer.

As a group of people said, the absolute value of the resistance is not important, but just repeatability. I checked: a (single!) resistor, which is 2000 ohms, pulled it out of the setting, left it on the bench during my lunch, and re-measured at 2000 ohms again. Good enough for me. (I am rash, but in fact I am worried that my editing may increase the measurability of the settings, and cannot be measured.)

However, even for DAC applications there are problems. I am actually trimming 1 k and 2 k resistors. In order to correctly achieve the 1:2 ratio, I can use all 2 k resistors and connect them in parallel to form 1 ks. But what I use is actually adjusted 1 k resistor. Therefore, if my meter offset is 1% (10 ohms?), it will be 1.010 and 2.010 respectively. The ratio is no longer fixed. In the case of 8 bits, this is all too large.

But the point is, you will read on Interweb that the R-2R DAC is only suitable for five or six digits with commercial resistors. That's true, but by trimming it yourself, you can easily get a higher precision than the eight bits required. I am very excited, it seems I can score ten, but I cannot test.

Make sure you can (make measurements): Any error in the R-2R DAC will cause nonlinearity, usually in a non-monotonic form, that is, when you add codes to it regularly, the step size will not all be the same. In some cases, it will actually lead to a decrease in output, which leads to an increase in code. Since it does not require any precise measurement, it can be verified on an oscilloscope. You just use it to generate a sawtooth, and then zoom in on the waveform so that you can see each individual step.

You should choose the 2k resistor from the two adjusted 1k resistors. This way, if you have an offset of 1%, you will get 1.01k and 2.02k

Necro-comment: I actually made another way, the -1k resistor is two 2k in parallel. Each other.

Consistency is undoubtedly the goal here, so if 1k resistors are all read as 1k, but actually 1.0001k, but always 1.0001k, then it's fine.

It is assumed that the meters are at least consistent.

For DAC, as long as the value is the same, it can work normally. The actual value of the resistance is not as important as the difference between the resistances.

The ratio of 1:2 is also very important.

It looks like you can use a bare resistor as a touch sensor. I want to know how humidity affects them.

This is how the resistive touch screen works

Resistive touch is a sandwich structure in which one layer has a series of tiny bumps to keep the layers separated when there is no touch. There is no electrical contact with fingers or stylus.

Maybe it can, but bare copper wires, or screws, would be better. It should also be long-term reliable.

If the meter you use is out of the calibration range, a system error will occur. Although if you only need matched resistors, it is no longer a problem.

I am curious what effect this technology has on the power rating of the resistors-I bet they can handle less current after modification. May be an interesting thing! This is also a good way to see if repainting is beneficial, because the exposed parts may oxidize quickly due to heating.

Power handling depends entirely on heat dissipation. I suspect he will remove enough material to produce any effect,

I think the hot spot may develop in a thinner area, but it is so detailed that it may not matter.

Trimming a point always creates a "hot spot" because it reduces the cross-sectional area of ​​the conductor, thereby increasing the current density at that point. In this application, a voltage of 5 V may be applied through about 4 kohm, which is only about 6 milliwatts, but in high power applications, this is definitely a problem. When the trimmed resistor fails due to excessive dissipation, it always occurs at the trim point.

If you look at the trimmed smt resistor or the resistor on the substrate, the trimming is done in an "L" shape. If the connection is considered at the north and south ends of the resistor, the coarse adjustment is in the east-west direction of the component, and the fine adjustment is in the north-south direction, which has a small effect on the resistance change.

This is indeed the case: the cut of the resistor is coarsely adjusted, and the one on the length is finely adjusted. Pruning is done very quickly, but the pruning will still show weakness (hot spots).

@Elliot Williams: You should check how time, humidity, light and vibration affect accuracy. Therefore, maybe only measure the resistance value again within a month or so, and then let us know the result.

The situation I encountered was 2 good resistors used to pull up some 74hc00 input lines. Even touch is enough to make the circuit inoperative from the beginning. Therefore, even enamel is not always a good insulator. Since then, I have maintained good spacing between the resistor and the circuit board and between each other.

The 74HC00 stuff is strange. I know CMOS is very sensitive, but still so. Maybe we can wire wound resistors (even like the spiral cut film in this article) to form a kind of transformer? Enough to couple a small current, but maybe enough voltage? It may be that there is a problem with them, and there is a problem with the insulating coating. What value resistors are they? In addition to the explanation provided, do you have your own thoughts on what happened?

They touched their bodies side by side. The terminal is not touched. This is because I tried to squeeze them to fit the 2.54 mm board spacing. They are usually 10 kOhm pull-ups.

No, I don’t know why this happens. The voltage is only 5 V, and the resistor will not overheat at any time.

When I separated them, the problem stopped.

"Their bodies were touched from side to side."

At first I thought it was completely out of date.

It sounds more like capacitive coupling.

Okay, I just made a set (original, trimmed, trimmed and nail polished).

Remind me within a month.

remind!

Okay, this is the Elliot of the future!

Short version: I remember testing the resistor in July 2017 and then forgot to publish it. They are all within 1 ohm of 2 ohms, which is equivalent to my measurement error.

It is April 2018 and the result is the same. (I remember b/c I just used nail polish in the same color as the insulator on another unrelated item.) Coated or uncoated trimmed (or untrimmed!) No measurable drift on the resistor .

This is the problem: I don't think leaving them in my desk drawer is a strong test. We do not have air conditioning, and the office is in the attic, so the temperature here can be as high as 30°C in summer and colder in winter (18°C?). But this is by no means absurdly hot, cold, humid or dry place.

I really like the idea of ​​this experiment, but I have to take the resistor to the Spanish beach or elsewhere. Does anyone raise money for my vacation?

In any case, the initial (non-)result is: in the absence of challenging family conditions, the original trimming results seem to be pretty good. Sealed or trimmed is fine.

Now you have exposed the originally sealed resistor element to the environment. The final result (maybe earlier than you think, not later) makes the job of adjusting the resistance worse than the initial attempt. In any case, if you need this tolerance level in your design, either (1) your design is poor, or (2) choose from a reputable manufacturer and (important) a reputable distributor of that manufacturer’s components Parts with higher tolerances (for example, China = Dangerous).

This may be good enough for the application, and cheaper.

I want to know what effect the fine adjustment has on the rated power. Because you only trimmed part of it, I think the power rating drops much faster than the resistance increases

The power rating depends on the heat dissipation. The shape and size of the resistors are still almost the same, so they should not be changed.

I want to know the stability, air will enter it, will it attack it over time? A good test is to put the newly calibrated resistors somewhere in the drawer and forget where they are, simulating actual usage.

Then in a year, I accidentally bumped into them while looking for capacitors and measured them. See how they are doing. It will be interesting, there will be some scientific data, and you will get paid twice for the same article.

In addition, will it definitely make money for the handmade DAC in the handmade audio market? If they want to buy a sterling silver power cord, then they will definitely need a handmade, fully analog DAC. Even the DAC in the box is a component that the manufacturer will sell separately, getting a chip to do the S/P-DIF interface. The output can be some precision operational amplifier or valve.

"Fully analog DAC." That almost let me slip away.

See the Wikipedia article:

In the paragraph about unequal steps, they involve fine-tuning to the accuracy of the circuit, one bit at a time, rather than fine-tuning to the exact resistance value. They didn't go into details, but it also compensates for other circuit variables, such as switch resistance and operational amplifier offset.

However, if you want to enter the enthusiast market, you must pay attention to sealing resistors with oxygen-free epoxy resin after trimming.

I once walked into a high-end audio store. I asked the salesperson what the buzz was. She didn't know what I was talking about until I figured out the culprit-the power transformer in the $10,000 amplifier. I think at some point in the early 1990s, the better the audio. Since then, there has been concern about how to make it more expensive.

I think enthusiasts are now thinking about discovering how expensive test equipment must be to discover defects: D In engineering, this is still interesting, and in consumers, it is a waste of money.

no. It is not connected to the test equipment. It is a matter of finding the right marketing buzzwords to make people pay for something 100 to 1000 times higher than its actual value. It relies on close relatives whose placebo acts. Basically, people must believe that it sounds better than cheap equipment to justify their astronomical exaggeration. Otherwise, they will promise that they have made a costly mistake.

Basically electronic homeopathy. There are dozens of similarities in its psychology, methods, cherry picking, subjectivity, and experimental design around obtaining the desired results. The same weaknesses in the human mind, as well as the advantages of all the ways that aggressive, despicable people can take.

Advertising is one thing, only done correctly, not boring and amateurish.

Use (usually) open loop valve amplifiers to destroy the output of precision DACs? That is something that only listeners can like. :-)

When the distortion of the tube is increased by 5%, it will definitely produce "tube sound". Yes, the money is well spent.

This is common when ancient resistors were composed of carbon. They are like a carbon rod (inanimate carbon rod?), you can cut them with a triangular file. With so many materials, it is much easier to adjust, and there is not much to do with the wattage or current carrying capacity of the resistor. Seal with a little shellac.

As a former laser trimming engineer of the "major manufacturer", I think you might think the wrong way, Elliot. This is not the thickness of the material you are removing; this is some width. The total resistance is proportional to the length/cross-sectional area. On the spiral, by filing parallel to the edge of the metal, the resistance can be well controlled whether it is in the middle of the track or at the edge. The groove is considered very narrow. You have to be careful not to cross the conductor, as this will leave a little bit of power dissipation capability. (I have often encountered the problem of step attenuators on some RF equipment-their rated power is 1 W, but the fault frequency is much lower than this value. It turns out that they are laser cut into resistors, this is They all fail. .) The problem of SMD parts may come from two different aspects: 1) The area of ​​the resistor is small, so you don’t have to remove too much material to increase the resistance, and the coating on the SMD resistor Too much can be difficult. My approach to SMD resistors is to polish or grind off the edges of the resistor area. Perhaps you can use Dremel with a cut-off wheel to cut in from the edge of the widest part. But I never really tried it.

Regardless, coatings on surface mount and lead components do more than just make them beautiful. This is to reduce water absorption, which will affect its value over time. After finishing, I should at least put a drop of super glue on the area where the coating has been removed. If you want your 12-bit DAC to maintain its accuracy, I will not believe that lacquer can provide adequate protection.

As for all discussions about 4-wire measurement and meter specifications, in the R-2R ladder DAC, the actual absolute resistance is only very large. The real important thing is to make them all match, so as long as you measure in the same way (same meter, same wire, same temperature, enough stabilization time), that should be fine. A 3-1/2 digit meter with a specification of 1% can still repeat to +/- 1 digit, which is .05% at 2 kohm, and you can even fabricate a number closer than this (even if you can't prove it) , If you can trim it to half the time it reads 2.000, the other half reads 2.001, because then you can be sure that it is close to 2.0005 k.

I also worked in a military avionics contractor. The contractor’s name cannot be said, and I was shuddered. They provided the location on the PCB for the critical adjustment of the two series resistors and then selected them in the test. However, are the resistors actually selected in these tests provided with the equipment? No, of course not, because testing technicians are not allowed to weld finished parts, and welding technicians are not allowed to make measurements. Therefore, once the test technician has fixed the appropriate resistors to the board, the welding technician will delete these resistors and obtain a new resistor with the same nominal value from the inventory (because it is not allowed to re-weld any part twice ) And welding. *Face*

In fact, once a "reference" resistor with the desired value is obtained, one way to accurately convert the next resistor to the same value is to provide a constant current supply for each resistor and pass a precision resistor The resistor provides voltage to each resistor. One op amp goes to the negative input, and the other goes to the positive input.

When the values ​​of the two resistors are the same, the output of the operational amplifier should tend to zero.

Yes-you have basically described the enlarged Wheatstone bridge. However, you must compensate for the offset of the test op amp by swapping inputs and comparing the results.

Moreover, once you have collected a trim resistor of one value, you can compare the two resistors in series with the resistor you want to trim to 2R. This results in almost exactly matched R and 2R values ​​without the need for a known accurate ohmmeter.

You can use conductive silver paint to reduce resistance, then dry it and scrape it off for calibration.

I once disassembled a UHF tuner and some parts. What I found was the conductive ink mark (carbon) between the various traces, apparently part of its factory alignment process.

In another era, I studied an altitude measurement radar system that uses a very large precision potentiometer (about 8 inches in diameter) to send angle information to an analog computing system. These antennas often wear out because they rotate as the antenna nods (24/7). I separated, it was a miracle of silver ink calibration. The X-acto blade cuts where the resistance is too low, and where the silver ink is too high.

Now, this is my expectation of HAD. My breasts became hairier as soon as I read them, those close-up photos, pfoorrr!

Especially for surface mount resistors, you can try to trim them with acid, just connect them to the tester, then pull them out and neutralize them when they hit the best point. The next step will be to have a complete electrochemical device where you can perform deposition, corrosion and testing, and use the MCU to control everything. Grow your own resistive film.

One thing leads to another. Before you know it, you are building a precision trimmed R-2R trapezoidal hybrid. good idea.

Next, can you tell us how to adjust our potentiometer?

I have heard of this technique before, but there are only a few details, but this article clears all my doubts about this issue. I won’t need high-precision resistors soon, but I think I’ll adopt this idea, which is the so-called proper Hack. As others have said, I want to know how to "re-seal" them to prevent moisture etc. It would be interesting to try some different seals (such as nail polish, enamel, etc.) and check for precise drift over time.

I was surprised that no one mentioned the Wheatstone bridge in the comments.

This article on precision electronics may be a bit outdated, but the information still seems to be relevant to this topic.

There is also some interesting information about random topics scattered throughout the rest of the website.

Thanks-good reading.

In 1968, I saw a tutor dial a resistor with a lighter.

Is it just me or the article does not actually state anywhere that the file reduces or increases the resistance of the part?

It's you. The article pointed out that you can only increase resistance.

All trimming increases resistance because by removing conductive material, it restricts the path through which current flows.

Just think about it-if you connect, for example, a 1k ohm resistor and a 20 ohm resistor in series, and propose a 20 ohm resistor, will it be easier to get accurate results? Will you get better control? In the end, all resistance pairs may be 1025 ohms, but if they are all the same, that should be fine.

It might be right. I was so surprised by the effect of the 1 k / 2 k experiment that I didn't bother with the lower resistance value. But there is a reason. Their metal layer is thicker and should be easier to trim and even more precise. If you have a precision ohmmeter to back it up, please try it and report it?

"Cool odd number" :-D

Don't forget to protect the exposed area after trimming, some varnish can prevent oxidation.

You will not add metal to the file.

Therefore, only one resistance value is needed in the kit, right? Absolutely not. Creating a 1.2kΩ resistor with 1kΩ original resistance will cause trouble"

Do you want to consider this part again? Of course, it sounds like you will only contradict yourself later: P

NVM, my misunderstanding. Less = more resistance?

Wow, there are many comments here, so this might get lost.

If you see this Elliot, I am surprised that I can't find a reference about thick film, especially thick film resistors and trimming.

In my university, I took a course on thick film design. In this practice, you silk printed traces and resistors on the ceramic substrate. What's interesting is that you have different pastes, such as 1k, 10k or 100k paste on the screen and then bake. The traces are made using OR paste.

After baking, you can solder on the trace-unless of course you put it on the dielectric layer of the glass.

Many designs involve the question of whether the wires cross. If necessary, another layer of dielectric and trace paste is required before proceeding.

The resistance design is too low, after baking, you can use a small precision sandblasting machine to trim the resistance value. This is a very interesting process, and research has been conducted on a process that only a few people use today. Ceramic has excellent thermal properties, so you can cool the back of the substrate and still get a good cooling.

On a 1 x 2 inch substrate, we made a 40W Class AB amplifier.

If you want, I can sort out the process and see if I can dig out more information about the project:) Email me!

Ultraviolet curing "blue light" nail polish :-)

Work for me. It also works when you break a very expensive glass lens (don't ask!) and need to re-stick it together when replacing it.

Hold it firmly when gluing, and scrape off the excess once it is set, then it can work normally.

It is also very convenient to adjust the "trimmer", fix the optics and other interesting but esoteric items, such as using a failed LCD panel and Greedbay fished out and then dried EL phosphor or other things peeled panels made of homemade EL sheet.

I am interested in more details about your LCD to EL panel project.

Will corrosion in exposed areas affect resistance over time?

It's not my idea, Jerry is the one.

I did notice that the recent E-ink mod uses uncured epoxy, while EL does require a solid dielectric.

Therefore, why not use a 3D printer to place a line of UV ink mixed with RYB phosphor

And make your own color monitor?

I think the main reason for not doing this is that TFEL has lower power consumption and lower manufacturing costs.

Some monitors have a mean time between failures of 20 years, and as far as I found out, they are still used in B-2.

It is also important to find a real old LCD panel (or an OLED TV that is damaged by some eejit) and get the RGB filter from it.

IIRC these are better than what you usually find, and are 1080P.

You can make a very reliable electronic ink color display from an old monochrome panel, what's the problem.

There is almost no hint: cutting with an X-acto knife for 10 seconds can be "quickly" harvested from a dead OLED TV, the actual filter is in the front plastic plate, and there is also an ITO conductor with rear stripes.

RE: trim the SMT resistance. I used to work in a factory that made equipment that can be tuned to a specific frequency by adjusting the value of the SMT resistor. We performed this operation using a sandblasting drill with tiny (sub-millimeter) nozzles under a high-magnification lens. We are adjusting the target frequency and bandwidth of the complete device, not the target resistance of any one resistor. We adjusted a resistor for frequency and a resistor for bandwidth. A further complication is that sandblasting will put pressure on the resistance, and in order to ensure long-term stability, it must be baked in a 200-degree oven, then checked again and re-adjusted through more sandblasting, and then baked To relieve stress. Then proceed to the final inspection. Resistor adjustment only makes tuning in one direction, so if you overshoot, you must replace the resistor and start over.

Please be kind and respectful to help make the comment section great. (

)

The site uses Akismet to reduce spam.

.

By using our website and services, you expressly agree to our placement of performance, functionality and advertising cookies.