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Questions tagged [flux]

Refers to flux chemicals used in soldering. Use the magnetic-flux tag when referring to magnetic field changes.

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Is there flux that doesn't brown under heat?

Adding flux (MG8341) to rework a component is resulting in ugly brown stains as shown in the picture below; this is a flexible circuit board with white cover-lay. The flux started to turn brown add ...
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Soldering flux and cleaner for analog SMT boards

I decided to build some precision analog circuits and will need to solder a few parts (on a surface mount board). So far I have soldered almost exclusively digital or non-precision analog and almost ...
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Example problem of induced emf in a 100 turn coil by a 100 turn coil which has 90kHz sin wave input voltage

Main Question: Let's say there are two coils each 100 turn and diameter 30 mm, And the second coil is perpendicular to the first coil's magnetic field (placed both coils next to each other; we can see ...
in.yssh's user avatar
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3 answers
246 views

Is soldering flux absolutely necessary for lead-free solder?

Looking through videos of people soldering fine-pitch IC packages (like SOIC, SSOP, SOT), they usually use a large amount of rosin-core flux to make the joints nice and shiny. I have lead-free solder (...
lemon's user avatar
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2 votes
2 answers
161 views

Ultrasound cIeaning of PCBs with isopropyl alcohol

I have tried to clean the flux remnants on a high-voltage PCB using isopropyl alcohol in ultrasound. The flux remnants were visible around the big SMD components such as transistors or in the creepage-...
Hyp's user avatar
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Adding PPF/PPFD / Scaling

When considering PPF or PPFD, can you multiply the PPF of the light source by a factor (for example x100) and divide the calculated PPFD value by it to obtain the same results? In another way - is PPF ...
Ocean's user avatar
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Soldering paste for SMD on a laptop motherboard

I want replace a SOIC8 SMD EEPROM on my laptop's motherboard. I have both a hot air gun and a soldering iron. I bought tin-bismuth soldering paste (Tin 42% - Bismuth 58%), but then I saw on most SMD ...
servabat's user avatar
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Transformer magnetics design

In transformer design, can someone help me understand how the no load flux is relevant to the transformer efficiency? What design parameters put constraints on the maximum core flux? Let's suppose I ...
dambi rambi's user avatar
4 votes
3 answers
1k views

Understanding the flux linkage in transformers

I am having difficulty understanding the concept of flux linkage in transformers, particularly how the secondary winding receives its flux when all the flux is said to be confined to the iron core. I ...
Adhithya S's user avatar
2 votes
2 answers
595 views

Removal of No-Clean Flux After Reflow

I'm looking for suggestions for fully removing no-clean, non-water soluble, liquid flux after reflow. Isopropanol alone is not doing the trick. What I've found from my research: Aggressive Flux ...
jemalloc's user avatar
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Spark gap Electroboom

I was watching this electroboom video on emp devices and he showed this simple circuit. My question was why is the spark gap in parallel with the coil? I know that the spark gap will act as a HV ...
Jelle's user avatar
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Can 70% vinegar be used as a solder flux in emergencies?

I wonder if I can use 70% vinegar in place of a solder flux for emergency repairs.
Karabin's user avatar
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2 answers
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Making a DIY wind generator for kid's project. How can we improve it?

My boy wants to make a wind generator and we have a 3D printer. We have decided to go with an axial flux style 140mm diameter with 12 iron free coils (4 per phase) so it can turn easily. Without gears,...
Craig's user avatar
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1 answer
1k views

Which flux type to use when soldering stranded wires that will be conformal coated?

I am doing a hobby project where I am weaving stranded wire through vias on the PCB. There is a matching copper trace and solder mask under the stranded wire. The stranded wire is soldered onto the ...
K0ICHI's user avatar
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3 answers
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Soldering wires to non-plated pins?

Product: QSB35024S24 Images: An image of the product I'm working on. The image depicts pins -Vo,+Vo,-Vin,+Vin- these four pins are the troublemakers. A sample image of the product as it was soldered ...
jfwork's user avatar
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3 votes
2 answers
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Storage of liquid flux

I have recently acquired a 1 L bottle of liquid flux. I only realised upon receipt that it is quite flammable and that I may not be able to provide the proper storage conditions. For now I have just ...
shimon's user avatar
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What happens to the permanent magnet flux of this synchronous motor?

Considering a synchronous motor with permanent magnets (1 pair) If there is a synchronous motor with permanent magnets and I was given the initial permanent magnet flux Y_mp = e0(at 15 rps) / w (at 15 ...
Nytro's user avatar
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262 views

Flux to lower solder ball melting point

Is there any such flux? I find the balls on BGAs very hard on my home made oven. From what I gather, mixing up solder types in order to lower the melting point is not the best idea, especially when ...
kellogs's user avatar
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5 votes
2 answers
1k views

Recovering from failure to clean off solder flux

I'm currently building a prototype device at work, that involves a QFN-64 0.5mm pitch IC (a PIC microcontroller) soldered onto a SchmartBoard|ez prototyping board. The SchmartBoard instructions call ...
jasonharper's user avatar
2 votes
0 answers
234 views

How does mutual flux in a synchronous generator remain constant like in a transformer?

Given is the flux per pole of of a synchronous generator 1)Is it field/rotor flux per pole ? 2)The generated emf per phase is given by E=4.44Nfφ where φ is the flux per pole But from transformers, we ...
Nigel Goveas's user avatar
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2 answers
180 views

Possible Contradiction in N87 ferrite material μa vs B graph

Why does this graph description (of N87 material) states ^B =< 0.25mT (which is peak flux density), even though horizontal axis goes up to 0.40T? Is the horizontal axis in tesla peak-to-peak? Is it ...
LoukasGr's user avatar
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65 views

How can the magentic flux be determined in a transformer with airgap?

I am planning to conduct chemical reactions in an AC magnetic field at 60Hz. The magnetic setup is made of two 1.4kW microwave transformers with HV coils and Iron I-cores removed. Then the two ...
ChrisOe's user avatar
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1 answer
219 views

Why it can be asserted that the bottom plate takes the highest potential and the top plates takes the lowest of the capacitor?

The ideal parallel capacitor has been filled with 2 dielectrics as shown in the above diagram. $$ V_{1} :=\text{potential at the top plate} $$ $$ V_{2} :=\text{potential at the bottom plate} $$ $$...
electrical apprentice's user avatar
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1 answer
227 views

Flux for removing LGA socket

I have been looking into the stackexchange searchbar and also I have been searching for a day or two globally, even the "similiar dialog on this website" when I was creating this post. I ...
Ketske's user avatar
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1 answer
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Coiling ac wire around iron rod bad or good?

I have around 4-5 meter excess wire length on extension board to power my computer. Power consumption is around max 500 watt. I know there are probably 2 more thread on same topic. But they mostly ...
Niranjan Wagh's user avatar
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4 answers
1k views

Using and maintaining lower end soldering iron tips without destroying them

I bought a low end soldering iron of eBay - it was advertised as a "15 in 1 Soldering Iron Kit", and was advertised as temperature adjustable. It has a dial to adjust the temperature with ...
a1kmm's user avatar
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1 vote
2 answers
107 views

Why does an additional primary current exist in a loaded transformer?

I think this has something to do with Faraday's Law but like, I don't get why having a secondary current produces a antiphase secondary current at the same instant. Not all currents produce a direct ...
AndroidV11's user avatar
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20 views

Are there other quantities besides voltage and current that can be expressed as instantaneous values in AC circuits?

https://www.electrical4u.com/emf-equation-of-transformer-turns-voltage-transformation-ratio-of-transformer/ I got really confused when all of a sudden they treated flux with the time domain equation ...
AndroidV11's user avatar
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1 answer
833 views

Reducing equivalent self inductance of an inductor

Let's say I have a coil of N turns and it is wound on a rectangular core and when we connect a voltage source through both terminal of coil flux is generated in core , now I wanted to reduce that flux ...
user215805's user avatar
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4 votes
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Are soldering fluxes safe to touch?

I'm new to PCB soldering. I just bought a cheap soldering iron, solder wire and flux to try something. I have no previous experience with soldering. I'm well aware of the potential risks of prolonged ...
John's user avatar
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5 votes
1 answer
1k views

What is "activity" in solder flux?

I'm trying to select a solder flux and so many references (and one or two SE questions) discuss the types and differences. They mention "activity", such as "Rosin Activated (RA) flux ...
Casey's user avatar
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2 votes
0 answers
172 views

Storing liquid soldering flux long-term. Is it light sensitive?

Is soldering flux known to be light sensitive? I got a big jug but the big jug it arrived in is deformed and doesn't look like it's going to hold so I am going to transfer it over to some bottles for ...
DKNguyen's user avatar
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4 votes
1 answer
1k views

Why does PCB copper surface oxidize when I apply flux on its surface?

I had to create a printed circuit board for a project, using the home method (PCB developer solution, iron chloride.) At first, after the PCB was etched, I cleaned it very well using paper towels and ...
Victoria's user avatar
1 vote
2 answers
1k views

Why is flux in field winding constant in DC shunt motor, but not series motor?

As titled, why is the field winding constant in DC shunt motor, but not series motor?
friendly_brett123's user avatar
0 votes
3 answers
6k views

Substitute for solder wire and flux [closed]

So I am trying to get started soldering, but I was wondering if there was any common household component that I could somehow take out the soldering wire or flux. Although any alternatives will be ...
nerdy nuclear nuts's user avatar
1 vote
1 answer
327 views

Current in delta connection

I know how to calculate current in delta connection but just for knowledge purpose I wanted to know from basics why this method(in image) of calculating phase and line current is completely wrong ...
user215805's user avatar
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0 answers
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Jumping ring demonstration

In demonstration of jumping ring if we assume dc source connected to solenoid, according to most of books, when we place a metallic ring over the solenoid and as soon as we turned on current, due to ...
user215805's user avatar
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0 votes
1 answer
46 views

Find the flux leaving the surface of the sphere: What will the position of line charges look like diagrammatically?

I am not able to understand how the two uniform line charges will look like in space. It would be of great help if someone could draw the uniform line charges in cartesian coordinates and upload it ...
Soumee's user avatar
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1 answer
1k views

Soldering paste or flux

There are a number of materials on the market that help with soldering, prevent oxidation. someone says flux, someone says soldering paste also someone says flux and soldering paste are same. ...
mehmet's user avatar
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1 vote
2 answers
3k views

What is this white stuff on the solder of this PCB?

These photos were taken from a new-in-box 16kB memory expander for a Timex Sinclair 1000 computer. As far as I'm aware, it was never used. The box was made of thin cardboard with a two part styrofoam ...
Zhro's user avatar
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0 votes
1 answer
65 views

What affects the current ratings on constant torque pole changing motors?

Two different motors, one is rated 1.49A on slow speed configuration and 1.43A on high speed. The other motor is rated 6.09A on slow speed and 6.99A on high speed. These are constant torque pole ...
Ph3ng's user avatar
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0 votes
1 answer
130 views

Mean Free Path of Magnetic Core

I don't understand how they got the mean free paths (ls) of each leg. I know that I should be calculating the longest + the shortest paths and divide them by two, but I don't know HOW I should be ...
user avatar
2 votes
3 answers
498 views

Transformer’s Flux and Back-EMF

I know that transformer is a constant flux device but there is one point I don't understand. As you know, when secondary of transformer is connected to a load, current starts to flow. This current ...
d.alex's user avatar
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5 votes
3 answers
1k views

Clean vs no-clean for high voltage circuit

I have a board that has fairly high working voltages up to 100V with small clearances down to 12 mil between the high voltage and ground or low voltage nets. This is unavoidable because the whole ...
Alex I's user avatar
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0 votes
1 answer
416 views

Relationship of Slip and Angle Between Rotor and Stator Flux for Induction Motor

I know how slip and flux angle individually affect torque of induction motors but I can't understand the relationship between slip and flux angle in terms of torque. Do they both have different effect ...
d.alex's user avatar
  • 235
0 votes
1 answer
154 views

solder wire makes solid & glassy residue

I know using flux makes some residue which makes unwanted contacts between components pins. I dont have any washing liquid or spray to remove it so i simply decided to not use them. But my solder ...
payam_sbr's user avatar
  • 117
0 votes
2 answers
199 views

A contradiction regarding flux conservation

Consider a simple circuit Initially switch S was opened till steady state is reached and then it was closed. My understanding regarding inductors is that you can't have a SUDDEN change in current ...
Shivansh J's user avatar
3 votes
2 answers
2k views

What would be the consequence of the inductor saturating?

The following is a section from a book where it is talking about decoupling by LRC at supply terminals. I highlighted the sentence where I didnt understand: I read that if an inductor has an iron ...
pnatk's user avatar
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4 answers
11k views

Beginner Question - Solder won't stick to a certain wire

I am trying to tin some wires as they won't stick to the IC pins that I'm soldering them to. The problem I am having is that the solder won't stick to the wire. My iron is fine as can solder other ...
Sef's user avatar
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1 answer
295 views

How does flux change polarity in full bridge SMPS transformer?

Take a full bridge switching circuit connected to the primary of a transformer. Assume: No load on secondary. Voltage into full bridge is DC. Duty cycle of switching is 50%. At t = 0, full bridge ...
Not Really's user avatar