Explanation of via cap oil and via opening

Simple Meaning of Nouns

The via cover oil, ie the solder ring of the via, is covered with ink.

Through-hole windowing: The through-hole (via) solder ring exposed (as exposed as a component pad) on the tin, generally can be used to debug the measurement signal, the disadvantage is likely to cause a short circuit.

Via treatment

The first type, windowing, is the same as the pad can be easily on the tin inspection standard: on the tin

Second, cover oil, inspection standards: it is not easy to apply tin on the surface of the patch. This is a process-determining process. The reason why the via hole does not cover the oil is as follows: because the solder resist oil is liquid, the middle of the via hole. It is also empty. During the process of baking, the solder resist oil on the solder mask ring can easily enter the via hole, resulting in yellowing of the via hole. In this case, the concentration of the solder resisted, the oven and the strength Relevant, so there will be some of the root causes that can appear green and some cannot appear,

The third, plug oil, inspection standards, opaque above the oil must have the second process of this kind of problem, and for bga like vias, the requirements are more demanding, so with the process of plug oil, It is an important supplement to the second kind. The process of plugging oil is to plug the entire hole of the via hole and plug it into the via hole so that the oil on the solder ring will not flow into the via hole. No yellowing of via holes occurs.

Why should have 0 ohm resistance, what effect does it have?

Circuit design commonly found 0 ohm resistor, we tend to be very confused: since it is 0 ohm resistor, that is the wire, why should it be installed? There are such resistance on the market to sell? In fact 0 ohm resistor Still quite useful. There are probably the following features, the most important and often used features are:

Highlights: Analog and digital single point grounding

As long as the ground will eventually be received together, and then into the earth. If not together is “floating”, there is pressure, easy to accumulate charge, resulting in static electricity. Ground is the reference 0 potential, all voltages are obtained from the reference ground to the same standards, so all kinds of ground should be short together. People think that the earth can absorb all the charges, always maintain a stable, is the ultimate reference point. Although some boards are not connected to the earth, but the power plant is connected to the earth, the power of the board will eventually return to the power plant into the ground. If analog and digital directly connected to a large area, will lead to mutual interference. Do not short and wrong, for the above reasons

There are four ways to solve this problem:

① with magnetic beads connected;

② with capacitor connection;

③ with inductance connection;

④ with 0 ohm resistor connection.

the difference:

① The equivalent circuit of the magnetic bead is equivalent to the band stop limiter, which only significantly inhibits the noise of a certain frequency point. When used, it is required to estimate the frequency of the noise in advance in order to select the appropriate model. For uncertain or unpredictable frequency, the beads do not fit.

② Capacitance across the exchange, resulting in floating.

③ inductance volume, stray parameters, unstable.

④ 0 European resistance is equivalent to a very narrow current path, can effectively limit the loop current, so that noise is suppressed. Resistance in all bands have a decay effect (0 ohm resistance also impedance), which is stronger than the magnetic beads.

In the image above, there are a total of five fields, signal ground, analog ground, digital ground, power ground, and clock ground.

0 ohm resistor other role

① in the circuit does not have any function, just for PCB debugging convenience or compatible design and other reasons.

② can do with jumpers, if a certain line do not directly do not paste the resistance (does not affect the appearance).

③ in the matching circuit parameters are not the time to 0 ohm instead of the actual debugging time to determine the parameters, and then the specific value of the components instead.

④ measure the current consumption of a part of the circuit, you can remove the 0ohm resistance, connected to the ammeter, so easy to measure the current consumption.

⑤ wiring, if the cloth is not gone, you can also add a 0 ohm resistor

⑥ in high-frequency signals, as inductors or capacitors. (Related to external circuit characteristics) Inductor, mainly to solve the EMC problem. Such as ground and ground, between power and ICPin

⑦ single-point grounding (referring to the protection of grounding, working ground, DC grounding in the equipment separated from each other, each become a separate system.)

⑧ fuse effect

⑨ jumper for the current loop, when the split electric ground plane, resulting in the shortest signal return path fracture, this time, the signal loop has to detour, forming a large loop area, the impact of electric and magnetic fields become stronger, Easy to interfere / disrupted. Splitting a 0 ohm resistor across the divider provides a short return path and reduces interference.

⑩ configuration circuit.

In general, do not appear on the product jumper and DIP switch. Occasionally, users will be set up, easily lead to misunderstanding, in order to reduce maintenance costs, the application of 0-ohm resistance instead of jumper and other welding on the board. Vacant jumper at the high frequency equivalent to the antenna, with a patch resistor effect.

⑾ Other uses

Crossover wiring, debugging / testing, temporary replacement of other chip devices, as a temperature compensation device, more often out of EMC’s response. In addition, 0 ohm resistance than the parasitic inductance of the hole is small, and the hole will affect the ground plane (because you want to dig holes), there is a different size 0 European resistance allows the current through different general 0603 1A, 0805 2A, So different current will choose different size. There is the magnetic beads, inductors and other reserved location, according to the beads, the size of the inductance package, so 0603,0805 have different sizes.

Usually 0805 package 0 resistance, the current should be normal within 2 A.

Usually the upper limit current electronic devices, mainly because the actual number of devices have some resistance, resistance is not 0, you must control the heat. There are wires similar to 0 resistors.

As for the superconductor, the allowable current is not infinite. Because superconductors have an upper current density, they can not maintain superconductivity above this upper limit.