1) Magnetic core
There are many methods for classifying magnetic cores. At present, there are many numbering methods for classifying by appearance. In the course of use, it is necessary to understand all aspects of the material in order to accurately determine whether the incoming material meets the requirements. Some materials have the same size, color, and inductance value, but they are two completely different materials. If the inspectors have limited understanding, the rash judgment will lead to heavy losses.
a. Network transformer appearance: The iron core is divided into many types according to the appearance, and has a ring shape (T shape), an E shape, a C shape, and the like. See below:
Network transformer
b. Coating: The coating of the magnetic ring protects the magnetic ring. Normally, the coating of the magnetic ring is expressed in the manufacturer's serial number, which is represented by an English letter. Different letters indicate different coating thicknesses and different withstand voltages. There are specific instructions in the numbering instructions below.
c. Material: In the case of the same size, the material of the magnetic ring is different, the inductance value of the magnetic ring is different, and there are more than a dozen parameters for characterizing the magnetic ring material. As a feed inspector, at least one must understand Three parameters:
Ui value: Chinese means relative magnetic permeability, no unit. At present, the magnetic ring ui values used by our company are: 850 (1000), 4700 (5000), 10000, etc. When the appearance of the magnetic ring is exactly the same, the higher the ui value, the higher the inductance value of the magnetic ring. . In addition, this parameter also characterizes the magnetic ring frequency characteristics, temperature characteristics, losses, and so on.
AL value: The AL value is defined as the single-turn inductance value of the magnetic ring. This parameter is directly used for the level sorting of the magnetic ring. When the appearance dimensions of the magnetic ring are exactly the same, the higher the ui value, the higher the AL value of the magnetic ring.关系 The relationship between the inductance value and the AL value:
Inductance value OCL=AL*T2 where T is the number of coils to be worn. (Note: When the winding has a center tap, T is the number of turns worn by 2)
Withstand current: For the magnetic ring used on 100/1000BASE products, it is required to withstand 8mA DC current. That is to say, the magnetic ring used for this kind of product needs to increase the DC8mA test when testing the feed. d. Examples of commonly used magnetic ring numbers:
2) Shell
Network Transformer At present, the main shells used by our company are: DIP and SMT. During use, it is necessary to pay attention to the following parameters:
a. Appearance Dimensions: According to the acknowledgment of the appearance size, it is usually measured with a “vernier caliper”. There are often many sizes available from suppliers. Based on the limitations of the test tools, we cannot test them one by one, usually measuring the main parameters. For some parameters that cannot be measured, test by the method of trial installation.
b. Visual inspection: inspection according to the requirements in the “Appearance Inspection Standard”
c. Heat resistance test:
Housing for direct insertion of PIN products: Generally, the outer casing is filled with glue, and there is no burn on the tin surface for about 3s.
The outer casing used for SMD products needs to pass IR to see if there is deformation or cracking. Generally required to withstand 260 degree IR furnace.
d. Material: DIP shell generally uses bakelite powder (usually 151J material), SMT is generally DAP material (commonly used DAP9100 series).
3) Enameled wire
a. The enameled wire is painted on the outside of the thin copper wire to protect the copper wire from external damage. The voltage resistance of the enameled wire can be determined according to the number of layers of the outer paint. The commonly used enameled wire has 1 layer and 2 layers. 4 layers, 4 layers, etc. 4 layers of paint film thickness. Different paint film materials have different heat resistance grades. There are three heat resistance grades commonly used: 130 ° C (Class B) (so-called low temperature enameled wire), 155 ° C (F grade), 180 ° C (H grade) and 200 ° C ( Class N) (so-called high temperature enameled wire). The inspection of enameled wire usually includes the following aspects: b. Heat resistance test c. Withstand voltage test
d. DC resistance test: Usually choose a certain length to test its DC resistance. e. Wire diameter test: It is divided into “diameter test” and “paint test”, and “bare test” is carried out after burning the paint film. The wire diameter test tool is a 'micrometer'. f. Pinhole test: This is to check whether there is a small hole in the outer patent skin of the enameled wire. The more the small hole, the worse the quality of the wire and the lower the withstand voltage capability. Usually this test needs to be assisted by chemical reagents.
g. Appearance inspection: Inspection according to the “Appearance Inspection Standard”.
4) Chemical materials
a. High temperature vinyl
Network transformer high temperature vinyl in the process of use, must pay attention to the following:
Verify that the vinyl is hardened at the specified time and temperature under the specified ratio conditions.
At the same time, whether the bubbles generated by hardening are more than usual, is it easy to produce glue, and after the black rubber is hardened, the surface is bright and there is no oil stain.
High temperature test: After the black rubber is hardened, it is reflow soldered to check whether the black glue after hardening is cracked.
Open situation. (mainly for SMD products)
When the black plastic is blended, the electronic scale is accurate, and the accuracy of the electronic scale meets the requirements; Before the black plastic is blended, the sediment on the bottom of the black plastic container should be evenly mixed with wood strips (usually the unopened whole barrel of black plastic) , put it down for a day, let the bottom sediment dissipate.) Then make the blending
The high-temperature black rubber A/B glue according to the quantity must be fully twisted and evenly mixed, so that the black glue and the curing agent are thoroughly mixed to ensure the curing of the black glue.
b. Low temperature vinyl
In the process of using low temperature vinyl, in addition to the matters needing attention in high temperature glue, the following items must be noted:
Do not adjust too much each time, if the prepared vinyl is not used up in time, it is easy to hard
Get rid of
Pay attention to the presence or absence of the pattern on the surface of the vinyl, and pay attention to verify whether the vinyl is easy at high temperatures.
Cracked with the outer casing.
c. Flux
There are many items to be tested for flux, including specific gravity, pH, composition, and halogen content. However, since the equipment required for these tests is extremely expensive, the general manufacturer uses the actual trial method to judge whether the incoming materials are qualified. Usually pay attention to the following points in the trial:
The soldering tips are generally divided into water-soluble fluxes and no-clean fluxes.
Solderability: Whether it is easier to solder when soldering, whether the tin point is smooth and round, whether it is easy to produce continuous welding or false welding.
Pay attention to the smoke and smell during welding. When the smoke is too large or the smell is very strong, attention should be paid.
Oxidation: The quality of the flux directly affects the oxidation of the PIN pin of the product. There are usually two cases worth noting: one oxidation condition is to form a yellow cover on the PIN pin of the product within a few minutes after soldering; In this case, the solder joints were beautiful after soldering, but after one or two days, the product PIN pin began to oxidize. Therefore, the trial production of the flux must allow the product to flow to the later stage to form a finished product. After a day or two, observe the conclusion.
d. Alcohol
You can commission a trial. Mainly to check its cleaning performance, as well as residual conditions after volatilization.
e. Printing white plastic printing white plastic as a chemical raw material, the test of its related parameters becomes very difficult due to the failure of the instrument. The test method is tested. After the test, the following aspects are mainly tested:
Whether it is hardened at the specified temperature and within the specified time. Is the print yellow? The print is off. f. UV glue
UV-curable printing ink with fast curing and good printability, and excellent heat resistance and electrical properties after drying.
5) Packing materials
a. packaging tube
Generally, PVC materials are used. In order to meet the halogen-free requirements, the PS material is now used. b. carton
Generally, the B three B material is used domestically, and the K two K material is used for export. Pay attention to the following issues for the packaging materials:
Strength, considering the vibration and collision during transportation, it is required to have a certain strength to ensure the quality of the product.
Internal fit size: In principle, the product inside the packaging tube is required to vibrate anyway, and the PIN pin of the product should not collide with the outer wall of the packaging tube to avoid deformation of the PIN foot. C, the tape material is PS material. The tape is generally composed of three parts, a carrier tape, a plastic disk and an upper tape. Different from the product, the shape of the carrier tape will change, but the rubber disk and the upper tape are fixed and have a certain relationship. The rubber disk generally uses a 13' disk, which is mainly matched with the upper tape by different widths.
13'' (inch) plastic disc (width 24mm) corresponding to the upper strip width 21.3mm 13'' (inch) plastic disc (width 32mm) corresponding to the upper strip width 25.5mm 13'' (inch) plastic disc (width 44mm) Corresponding to the upper tape width of 37.5mm
6) PIN pin
1. Material: copper clad steel
2, PIN plating tin, can not have surface blackening, oxidation phenomenon 3, can not have copper, scratches, etc. 4, can not have defects, bending, need to pay attention to the following points:
Size: size, length, width and thickness and related mating dimensions
Smoothness: The PIN pin is not smooth, and the product PIN pin will produce “tin tumor” after tin plating. Solderability: Whether it is easy to tin;
Antioxidant: How long does the PIN be placed in the gas to cause oxidation? Once oxidized, the PIN is
It is impossible to plate tin, and the difficulty of operation is greatly increased.
7) Tin material
Commonly used are tin copper, tin silver copper and tin beryllium copper. Among them, tin copper is divided into 0.7Cu and 4.0Cu. Tin-silver-copper is divided into 0.3Ag and 3.0Ag
Parameter description of network transformer
Description of various measurement parameters of magnetic components such as transformers, inductors and coils
1. The ratio of turns is TR: the ratio of the primary and secondary windings, and the turns ratio and coupling coefficient of the transformer winding are detected. 2. Phase PH: Winding direction. Detect the winding direction of the main secondary of the transformer.
3. Inductance Lx: The proportional coefficient of the rate of change of voltage and current time (e = L). Detect the magnetic permeability coefficient μ, mechanical size, integrity, and absolute number of windings of the core. 4. Inductance Lx overlap DC Bais: Detects the magnetic saturation characteristics of the core.
5. Leakage inductance LK: The equivalent inductance formed by the leakage flux beam cutting. The magnetic permeability μ of the iron core and the coupling coefficient formed by the winding are detected.
6. Quality factor Q: The ratio of the inductive reactance (2πfL) of the inductor to the resistance (ACR).
7. Distributed capacitance between coils Cp: stray static capacitance between coils. Detect the distance between the coils, the insulation material and the isolation design. 8. DC resistance DCR: copper wire resistance. Detect PIN solder joints, copper wire materials, design line lengths, and short circuits. 9. AC resistance ACR: Copper wire resistance plus equivalent resistance due to hysteresis loss and eddy current loss. In addition to detecting copper wires, the magnetization and insulation of the core material are also detected. 10. Impedance Zx: The absolute impedance of the transformer's AC.
11. Balanced BL: A balance test between two groups of transformer windings. Detect inductive balance, leakage inductance balance, and resistance balance. 12. Short circuit of the foot PS: Do not short circuit between the foot. Detect the short circuit caused by the lacquer or solder between the coils. Transformer measurement common problem handling
1. The measured value of the transformer inductance is quite different from the measured value of the acceptance manufacturer, resulting in a return.
When the manufacturer uses the instrument and the instrument system used by the acceptance manufacturer, if the product itself has a nonlinear characteristic or the test range is out of the linear range
(Production or acceptance of the manufacturer), it is possible to obtain different measurement results due to the difference in the test current (magnetic field strength). The processing method is that both the supply and demand sides should use the same test current mode. 2. Inductance, DC resistance (DCR) or turns ratio measurement error.
The general measurement error comes from poor contact or the test frequency exceeds the resonant frequency of the coil. There are several situations in which this type of contact is caused:
1 The transformer is deformed and bent. The treatment method is to strengthen the whole foot work or adjust the thrust of the jig.
2 The insulating paint is attached to the output of the transformer. The treatment method is to remove the paint before the test to ensure that the feet are clean. 3 The pressure of the fixture is insufficient, and the push handle is loose or improperly adjusted. The treatment method is to regularly check the air pressure and adjust the distance of the push handle reasonably. 4 The jig (probe) is deformed or contaminated with impurities. The treatment method is to periodically clean the surface of the shrapnel (probe) or replace the jig.
3. When the transformer primary and secondary turns have a large difference, the phase is misjudged.
When the difference between the primary and secondary turns is large, the secondary induced voltage is lower, and the effective number of bits is less likely to cause misjudgment. The treatment method is to appropriately increase the test voltage.
If there is another group of coils closer to the number of secondary turns, it can be used as a multiple set of primary settings (3259 independent group test function), measured in a closer number of groups.
4. How to detect the inconsistency of multi-wire and transformer windings?
In addition to the number of turns, add the primary Q value. When the primary Q value is measured, the Q value lower than the normal normal product is obtained due to the power consumption of the secondary high and low turns.
The main parameters
1. Open Circuit Inductance (OCL): Open Circuit Inductance,
2. Leakage inductance: Leakage Inductance, related to transformer coupling coefficient (depending on winding technology and core)
3. Inter-winding capacitor: Interwinding Capacitance, C12 is also. If it is small, it has no effect on the transformer signal. If it is too large, it will provide a low impedance path for the common mode current, which will have adverse effects.
4. DC Impedance: RL1, RL2 in DC Resistance
5. Transformer transformation ratio: Turn RaTIo, primary and secondary coil turns ratio
6. Insertion loss dB: InserTIon Loss=20Xlog(V1/V2), where V1 is the level of the output after the transformer is inserted, and V2 is the output level when the transformer is not plugged. This parameter is used to measure the effect on the transmitted signal after the transformer is inserted. The smaller the better. Generally refers to the relationship between the degree of signal attenuation and the signal frequency of the network transformer.
7. Return Loss dB: Return Loss, which measures the relationship between the impedance mismatch of the system and the signal frequency after plugging into the network transformer. Return Loss=20Xlog(Vr/Vi), where Vr is the amplitude of the reflected signal and Vi is the amplitude of the incident signal.
8. Crossover interference dB: Cross Talk, the ratio of the signal V1 in one of the two unit circuits to the signal V2 in the other unit circuit Cross Talk = 20Xlog (V2/V1)
9. Common mode rejection ratio dB: CMRR=20Xlog(Vout/Vin), the ratio of the common mode interference signal amplitude Vin at the input end of the network transformer to the common mode interference signal amplitude Vout at the output end