The whole process of making high frequency transformer

2019-06-26 13:05:18 JuKe Technology (DongGuan) Co., Ltd. Read

The whole process of making high frequency transformer

The circuit diagram of the High frequency transformer is shown in Figure 1.
High-frequency transformer circuit diagram.jpg

Figure 1 Circuit diagram of high frequency transformer

The production process of the high frequency transformer is shown in Figure 2.
High-frequency transformer production process.jpg

Figure 2 Production process of high frequency transformer

The fabrication of high-frequency transformers generally includes the following ten processes, which provide detailed analysis of the process, process and precautions of each process.


(1) Material confirmation

1) Confirmation of the transformer skeleton (BOBBIN) specifications.

2) When the unused pins are cut, they should be cut off before unwinding, in case the wire will be scratched or the wrong foot will be cut when the wire is cut, and the wrong foot can be avoided when winding.

3) Confirm that the skeleton is intact and there must be no damage or cracks.

4) Insert the skeleton correctly into the fixture, generally marked as pin 1 (PIN1). If the drawing is not specified, pin 1 is facing the machine.

5) The acetate cloth should be wrapped according to the requirements of the engineering drawings, close to the two sides of the skeleton, and then the wire is wound (or the first hook wire) on the specified pin, and then the winding is started. In principle, the winding should be specified. Winding within the range.

(2) Winding method

1) Winding method

According to the requirements of the transformer, the way of winding can be roughly divided into the following types:

1 layer of dense winding: the wiring only occupies one layer, there is no gap between the tight line and the line, and the neat winding is shown in Figure 3a.

2 Equal winding: Winding at equal intervals within the winding range; spacing error within 20% can be accepted, as shown in Figure 3b.
Winding method.jpg

Figure 3 winding method

3 multi-layer dense winding: in one winding layer can not be completed, must be wound to the second layer or more than two layers, the winding method is divided into three cases:

a) Arbitrary winding: Arranged neatly to a certain extent. When the uppermost layer is reached, the wiring is disordered and uneven, which is the roughest winding method in the winding.

b) The entire column is closely wound: almost all the wirings are neatly arranged, but there are a number of wirings that are disorderly (about 30% of the total, and about 5% of the REF is less).

c) Completely arranged and tightly wound: the winding to the uppermost layer is not disorderly, and the windings are arranged neatly, which is the most difficult winding method in the winding.

4 positioning winding: wiring is specified in a fixed position, generally divided into five cases, as shown in Figure 4.
Positioning winding.jpg

Figure 4 positioning winding

5 and winding: two or more lines are parallel to the same group of lines, each parallel winding, can not be crossed, this winding method can be roughly divided into four cases, as shown in Figure 5.
Winding way.jpg

   Figure 5 and winding

2) Leading essentials:

The length of the flying lead wire is controlled according to the engineering drawing requirements. If the stranding wire is required, the length must be reserved for 10%. The casing must be deeper than the retaining wall by more than 3 mm, as shown in Figure 6.
Flying line and lead schematic.jpg

Figure 6 schematic diagram of flying leads and leads

3) Note:

1 When the START and FINISH lines are on the same side of the skeleton, a cross-over tape (CROSSOVERTAPE) must be applied for isolation before the end is returned.

2 When the access line is used, when the groove of the skeleton is out of the line, in principle, the line is made by one line and one groove. If there are multiple sets of the same pin, the same groove or adjacent groove can be used for the wire, only in the solder and casing. Take care to avoid short circuits.

3 When winding, it is necessary to evenly and neatly wrap the winding area of the skeleton. Except when there is a special regulation method on the engineering drawing, the drawing is subject to the standard.

4 When there is a Teflon sleeve in the transformer and there is a folding line, the Teflon casing of the access line must be flush with the groove of the skeleton (or at least 2/3 height), and the wire is taken out from the groove of the skeleton. Prevent the pulling force from breaking the wire due to the excessive length of the bushing. However, if the L-shaped pin is wrapped horizontally, the sleeve should be flush with the skeleton edge (or at least 2/3 length), as shown in Figure 7.
Schematic diagram of the length of the casing.jpg

Figure 7 is a schematic view of the length of the sleeve

5 When the acetate cloth is added as the wall tape, the wall tape must be close to the two sides of the model. In order to avoid over-fat and affect the leakage inductance, it is required that the overlap of the acetate cloth above 2TS should not exceed 5mm, and the acetate cloth wrapped in one circle only needs to pack 0.9T, leaving the gap to facilitate the good penetration of the varnish into the bottom layer. The width of the acetate cloth is related to the safety requirements of the transformer. The VED winding method has a width of 3.2 mm on both sides of the package and must be sleeved. Winding method: PIN end 6mm/4.8mm/4.4mm/4mm; TOP end 3mm/2.4mm/2.2mm/2mm without bushing. When winding, the copper wire should not be on the wall. If there is a casing, the casing must extend more than 3mm into the wall.

 2. Copper foil

(1) Copper foil winding method

1) Types of copper foil and its role in the transformer: We have two kinds of bare copper backing rubber in the shape of copper foil: the surface of the copper foil is covered with a layer of adhesive tape, and vice versa is bare copper; The position in the middle is divided into inner copper and outer copper. The bare copper is generally used for the outer copper and copper foil of the transformer. The shielding function is generally used in the transformer, mainly to reduce the leakage inductance, the excitation current, and the current passing through the winding is too high. When it replaces the copper wire, it acts as a conductor.

2) Processing of copper foil

1Inner copper foil general processing method: welding lead → copper foil both ends flat on the center of acetic acid cloth → fold back the acetate cloth (acetate cloth must completely cover the solder joint) → cut the acetate cloth (both sides of the copper foil must be more than 1mm), such as Figure 8 shows.
Internal copper foil processing schematic.jpg

Figure 8 shows the copper foil processing

2 copper copper fly macro processing method shown in Figure 9.
Inner copper fly macro processing method.jpg

Figure 9 copper fly macro processing method

3 external copper processing method shown in Figure 10.
External copper processing method.jpg

Figure 10 external copper processing method

(2) Working method requirements for using copper foil in transformers

1) The copper foil winding method must be flattened at the solder joint. The outer copper foil should be wound around the corner of the skeleton. It should be wound from the center of the skeleton to prevent the second layer of copper foil from interfacing with the first layer. Squeeze the tape to form a short circuit, as shown in FIG.
Working method requirements for using copper foil.jpg

Figure 11: Working method requirements for using copper foil

2) When the inner copper sheet is used as the shield winding between the layers, the width should cover the area of the winding area of the layer as much as possible, and the thickness of the inner layer can be rounded off when the thickness is below 0.025 mm (1 mil), but the thickness is 0.05 mm. (2 mils) (inclusive) copper foil above the two ends need to be rounded.

3) The copper foil must be wrapped flat, not to one side, not to the retaining wall, as shown in Figure 12.
Schematic diagram of copper clad.jpg

Figure 12 is a schematic view of a copper foil

4) Soldering copper, as shown in Figure 13.
Schematic diagram of welding copper.jpg

Figure 13 Schematic diagram of welding copper

 (3) Precautions

1) Copper foil solder joints According to the engineering drawing, the copper foil must be tightly packed and not biased to one side;

2) Point tin, the solder joints should be smooth, not thorny, and the tin time should not be too long to avoid burning the tape;

3) In the physical object, the thickness of the short-circuited copper foil can be 0.64 mm, and the width of the copper foil only needs half of the width of the copper window winding.

 3. Packing tape

There are generally the following methods for wrapping tape, as shown in Figure 14.
Way of wrapping tape.jpg

Figure 14 way of wrapping tape

Note: The tape must be tightly packed, not pierced, not exposed, and the outermost tape should not be packed too tightly to avoid affecting the appearance of the product. The bonding method of the crimping tape is shown in Fig. 15.
Pressure tape bonding method.jpg

Figure 15 is a method of applying pressure tape

 4. Presser foot

1) straighten the copper wire and wrap it around the corresponding foot;

2) Tangle the copper wire with a diagonal pliers and press it to the bottom of the foot against the wall;

3) Cut off the excess thread;

4) The number of wound coils depends on the number of wire diameters, as shown in Figure 16.
Presser foot method.jpg

Figure 16 presser foot mode

Note: The copper wire must be close to the foot. It is expected that the height will not exceed the pier point after soldering. Do not leave the wire head, do not crush the foot, do not break the copper wire, and cannot damage the model.

In addition, the twisted wire with too many copper wires is shown in FIG.
Twisting too much copper wire.jpg

Figure 17 twisted too much copper wire

 5. Solder

(1) Soldering procedure

1) tidy the product;

2) clip a row of products with a clip;

3) The foot is covered with flux;

4) Scratch the tin surface with a white hand;

5) Solder: When the vertical model is tinned, the foot is inserted vertically into the tin bath (the horizontal model inserts the foot into the solder bath), and the tin plating depth is as shown in Fig. 18.
Schematic diagram of solder.jpg

Figure 18 Schematic diagram of solder

(2) Requirements

The tin plating shall be uniform and smooth, and there shall be no cold welding, cladding welding, leakage welding, continuous welding, oxygen welding or tin soldering. The soldering standard is shown in Fig. 19. The requirements for soldering are as follows:
Solder standard.jpg

Figure 19 Standard for soldering

1) When the pin is a vertical pin, the tin tip can be left, but the tin tip length does not exceed 1.5 mm.

2) When the pin is an L-shaped pin and is wound in the horizontal direction, the tin pin should not be left in the horizontal direction, the tin pin can be left in the vertical direction pin and the tin tip length should not exceed 1.5 mm.

3) The bare wire part (multi-strand wire) of the PVC wire shall not be scored or broken, and shall not be exposed to copper or glue after soldering, or contaminated with other impurities.

4) Flux (FLUX) must use a neutral solvent.

5) The tin furnace temperature must be maintained between 450 and 500 °C. The soldering time varies with the wire diameter, as follows: AWG#30 line above 1~2s; AWG#21~AWG#29 line 2~3s; AWG#20 line below 3 to 5s.

6) Tin bar for tin furnace, the standard ratio of tin to lead is 60/40. Approximately 1/3 tin of new tin must be added every month.

        7) Once the tin surface is welded, it must be scraped for a second time.

        8) Clean the tin furnace once a week and add new tin to the tin furnace.

(3) Precautions

1) The white bag model contains more tin oil, and the soldering time should not be too long.

2) The plastic model is not resistant to high temperatures and is prone to over-welding or pin displacement.

3) Non-burnable tape, three layers of insulated wire must be peeled and tinned first;

4) The minimum clearance between solder joints must be above 0.5mm, as shown in Figure 20.
Distance between solder joints.jpg

Figure 20 Distance between solder joints

 6. Assembling the core

(1) Iron core assembly operation process

1) Iron core confirmation: not damaged or deformed;

2) The engineering drawings stipulate that the core shall be ground with an air gap, and the core to be processed;

3) Assembly: If there is no special regulation, the horizontal model has been ground on the primary end of the core, and the vertical end of the model has been ground;

4) The core fixing method can be fixed by iron clip (CLIP) or three-layer adhesive tape, and can be fixed by epoxy resin glue (EPOXY) at the joint of the core. After dispensing, it must be dried for half an hour and then baked in an oven at 120 °C. One hour. The fixing tape of the iron core shall be of the same color as the wire package (except for the special requirements of the drawing), and the manufacturer shall comply with the UL specification. The assembly process is shown in Figure 21.
Schematic diagram of assembling the transformer process.jpg

Figure 21 Schematic diagram of assembling the transformer process

Note: the core tape wraps around and ends; the vertical wraps around the center of the pin end and ends at the center; the horizontal wraps around pin 1 and ends at pin 1. Some copper foils are wound around the solder joints and end at the solder joints.

(2) Precautions for assembling the core

1) When assembling the core, the cores of different materials cannot be assembled on the same product;

2) For transformers and inductors with air gap (GAP), the air gap (GAP) method shall be in accordance with the air gap (GAP) method specified in the drawing, and the material placed in GAP shall be capable of withstand temperature above 130 °C, and Have material certification or iron core processing and grinding;

3) Whether it is a combination of iron core with or without air gap, the contact surface between the core and the iron should be kept clean, otherwise the inductance value will decrease after the impregnation operation;

4) The width of the tape of the iron core is specified, with the physical appearance as the priority, and the width of the iron new width reduction tape is about 0.3mm~0.7mm.

 7. Impregnation

(1) Operation steps

The operation process is shown in Figure 22, and the operation requirements are as follows:
Schematic diagram of impregnation.jpg

Figure 22 Schematic diagram of the impregnation process

1) Place the product neatly in the iron pan.

2) Adjust the concentration of insulating varnish (Fan Lishui): 0.915±0.04.

3) Place the iron plate on which the product is placed in the impregnation tank.

4) Start the vacuum impregnation machine, pump air to 40~50cm/kg, put insulation paint, and then pump to 65~75cm/kg. It must be vacuumed continuously, vacuum 3-5 times, impregnation 10~15min, depending on the product No bubble overflow.

5) Deflating, put down the insulating varnish, and then pump back to 65~75cm/kg once, deflate, wait for the product to dry slightly, then take it out and put it on the filter dry.

6) Filter out for more than 10min, depending on the product without insulating paint dripping.

7) Drying: first adjust the temperature of the oven to 80 ° C, preheat for 1 h and then adjust the temperature to 100 ° C, bake for 2 h, then adjust the temperature to 110 ° C, bake for 4 h, and confirm the sample.

8) Take the product out of the oven.

9) Cooling: Use a fan to supply air to accelerate cooling.

10) Send the plate to the production line.

(2) Notes

1) The ratio of insulating varnish to thinner is 2:1

2) When insulating paint is placed, the height of the insulating paint is subject to the completely submerged product, but the insulating paint cannot be on the copper foot (except for special models).

 8. Labeling (or word)

1) Label confirmation: Check whether the label content is correct, whether there is any missing word typo, whether the writing is clear, and check whether the label is out of date. When printing, you must confirm that the set label is completely correct, as shown in Figure 23.
What the tag contains.jpg

Figure 23 contains the contents of the label

2) When labeling, place the product in the same direction in the same direction. When spraying, place the printing surface of the product on the conveyor head and place it on the conveyor belt. The product must be placed in the positive direction.

3) Labeling: The material number label and the dangerous label shall be stamped or pasted according to the direction and direction specified in the drawing. The label “DANGER” or “HIGHVOLTAGE” and the lightning symbol should be applied to the upper center of the transformer. The direction of the label is in the direction of the “DANGER” arrow toward the primary winding of the transformer, as shown in Figure 24.
Label schematic.jpg

Figure 24 label diagram

(4) Precautions: The label must be affixed to the flat. After the paste is finished, it must be clicked by hand to make it completely in contact with the product; the label should not be mislabeled, reversed, affixed or missed.

9. Appearance

The visual inspection includes the following aspects:

(1) Confirm that the product is complete

1) Whether the model has cracks and is disconnected;

2) Whether the core is damaged;

3) Whether the tape is punctured;

4) Is the casing damaged or not too short;

5) Whether to cut the wrong foot.

(2) remove dirt

1) After the impregnation, there should be no residual glue (solid insulation paint) around the core of the transformer to prevent the transformer from flattening on the PCB (printed circuit board), or it cannot be flattened when the label is attached;

2) Remove copper slag dross.

(3) The horizontal core should not be inclined after impregnating the insulating varnish (the wire package should not exceed the skeleton).

(4) The PCB has a transformer marked with three points (STAND-OFF), which allows three points to be flat on the PCB when inserted into the PCB.

(5) The iron core must not be loose.

(6) The feet shall be vertical and smooth, and shall not be loose or broken, and shall not have nicks.

(7) The pin must not be bent or dew-oxidized. The interval (PITCH) is based on the specified or actual PC board on the drawing. The length of the lead of the frame is subject to the specifications on the drawing.

(8) Check if the solder is complete.

(9) Check if the label is correct, whether it is mislabeled, reversed or missing.

(10) Check whether the check is clear, whether the position is correct, whether there is a wrong, reverse or missed.

(11) Defective products must be repaired and cannot be repaired before they can be scrapped.

(12) Tape repair: If the outermost tape is damaged and the coil is exposed, it must be covered with tape to completely cover the damaged place, and the layer of tape should be the same as the layer of the outermost tape specified in the original, and coated with insulation. After the paint is baked, it can be dried. The tape of the attached tape shall extend into the two sides of the core, and the length of the tape extending into the sides of the core shall not exceed the thickness of the core. (The tape extends at least 2/3 core thickness).

 10. Electrical testing

Electrical testing mainly includes the following three aspects:

(1) Inductance test: Test the inductance of the main coil. When testing semi-finished products, the range of inductance values must be appropriately reduced.

(2) lap test: test the number of laps of the product, the phase is the same name end and the different name end.

(3) High voltage test.