What is the main point of FPC fake stickers, hot pressing and screen printing processes

Fake post

Fake sticky protective film, strong board and back glue; the protective film mainly has the functions of insulating, protecting the circuit against soldering, and increasing the flexibility of the soft board; the strong board is mainly to improve the mechanical strength and guide the insertion of the FPC terminal The role of the connector; the adhesive mainly plays the role of fixing.

Working procedure:

1. Prepare tools, determine the semi-finished product number to be faked, and prepare the real coverlay semi-finished product.

2. Tear off the release paper of the Coverlay.

3. The copper foil should not be oxidized. Check and clean the copper foil: brush the surface lightly with a brush to remove dander or impurities.

4. Align the correct coverlay according to the work instructions and the correct coverlay according to the work instructions and the position and regulations of the inspection standard card, and fix it with an electric iron.

5. The semi-finished products after fake paste should be sent to the hot pressing station as soon as 

possible to avoid oxidation. Quality control focus:

1. It is required that the work instruction and inspection standard card's physical control coverlay exposure and drilling position are completely correct.

2. The exact offset of the coverlay alignment of the welding and outlet ends should not exceed the requirements of the work instruction and inspection standard card.

3. Those who need to be electroplated with tin or nickel-gold must leave a plating bite, generally 5cm.

4. There should be no oxidation on the copper foil, no burrs on the exposed edges of the coverlay, and no impurities remaining in the coverlay.

5. Perform quality inspection.

6. Do not put work tools on the wrench, otherwise it may cause scratches or crushes.

Visual inspection:

1. The copper foil cannot be oxidized.

2. There should be no burrs on the exposed edges of the coverlay and on the reinforced edges.

3. There should be no impurities in the coverlay and paving.

3. There should be no leakage of the paving.

4. For products operated by machines, it is necessary to check that there are no air bubbles, poor fit, or combination displacement.

Hot pressing

The hot pressing operation includes several steps such as traditional pressing, cold pressing, rapid pressing, and B-baking; the purpose of hot pressing is to make the protective film or plywood completely adhere to the wrench, which can be divided into pressure sensitive according to its curing method Adhesives and thermosetting adhesives can achieve good adhesion through the control of temperature, pressure, lamination time, stacking and combination of auxiliary materials, etc., and minimize pressure injuries, bubbles, wrinkles, overflows in the operation. For defects such as glue and wire breakage, it can be divided into single-sided pressing method and double-sided pressing method according to the combination of auxiliary materials.

One, quick press:

1. Combination method: single-sided pressing and double-sided pressing, generally single-sided pressing is commonly used.

2. The auxiliary materials used and their functions

(1) Fiberglass cloth: isolation, release

(2) Neflon: dustproof, anti-pressure injury

(3) Burning iron plate: heating, gas

2. Traditional pressure:

1. Combination method: single-sided pressing and double-sided pressing

2. The auxiliary materials used are extremely useful:

(1) Talc: reduce stickiness and prevent wrinkles

(2) T.P.X: isolation, dust prevention, impurity prevention

(3) Cardboard: buffer pressure

(4) Aluminum alloy plate: Flatness

3. Important work

Parameters: temperature, pressure, typesetting method, pressing time four, common faults and extremely probable causes:

1. Bubble:

(1) Auxiliary materials such as silicone film and cardboard are unusable

(2) The steel plate is not flat

(3) The protective film has expired

(4) The parameter setting is wrong, such as the pressure is too high and the preloading time is too short.

(5) Typesetting is wrong

2. Crushing:

(1) The auxiliary materials are not clean

(2) T.P.X placement problem

(3) The placement of glass fiber cloth

3. Reinforcing plate displacement

(1) Instantaneous pressure is too large

(2) The reinforcement is too thick

(3) Reinforcing the fake sticker is not strong (the grinding quality is not good)

4. Glue overflow:

(1) Insufficient adhesive resistance of auxiliary materials

(3) The protective film has serious burrs

(4) The parameters and their layout are wrong, for example, the quick pressure is too large.

5. The total pitch is bad:

(1) The pressing method is wrong

(2) The calculation of the shrinkage rate is wrong. 5. Quality confirmation:

1. After pressing, it must be flat, and there should be no wrinkles, pressure injuries, air bubbles, curling and other phenomena.

2. The line should not be pulled and broken due to the influence of pressing.

3. The Coverlay or the plywood must be completely sealed, and it should not be peeled off when peeled off by hand.

Screen printing

 1.the basic principle of screen printing:

 Using polyester or stainless steel mesh as a carrier, the pattern of positive and negative films is transferred to the mesh in direct latex or indirect plate mode to form a mesh, which is used as a tool for printing on the opposite side.

 2. Classification of inks used in printing and their functions:

 Solder mask ink----insulation, protection circuit

 Text-------mark line mark, etc.

 Silver paste-------anti-electromagnetic interference

 Peelable glue ------ anti-plating

 Acid resistance--------filling, corrosion inhibitor

3. quality confirmation

1. The position and direction of the printing must be consistent with the actual object on the work instruction and inspection standard card.

2. There should be no dizziness, fixed disconnection, or pinholes.

3. Generally, the overprint mark should be aligned with +0.5mm/-0.5mm. If there are special screen printing requirements on the work instruction and inspection standard card, it is better.

4. After conveying the heat drying degree, it should be tested with 3M tape, and there should be no ink falling off.

Note: The temperature of the conveying hot baking should be suitable to avoid melting of the tin and lead of some shiny tin and lead semi-finished products.

SMT

Principle understanding:

SMT is surface mount technology, which is a process of flat welding parts on the surface of the circuit board, so that the pads on the board surface and the end of the parts are combined with solder. The main conditions for good welding: a. To ensure good solderability of the metal surface and the matching conditions required for good welding

b. Select the appropriate flux

c. Correct solder alloy composition

d. Sufficient heat and suitable heating curve. Common adverse phenomena:

1.conn: The parts are deformed, the feet are crooked, and the solder resist crawls away.

2.FPC: Bubble, crush, wrinkle, printed layer peeling, mis-soldered parts.

3. Soldering pads: short circuit, air soldering, cold soldering, tin penetration, tin tip, tin more, wrap soldering, separation

4.other: tin bead, tin slag, sticky solder resist, crumb residue.