Huizhou double-sided flexible circuit board manufacturing process full solution process

Flexible circuit board - double - sided flexible circuit board manufacturing process  

Flexible circuit board in addition to some materials, flexible circuit board materials are basically rolled.  Because not all processes must be processed with the coil process, some processes must be cut into sheets to process, such as double-sided flexible circuit board metallized hole drilling, currently can only be drilled in sheet form, so the first process of double-sided flexible circuit board is cutting.  

Flexible copper-clad laminates are easy to be injured due to their poor bearing capacity to external forces.  If the material is damaged during opening, it will have a serious impact on the pass rate of subsequent processes.  Therefore, even if it appears to be very simple material, in order to ensure the quality of the material, it must be given enough attention.  If the amount is relatively small, you can use manual shears or hob cutters, large quantities, available automatic shears.  

Whether it is single side, double side copper foil laminate or covering film, the precision of cutting size can reach ± o.33.  High reliability of opening material, open good materials automatically neatly stacked, in the exit does not need personnel to collect material.  Can control the damage to the material in the minimum, using the change of the size of the feeding roller, the material almost no wrinkle, scar.  And the latest device can also roll tape etching process after the flexible circuit board for automatic cutting, the use of optical sensors can detect corrosion positioning graphics, automatic opening positioning, opening accuracy up to O. 3mm, but not the opening frame as the next process positioning.  

Flexible circuit board drilling through hole - manufacturing process of double-sided flexible circuit board  

The through holes of the flexible circuit board can also be drilled by NUMERICAL control as well as the rigid printed board, but it is not suitable for hole machining of circuits with double-sided metallized holes.  With the high density of the circuit graphics and the small aperture of the metallized hole, plus the aperture of nc drilling has a certain limit, now many new drilling technology has paid the practical application.  These new drilling techniques include plasma etching hole, laser drilling, punching hole, chemical etching hole, etc. These drilling techniques are easier to meet the requirements of the winding process than CNC drilling.  

The through holes of the flexible circuit board can also be drilled by NUMERICAL control as well as the rigid printed board, but it is not suitable for hole machining of circuits with double-sided metallized holes.  With the high density of the circuit graphics and the small aperture of the metallized hole, plus the aperture of nc drilling has a certain limit, now many new drilling technology has paid the practical application.  These new drilling techniques include plasma etching hole, laser drilling, micro-aperture punching, chemical etching hole, etc. These drilling techniques are easier to meet the hole formation requirements of the winding process than CNC drilling.  

1.  Nc drilling  

Double-sided flexible circuit board through the drilling is still most of the CNC drilling machine drilling, CNC drilling machine and flexible circuit board use basically the same, but the drilling conditions are different.  Because the flexible circuit board is very thin, it can put many pieces of overlapping drilling, if the drilling conditions are good, 10 ~ 15 pieces can be overlapped together for drilling.  The backing plate and cover plate can use paper based phenolic laminate or glass fiber cloth epoxy laminate, and also can use 0.2 ~ 0.4mm thick aluminum plate.  Drills for FPC boards are available on the market, drills for drilling rigid printed boards and milling cutters for contour milling can also be used for flexible boards.  

 Drilling, milling cover film, and reinforcement plate profiles are basically the same, but due to the softness of the adhesive used by the flexible PRINTED board material, it is very easy to adhere to the bit, requiring frequent testing of the bit condition and increasing the bit speed.  For multi-layer flexible circuit board or double-layer flexible circuit board drilling should be particularly careful.  

 2.  punching  

Microaperture punching is not a new technology and has been used for mass production.  Because the winding process is continuous production, there are many examples of using punching to process the winding through hole.  But batch punching technology is limited to blunt o. diameter 6 ~ 0.8 mm hole, compared with nc drilling machine drilling processing cycle is long and need manual operation, due to the large size of original process, the punching mould accordingly, so the mold price is very expensive, although mass production to reduce the cost advantage, but the burden of equipment depreciation,  Small volume production and flexibility cannot compete with CNC drilling, so it is still not popular.  

But in recent years, the precision of punching technology and CNC drilling have made great progress, punching in the practical application of flexible circuit board has been very feasible.  The latest mold manufacturing technology can produce a hole with a diameter of 75um that can punch and cut the base material 25um thick non-adhesive adhesion-type copper clad foil laminate. The reliability of punching is also quite high. If the punching conditions are suitable, it can even punch holes with a diameter of 50um.  Punching device has also been CNC, mold can be miniaturized, so it can be well applied to the flexible circuit board punching, CNC drilling and punching can not be used for blind hole processing.  

3.  Laser drilling  

With laser can drill the most fine through hole, for flexible circuit board drilling through hole laser drilling machine has excited excimer laser drill, impact carbon dioxide laser drill, YAG(yttrium aluminum garnet) laser drill, argon laser drill.  

Impact type carbon dioxide laser drill only can carry on the drilling to the base material of insulation layer, and YAG laser drill insulating layer of the base material and copper foil for drilling, drilling and the speed of the insulating layer significantly faster than the speed of drilling and copper foil, in just the same kind of laser drilling machine for all drilling could not have a high production efficiency.  Copper foil is etched first to form a pattern of holes, then the insulation is removed to create a through-hole, so that lasers can drill holes of extremely small sizes.  However, due to the position accuracy of upper and lower holes, the hole diameter may be restricted.  If the blind hole is drilled, as long as the copper foil etching off one side, there is no up and down position accuracy problem.  The process is similar to the plasma and chemical etching holes described below.  

At present, the holes processed by excimer laser are the smallest.  Excited excimer laser is ultraviolet light, directly destroy the structure of the base layer resin, so that the resin molecules dispersed, the heat generated is very small, so you can limit the damage degree of heat around the hole to the minimum range, the hole wall is smooth and vertical.  If the laser beam could be shrunk further, it would be possible to process holes between 10 and 20 μ m in diameter.  Of course, the larger the plate thickness aperture ratio, the more difficult the wet copper plating.  The problem with stimulated excimer laser drilling is that the breakdown of polymers results in carbon black sticking to the hole wall, so some means must be taken to clean the surface to remove the carbon black prior to plating.  However, when laser processing blind holes, there are also some problems in laser uniformity, which will produce bamboo-like residues.  

The biggest difficulty of excimer laser is slow drilling speed and high processing cost.  Therefore, it is limited to the processing of small holes with high precision and high reliability.  

Impact type carbon dioxide laser is generally used carbon dioxide gas as laser source, radiation is infrared, and excited excimer laser combustion decomposition resin molecules due to thermal effect is different, it belongs to thermal decomposition, processing hole shape is much worse than the excited excimer laser, can be processed aperture is basically 70 ~ 100um,  But the processing speed is significantly faster than the excited excimer laser speed, and the cost of drilling is much lower.  Even so, the processing cost is much higher than plasma etching hole method and chemical etching hole method described below, especially if there are many holes per unit area.  

It should be noted that when processing blind holes, the laser can only be fired to the surface of the copper foil, and the organic matter on the surface need not be removed at all. In order to stably clean the copper surface, chemical etching or plasma etching should be used as post-processing.  Considering from the possibility of technology, laser drilling process is basically no difficulty in winding process, but considering the balance of the process and the proportion of equipment investment, it is not dominant, but the width of the Tape chip Automated welding process (TAB, Tape Automated Bonding) is narrow,  Practical examples have been made of the use of a winding process to increase the rate of drilling.  

Flexible circuit board manufacturing process product drawing  

Hole metallization - manufacturing process of double-sided flexible circuit board  

The hole metallization of flexible circuit board is basically the same as the hole metal process of rigid printed board.  

In recent years, instead of electroless plating, direct electroplating has been used to form carbon conductive layer.  Hole metallization of flexible circuit boards also introduces this technique.  

Flexible circuit board because of its softness, the need to have a special fixture, fixture can not only fix the flexible printed board, but also must be stable in the plating solution, otherwise the thickness of copper plating is not uniform, which is also an important cause of wire breaking and bridging in the etching process.  To achieve uniform copper plating, the flexible PCB must be taut in the fixture, and the position and shape of the electrodes must be worked out.  

Hole metalization outsourcing processing, as far as possible to avoid outsourcing to no flexible printed board perforation experience of the factory, if there is no flexible circuit board special plating line, the quality of perforation is not guaranteed.  

Copper foil surface cleaning - flexible circuit board manufacturing process  

In order to improve the adhesion of the resist mask, the surface of the copper foil should be cleaned before coating the resist mask. Even this simple process requires special attention for the flexible circuit board.  

Flexible circuit board cleaning generally has chemical cleaning process and mechanical grinding process, for the manufacture of precision graphics, most occasions are to combine the two clean flow process for surface treatment.  Mechanical grinding using brush method, brush material too hard will cause damage to the copper foil, too soft and insufficient grinding.  Nylon brush is generally used, and the length and hardness of the brush must be carefully studied.  Use two brush rollers, placed on the conveyor belt, the direction of rotation is opposite to the direction of belt transmission, but at this time if the brush roller pressure is too large, the substrate will be stretched by a great tension, which is one of the important reasons for the size change.  

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