Views: 0 Author: Site Editor Publish Time: 2024-06-28 Origin: Site
Flexible Printed Circuit Board (Flexible Printed Circuit abbreviated as FPC), also known as flexible circuit boards, flexible circuit boards, is made of polyimide or polyester film as a substrate with a high degree of reliability, excellent flexible printed circuit boards. It is characterized by high wiring density, light weight, thin thickness, and good bendability.
1. FPC Selection Points
A. Selection of Side Keys/Keys
Side keys choose 18/12.5 double-sided electrolytic copper (except for special), the main keys choose 18/12.5 double-sided electrolytic copper (except for special). Side keys, the main key in the bending of no special requirements, welded to the motherboard above the fixed line, but must ensure that the bending back and forth more than 8 times without exception before use. The thickness of the keys have strict requirements, otherwise it will affect the feel of the keys, so we must meet the customer's total thickness requirements.
B. Selection of connecting cables
Connecting wire selection 18/12.5 double-sided electrolytic copper (except for special). The main role is to play a role in connecting, there is no special requirements for bending requirements. Welding at both ends can be fixed, but must ensure that the bending back and forth more than 8 times without exception before use.
C. Selection of materials for slipcovers
Choose 1/30Z single sided non-adhesive electrolytic copper for double sided slider, the material is soft and ductile; choose 1/30Z double sided non-adhesive electrolytic copper for double sided slider, the material is soft and ductile. 1/30Z double sided non-adhesive electrolytic copper for slider, the life span of double sided slider will be better than 1/30Z single sided non-adhesive electrolytic copper for double sided slider. If there is no structural problem, it is recommended to design the FPC as a double-sided slider as much as possible. Cost, the use of 1/30Z double sided electroless copper, than the use of 1/30Z single sided electroless copper main material cost increase of about 30%, but the use of this material production yield will be improved, the test life can also be improved to ensure that the use of this type of board stability.
D. Selection of materials for multilayer boards
Multilayer boards are made of 1/30Z unglued electrolytic copper, which is soft and malleable. With no structural problems, the flip-flops are made to pass the test.
E. Selection of auxiliary materials
Adhesive paper selection, ordinary board does not require SMT can be used without high temperature resistance of the adhesive paper (such as the side keypad class), the need for SMT must be selected high temperature resistance of the adhesive paper (such as the keypad are required to SMT).
F. Selection of conductive materials
Conductive adhesive paper selection, ordinary conductive adhesive for conductivity requirements are not high (such as ordinary keypad class), conductive performance is better for conductive performance requirements are high and must use adhesive paper class (such as special keypad, etc.), but this adhesive paper is not recommended in general, because the price is too high.
Conductive cloth can be conductive, but the viscosity is not ideal, generally applicable to keypad class.
Conductive pure adhesive is a high-intensity conductive substances, generally used to paste steel, but it is not recommended to use this conductive pure adhesive, because the price is too high.
2. FPC Design Points of Attention
A. Gold surface reinforcement, silver paste conductive material
The gold side of the reinforcement using pure adhesive lamination, reinforcement and pure adhesive are drilled, and then drop silver paste from the holes to make the board and the reinforcement of good grounding, the resistance value of this method is close to 0 ohms. Currently for the more ideal production method, the scope of use is mainly with the connector of the multilayer board (grounding requirements) and other requirements and grounding requirements with the connector of the various types of boards.
B. Selection of reinforcement
PI reinforcement is suitable for plug boards with pull-out fingers. Such boards must use PI reinforcement, other types of boards and other positions except the plug position is not recommended to use PI reinforcement, the material is not strong enough and the price is higher.
FR-4 reinforcement is suitable for most of the boards such as keys, side keys, etc., but this reinforcement should be pressed with pure glue in order to play a better role in reinforcement.
Steel reinforcement is suitable for multilayer boards with connectors and single and double-sided boards. The hardness of this reinforcement is relatively high, and the boards produced are relatively flat, and the SMT is also better operated. It is recommended that all types of boards with connectors can use steel reinforcement (except for those that need to be grounded with gold reinforcement).
C. Design of perforations
The over-hole must not be designed in the bending area, or it will not pass the test.
D. Electromagnetic film grounding hole design
The grounding hole of the electromagnetic film must not be designed in the bending and sliding area, or it will seriously affect the bending and sliding life of the FPC.
E. Text design
Text should not be designed in the bending and sliding area, otherwise it will seriously affect the bending and sliding life of the FPC.
F. Pure adhesive window for flip and slide panels
Pure rubber openings should be located as close as possible to the ends of the bending and sliding areas to ensure the longevity of this product.
3. FPC Circuit Design
A. Keypad Hole Design
The hole in the center of the key should be moved to the edge, not in the center of the key, to avoid poor contact of the key in use. The keys are divided into two types: round keys and oval keys, DOME sheet size 3, 4, 5 and 3 × 3, 3 × 4, 4 × 5, FPC keyboard single edge than dome sheet is 0.3mm larger than the keys on the FPC is at least 3.6, 4.6, 5.6 and 3.6 × 3.6, 3.6 × 4.6, 4.6 × 5.6, if the size of the size is not enough to make the appropriate compensation.
B. Placement of perforation design
The over-hole in the bending area should be moved to the non-bending area to avoid hole breakage during bending; the line in the bending area is best in a straight line and thicken the line as much as possible.
C. Standard Compensation for Master Keys
The lamp/resistor/capacitor pads of the master key are to be compensated according to the standard design.
D. Button connection line design
The line width of the key connecting line is minimum 0.2mm, in the intersection with the key to add a smooth transition of the inner drop, so the pads should be added to the inner drop.
E. Key earpiece, microphone pad design
Key handset, microphone pads as a result of the general manual welding, so if the operation is not appropriate, the pad is easy to fall off, so the pads must be increased, so that the package seal pressure (as shown below in green for the package seal open window).
F. Connector elongation design
The connector of the main key is elongated by 0.2mm on one side under the permitted conditions, so that the package seal is pressed, and the connected fingers are modified as much as possible to be connected outside the open window of the package seal, and the grounding fingers are made as big as the standard fingers to avoid connecting tin and affecting the quality of SMT.
G. Side button shrinkage design
If the side buttons have keys to the edge of the board, they should be shrunk by more than 0.15mm to prevent the copper skin of the buttons from flipping over.
H. Side button cable routing design
Side button key faces with wires to the buttons are best moved to the opposite side.
I. Envelope window design requirements
The envelope window should be 0.1mm larger than the pads, and if it can be modified, it should be as large as possible to avoid alignment difficulties. Lamp/capacitor/resistor windows on the main key allow the package to press down on the pads to prevent the pads from falling off (the green color in the following figure is the package window).
J. Pad and pad window design
Pad and pad wired, try not to open the window (except in special circumstances), so as not to cause even tin, affecting the quality of SMT (the following figure green for the package seal open window).
K. Bending design
Keyboard bending is not much, mainly assembly bending, but if the curved area of the part of the design is not appropriate, will also affect the installation and use, the following points need to be considered in the design process: front and back finger window should not be designed in the same straight line, to avoid causing stress concentration, front and back finger window need to be staggered by 0.5mm (soldered to the motherboard on the side of the short side of the tin on the side of the long side), the front of the finger is designed to be jagged, and To add tin leakage holes, tin leakage holes should be staggered.
L. Bending area design
The bending area should be made soft, with the large copper skin made into a mesh or de-coppered and de-encapsulated.
M. Main key grounding design
The grounding location of the main key should be made soft, the front side is made into a grid, the reverse side of the bend area to remove the copper and remove the envelope, but in the grounding place to add the over-hole (as shown below in green for the envelope open window).
4. Design Requirements for Slipcovers
A. Line design and modification
Inside the shape of the right angle should be chamfered to improve the FPC sliding force, sliding area of the line as far as possible to go straight (such as a figure), can not go to the level of straight line should be chamfered (such as b figure), if the line can be compensated for the compensation (the following figure in green for the pure rubber open window).
B. Sliding area design
Slide cover plate over-hole can not be in the sliding area, otherwise it will affect the bendability, over-hole closer to the bending area to move away.
C. Plug board design
For boards with plugs, the targeting holes must be placed on the finger side, IC bits with connectors should be stretched as far as possible and allowed to be pressed down by the package seal, and the tube position at the plug must be placed in the center of the finger.
D. Slide cover area grounding
Slide cover plate generally have shielding design requirements, can use tin aluminum foil and silver paste shielding (some use a separate shielding board, generally used in the flip-flop machine), silver paste in the bending number of times higher, easy to fall off, and thus in the bending number of times required for higher, it is recommended that the use of tin aluminum foil shielding, tin aluminum foil must be grounded, so as to play a shielding effect, tin aluminum foil grounding position as far as possible to do in the two ends of the non-sliding area, if the Can only be grounded in the sliding area, the grounding position should not be done on the outside as far as possible, and the position of the two ends of the tin-aluminum foil should be more than the pure rubber position.
E. Flash plating process requirements
In order to ensure the softness of the sliding area, to avoid copper plating to thicken the copper foil and affect the bending life, in addition to the bending area is not copper-plated, the other areas are copper-plated, but to be larger than the pure rubber window, the joint can not be done in the delamination area, and to do the wave shape, to prevent the concentration of stress (the following figure in yellow for the secondary copper-plated area).
F. Flash Plating Process
Flash plating requires 3 minutes, secondary copper plating to indicate area.
G. Bending area design
The large copper skin in the bending area should be gridded as much as possible, and if there are no lines on the reverse side, go for a wrap-around finish.
H. Line modification and precautions
All right angles within the shape should be chamfered, the area of the bend area should be chamfered and rounded, the line in the bend area should be aligned with straight lines and arcs as much as possible, and when the conditions permit, anti-tear lines should be added, and there should be no overbore in the bend area.
I. Addition of anti-tear lines
The corner area of the profile needs to be protected from tearing by adding ripcord.
J. Pure rubber casement window design
Pure rubber window openings as large as possible, there are grounding corners of the location are generally installed curved area requirements, to do soft. For multi-layer boards, grounding angle should also take into account the grounding copper thickness, too thick to weld.
K. Grounding angle flexibility design
The following figure is a six-layer board grounding angle modification schematic, grounding angle pure rubber area as large as possible, grounding angle copper skin only three layers (top and bottom layer and a layer of the inner layer, the other layer of copper), grounding wire go in the inner layer and add the overbore, the top and bottom of the package to remove, so as to maximize the softness of the grounding angle to ensure that the grounding of the copper at the ground thickness.
L. Connector IC elongation design
Connector IC as far as possible to both sides of the elongation, the package can be pressed to the best, the package in the permissible range to the outside of the wider, in order to facilitate SMT welding, and in the diagonal plus 0.3mm MARK point, the specific approach to refer to the keypad connector practice. Pure rubber drilling holes to paste the soft board (paste pure rubber when the holes on the soft board) holes are all drilled out to prevent pure rubber overflow, affecting the line production. Tin-aluminum foil must be grounded, grounding position as far as possible in the non-bending area, and tin-aluminum foil to cover the non-glue area, tin-aluminum foil from the welding IC package must be more than 0.8mm above the window bit to prevent welding short circuit.
M. Anti-dulling design of two-drill profile for flip-flop
The pin holes of the multi-layer flip-flap plate two-drill data must be made anti-dull treatment, and should be separated from the profile positioning holes.
N. Pure glue window design
Multi-layer flap plate pure glue window from the hole minimum 0.8mm, all drilling can not be drilled into the non-glue area, in the CAM add alignment holes and auxiliary holes must be opened pure glue window.
O. Connector pad design at both ends
For layered boards have to do a test, wrapping/adhesive paper/reinforcement to cover the shape of the tube position holes have to do to make way for the processing, make way for the hole minimum 3.0 (shape positioning holes 2.5). Multi-layer flip-flop board inner line away from the shape as large as possible, generally do more than 0.25mm, the outer layer generally do more than 0.25mm (minimum 0.0.2mm), to prevent the line from rushing to the line. Connector IC ends of the four pads shall be increased, increased to the middle of the pad 1-2 times (on the basis of space permitting), so that the design can prevent the connector in the assembly of the use of shedding.
5. LCD Board Design Requirements
A. Line to enhance the design of solderability
Pressure welding finger end of the front and back window staggered 0.5mm, and the front and back of the package to press the finger to prevent finger breakage and to increase the leakage of tin holes and half-hole, to enhance the weldability.
B. Thin finger elongation design
Fine finger end independent finger to be elongated so that the package seal is pressed more than 0.3mm, the outer end of the shape out 0.5mm, to improve the adhesion of the finger on the board, to prevent flanging in the mold punching.
C. Middle finger encapsulation design
The finger position in the middle of the LCD board should be allowed to be pressed by the package seal for more than 0.3mm.
D. The middle of the pad alignment design
Line on the pad window is generally drilled, and to press the corners of the pad, the pad in the middle of the alignment to be centered (away from the envelope open window distance is equal), the size of the pad to meet the standard requirements, inconsistent with the requirements to be compensated.
E. Thin finger reverse design
The thin finger reverse bend area should be de-wrapped and the thin finger reverse should be left wrapped to strengthen the finger end.
F. Bending area copper skin change grid design
The large copper skin in the bending area is converted to a grid treatment, and the encapsulation is removed from the bending area where the encapsulation of the wireless seed is removed.
G. In-board MARK point design
In order to facilitate SMT, the LCD board requires the addition of MARK points within the board, the size of 1.0mm (encapsulated window 1.5mm) position placed at the ends of the component bits, the location of the following figure size 1.0mm.
H. Plug shape design
There are plugs should pay attention to the plug left and right distance profile to be equal, not equal to be adjusted, and to use the target, the target ring must be done on the side of the plug.
I. Mold requirements
Mold fine fingers and plugs must indicate the location and face, with plugs to indicate the important dimensions, the shape of the mold are required to open the jump die (first punch fine fingers, information to add jump holes), for the location of the reinforcement to indicate the location and face. Liquid crystal boards are required to be shipped in series, the connection point is required to be added in the appropriate location, the reinforcement bit as far as possible not to add the finger bit / plug bit / bending bit / offline or pads closer to the location can not be added.
FPC production flow chart
Dynamic FPC conventional flow analysis of the following chart, the production process of each factory practice is basically the same, but in order to enhance the performance of dynamic FPC, the company mainly through the process as above, black holes instead of copper + thin copper, plasma instead of chemical de-gumming, to make a precise fine line; and in the selection of materials and equipment performance and process breakthroughs.
RUOMEI has rich experience in FPC manufacturing and production, with high and reliable shipment quality. RUOMEI is able to provide soft boards up to 12 layers, so that RUOMEI can better satisfy diversified needs of customers.
