CN201066955Y - A flexible printed line board - Google Patents

Abstract

The utility model discloses a flexible printed circuit board, which includes a cover film, a flexible circuit, a gold finger, and a reinforcing plate. The cover film covers the flexible circuit, and the gold finger is carried on the end of the cover film and connected connected, the reinforcing plate is attached to the back of the end of the covering film carrying the golden finger; the outer edge of the end of the covering film is located within the range of the reinforcing plate. Due to the adoption of the above scheme, there is a certain distance between the end of the plating lead of the flexible printed circuit board and the edge of the reinforcing plate, and the supporting function of the reinforcing plate is not affected at all; during use, because the plating lead has shrinkage treatment , its end will not directly touch the friction connector or other external objects, thus avoiding the situation of being lifted by friction or falling metal debris and causing a short circuit of the gold finger, effectively improving the reliability of the connection and the FPC itself service life.

Description

A flexible printed circuit board

【Technical field】

The utility model relates to a flexible printed circuit board.

【Background technique】

The development and wide application of flexible printed circuit boards (FPC) is due to its significant advantages, such as its flexible structure, small size and light weight (composed of thin films). In addition to static flexing, it can also be dynamically flexed, curled and folded. It can expand to three-dimensional space, which improves the freedom and flexibility of circuit design and mechanical structure design. It can be wired on X, Y, and Z planes, reducing interface connection points, which not only reduces the workload of the whole machine and assembly errors, It also greatly improves the reliability and stability of the entire system of the electronic equipment. Flexible printed boards are used in a wide range of fields, such as computers, communications, instrumentation, medical equipment, military and aerospace. As a part of electronic equipment, the flexible printed circuit board must be connected with other parts or the main circuit board to play its role. There are usually two ways in the form of connection: one is welding, that is, soldering the pads on the flexible printed circuit board to other circuit boards or electronic components through solder paste welding or ACF pressure welding; One is plug-in, that is, finger-shaped pads are made on the edge of the flexible printed circuit board, and after gold-plated treatment, they become gold fingers, which can be directly inserted into the connector of another circuit board to achieve conduction, similar to this The network card board and display card board with plug-in function in the personal computer are connected with the circuit of the main board by inserting the golden finger into the card slot on the main board.

Different from the golden finger card in the rigid printed circuit board, because the material of the flexible printed circuit board itself is soft and its mechanical strength is low, it cannot be directly inserted into the connector. As shown in Figure 1, a hard The reinforcing plate 1 is attached to the back of the gold finger as an auxiliary layer to increase the mechanical strength of the gold finger, so as to better realize the plug-in function.

The production process of this kind of flexible printed circuit board with gold fingers is: copper foil cutting → CNC drilling → black hole → copper plating → dry film → exposure → development → etching → film peeling → double-sided covering Film→hot pressing cover film→gold-plated pad→printing text→attach reinforcement board→press reinforcement board→punching product shape, after punching the shape, the gold finger and the reinforcement board on its back are punched out at one time, and the gold finger can be realized plug-in function. There is a certain distance between the gold finger 2 and the shape of the product, as shown in Figure 2, where the FPC pads are plated with gold during processing. To the edge of the entire product and connected to the positive and negative poles of the electroplating tank. When the electroplating lead 3 is cut off together with the shape, the end of the lead is flush with the reinforcing plate, and the electroplating lead 3 with a length W of about 0.3mm is left. The finished flexible printed circuit board is shown in Figure 3. If the product is plugged and pulled out many times during the assembly process, the electroplated lead at the end will repeat the plugging and pulling action several times during the trial assembly process. Due to the tight bayonet of the connector, the front end of the golden finger will Touching the edge of the card slot of the connector, that is to say, the end of the plating lead will touch the edge of the card slot, and will be lifted or even dropped due to friction. If these metal debris fall between the gold finger pads, the gold finger will be damaged. Short circuit and burn out the whole electronics.

【Content of invention】

The main purpose of the utility model is to provide a flexible printed circuit board which can effectively improve the connection reliability and service life.

In order to achieve the above purpose, the utility model proposes a flexible printed circuit board, including a cover film, a flexible circuit, a gold finger, and a reinforcing plate. The cover film covers the flexible circuit, and the gold finger is carried on the cover The end of the film is connected to the flexible circuit, and the reinforcing plate is attached to the back of the end of the covering film carrying the golden finger; the outer edge of the end of the covering film is located within the range of the reinforcing plate, There is a certain distance from the outer edge of the reinforcing plate. .

Or a flexible printed circuit board, including a cover film, a flexible circuit, and a reinforcing plate; the cover film covers the flexible circuit, and a gold finger is provided at the end of the flexible circuit exposed to the cover film, so The electroplating lead for electroplating is extended from the end of the gold finger; the reinforcing plate is attached to the back of the cover film provided with the gold finger; the end of the electroplating lead is retracted, located within the range of the reinforcing plate, and There is a certain distance between the outer edges of the reinforcing plates.

In the above flexible printed circuit board, the length of the electroplating lead is less than the distance from the end of the electroplating lead to the outer edge of the reinforcing plate.

The length of the electroplating lead is less than or equal to 0.1 mm.

The distance between the end of the electroplating lead wire and the outer edge of the reinforcing plate is greater than or equal to 0.2 mm.

Due to the adoption of the above scheme, there is a certain distance between the end of the plating lead of the flexible printed circuit board and the edge of the reinforcing plate, and the supporting function of the reinforcing plate is not affected at all; , its end will not directly touch the friction connector or other external objects, thus avoiding the situation of being lifted by friction or falling metal debris and causing a short circuit of the gold finger, effectively improving the reliability of the connection and the FPC itself service life.

【Description of drawings】

Figure 1: Schematic diagram of the back structure of a flexible printed circuit board with plug-in function.

Fig. 2: A schematic diagram of the front structure of a flexible printed circuit board in the prior art.

Figure 3: Schematic diagram of gold fingers and product appearance of a flexible printed circuit board in the prior art.

Fig. 4: A schematic diagram of punching off the electroplating lead in the embodiment of the present invention.

Figure 5: Schematic diagram of the gold finger and the product appearance of the embodiment of the utility model.

【Detailed ways】

The utility model will be described in further detail below through specific embodiments in conjunction with the accompanying drawings.

The flexible printed circuit board in this example is produced according to the following process: copper foil cutting → CNC drilling → black hole → copper plating → dry film pressing → exposure → development → etching → peeling film → covering film on both sides → hot pressing covering Film→gold plating on the pad→printing text→punching and electroplating leads→attaching the reinforcing plate→pressing the reinforcing plate→punching the product shape, and the product is assembled on the connector for testing. Among them, after the electroplating lead is punched, the distance between the end of the electroplating lead and the outer edge of the final shape of the product is greater than or equal to 0.2mm, which can fully guarantee that the end of the electroplating lead will not touch the connector during use.

As shown in accompanying drawings 4 and 5, the flexible printed circuit board of this example includes a cover film 4, a flexible circuit, a gold finger 2, and a reinforcing plate 1, the cover film 4 covers the flexible circuit, and the gold finger is carried on the cover film 4 ends, one end of the gold finger 2 is connected to the flexible circuit, and the other end extends the electroplating lead 3; before the reinforcing plate 1 is attached, the lead area 5 is first punched in this example, and the punched position is relative to the final shape of the product. One shrinkage treatment, after punching, the outer edge of the cover film end, the end of the electroplating lead 3 and the final shape of the product are not flush, there is a distance W1 greater than or equal to 0.2mm, and the length W2 of the electroplating lead 3 itself is less than or equal to 0.1mm. After punching the electroplating lead wire 3, paste the reinforcing plate 1, press the reinforcing plate, and finally punch out the shape of the reinforcing plate when punching the product shape. At this time, the reinforcing plate is consistent with the final shape of the finished product, and the covering film end There is a certain distance between the outer edge of the part, the end of the electroplating lead wire 3 and the edge of the reinforcing plate 1, and the supporting effect of the reinforcing plate is not affected at all. During use, because the electroplating lead is retracted, its end will not touch external objects, thus avoiding the situation of being lifted by friction and causing a short circuit, effectively improving the reliability of electronic equipment and the reliability of FPC itself. service life.

Comparative example:

A double-sided flexible printed circuit board, according to the production process of the utility model is as follows: double-sided copper foil cutting → CNC drilling → black hole → copper plating → dry film pressing → exposure → development → etching → stripping → Covering film on both sides → hot pressing covering film → gold plating on pads → printing text → punching electroplating leads → pasting reinforcement board → pressing reinforcement board → punching product shape, product assembly test. Take the connector for a plug-in test, record the results, and detect whether there is a short circuit. The results are shown in Figure 1.

Also make this double-sided flexible printed circuit board, if according to the previous practice, the production process is as follows: copper foil cutting → CNC drilling → black hole → copper plating → dry film pressing → exposure → development → etching → stripping Film→covering film on both sides→hot-pressing covering film→gold-plated pads→printing text→attaching reinforcement board→pressing reinforcement board→punching the product shape, taking the connector for plug-in test, recording the result, and detecting whether there is a short circuit. The results are shown in Figure 1.

Schedule 1

project  Number of Tested Products Insertion times short circuit ratio Technological process of the present utility model 100 400 0% Process flow of prior art 100 400 5%

Claims (5)

1. A flexible printed circuit board, comprising a cover film, a flexible circuit, a gold finger, and a reinforcing plate, the cover film covers the flexible circuit, the gold finger is carried on the end of the cover film, and is connected with the The flexible circuit is connected, and the reinforcing plate is attached to the back of the end of the covering film carrying the golden finger; the feature is that: the outer edge of the end of the covering film is located within the range of the reinforcing plate, and the There is a certain distance between the outer edges of the reinforcing plates. 2. A flexible printed circuit board, comprising a cover film, a flexible circuit, and a reinforcing plate; the cover film covers the flexible circuit, and gold fingers are provided at the end of the flexible circuit exposed to the cover film, The electroplating lead for electroplating is extended from the end of the gold finger; the reinforcing plate is attached to the back of the covering film provided with the gold finger; the feature is that: the end of the electroplating lead retracts and is located on the reinforcing plate Within the range, there is a certain distance from the outer edge of the reinforcing plate. 3. The flexible printed circuit board according to claim 1 or 2, wherein the length of the electroplating lead is shorter than the distance from the end of the electroplating lead to the outer edge of the reinforcing plate. 4. The flexible printed circuit board according to claim 3, wherein the length of the plating lead is less than or equal to 0.1 mm. 5 . The flexible printed circuit board according to claim 3 , wherein the distance from the end of the plating lead to the outer edge of the reinforcing plate is greater than or equal to 0.2 mm. 5 .

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