Treatment Methods for Broken Flexible Flat Cables

In products such as liquid crystal color TVs, mobile phones, notebook computers, and cameras, flexible flat cables are widely used for signal transmission.

The surface layer of such flexible flat cables is a plastic film with relatively high toughness, and there are multiple very thin metal strips arranged in the middle, as shown in the figure. Since some flexible flat cables are located in positions that are frequently moved, they are prone to breakage over time. If there is no new cable available for replacement, the following methods can be adopted.

Step 1: Locate the break point. First, observe the structures at both ends of the cable and the fixing method of the plug, and then carefully separate the plug of the flexible flat cable from the motherboard and gently pull out the cable, as shown in the figure. During this operation, it is necessary to observe carefully first and determine the removal method. Do not act rashly to avoid serious damage to the flexible flat cable or the plug.

Next, use the observation method to find the break point, that is, use the naked eye to see where there are obvious creases on the cable. The broken parts are all caused by creases. If it is difficult to see clearly with the naked eye, you can use a high-power magnifying glass and place the flexible flat cable under strong light to search. Since most flexible flat cables are relatively thin, under the illumination of strong light, the break point can generally be clearly seen. To ensure the accuracy of the found break point, a digital multimeter can be used for "confirmation" at this time. Since the tips of the test leads of ordinary multimeters are too thick, it is recommended to fix a sewing needle on the tip of the test lead and set the multimeter to the 200Ω resistance range.

Step 2: Deal with the break point. After finding the break point, use a blade to gently scrape off the film on the surface of the break point. Since the flexible flat cable is too thin and too fine, this operation must be carried out carefully and the strength should be moderate. The metal wire should be exposed with a metallic luster as the standard. Do not break the thin cable, and do not scrape a hole in the cable.

Step 3: Soldering. First, use a blade to scrape a little rosin powder and sprinkle it on the scraped cable, as shown in the figure. Then, after the soldering iron reaches the normal temperature, unplug the power plug of the soldering iron (this step is to prevent the static electricity of the ordinary soldering iron from damaging the motherboard). Utilize the residual heat, dip a little solder on the tip of the soldering iron slightly, and then quickly solder the break point.

During this step, the soldering time must be short, otherwise the cable is easily burned by the heat. If one soldering is not enough, it can be repeated several times until it is detected by the multimeter that the circuit is connected.

Step 4: Reinforcement. After the break point is soldered, evenly apply a layer of 703 silicone rubber on the front and back sides of the solder joint and the crease, as shown in the figure. After the applied 703 silicone rubber dries naturally (about one or two hours), apply it one or two more times. Wait until the silicone rubber is completely dried again before installing and testing the device.

Since the 703 silicone rubber has elasticity after drying, such treatment can not only play the role of fixing the solder joint but also protect the flexible flat cable at the crease and avoid it from breaking again.