As the miniaturization of electronic components and patch, the fuse has been towards a small patch, patch fuse is getting more and more widely used, they are on the computer and peripheral interface, flat screen TV, mobile phone, automobile electronic circuit and battery pack, etc of the over-current protection has. In addition to the common fuse type fuse, in recent years, the rise of PPTC self-compound fuse (thermal resistance of polymer positive temperature coefficient) has brought new situation to the protection of IT equipment. There is no unified calibration method for the patch fuse, which is the same as the chip ii, triode, and chip IC, so the code used by each manufacturer is different. Sometimes even the same code (in different series) is used to represent different rated currents. Even more strange code, even the identification of the difficulty, the maintenance of the replacement of a lot of trouble. This paper enumerates the general identification methods of patch fuse in the industry and the identification method of large capacity electronic patch fuse, so as to meet the needs of maintenance substitution. It is hoped that readers will gradually accumulate the method to identify the patch type insurance and improve their ability in practice.

Commonly used fuse type patch fuse identification.

Type fuse SMD fuse (SMD fuse) and commonly used fuse function basically the same, it down in the rated electric circuit (normal) can work normally, when circuit fails to reach or exceed the fusing current value fusing, this can avoid the fault further, so as to protect the circuit. Fuse (fuse) is divided into: according to the fusing speed slow fuse (TT) is commonly used in, and slow the fuse (T in general), medium (M) is commonly used in fuse, fast fuse F in (a) and the fast fuse (FF) is commonly used in five types. The maximum breaking current can be divided into two types: low breaking type (L) and high scoring (H). According to whether self-recovery is divided into one-time patch current fuse and patch self-restoring fuse. Fusing marking method of the patch fuses can generally be divided into direct marking method, two kinds of labeling law and code, the code marking method and can be subdivided into the letter (or number) labeling method and graphic marking method.

1. Direct labeling

Patch fuse, the main characteristic parameters are directly marked on the front of the element, known as the direct labeling method. The direct standard method is generally used for the "square head" porcelain tube insurance and cuboid plastic cover insurance. Figure 1 is a SMD1812 products, standard size is 4.572 * 3.048 mm, slightly bigger printing code in two lines, the first line of the symbol "R" as the manufacturer the large electronics factory, the second line 300 is rated current, on behalf of the rated current of 3 a. FIG. 2 is A product of SMD1210, with A standard size of 3.048*2.54mm, and R represents the manufacturer's large capacity, and 3 represents the current of 0.3A, because the surface area is small, so the printing code is in the same line. Figure 3 is an SMD0603 product with A smaller volume, with A single digit 1, representing 0.1A, and so on.

2. code labeling

Code labeling is generally applicable to small size patches. Due to limit of the surface of components, the inconvenience using standard method, only in a component on the front of one or a few simple symbols (letters, Numbers, or geometry), code labeling law is divided into the letter (or number) method and graphical notation. The new product that the big capacity is about to launch is a one-time patch fuse is to use letter labeling method.

The letter (or number) indicates that the element is printed with only one capital letter, and the corresponding relationship between the letter (code) and the rated current is shown in the table. The graphic notation, which is printed on the element, is a geometric figure, and the graph (code) corresponds to the rated current.