Surface-mount type overcurrent protection element

A surface-mount type over-current protection element, comprising:

• two single-layer PTC multiple chips (10) (10′), the chip (10) is made up of the first PTC chip material (12) the first metal foil layer (11) and the second metal foil layer (13), which are pasted on both surfaces of the first PTC chip material (12), the other chip (10′) is made up of the second PTC chip material (16) the third metal foil layer (15) the fourth metal foil layer (17), which are pasted on both upper and lower surfaces of the second PTC chip material (16), comprising:
• There is the third insulation layer (14) between the two single-layer PTC multiple chips (10) (10′) to insulate the second metal foil layer (13) from the third metal foil layer (15) and also bond them so as to constitute the double-layer PTC multiple chip (20);
• There are the etching figures (18) (19) on the eccentric center position of the double-layer PTC multiple chip (20), on the relative position of both the first metal foil layer (11) and the fourth metal foil layer (17) to expose the first PTC chip material (12) and the second PTC chip material (16) so as to constitute the small multiple chip (30);
• There is the isolating layer (21) surrounding the double-layer PTC multiple chip (20) the isolating layer (21) so as to constitute the covered chip (40):
• The first insulation layer (23) and the second insulation layer (24) are fitted on both upper and lower surfaces of the covered chip (40):
• The first insulation layer (23) insulate the first metal electrode (25a) and the third metal electrode (25b), which are on both side of its upper surface, from the first metal foil layer (11) and also bond them, moreover, there is a spacing between the first metal electrode (25a) and the third metal electrode (25b) to expose the first insulation layer (23):
• The second insulation layer (24) insulate the second metal electrode (26a) and the fourth metal electrode (26b), which are on both side of its lower surface, from the fourth metal foil layer (17) and also bond them, moreover, there is a spacing between the second metal electrode (26a) and the fourth metal electrode (26b) to expose the second insulation layer (24);
• There are the copper plates (33a) (33b) (34a) (34b) plating on the surfaces of the first metal electrode (25a) the third metal electrode (25b) the second metal electrode (26a) and the fourth metal electrode (26b);
• There is the inner through hole (29) at the etching figures (18) (19), the inner through hole (29) is concentric with the etching figures (18) (19), and its inner diameter is shorter than the diameter of the etching figures (18) (19);
• There are the end through holes (31) (32) at both the end;
• There are the blind holes (27) (28) on both upper and lower surfaces of the symmetrical position of the inner through hole (29) to expose the first PTC chip material (12) and the second PTC chip material (16);
• There are metallic conductors being located on the inner surface of the inner through hole (29) the end through hole (31) (32) and the blind holes (27) (28), among the metallic conductors,
• The first metallic conductor (38) is located on the inner surface of the end through hole (31) to connect up the first metal electrode (25a) and the second metal electrode (26a);
• The third metallic conductor (39) is located on the inner surface of the end through hole (32) to connect up the third metal electrode (25b) and the fourth metal electrode (26b):
• The second metallic conductor (37) is located on the inner surface of the inner through hole (29) to connect up the first metal electrode (25a) the second metal foil layer (13) the third metal foil layer (15) and the second metal electrode (26a);
• The fourth metallic conductor (35) is located on the inner surface of the blind hole (27) to connect up the third metal electrode (25b) and the first metal foil layer (11);
• The fifth metallic conductor (36) is located on the inner surface of the other blind hole (28), to connect up the fourth metal electrode (26b) and the fourth metal foil layer (17);
• The fourth insulation layer (41) insulate the first metal electrode (25a) from the third metal electrode (25b) and obstruct the portholes of the inner through hole (29) and the blind hole (27);
• The fifth insulation laver (42) insulate the second metal electrode (26a)from the fourth metal electrode (26b) and obstruct the portholes of the inner through hole (29) and the blind hole (28).