Patent Publication Number: US-2022223774-A1

Title: Light emitting diode (led) package and illuminating device including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0004924, filed on Jan. 13, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     The inventive concept relates to a light-emitting diode (LED) package and an illuminating device including the same. 
     An LED chip and an LED package including the LED chip have various advantages such as low power consumption, high brightness, and a long lifetime, and thus, their fields of application as light sources are gradually expanding. An example of using an LED package as a light source is an illuminating device for vehicles. Due to the adoption of advanced intelligent automotive illuminating devices such as adaptive front-lighting systems (AFS), head-up displays (HUD), etc., the use of LEDs in vehicles is further increasing. 
     When the LED package is applied to an illuminating device for a vehicle, mechanical robustness and electrical reliability may be important. Accordingly, various technologies have been studied to improve mechanical robustness and electrical reliability of solders used for connection between the LED package and a printed circuit board on which the LED package is mounted. 
     SUMMARY 
     The inventive concept provides a light-emitting diode (LED) package having improved mechanical robustness and electrical reliability and an illuminating device including the LED package. 
     The objective of the inventive concept is not limited by the above-described one, and other objectives not stated herein will be clearly understood by those skilled in the art from the following description. 
     According to an aspect of the inventive concept, there is provided a light-emitting diode (LED) package including a package substrate, an LED chip disposed on a first surface of the package substrate, and a first external connection pad and a second external connection pad disposed on a second surface of the package substrate opposite the first surface. The first external connection pad includes a first side, a second side, a third side and a fourth side, the first side being parallel to the second side, and the third side being parallel to the fourth side. The first side is spaced farther from a center of the package substrate than the second side. A length of the first side is shorter than a length of the second side. 
     According to an aspect of the inventive concept, there is provided a light-emitting diode (LED) package, including a package substrate including a first surface on which an LED chip is disposed, and a first external connection pad and a second external connection pad disposed on a second surface of the package substrate, the first external connection pad and the second external connection pad being electrically connected to the LED chip. The first external connection pad includes a first side, a second side, a third side and a fourth side, a first corner connected to the first side and the third side, the first corner having having a round profile, a second corner connected to the first side and the fourth side, the second corner having a round profile, a third corner connected to the second side and the third side, the third corner having a round profile, and a fourth corner connected to the second side and the fourth side, the fourth corner having a round profile. The first side and the second side extend in a first direction. The third side and the fourth side extend in a second direction perpendicular to the first direction. The first side and the second side are respectively longer than the third side and the fourth side. The first corner is spaced farther from a center of the package substrate than the third corner. A radius of the first corner is larger than a radius of the third corner. 
     According to another aspect of the inventive concept, there is provided a light-emitting diode (LED) package including a package substrate including a first surface on which an LED chip is disposed, and a first external connection pad and a second external connection pad disposed on a second surface of the package substrate, the first external connection pad and the second external connection pad being electrically connected to the LED chip. The first external connection pad includes a first side and a second side extending in a first direction, a third side and a fourth side extending in a second direction perpendicular to the first direction, and a fifth side connected to each of the first side and the third side, the fifth side extending in a direction oblique to each of the first direction and the second direction. The first side is spaced farther from a center of the package substrate than the second side. 
     According to another aspect of the inventive concept, there is provided a light-emitting diode (LED) package including a package substrate including a first surface on which an LED chip is disposed, and a first external connection pad and a second external connection pad disposed on a second surface of the package substrate, the first external connection pad and the second external connection pad being electrically connected to the LED chip. The first external connection pad includes a first side and a second side extending in a first direction, a third side and a fourth side extending in a second direction perpendicular to the first direction, and a stress relief finger recessed into the first external connection pad from the first side toward the second side. The first side is spaced farther from a center of the package substrate than the second side. 
     According to another aspect of the inventive concept, there is provided a light-emitting diode (LED) package including a package substrate including a first surface on which an LED chip is disposed, a first external connection pad and a second external connection pad disposed on a second surface of the package substrate, the first external connection pad and the second external connection pad being electrically connected to the LED chip, and a third external connection pad disposed on the second surface of the package substrate, the third external connection pad being electrically insulated from the LED chip. A length of each of the first external connection pad and the second external connection pad in a first direction is longer than a length of each of the first external connection pad and the second external connection pad in a second direction perpendicular to the first direction, a length of the third external connection pad in the first direction is shorter than a length of the third external connection pad in the second direction, and a sum of areas of the first external connection pad and the second external connection pad is in a range of about 0.95 times to about 1.2 times an area of the third external connection pad. 
     According to another aspect of the inventive concept, there is provided an illuminating device including a printed circuit board (PCB) including a substrate base including aluminum, and a first pad and a second pad disposed on the substrate base, an light-emitting diode (LED) package disposed on the PCB and including a first external connection pad connected to the first pad, and a second external connection pad connected to the second pad, a first solder interposed between the first external connection pad and the first pad, and a second solder interposed between the second external connection pad and the second pad. The PCB further includes a conductive plate disposed inside the substrate base and overlapping the LED package in a first direction perpendicular to an upper surface of the PCB, and a stress relief groove exposing an upper surface of the conductive plate and surrounding the first external connection pad and the second external connection pad in a second direction parallel to the upper surface of the PCB. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the inventive concept will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1A  is a perspective view of an illuminating device including a light-emitting diode (LED) package according to embodiments; 
         FIG. 1B  is a cross-sectional view of the illuminating device taken along line I-I′ of  FIG. 1A ; 
         FIG. 2A  is a plan view illustrating a lower surface of an LED package according to embodiments; 
         FIG. 2B  is a partial plan view illustrating a part of a printed circuit board (PCB) according to embodiments; 
         FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, 3I and 3J  are plan views illustrating LED packages according to other embodiments; 
         FIG. 4  is a perspective view of an illuminating device according to other embodiments; 
         FIG. 5  is a cross-sectional view of the illuminating device taken along line II-II′ of  FIG. 4 ; 
         FIG. 6  is a plan view illustrating a lower surface of an LED package included in the illuminating device of  FIG. 4 ; and 
         FIG. 7  is a partial plan view illustrating part of a PCB on which the LED package of  FIG. 6  is mounted. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the inventive concept will be described in detail with reference to the attached drawings. In the drawings, like reference numerals are used for like elements, and repeated description thereof may be omitted. 
       FIG. 1A  is a perspective view of an illuminating device  10  including a light-emitting diode (LED) package  200  according to embodiments. 
       FIG. 1B  is a cross-sectional view of the illuminating device  10  taken along line I-I′ of  FIG. 1A . 
     Referring to  FIGS. 1A and 1B , as a non-limiting example, the illuminating device  10  may be a vehicle illuminating device. According to some embodiments, the illuminating device  10  may be a light source outside the vehicle including, for example, a stop signal lamp such as a front turn signal lamp, a mirror mounted side turn signal lamp, a rear turn signal lamp, a center high mounted stop lamp (CHMSL), etc., a head lamp such as a daytime running light (DRL), a high beam lamp, and a low beam lamp, a side marker lamp, a fog lamp, and a license plate lamp. According to other embodiments, the illuminating device  10  may be a light source inside a vehicle including an instrument panel and ambient, reading &amp; dome lights. 
     According to embodiments, the illuminating device  10  may include a printed circuit board (PCB)  100  and the LED packages  200 . 
     The PCB  100  may be designed by, for example, a surface mounting technique. 
     The PCB  100  may include a substrate base  101 , conductive patterns including first and second pads  111  and  112 , and an insulating layer  120  surrounding the conductive patterns. 
     The substrate base  101  may include aluminum. The substrate base  101  including aluminum has a high thermal conductivity, thereby effectively dissipating heat generated by the LED packages  200 . Accordingly, the operating temperature of the illuminating device  10  may be reduced, and the life of the illuminating device  10  may be extended. In addition, because a separate radiator is not required, the volume of the illuminating device  10  is greatly reduced, and mechanical strength is excellent. A coefficient of thermal expansion of the substrate base  101  may be about 23.5 parts per million (ppm), but is not limited thereto. 
     According to embodiments, the conductive pattern including the first and second pads  111  and  112  may include a conductive material such as copper. The insulating layer  120  may include, for example, a photo-sensitive resist. One of a cathode and an anode of the LED package  200  may be connected to the first pad  111 , and the other may be connected to the second pad  112 . 
     According to embodiments, the first and second pads  111  and  112  may provide a path for supplying operating power to the LED package  200 . According to embodiments, the first and second pads  111  and  112  may provide a path for dissipating heat generated by the LED package  200 . 
     A plurality of LED packages  200  may be mounted on the PCB  100 . The plurality of LED packages  200  may be fixed to and connected to the PCB  100  by first and second solders  151  and  152 . The first solder  151  may be connected to the first pad  111 , and the second solder  152  may be connected to the second pad  112 . 
     Each of the LED packages  200  may generate white light, but is not limited thereto. Each of the LED packages  200  may include a package substrate  201 , an LED chip  210 , an encapsulant  220 , a side reflective layer  230 , and external connection pads  241  and  242 . 
     The LED chip  210  may be mounted on the package substrate  201 . The package substrate  201  may be, for example, a PCB. In an example, the package substrate  201  may include a metal and/or a metal compound. The package substrate  201  may be, for example, a metal-core PCB (MCPCB), and may include copper (Cu). The package substrate  201  may be a ceramic substrate including, for example, aluminum nitride (AlN). 
     In another example, the package substrate  201  may be a flexible PCB (FPCB) that is flexible and easily deformable into various shapes. In another example, the package substrate  201  may be a FR4 type PCB, and may include a resin material including epoxy, triazine, silicone, polyimide, etc. or may also include a ceramic material such as silicon nitride, AlN, Al 2 O 3 , etc. 
     According to embodiments, the package substrate  201  may have a lower coefficient of thermal expansion than the substrate base  101 . The coefficient of thermal expansion of the package substrate  201  may be about 4.4 ppm, but is not limited thereto. 
     Two directions parallel to a lower surface of the package substrate  201  (that is, a surface on which the first and second external connection pads  241  and  242  are formed) and perpendicular to each other are defined as an X direction and the Y direction, respectively, and a direction perpendicular to the lower surface of the package substrate  201  is defined as a Z direction. Unless otherwise stated, definitions of the directions are the same in the following drawings. 
     According to embodiments, a planar shape of the package substrate  201  may be a rectangle. A pair of sides of the package substrate  201  may be parallel to the X direction and the other pair of sides may be parallel to the Y direction. 
     According to some embodiments, the LED chip  210  may be mounted on the package substrate  201  in the form of, for example, a flip chip. In this case, solder and bumps interposed between the package substrate  201  and the LED chip  210  may be further provided. According to some other embodiments, the LED chip  210  may be mounted on the package substrate  201  in an epi-up form. In this case, the LED chip  210  may be electrically connected to the package substrate  201  by a bonding wire, and the bonding wire may be molded by the side reflective layer  230 . The LED chip  210  may generate blue light, but is not limited thereto. 
     The LED chip  210  may include a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer. According to embodiments, the first conductivity type semiconductor layer may include a single-crystal nitride having a composition of Al x In y Ga 1-x-y N (0≤x≤1, 0≤y≤1, and 0≤x+y≤1). The first conductivity type semiconductor layer may include a semiconductor doped with an n-type impurity. According to embodiments, the first conductivity type semiconductor layer may include GaN doped with Si or the like. 
     The active layer may be arranged on the first conductivity type semiconductor layer. The active layer may emit light having energy via recombination of electrons and holes. According to embodiments, the active layer may include a multiple quantum well (MQW) structure in which quantum well layers and quantum barrier layers are alternately stacked. In this case, a thickness of each of the quantum well layers and the quantum barrier layers may be equal to or greater than 3 nm and equal to or less than 10 nm. According to embodiments, the MQW structure may include a multiple stack structure of InGaN and GaN. However, the inventive concept is not limited thereto, and according to embodiments, the active layer may include a single quantum well (SQW) structure. 
     The second conductivity type semiconductor layer may include a single-crystal nitride having a composition of Al x In y Ga 1-x-y N (0≤x≤1, 0≤y≤1, and 0≤x+y≤1) doped with a p-type impurity. A p-type impurity may include, for example, Mg, but is not limited thereto. 
     The encapsulant  220  may be disposed on the LED chip  210 . The encapsulant  220  may contact the LED chip  210 . According to embodiments, the encapsulant  220  may be a film in which a fluorescent material is mixed with a transparent resin such as Si. According to embodiments, the encapsulant  220  may reduce color dispersion of light generated by the LED chip  210 . According to embodiments, the encapsulant  220  may convert blue light generated by the LED chip  210  into white light, but is not limited thereto. 
     According to embodiments, the side reflective layer  230  may cover side surfaces of the LED chip  210  and the encapsulant  220 . The side reflective layer  230  may prevent the LED chip  210  from emitting light in a direction other than a designed direction, and thus the luminous efficiency of the illuminating device  10  may be improved. The side reflective layer  230  may include a material having high reflectivity. The side reflective layer  230  may include white resin. The white resin may be, for example, a Si resin to which TiO 2  is added, but is not limited thereto. 
     The LED package  200  may include a first external connection pad  241  and a second external connection pad  242 . The first external connection pad  241  may be configured to be electrically connected to the first pad  111  through the first solder  151 . The second external connection pad  242  may be configured to be electrically connected to the second pad  112  through the second solder  152 . One of the first external connection pad  241  and the second external connection pad  242  may be a cathode of the LED package  200 , and the other may be an anode of the LED package  200 . One of the first external connection pad  241  and the second external connection pad  242  may be configured to be electrically connected to the first conductivity type semiconductor layer of the LED chip  210 , and the other may be configured to be electrically connected to the second conductivity type semiconductor layer. 
       FIG. 2A  is a plan view illustrating a lower surface of the LED package  200  according to embodiments. 
     Referring to  FIG. 2A , lengths of sides parallel to the X direction of a lower surface of the package substrate  201  may be greater than lengths of sides of a lower surface of the package substrate  201  parallel to the Y direction. 
     According to embodiments, the first and second external connection pads  241  and  242  may be symmetric to each other with respect to an axis passing through a center  201 C of the lower surface of the package substrate  201  and parallel to the X direction. Each of the first and second external connection pads  241  and  242  may be symmetric with respect to an axis passing through the center  201 C of the lower surface of the package substrate  201  and parallel to the Y direction. 
     Each of the first and second external connection pads  241  and  242  may have a substantially rectangular planar shape. A length of each of the first and second external connection pads  241  and  242  in the X direction may be greater than a length of each of the first and second external connection pads  241  and  242  in the Y direction. 
     According to embodiments, the first external connection pad  241  may include first to fourth sides  241 S 1 ,  241 S 2 ,  241 S 3 , and  241 S 4  and first to fourth corners  241 C 1 ,  241 C 2 ,  241 C 3 , and  241 C 4 . 
     According to embodiments, the first and second sides  241 S 1  and  241 S 2  may be parallel to the X direction. The first side  241 S 1  may be spaced farther from the center  201 C than the second side  241 S 2 . The length of the first side  241 S 1  may be shorter than the length of the second side  241 S 2 . 
     According to embodiments, the third and fourth sides  241 S 3  and  241 S 4  may be parallel to the Y direction. The length of the third side  241 S 3  may be substantially the same as the length of the fourth side  241 S 4 . 
     The first corner  241 C 1  may be interposed between the first side  241 S 1  and the third side  241 S 3 . The first corner  241 C 1  may be connected to each of the first side  241 S 1  and the third side  241 S 3 . The second corner  241 C 2  may be interposed between the first side  241 S 1  and the fourth side  241 S 4 . The second corner  241 C 2  may be connected to each of the first side  241 S 1  and the fourth side  241 S 4 . The third corner  241 C 3  may be interposed between the second side  241 S 2  and the third side  241 S 3 . The third corner  241 C 3  may be connected to each of the second side  241 S 2  and the third side  241 S 3 . The fourth corner  241 C 4  may be interposed between the second side  241 S 2  and the fourth side  241 S 4 . The fourth corner  241 C 4  may be connected to each of the second side  241 S 2  and the fourth side  241 S 4 . 
     Each of the first to fourth corners  241 C 1 ,  241 C 2 ,  241 C 3 , and  241 C 4  may have a round profile. According to embodiments, each of the first and second corners  241 C 1  and  241 C 2  may have an intentionally formed round profile, and each of the third and fourth corners  241 C 3  and  241 C 4  may have a round profile accompanied by a characteristic of a patterning process. 
     According to embodiments, a radius R of each of the first and second corners  241 C 1  and  241 C 2  may be larger than a radius of each of the third and fourth corners  241 C 3  and  241 C 4 . According to embodiments, the radius R of each of the first and second corners  241 C 1  and  241 C 2  may be equal to or greater than about 2 times the radius of each of the third and fourth corners  241 C 3  and  241 C 4 . According to embodiments, the radius R of each of the first and second corners  241 C 1  and  241 C 2  may be equal to or greater than about 5 times the radius of each of the third and fourth corners  241 C 3  and  241 C 4 . According to embodiments, the radius R of each of the first and second corners  241 C 1  and  241 C 2  may be equal to or less than about 10 times the radius of each of the third and fourth corners  241 C 3  and  241 C 4 . 
     According to embodiments, the radius R of each of the first and second corners  241 C 1  and  241 C 2  may depend on a distance DM between an intersection point IP of an extension line of the first side  241 S 1  and an extension line of the third side  241 S 3  and the center  201 C. According to embodiments, the radius R of each of the first and second corners  241 C 1  and  241 C 2  may be in the range of about 0.2 times to about 0.5 times the distance DM between the intersection point IP and the center  201 C. 
     According to embodiments, the radius R of each of the first and second corners  241 C 1  and  241 C 2  may be in the range of about 100 μm to about 500 μm. According to embodiments, the radius of each of the third and fourth corners  241 C 3  and  241 C 4  may be in the range of about 10 μm to about 100 μm. 
     According to embodiments, the second external connection pad  242  may include first to fourth sides  242 S 1 ,  242 S 2 ,  242 S 3 , and  242 S 4  and first to fourth corners  242 C 1 ,  242 C 2 ,  242 C 3 , and  242 C 4 . 
     Connection relationships and geometric and dimensional characteristics described above with respect to the first to fourth sides  241 S 1 ,  241 S 2 ,  241 S 3 , and  241 S 4  and the first to fourth corners  241 C 1 ,  241 C 2 ,  241 C 3 , and  241 C 4  may be similarly applied to the first to fourth sides  242 S 1 ,  242 S 2 ,  242 S 3 , and  242 S 4  and the first to fourth corners  242 C 1 ,  242 C 2 ,  242 C 3 , and  242 C 4 , and thus redundant descriptions thereof may be omitted. 
     A first distance D 1  that is a distance between a center  242 C of the second external connection pad  242  and the first corner  242 C 1  and a second distance D 2  that is a distance between the center  242 C and the second corner  242 C 2  may be respectively greater than a third distance D 3  that is a distance between the center  242 C and the third corner  242 C 3  and a fourth distance D 4  that is a distance between the center  242 C and the fourth corner  242 C 4 . Accordingly, the second external connection pad  242  may have an asymmetric shape with respect to an axis passing through the center  242 C of the second external connection pad  242  and parallel to the X direction. Here, the center  242 C of the second external connection pad  242  may be a midpoint of both ends of the second external connection pad  242  in the X direction and a midpoint of both ends of the second external connection pad  242  in the Y direction. 
     Due to the symmetry between the first and second external connection pads  241  and  242 , a distance between the center of the first external connection pad  241  and each of the first to fourth corners  241 C 1 ,  241 C 2 ,  241 C 3 , and  241 C 4  is similar to that described with respect to the second external connection pad  242 . 
     In the case of an illuminating device of the related art, due to a difference in the coefficient of thermal expansion between a package substrate of an LED package and a PCB on which the LED package is mounted, there is a problem in that a defect such as a crack occurs in a solder connecting the package substrate of the LED package and the PCB. Such a crack occurs by stress due to a difference in the coefficient of thermal expansion, and the stress increases as a distance from the center of the package substrate increases. 
     According to embodiments, the first and second corners  241 C 1  and  241 C 2  of the first external connection pad  241  and the first and second corners  242 C 1  and  242 C 2  of the second external connection pad  242  have the relatively large radius R, thereby reducing a maximum distance between the first external connection pad  241  and the center  201 C and a maximum distance between the second external connection pad  242  and the center  201 C. Accordingly, stress applied to the first and second solders  151  and  152  (see  FIG. 1B ) may be relieved, defects in the first and second solders  151  and  152  may be reduced, and reliability of the illuminating device  10  may be improved. 
     Here, the maximum distance between the first external connection pad  241  and the center  201 C means a distance between a part of the first external connection pad  241  that is the farthest from the center  201 C and the center  201 C. 
     When the radius R is too large, an area of the first and second external connection pads  241  and  242  decreases, and thus an operating temperature of the LED package  200  may increase, which may cause a decrease in the product life of the illuminating device  10  (see  FIG. 1A ). According to embodiments, the radius R is equal to or less than about 0.5 times the distance DM between the intersection point IP and the center  201 C, thereby preventing the life of the LED package  200  from being shortened. 
       FIG. 2B  is a partial plan view illustrating a part of the PCB  100  according to embodiments. More specifically,  FIG. 2B  shows a mounting portion  100 M of the PCB  100  on which the LED package  200  (see  FIG. 2 ) is mounted. 
     Referring to  FIGS. 2A and 2B , first and second pads  111  and  112 , a first connecter  116  connected to the first pad  111 , and a second connecter  118  connected to the second pad  112  may be provided in the mounting portion  100 M of the PCB  100 . 
     The first pad  111  may have substantially the same planar shape as the first external connection pad  211 , and the second pad  112  may have substantially the same planar shape as the second external connection pad  212 . According to embodiments, the first and second pads  111  and  112  having shapes similar to those of the first and second external connection pads  211  and  212  are provided, thereby relieving stress applied to the first and second solders  151  and  152  (see  FIG. 1B ) and simultaneously preventing the life of the LED package  200  (see  FIG. 1B ) from being shortened. 
     An embodiment in which the first and second pads  111  and  112  have respectively shapes similar to those of the first and second external connection pads  241  and  242  of  FIG. 2A  is described with reference to  FIG. 2B , but this is an example, and the scope of the inventive concept is not limited thereto. Those of ordinary skill in the art, based on the description herein, may easily reach embodiments in which the first and second pads  111  and  112  have the same shapes as first and second external connection pads shown in  FIGS. 3A to 3F  respectively and embodiments in which three external connection pads having shapes corresponding to the first to third external connection pads shown in  FIGS. 3G to 3J  are formed on the mounting portion  100 M of the PCB  100 . 
       FIG. 3A  is a plan view illustrating an LED package  200   a  according to other embodiments. More specifically,  FIG. 3A  shows a part corresponding to  FIG. 2A . 
     Referring to  FIG. 3A , the LED package  200   a  may include first and second external connection pads  241   a  and  242   a  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   a  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     According to embodiments, the first and second external connection pads  241   a  and  242   a  may be symmetric to each other with respect to an axis passing through the center  201 C of the lower surface of the package substrate  201  and parallel to the X direction. Each of the first and second external connection pads  241   a  and  242   a  may be symmetric with respect to an axis passing through the center  201 C of the lower surface of the package substrate  201  and parallel to the Y direction. 
     A length of each of the first and second external connection pads  241   a  and  242   a  in the X direction may be greater than a length thereof in the Y direction. The first external connection pad  241   a  may include first to sixth sides  241 aS 1 ,  241 aS 2 ,  241 aS 3 ,  241 aS 4 ,  241 aS 5 , and  241 aS 6 , and the second external connection pad  242   a  may include first to sixth sides  242 aS 1 ,  242 aS 2 ,  242 aS 3 ,  242 aS 4 ,  242 aS 5 , and  242 aS 6 . 
     According to embodiments, the first and second sides  241 aS 1  and  241 aS 2  may be parallel to the X direction. The first side  241 aS 1  may be spaced farther from the center  201 C than the second side  241 aS 2 . The length of the first side  241 aS 1  may be shorter than the length of the second side  241 aS 2 . 
     According to embodiments, the third and fourth sides  241 aS 3  and  241 aS 4  may be parallel to the Y direction. The length of the third side  241 aS 3  may be substantially the same as the length of the fourth side  241 aS 4 . 
     According to embodiments, the fifth side  241 aS 5  may be interposed between the first side  241 aS 1  and the third side  241 aS 3 . The fifth side  241 aS 5  may be connected to each of the first side  241 aS 1  and the third side  241 aS 3 . The fifth side  241 aS 5  may extend in a direction oblique to each of the X and Y directions. 
     The sixth side  241 aS 6  may be interposed between the first side  241 aS 1  and the fourth side  241 aS 4 . The sixth side  241 aS 6  may be connected to each of the first side  241 aS 1  and the fourth side  241 aS 4 . The sixth side  241 aS 6  may extend in a direction oblique to each of the X and Y directions. 
     An intersection point IPa is defined as an intersection point between extension lines of each of the first and third sides  241 aS 1  and  241 aS 3  similarly to  FIG. 2A . In addition, an X-direction distance between one end of the fifth side  241 aS 5  (that is, an intersection of the third and fifth sides  241 aS 3  and  241 aS 5 ) and the intersection point IPa is defined as a first exclusion width EX, and a Y-direction distance between the other end of the fifth side  241 aS 5  (that is, an intersection of the first and fifth sides  241 aS 1  and  241 aS 5 ) and the intersection point IPa is defined as a second exclusion width EY. The first and second exclusion widths EX and EY with respect to the sixth side  241 aS 6  are similarly defined. 
     According to embodiments, each of the first and second exclusion widths EX and EY may be in the range of about 0.2 to about 0.5 times the distance DM between the center  201 C of the package substrate  201  and the intersection point IPa. Accordingly, the first external connection pad  241   a  may have a shape in which some of approximately rectangular corners are removed by chamfering. 
     According to embodiments, the first and second exclusion widths EX and EY may be substantially the same as each other. In this case, a first angle θ 1  that is an angle between the sixth side  241 aS 6  and the Y direction may be substantially the same as a second angle θ 2  that is an angle between the sixth side  241 aS 6  and the X direction. According to some other embodiments, the first and second exclusion widths EX and EY may be different from each other. In this case, the first angle θ 1  may be different from the second angle θ 2 . 
     According to embodiments, due to the formation of the fifth and sixth sides  241 aS 5  and  241 aS 6 , the first external connection pad  241   a  may have an asymmetric shape with respect to an axis passing through a center of the first external connection pad  241   a  and parallel to the X direction. 
     Connection relationships and geometrical and dimensional characteristics described above with respect to the first to sixth sides  241 aS 1 ,  241 aS 2 ,  241  aS 3 ,  241 aS 4 ,  241  aS 5 , and  241 aS 6  of the first external connection pad  241   a  may be similarly applied to the first to sixth sides  242 aS 1 ,  242 aS 2 ,  242  aS 3 ,  242 aS 4 ,  242  aS 5 , and  242 aS 6  of the connection second external pad  242   a , and thus redundant descriptions thereof may be omitted. 
     According to embodiments, a maximum distance from the center  201 C of the package substrate  201  with respect to each of the first and second external connection pads  241   a  and  242   a  may be reduced, thereby relieving stress applied to the first and second solders  151  and  152  (see  FIG. 1B ), and continuously preventing the life of the LED package  200   a  from being shortened due to an increase in the operating temperature of the LED package  200   a.    
       FIG. 3B  is a plan view illustrating an LED package  200   b  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A to 3A  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3B , the LED package  200   b  may include first and second external connection pads  241   b  and  242   b  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   b  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     According to embodiments, the first external connection pad  241   b  may have a different planar shape than the second external connection pad  242   b . According to embodiments, the first external connection pad  241   b  may have a planar shape similar to the first external connection pad  241  of  FIG. 2A , and the second external connection pad  242   b  may have a planar shape similar to the second external connection pad  242   a  of  FIG. 3A . 
     According to embodiments, the first and second external connection pads  241   b  and  242   b  may have an asymmetric shape with respect to an axis passing through the center  201 C of the package substrate  201  and parallel to the X direction. According to embodiments, the first external connection pad  241   b  may have a symmetric planar shape with respect to an axis passing through the center  201 C of the package substrate  201  and parallel to the Y direction. According to embodiments, the second external connection pad  242   b  may have a symmetric planar shape with respect to an axis passing through the center  201 C of the package substrate  201  and parallel to the Y direction. 
       FIG. 3C  is a plan view illustrating an LED package  200   c  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A to 3A  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3C , the LED package  200   c  may include first and second external connection pads  241   c  and  242   c  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   c  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     According to embodiments, the first and second external connection pads  241   c  and  242   c  may be symmetric to each other with respect to an axis passing through a center  201 C of the lower surface of the package substrate  201  and parallel to the X direction. According to embodiments, the first external connection pad  241   c  may have an asymmetric planar shape with respect to an axis passing through the center  201 C of the package substrate  201  and parallel to the Y direction. According to embodiments, the second external connection pad  242   c  may have an asymmetric planar shape with respect to an axis passing through the center  201 C of the package substrate  201  and parallel to the Y direction. 
     According to embodiments, an upper portion of each of the first and second external connection pads  241   c  and  242   c  may include round corners of relatively large radius, similarly to the first and second external connection pads  241  and  242  of  FIG. 2A . According to embodiments, a lower portion of each of the first and second external connection pads  241   c  and  242   c  may have a chamfered shape similarly to the first and second external connection pads  241   a  and  242   a  of  FIG. 3A . 
       FIG. 3D  is a plan view illustrating an LED package  200   d  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A to 3A  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3D , the LED package  200   d  may include first and second external connection pads  241   d  and  242   d  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   b  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     According to embodiments, each of the first and second external connection pads  241   d  and  242   d  may have a substantially rectangular planar shape. A length of each of the first and second external connection pads  241   d  and  242   d  in the X direction may be greater than a length thereof in the Y direction. 
     According to embodiments, the first external connection pad  241   d  may include first to fourth sides  241 dS 1 ,  241 dS 2 ,  241 dS 3 , and  241 dS 4 . Each of the first and second sides  241 dS 1  and  241 dS 2  may be parallel to the X direction. The first side  241 dS 1  may be spaced farther from the center  201 C than the second side  241 dS 2 . 
     According to embodiments, the third and fourth sides  241 dS 3  and  241 dS 4  may be parallel to the Y direction. The length of the third side  241 dS 3  may be substantially the same as the length of the fourth side  241 dS 4 . 
     According to embodiments, a first external connection pad  241   d  may include first stress relief fingers  241 dSF recessed from the first side  241 dS 1  toward the second side  241 dS 2 . According to embodiments, the distance DM between an intersection point of the first and third sides  241 dS 1  and  241 dS 3  and a center  201 C of the package substrate  201  may be equal to or greater than about 1.5 mm. According to embodiments, a distance DF between a part on the first side  241 dS 1  where the first stress relief fingers  241 dSF start and the center  201 C of the package substrate  201  may be in the range of about 0.5 times to about 0.8 times the distance DM. 
     Due to the formation of the first stress relief fingers  241 dSF, the first side  241 dS 1  may be divided into three portions  241 dS 1 _ 1 ,  241 dS 1 _ 2 , and  241 dS 1 _ 3 . The sum of lengths of the three portions  241 dS 1 _ 1 ,  241 dS 1 _ 2 , and  241 dS 1 _ 3  may be smaller than a length of the second side  241 dS 2 . 
     The length of the first stress relief fingers  241 dSF in the Y direction may be shorter than the length of each of the third and fourth sides  241 dS 3  and  241 dS 4  in the Y direction. Accordingly, because the first external connection pad  241   d  is not separated by the first stress relief fingers  241 dSF, the first external connection pad  241   d  may include only a single continuous element. 
     According to embodiments, the second external connection pad  242   d  may include first to fourth sides  242 dS 1 ,  242 dS 2 ,  242 dS 3 ,  242 dS 4  and second stress relief fingers  242 dSF formed on the first side  242 dS 1 . 
     According to embodiments, the first and second external connection pads  241   d  and  242   d  may be symmetric to each other with respect to an axis passing through the center  201 C of the package substrate  201  and parallel to the X direction. Accordingly, connection relationships and geometric characteristics, and dimensional characteristics described above with respect to the first to fourth sides  241 dS 1 ,  241 dS 2 ,  241 dS 3 ,  241 dS 4  and the first stress relief fingers  241 dSF may be similarly applied to the first to fourth sides  242 dS 1 ,  242 dS 2 ,  242 dS 3 , and  242 dS 4  and the second stress relief fingers  242 dSF, and thus redundant descriptions thereof may be omitted. 
     When the distance DM between the intersection point of the first and third sides  241 dS 1  and  241 dS 3  and the center  201 C of the package substrate  201  is equal to or greater than 1.5 mm, a stress relaxation effect may be insufficient only by forming corners of a round profile having a large radius in the first and second external connection pads  241  and  242  as shown in  FIG. 2A , or providing the first and second external connection pads  241   a  and  242   a  having a chamfered shape as shown in  FIG. 3A . The first and second external connection pads  241   d  and  242   d  according to embodiments include the first and second stress relief fingers  241 dSF and  242 dSF capable of reducing stress due to a difference in thermal expansion coefficient, thereby relieving stress applied to the first and second solders  151  and  152  (see  FIG. 1B ), and improving reliability of the illuminating device  10  (see  FIG. 1B ). 
       FIG. 3E  is a plan view illustrating an LED package  200   e  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIG. 3D  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3E , the LED package  200   e  may include first and second external connection pads  241   e  and  242   e  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   e  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     According to embodiments, each of the first and second external connection pads  241   e  and  242   e  may have a substantially rectangular planar shape. A length of each of the first and second external connection pads  241   e  and  242   e  in the X direction may be greater than the length thereof in the Y direction. 
     According to embodiments, the first external connection pad  241   e  may include first to fourth sides  241 eS 1 ,  241 eS 2 ,  241 eS 3  and  241 eS 4 . Each of the first and second sides  241 eS 1  and  241 eS 2  may be parallel to the X direction. The first side  241 eS 1  may be spaced farther from the center  201 C than the second side  241 eS 2 . 
     The second external connection pad  242   e  may include first to fourth sides  242 eS 1 ,  242 eS 2 ,  242 eS 3 , and  242 eS 4 . Each of the first and second sides  242 eS 1  and  242 eS 2  may be parallel to the X direction. The first side  242 eS 1  may be spaced farther from the center  201 C than the second side  242 eS 2 . 
     According to embodiments, the first and second external connection pads  241   e  and  242   e  are similar to the first and second external connection pads  241   d  and  242   d  of  FIG. 3D  while the first stress relief fingers  241 eSF may be formed on the second side  241 eS 2 , and the second stress relief fingers  242 eSF may be formed on the second side  242 eS 2 . 
     According to embodiments, the distance DM between an intersection point of the first and third sides  241 eS 1  and  241 eS 3  and the center  201 C may be equal to or greater than about 1.5 mm. According to embodiments, the distance DF between a point on the first side  241 eS 1  facing ends of the first stress relief fingers  241 eSF and the center  201 C of the package substrate  201  may be in the range of about 0.5 times to about 0.8 times the distance DM. 
       FIG. 3F  is a plan view illustrating an LED package  200   f  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 3D and 3E  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3F , the LED package  200   f  may include first and second external connection pads  241   f  and  242   f  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   f  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     According to embodiments, each of the first and second external connection pads  241   f  and  242   f  may have a substantially rectangular planar shape. A length of each of the first and second external connection pads  241   f  and  242   f  in the X direction may be greater than a length thereof in the Y direction. 
     According to embodiments, the first external connection pad  241   f  may include first to fourth sides  241   f S 1 ,  241 fS 2 ,  241 fS 3  and  241 fS 4 . Each of the first and second sides  241   f S 1  and  241 fS 2  may be parallel to the X direction. The first side  241   f S 1  may be spaced farther from the center  201 C than the second side  241 fS 2 . 
     The second external connection pad  242   f  may include first to fourth sides  242   f S 1 ,  242 fS 2 ,  242 fS 3 , and  242 fS 4 . Each of the first and second sides  242   f S 1  and  242 fS 2  may be parallel to the X direction. The first side  242   f S 1  may be spaced farther from the center  201 C than the second side  242 fS 2 . 
     According to embodiments, the first and second external connection pads  241   f  and  242   f  are similar to the first and second external connection pads  241   d  and  242   d  of  FIG. 3D  while the first stress relief fingers  241 fSF may be formed on each of the first and second sides  241   f S 1  and  241 fS 2 , and the second stress relief fingers  242 fSF may be formed on each of the first and second sides  242   f S 1  and  242 fS 2 . 
     According to embodiments, the distance DM between an intersection point of the first and third sides  241   f S 1  and  241 fS 3  and the center  201 C may be equal to or greater than about 1.5 mm. According to embodiments, the distance DF between a point on the first side  241 fS 1  where the first stress relief fingers  241 fSF are formed and the center  201 C of the package substrate  201  may be in the range of about 0.5 times to about 0.8 times the distance DM. 
       FIG. 3G  is a plan view illustrating an LED package  200   g  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A to 3A  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3G , the LED package  200   g  may include first to third external connection pads  241   g ,  242   g , and  243   g  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   g  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     The LED package  200   g  may be a 3-pad package. One of first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ) may be connected to the first external connection pad  241   g , and the other may be connected to the second external connection pad  242   g . The third external connection pad  243   g  may be a heat dissipation pad. The third external connection pad  243   g  may be floated. The third external connection pad  243   g  may be insulated from each of the first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ). 
     According to embodiments, each of the first to third external connection pads  241   g ,  242   g , and  243   g  may have a substantially rectangular planar shape. A length of each of the first and second external connection pads  241   g  and  242   g  in the X direction may be greater than a length of each of the first and second external connection pads  241   g  and  242   g  in the Y direction. The length of the third external connection pad  243   g  in the X direction may be smaller than the length thereof in the Y direction. 
     According to embodiments, an area S 1  of the first external connection pad  241   g , an area S 2  of the second external connection pad  242   g , and an area S 3  of the third external connection pad  243   g  may satisfy Equation 1 below. 
       0.95· S 3≤( S 1+ S 2)≤1.2· S 3  [Equation 1]
 
     According to embodiments, the first to third external connection pads  241   g ,  242   g , and  243   g  having an area relationship of Equation 1 may be provided, thereby relieving stress applied to each of corners of the first to third external connection pads  241   g ,  242   g , and  243   g  spaced farthest from the center  201 C of the package substrate  201  by about 20% or more. Accordingly, the reliability of the LED package  200   g  may be improved. 
       FIG. 3H  is a plan view illustrating an LED package  200   h  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A to 3A  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3H , the LED package  200   h  may include first, second and third external connection pads  241   h ,  242   h  and  243   h  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   h  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     The LED package  200   h  may be a 3-pad package. One of first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ) may be connected to the first external connection pad  241   h , and the other may be connected to the second external connection pad  242   h . The third external connection pad  243   h  may be a heat dissipation pad. The third external connection pad  243   h  may be floated. The third external connection pad  243   h  may be insulated from each of the first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ). 
     According to embodiments, each of the first to third external connection pads  241   h ,  242   h , and  243   h  may have a substantially rectangular planar shape. A length of each of the first and second external connection pads  241   h  and  242   h  in the X direction may be greater than a length of each of the first and second external connection pads  241   h  and  242   h  in the Y direction. The length of the third external connection pad  243   h  in the X direction may be smaller than the length of the third external connection pad  243   h  in the Y direction. The first to third external connection pads  241   h ,  242   h , and  243   h  together may be symmetric to each other with respect to an axis passing through the center  201 C of the lower surface of the package substrate  201  and parallel to the X direction. 
     According to embodiments, the first external connection pad  241   h  may include first to fourth corners  241 hC 1 ,  241 hC 2 ,  241 hC 3 , and  241 hC 4 , the second external connection pad  242   h  may include first to fourth corners  242 hC 1 ,  242 hC 2 ,  242 hC 3 , and  242 hC 4 , and the third external connection pad  243   h  may include first to fourth corners  243 hC 1 ,  243 hC 2 ,  243 hC 3 , and  243 hC 4 . 
     According to embodiments, the first corner  241 hC 1  of the first external connection pad  241   h  farthest from the center  201 C of the package substrate  201 , the first corner  242 hC 1  of the second external connection pad  242   h , and the second and fourth corners  243 hC 2  and  243 hC 4  of the third external connection pad  243   h  may have relatively large radiuses compared to the other corners, like the first corner  242 C 1  of  FIG. 2A . The size of a radius of each of the first corner  241 hC 1  of the first external connection pad  241   h  farthest from the center  201 C of the package substrate  201 , the first corner  242 hC 1  of the second external connection pad  242   h , and the second and fourth corners  243 hC 2  and  243 hC 4  of the third external connection pad  243   h  is similar to that described with reference to  FIG. 2A . 
       FIG. 3I  is a plan view illustrating an LED package  200   i  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A to 3A  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3I , the LED package  200   i  may include first, second and third external connection pads  241   i ,  242   i  and  243   i  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   i  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     The LED package  200   i  may be a 3-pad package. One of the first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ) may be connected to the first external connection pad  241   i , and the other may be connected to the second external connection pad  242   i . The third external connection pad  243   i  may be a heat dissipation pad. The third external connection pad  243   i  may be floated. The third external connection pad  243   i  may be insulated from each of the first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ). 
     A length of each of the first and second external connection pads  241   i  and  242   i  in the X direction may be greater than a length of each of the first and second external connection pads  241   i  and  242   i  in the Y direction. The length of the third external connection pad  243   i  in the X direction may be smaller than the length thereof in the Y direction. The first and second external connection pads  241   i  and  242   i  may be symmetric to each other with respect to an axis passing through the center  201 C of the lower surface of the package substrate  201  and parallel to the X direction. The third external connection pad  243   i  may be symmetric with respect to an axis passing through the center  201 C of the lower surface of the package substrate  201  and parallel to the X direction. 
     According to embodiments, the first external connection pad  241   i  may include first to fifth sides  241 iS 1 ,  241 iS 2 ,  241 iS 3 ,  241 iS 4 , and  241 iS 5 , the second external connection pad  242   i  may include first to fifth sides  242 iS 1 ,  242 iS 2 ,  242 iS 3 ,  242 iS 4 , and  242 iS 5 , and the third external connection pad  243   i  may include first to sixth sides  243 iS 1 ,  243 iS 2 ,  243 iS 3 ,  243 iS 4 ,  243 iS 5 , and  243 iS 6 . 
     Each of the first and second sides  241 iS 1 ,  241 iS 2 ,  242 iS 1 ,  242 iS 2 ,  243 iS 1 , and  243 iS 2  may be parallel to the X direction, and each of the third and fourth sides  241 iS 3 ,  241 iS 4 ,  242 iS 3 ,  242 iS 4 ,  243 iS 3 ,  243 iS 4  may be parallel to the Y direction. Each of the fifth and sixth sides  241 iS 5 ,  242 iS 5 ,  243 iS 5 , and  243 iS 6  may be oblique to the X and Y directions. 
     The first side  241 iS 1  may be shorter than the second side  241 iS 2 , the first side  242 iS 1  may be shorter than the second side  242 iS 2 , and the fourth side  243 iS 4  may be shorter than the third side  243 iS 3 . 
     The fifth side  241 iS 5  may be interposed between the first and third sides  241 iS 1  and  241 iS 3  and may be connected to each of the first and third sides  241 iS 1  and  241 iS 3 . The fifth side  242 iS 5  may be interposed between the first and third sides  242 iS 1  and  242 iS 3  and may be connected to each of the first and third sides  241 iS 1  and  241 iS 3 . The fifth side  243 iS 5  may be interposed between the first and fourth sides  243 iS 1  and  243 iS 4 , and may be connected to each of the first and fourth sides  243 iS 1  and  243 iS 4 . The sixth side  243 iS 6  may be interposed between the second and fourth sides  243 iS 2  and  243 iS 4 , and may be connected to each of the second and fourth sides  243 iS 2  and  243 iS 4 . 
     According to embodiments, dimensional characteristics of the fifth and sixth sides  241 iS 5 ,  242 iS 52 ,  243 iS 5 , and  243 iS 6  are similar to those described with respect to the fifth side  241 aS 5  with reference to  FIG. 3A , and thus redundant descriptions thereof may be omitted. 
       FIG. 3J  is a plan view illustrating an LED package  200   j  according to other embodiments. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A to 3A  may be omitted, and differences will be mainly described. 
     Referring to  FIG. 3J , the LED package  200   j  may include first and second external connection pads  241   j  and  242   j  formed on a lower surface of the package substrate  201 . In addition, the LED package  200   j  may further include the package substrate  201 , the LED chip  210 , the encapsulant  220 , and the side reflective layer  230  shown in  FIG. 1B . 
     The LED package  200   j  may be a 3-pad package. One of first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ) may be connected to the first external connection pad  241   j , and the other may be connected to the second external connection pad  242   j . The third external connection pad  243   j  may be a heat dissipation pad. The third external connection pad  243   j  may be floated. The third external connection pad  243   j  may be insulated from each of the first and second conductivity type semiconductor layers of the LED chip  210  (see  FIG. 1B ). 
     According to embodiments, each of the first to third external connection pads  241   j ,  242   j , and  243   j  may have a substantially rectangular planar shape. A length of each of the first and second external connection pads  241   j  and  242   j  in the X direction may be greater than a length of each of the first and second external connection pads  241   j  and  242   j  in the Y direction. The length of the third external connection pad  243   j  in the X direction may be smaller than the length in the Y direction. The first to third external connection pads  241   j ,  242   j , and  243   j  together may be symmetric to each other with respect to an axis passing through the center  201 C of the lower surface of the package substrate  201  and parallel to the X direction. 
     According to embodiments, the first external connection pad  241   j  may include first to fourth sides  241   j S 1 ,  241   j S 2 ,  241   j S 3 , and  241   j S 4 , the second external connection pad  242   j  may include first to fourth sides  242   j S 1 ,  242   j S 2 ,  242   j S 3 , and  242   j S 4 , and the third external connection pad  243   j  may include first to fourth sides  243   j S 1 ,  243   j S 2 ,  243 jS 3 , and  243   j  S 4 . 
     According to embodiments, a first stress relief finger  241   j  SF may be formed on the first side  241   j S 1 , and a second stress relief finger  242   j  SF may be formed on the first side  242   j S 1 . Dimensional and shape characteristics of the first and second stress relief fingers  241   j SF and  242   j  SF are similar to those described with reference to  FIG. 3D , and thus redundant descriptions thereof may be omitted. 
     The third external connection pad  243   j  may have substantially the same shape as the third external connection pad  243   h  of  FIG. 3H . 
       FIG. 4  is a perspective view of an illuminating device  10 ′ according to other embodiments. 
       FIG. 5  is a cross-sectional view of the illuminating device  10 ′ taken along line II-IF of  FIG. 4 . 
       FIG. 6  is a plan view illustrating a lower surface of an LED package  200 ′ included in the illuminating device  10 ′ of  FIG. 4 . 
       FIG. 7  is a partial plan view illustrating a part  100 M′ of a PCB  100 ′ on which the LED package  200 ′ of  FIG. 6  is mounted. 
     For convenience of description, redundant descriptions with those described with reference to  FIGS. 1A and 1B  may be omitted, and differences will be mainly described. 
     Referring to  FIGS. 4 to 6 , as a non-limiting example, the illuminating device  10 ′ may be a vehicle illuminating device similar to the illuminating device  10  of  FIG. 1 . 
     According to embodiments, the illuminating device  10 ′ may include the PCB  100 ′ and LED packages  200 ′. 
     The PCB  100 ′ may include, for example, a substrate base  101 ′ including aluminum, conductive patterns including first to third pads  111 ′,  112 ′, and  113 ′ formed on the substrate base  101 ′ and an insulating layer  120  surrounding the conductive patterns. 
     The substrate base  101 ′ is similar to the substrate base  101  described with reference to  FIGS. 1A and 1B , but may further include a stress relief groove SRG and a conductive plate  103 . 
     The stress relief groove SRG may horizontally surround the first and second pads  111 ′ and  112 ′ in X and Y directions. The stress relief groove SRG may surround the first and second pads  111 ′ and  112 ′, excluding a part where a first connecter  116 ′ is formed and a part where a second connecter  117 ′ is formed. Accordingly, the first and second connectors  116 ′ and  117 ′ may be interposed between ends EP of the stress relief groove SRG. 
     The stress relief groove SRG may horizontally surround the third pad  113 ′. According to embodiments, the stress relief groove SRG may not completely surround the third pad  113 ′ horizontally so that the substrate base  101 ′ disposed below the third pad  113 ′ is not completely separated. 
     The stress relief groove SRG may expose an upper surface of the conductive plate  103  disposed in the substrate base  101 . The depth of the stress relief groove SRG in a Z direction may be in the range of about 35% to about 50% of the thickness of the substrate base  101 ′. 
     The conductive plate  103  may at least partially overlap the LED package  201 ′ in the Z direction. In  FIG. 3A , it is shown that one LED package  201 ′ is provided on one conductive plate  103 , but this is an example, and the scope of the inventive concept is not limited thereto. For example, two or more LED packages may be provided on one conductive plate. 
     According to embodiments, a conductive pattern including the first to third pads  111 ′,  112 ′, and  113 ′ and the first and second connectors  116 ′ and  117 ′ may include conductive materials such as copper. The insulating layer  120 ′ may include, for example, a photo-sensitive resist. One of a cathode and an anode of the LED package  200 ′ may be connected to the first pad  111 ′, and the other may be connected to the second pad  112 ′. 
     According to embodiments, the first and second pads  111 ′ and  112 ′ may provide a path for supplying operating power to the LED package  200 ′. According to embodiments, the first to third pads  111 ′,  112 ′, and  113 ′ may provide a path for dissipating heat generated by the LED package  200 . 
     A plurality of LED packages  200 ′ may be mounted on the PCB  100 ′. The plurality of LED packages  200 ′ may be fixed to and connected to the PCB  100 ′ by a first solder  151 ′, a second solder, and a third solder  153 ′. The first solder  151 ′ may be connected to the first pad  111 ′, the second solder may be connected to the second pad  112 ′, and the third solder  153 ′ may be connected to the third pad  113 ′. 
     Each of the LED packages  200 ′ may be similar to the 3-pad LED package  200   g  shown in  FIG. 3G . Each of the LED packages  200 ′ may include the package substrate  201 , the LED chip  210 , the encapsulant  220 , the side reflective layer  230 , and first to third external connection pads  241 ′,  242 ′, and  243 ′. The shapes of the first to third external connection pads  241 ′,  242 ′ and  243 ′ are sequentially similar to the shapes of the first to third external connection pads  241   g ,  242   g , and  243   g  (see  FIG. 3G ). 
     The first external connection pad  241 ′ may be connected to the first pad  111 ′ through the first solder  151 ′, the second external connection pad  242 ′ may be connected to the second pad  112 ′ through the second solder, and the third external connection pad  243 ′ may be connected to the third pad  113 ′ through the third solder  153 ′. 
     While the inventive concept has been shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.