Patent Publication Number: US-2021184087-A1

Title: Packaged ultraviolet light-emitting device and production method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a bypass continuation-in-part application of International Application No. PCT/CN2018/104008 filed on Sep. 4, 2018. The entire content of the international patent application is incorporated herein by reference. 
    
    
     FIELD 
     The disclosure relates to a packaged light-emitting device and a production method thereof, and more particularly to a packaged ultraviolet light-emitting device and a production method thereof. 
     BACKGROUND 
     Light-emitting diodes (LEDs) are solid semiconductor lighting devices, and deep-ultraviolet LEDs area type of LEDs. With improvement of technology, the production cost and efficiency of deep-ultraviolet LEDs can be respectively reduced and enhanced, and deep-ultraviolet LEDs can have a broader applicability. In particular, since mercury-containing lamps are phasing out, the demand of deep-ultraviolet LEDs is increasing. 
     Referring to  FIG. 1 , a conventional packaging structure for a deep-ultraviolet LED chip  104  (having a substrate) includes a support base  101  made of ceramic and a cover  102  made of quartz glass. The support base  101  is formed with a cavity  103  for accommodating the deep-ultraviolet LED  104  therein, and hence substantially has a U-shape section. The cover  102  is disposed on the support base  101  to cover the cavity  103 . Due to its U-shape section for forming the cavity  103 , the support base  101  has an unsatisfactorily large overall thickness, such that the conventional packaging structure is undesirably large in size and has a high production cost. In addition, since a gap normally exists between the deep-ultraviolet LED chip  104  and the cover  102  due to the U-shape section of the support base  101 , the light generated by the deep-ultraviolet LED chip  104  is required to travel from the substrate thereof (e.g. a sapphire substrate having a refractive index of 1.76) first to the air in the gap and then to the cover  102  (having a refractive index of 1.40 attributed to its quartz glass material), thus lowering the light emission efficiency of the deep-ultraviolet LED chip  104 . 
     Besides, some other packaging structures may include a flat ceramic substrate and a silicone encapsulant for encapsulating a deep-ultraviolet LED chip. However, deep ultraviolet light (having a wavelength lower than or equal to 290 nm) emitted might strongly damage the silicone encapsulant, such that the silicone encapsulant might break after long-term irradiation by deep ultraviolet light. Furthermore, the silicone encapsulant has a lower transmittance for deep ultraviolet light. 
     Inorganic encapsulants made of a fluororesin normally have a refractive index of 1.35 and a higher transmittance for ultraviolet light, thereby being reliable and serving as promising encapsulants for deep-ultraviolet LED chips. However, fluororesins, which have unsatisfactory adhesiveness, are difficult to be firmly attached to desired components, hence being easily detached due to a cutting process or vibration and causing formation of voids during reflow soldering. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a packaged ultraviolet light-emitting device and a production method thereof that can alleviate at least one of the drawbacks of the prior art. 
     The packaged ultraviolet light-emitting device includes a support member, at least one ultraviolet light-emitting chip, and an encapsulating cover. The support member has a top surface and a bottom surface opposite to each other, and a side surface interconnecting the top and bottom surfaces. The support member further has at least one indentation. The ultraviolet light-emitting chip is disposed on the top surface of the support member. The encapsulating cover is made from a fluorine-containing resin, and is disposed over and in contact with the ultraviolet light-emitting chip and the top surface and the indentation of the support member. The encapsulating cover extends into the indentation. 
     The production method includes the following steps. A substrate is provided, and has an upper surface and a lower surface opposite to each other, and a lateral surface interconnecting the upper and lower surfaces. A plurality of indentations are formed on the substrate. A plurality of ultraviolet light-emitting chips are disposed respectively on surfaces of portions of the substrate that together constitute the upper surface of substrate. An encapsulant is formed over and in contact with the ultraviolet light-emitting chips, the indentations, and the surfaces of the portions of the substrate. The encapsulant is made from a fluorine-containing resin, and extends into the indentations. The substrate is cut to obtain a plurality of separated support members. The support members respectively have the indentations and are the portions of the substrate. The encapsulant is cut to obtain a plurality of separated encapsulating covers. The encapsulating covers respectively cover the indentations and the ultraviolet light-emitting chips. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment (s) with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic view illustrating a conventional packaging structure for a deep-ultraviolet LED (light-emitting diode) chip; 
         FIGS. 2 to 7  are schematic sectional views illustrating steps in a first embodiment of a production method according to the present disclosure, which is for producing a first embodiment of a packaged ultraviolet light-emitting device according to the present disclosure; 
         FIGS. 8 to 9  are schematic sectional views illustrating steps in a second embodiment of the production method according to the present disclosure, which is for producing a second embodiment of the packaged ultraviolet light-emitting device according to the present disclosure; 
         FIG. 10  is a schematic sectional view illustrating a third embodiment of the packaged ultraviolet light-emitting device according to the present disclosure; 
         FIGS. 11 to 14  are schematic sectional views illustrating steps in a fourth embodiment of the production method according to the present disclosure, which is for producing a fourth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure; 
         FIG. 15  is a schematic sectional view illustrating a fifth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure; 
         FIG. 16  is a schematic sectional view illustrating a sixth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure; 
         FIG. 17  is a schematic sectional view illustrating a seventh embodiment of the packaged ultraviolet light-emitting device according to the present disclosure; 
         FIG. 18  is a schematic sectional view illustrating an eighth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure; and 
         FIG. 19  is a schematic sectional view illustrating a ninth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. 
     In reference to the disclosure herein, for the purpose of illustration only, directional terms, such as, “top”, “bottom”, “upper”, “lower”, “side”, and “lateral”, are used with respect to the relative positions. Such directional terms should not be construed to limit the scope of the disclosure in any manner. 
     Referring to  FIGS. 2 to 7 , a first embodiment of a method for producing a packaged ultraviolet light-emitting device according to the present disclosure is illustrated and includes steps 1 to 6. 
     In step 1, as shown in  FIG. 2 , a substrate  21  and a plurality of electrodes  22  are provided. The substrate  21  has an upper surface  211  and a lower surface  213  opposite to each other, and a lateral surface  212  interconnecting the upper and lower surfaces  211 ,  213 . In this embodiment, the electrodes  22  are formed on both of the upper and lower surfaces  211 ,  213  through metal plating. 
     The substrate  21  may be made from a material selected from the group consisting of ceramic, glass (e.g. quartz glass, regular glass, etc.), and a combination thereof. In this embodiment, the substrate  21  is made from low temperature co-fired ceramic (LTCC). The substrate  21  may have a thickness ranging from 0.25 mm to 0.5 mm. 
     In step 2, as shown in  FIG. 3 , a plurality of cutting recesses  23  are formed to be recessed from the lower surface  213  of the substrate  21  toward the upper surface  211  by cutting with a soft blade (normally a resin blade) or laser. Specifically, each of the cutting recesses  23  is formed between two adjacent pairs of the electrodes  22  on the lower surface  213  of the substrate  21 , or at a respective one of two opposite terminal ends of the substrate  21 . 
     Each of the cutting recesses  23  may have a depth that is one third to a half of the thickness of the substrate  21 . Cutting may be operated using more than one soft blade. For example, a first cutting operation may use a soft blade having a blade width of 0.2 mm, and a second cutting operation may use a soft blade having a blade width of 0.1 mm, so that a cutting recess  23  formed can be further split to obtain indentations having a width of 0.05 mm. In addition to cutting with a soft blade or laser, other approaches may be applied to form the cutting recesses  23 . For instance, during a sintering process for preparing the substrate  21  using ceramic, a pressing tool may be used to press the substrate  21  to form the cutting recesses  23 . 
     In step 3, as shown in  FIG. 4 , the substrate  21  is cut along a centerline of the respective cutting recess  23 , for instance, using a soft blade having a blade width (e.g. 0.05 mm to 0.1 mm), so that a plurality of separated support members  214  are obtained (namely, the support members  214  are portions of the substrate  21 ), and so that each cutting recess  23  is split in half to obtain two indentations  231  equal in size (namely, the centerline of the respective cutting recess  23  serves a border of the two of the indentations  231  adjoined to each other). Each of the support members  214  has a top surface  2141  and a bottom surface  2143  opposite to each other, a side surface  2142  interconnecting the top and bottom surfaces  2141 ,  2143 , and two of the indentations  231 . In this embodiment, each of the indentations  231  is indented from the side and bottom surfaces  2142 ,  2143  of the corresponding support member  214 . 
     It should be noted that the aforesaid portions of the substrate  21  may refer to the separated support members  214  for ultraviolet light-emitting chips to be disposed thereon (in this embodiment), or may refer to regions of the uncut substrate  21  for ultraviolet light-emitting chips to be disposed thereon and for being later separated to serve as the support members  214  (in other embodiment). 
     In this embodiment, the substrate  21  is cut from the upper surface  211  thereof opposite to the cutting recesses  23 , since the support members  214  obtained might be damaged at the cut edges when the substrate  21  is cut from the cutting recesses  23  directly. 
     In step 4, the support members  214  and the respective electrodes  22  are transferred to a protective film  500  (see  FIG. 4 ) using, for instance, a heat-resistant tape (e.g. a polyimide tape). Subsequently, a plurality of ultraviolet light-emitting chips  300  are respectively disposed on the support members  214  (see  FIG. 5 ). To be exact, each ultraviolet light-emitting chip  300  is attached to the two electrodes  22  on the top surface  2141  of the corresponding support member  214  by virtue of a flux and reflow soldering. 
     Optionally, the protective film  500  may be expanded, for instance, 1.05-fold to 1.25-fold, so as to increase a space between two adjacent ones of the support members  214  for facilitating subsequent processing. 
     It should be noted that the ultraviolet light-emitting chips  300  may have a flip-chip structure, a horizontal structure, a vertical structure, or a high-voltage structure. Since the ultraviolet light-emitting chips  300  may be those known in the art, the detail thereof is omitted herein for the sake of brevity. 
     In step 5, as shown in  FIG. 6 , an encapsulant  40  is formed over and in contact with the following: the ultraviolet light-emitting chips  300 ; the indentations  231  of each support member  214 ; the electrodes  22  on the top surface  2141  of the respective support member  214 ; and the top, bottom, and side surfaces  2141 ,  2143 ,  2142  of each support member  214 . The encapsulant  40  is made from a fluorine-containing resin, and is integrally formed in this embodiment. The disposition of the encapsulant  40  may be conducted through hot pressing or dispensing. 
     In this embodiment, the indentations  231  each have an L-shaped section, so that each indentation  231  and the side surface  2142  of the corresponding support member  214  define a stepped structure. Alternatively, the indentations  231  may have a U-shaped section, a V-shaped section, or an arch-shaped section in other embodiments. Still alternatively, the section of the indentations  231  may have a substantially polygonal shape (e.g. square, rectangle, triangle, trapezoid, etc.) in other embodiments. 
     The encapsulant  40  is tightly attached to the ultraviolet light-emitting chips  300  to eliminate gap formation between the encapsulant  40  and the ultraviolet light-emitting chips  300 , thereby preventing total reflection and enhancing light emission. In addition, the tight attachment of the encapsulant  40  can provide excellent sealing and protection for the ultraviolet light-emitting chips  300 , hence securing the stability of the ultraviolet light-emitting chips  300 . 
     Examples of the fluorine-containing resin include, but are not limited to, polytetrafluoroethylene (PTFE) (e.g. modified PTFE or unmodified PTFE), fluorinated ethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and combinations thereof. 
     In step 6, as shown in  FIG. 7 , the encapsulant  40  is cut to obtain a plurality of separated encapsulating covers  400 . Each of the encapsulating covers  400  covers two of the indentations  231  and the top, bottom, and side surfaces  2141 ,  2143 ,  2142  of the corresponding support member  214 , as well as the corresponding ultraviolet light-emitting chip  300 . Specifically, the encapsulant  40  is cut at midway locations, each of which is between and equidistant to the two adjacent ones of the support members  214 . 
     After step 6, a plurality of packaged ultraviolet light-emitting devices (i.e. a first embodiment of the packaged ultraviolet light-emitting device according to the present disclosure) are produced. It should be noted that the protective film  500  may be removed, or may be not removed for the packaged ultraviolet light-emitting devices to be temporarily disposed thereon. 
     Since the indentations  231  with an L-shaped section each can allow the corresponding encapsulating cover  400  to extend therein, the attachment of the encapsulating cover  400  to the support member  214  can be enhanced. 
     A second embodiment of the production method and the packaged ultraviolet light-emitting device according to the present disclosure is similar to the first embodiment, except for the following differences. 
     In step 2, referring to  FIG. 8 , between two adjacent ones of the aforesaid portions of the substrate  21  for the ultraviolet light-emitting chips  300  to be disposed thereon (each of the two adjacent ones of such portions has four electrodes  22  disposed thereon), two separated indentations  231  are formed, instead of the two adjoined indentations  231  constituting the corresponding cutting recess  23  as shown in  FIG. 3 . At each of the two opposite terminal ends of the substrate  21 , only one indentation  231  is formed. Since the originally separated indentations  231  with a substantially rectangular section (see  FIGS. 8 and 9 ) have a larger surface area compared to the later separated indentations  231  with an L-shaped section (see  FIG. 7 ), and since the originally separated indentations  231  with a substantially rectangular section allow the corresponding encapsulating cover  400  to extend therein and engage therewith, the attachment of each encapsulating cover  400  to the corresponding support member  214  can be enhanced. 
     Referring to  FIG. 9 , a side part of the encapsulating cover  400  on the side surface  2142  of the corresponding support member  214  has a thickness (D) ranging from 20 μm to 500 μm. When the thickness (D) of the side part of the encapsulating cover  400  is too small, the encapsulating cover  400  might be unable to sufficiently encapsulate the corresponding support member  214 . Moreover, when the thickness (D) of the side part of the encapsulating cover  400  is too large, light emitted from the corresponding ultraviolet light-emitting chip  300  might undesirably travel along the side part of the encapsulating cover  400  toward the support member  214 , thus reducing luminance. 
     A third embodiment of the packaged ultraviolet light-emitting device according to the present disclosure is similar to the second embodiment, except that the indentations  231  in the third embodiment each have an arch section (see  FIG. 10 ), instead of the substantially rectangular section in the second embodiment (see  FIG. 9 ). 
     A fourth embodiment of the production method and the packaged ultraviolet light-emitting device according to the present disclosure is similar to the first embodiment, except for the following differences. 
     The fourth embodiment of the production method includes steps A to E. 
     Step A of the fourth embodiment is the same as step 1 of the first embodiment. 
     In step B, as shown in  FIG. 11 , each ultraviolet light-emitting chip  300  is attached to the two electrodes  22  on the corresponding one of the portions of the uncut substrate  21 . 
     In step C, as shown in  FIG. 12 , each of the cutting recesses  23  is formed to be recessed from the upper surface  211  of the substrate  21 . Specifically, each of the cutting recesses  23  is formed between two adjacent ones of the ultraviolet light-emitting chips  300  (i.e. between the two adjacent ones of the portions of the substrate  21  to be separated), and at the two opposite terminal ends of the substrate  21 . 
     In step D, as shown in  FIG. 13 , in addition to the ultraviolet light-emitting chips  300  and the cutting recesses  23  (i.e. the indentations  231 ) of the substrate  21 , the encapsulant  40  is further formed over and in contact with only the upper surface  211  of substrate  21  and the electrodes  22  thereon. 
     In the fourth embodiment, the indentations  231  of the substrate  21  have a roughness larger than those of the upper, lower, and lateral surfaces  211 ,  213 ,  212  of the substrate  21 . For instance, the indentations  231  of the substrate  21  may have a roughness not smaller than 0.5 μm, and at least one of the upper, lower, and lateral surfaces  211 ,  213 ,  212  of the substrate  21  hence may have a roughness not smaller than 0.2 μm. Due to the roughness of the indentations  231  of the substrate  21 , the encapsulant  40  can be more strongly attached to the substrate  21 , thereby enhancing sealing and protection for the ultraviolet light-emitting chips  300  and securing the stability of the ultraviolet light-emitting chips  300 . 
     In step E, as shown in  FIG. 14 , the encapsulant  40  and the substrate  21  are cut to obtain the separated encapsulating covers  400  and the separated support members  214 . Specifically, the encapsulant  40  and the substrate  21  are cut at midway locations, each of which is between and equidistant to the two adjacent ones of the ultraviolet light-emitting chips  300 . 
     After step E, the packaged ultraviolet light-emitting devices in the fourth embodiment are produced. The protective film  500  used in the first embodiment is dispensed with in the fourth embodiment. 
     A fifth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure is similar to the fourth embodiment, except that the indentations  231  in the fifth embodiment each have a substantially rectangular section (see  FIG. 15 ), instead of the L-shaped section in the fourth embodiment (see  FIG. 14 ). 
     A sixth embodiment of the production method and the packaged ultraviolet light-emitting device according to the present disclosure is similar to the first embodiment, except for the following differences. 
     The indentations  231  are formed after the substrate  21  is cut to obtain the support members  214 . Specifically, each of the indentations  231  is formed to be indented from the side surface  2142  of the corresponding support member  214  (see  FIG. 16 ). The ultraviolet light-emitting chips  300  are disposed on the electrodes  22  on the support members  214  after the formation of the indentations  231 . The indentations  231  in the sixth embodiment, which allow the side part of the encapsulating cover  400  to extend therein and engage therewith, can strengthen the attachment of the side part of the encapsulating cover  400  to the side surface  2142  of the corresponding support member  214 , thus enhancing sealing and protection for the corresponding ultraviolet light-emitting chip  300 . 
     In other embodiments, the indentations  231  indented laterally may be formed through sintering before the substrate  21  is cut (e.g. the indentations  231  indented laterally may be formed through sintering in parts of the substrate  21  not to be cut). 
     A seventh embodiment of the packaged ultraviolet light-emitting device according to the present disclosure is similar to the second embodiment, except for the following differences. 
     Referring to  FIG. 17 , the packaged ultraviolet light-emitting device in the seventh embodiment has three ultraviolet light-emitting chips  300  disposed on one support member  214 . Between the two adjacent ones of the ultraviolet light-emitting chips  300 , two separated indentations  231  are formed to be each indented from both the top and bottom surfaces  2141 ,  2143  of the support member  214 . At each of opposite terminal ends of the support member  214 , one indentation  231  is formed to be indented from both the top and bottom surfaces  2191 ,  2143  of the support member  214 . Namely, these indentations  231  are through holes. The fluorine-containing resin in an amorphous form may fill the through holes, and may be disposed completely or partially in spaces around the bottom surface  2143  of the support member  214  and the electrodes  22  thereunder. The number of the through holes may be varied when needed. 
     In the seventh embodiment, the ultraviolet light-emitting chips  300  on the support member  214  may be electrically connected with one another in series or parallel. 
     An eighth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure is similar to the second embodiment, except for the following differences. 
     Referring to  FIG. 18 , in addition to the two bottom indentations  231  indented from the bottom surface  2143  of the support member  214 , the support member  214  further has two top indentations  231  indented from the top surface  2141  of the support member  214 . The top and bottom indentations  231  adjacent to each other are completely staggered (namely, imaginary projections of such top and bottom indentations  231  are not overlapped at all), therefore increasing the strength of the attachment of the encapsulating cover  400  to the support member  214 . 
     A ninth embodiment of the packaged ultraviolet light-emitting device according to the present disclosure is similar to the eighth embodiment, except for the following differences. 
     Referring to  FIG. 19 , each of the bottom indentations  231  is indented from both of the bottom and side surfaces  2143 ,  2142  of the support member  214 , and has an L-shaped section instead of the substantially rectangular section shown in  FIG. 18 . The top and bottom indentations  231  adjacent to each other are partially staggered (namely, the imaginary projections of such top and bottom indentations  231  are partially overlapped). The bottom indentations  231  in the ninth embodiment, which allow the side part of the encapsulating cover  400  to extend therein and have a larger thickness, can further enhance sealing and protection for the corresponding ultraviolet light-emitting chip  300 . 
     The advantages of the packaged ultraviolet light-emitting device and the production method thereof according to the present disclosure are summarized below. 
     Compared to conventional packaged ultraviolet light-emitting devices, the packaged ultraviolet light-emitting device of the present disclosure is not required to have a cavity for accommodation, and has no gap between the ultraviolet light-emitting chip  300  and the encapsulating cover  400 , thereby being smaller in size and having a broader applicability. The packaged ultraviolet light-emitting device of the present disclosure may have a length smaller than 1.5 mm and a thickness smaller than 1 mm. 
     In addition, the indentations  231  of the packaged ultraviolet light-emitting device of the present disclosure can allow the encapsulating cover  400  to extend therein or further engage therewith, and can have a sufficient surface area in contact with the encapsulating cover  400 , thus securing the attachment of the encapsulating cover  400  to the support member  214 . Moreover, the indentations  231  may have a sufficient roughness to further enhance the attachment of the encapsulating cover  400  to the support member  214 . 
     Lastly, the encapsulating cover  400  can be tightly attached to the ultraviolet light-emitting chip  300 , hence enhancing the stability thereof, reducing total reflection, and increasing light emission efficiency. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. 
     While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.