Wlcsp packages with different solder volumes

Abstract

Embodiments of the present disclosure relate to WLCSP packages having different solder volumes. The present disclosure relates to wafer-level chip-scale packages (WLCSPs) having various combinations of contacts and under bump metallization (UBM) with different structures and different amounts of solder coupled to the contacts and UBM. Despite the different structures of the contacts and the different volumes of solder, the overall standoff height along the WLCSP remains substantially the same. Each portion of solder coupled to each respective contact and UBM includes a point furthest from an active surface of a die of the WLCSP. Each point of each respective portion of solder is coplanar with respective points of other respective portions of solder. Additionally, the contacts having various and different structures are positioned on the active surface of the die of the WLCSP accordingly to reduce failures that can result from the WLCSP being exposed to thermal cycling or the WLCSP being dropped.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a wafer level chip scale package (WLCSP) comprising contacts and solder bumps. BACKGROUND

[0002] Generally, semiconductor device packages, such as chip scale packages or wafer level chip scale packages (WLCSPs), are electrically coupled to a printed circuit board (PCB) by solder bumps or conductive adhesive material having the same shape, height, and volume.

[0003] As the demand for providing more WLCSPs in electronic devices to perform increasingly complex functions increases, while at the same time reducing manufacturing costs, increasing resistance to external stresses to reduce the likelihood of failure, and increasing board level reliability of the WLCSPs, there are significant challenges in balancing all of the above preferences. Examples of electronic devices include a notebook computer, a display, a television, a smart phone, a tablet computer, or any other electronic device. SUMMARY

[0004] Embodiments of the present disclosure overcome various significant challenges associated with wafer level chip scale packages (WLCSPs), such as increasing resistance to external stresses to reduce the likelihood of failure and increasing board level reliability of the WLCSPs.

[0005] One significant challenge is increasing the strength of electrical connections between the WLCSP and the PCB to reduce failure while maintaining strong electromigration performance. For example, failures that can occur due to external stresses and forces can include cracking, delamination, melting, or any other type of failure that can occur in the WLCSP while in use. It is desirable to have a strong physical connection of the WLCSP and the PCB and strong electrical communication between each other. However, a particular electrical connection in a particular location between the WLCSP and the PCB is more susceptible to failure due to external stresses and forces than other electrical connections at other locations. Accordingly, it is desirable to provide different types of electrical connections at different locations between the WLCSP and the PCB to maintain good electrical communication while reducing the likelihood of failure of the electrical connections that are most susceptible to failure.

[0006] Another significant challenge is providing electrical connections for the WLCSP that all have the same height but are made of different amounts of conductive material to improve board level reliability of the WLCSP and to improve resistance of the WLCSP to external forces and stresses. These external forces or stresses can be caused by the WLCSP being dropped, being exposed to thermal cycling, or other external forces and stresses that the WLCSP can be exposed to during use.

[0007] Yet another significant challenge is to provide different types of electrical connections for the semiconductor die or WLCSP. For example, different types of electrical connections can carry different amounts of current to improve the energy efficiency of the electronic device and increase the life of the semiconductor die, WLCSP, and the entire electronic device.

[0008] In view of these challenges, which are not an exhaustive list, it is desirable to provide WLCSPs that can perform more complex functions while improving the resistance to failure, such as cracking or delamination, of electrical connections between the WLCSP and a PCB, enhancing the electromigration strength at particular contacts to improve electrical communication between the WLCSP and various electrical components within the electronic device, and providing electrical connections with the same standoff height so that the WLCSPs can be coupled to other electrical components without any further processing or adding more solder material or conductive material.

[0009] The present disclosure relates to various embodiments of WLCSPs having electrical connections of under bump metal (UBM) made of different amounts of solder material and shaped differently to increase electromigration at particular electrical connections, increase the resistance to cracking or delamination at particular electrical connections due to external stresses, and reduce the cost of manufacturing WLCSPs having electrical connections of UBM made of different amounts of solder material and shaped differently.

[0010] According to one or more embodiments, a WLCSP includes a die having an active component, an active surface, and a passive surface. The passive surface faces away from the active surface. An electrical contact is on the active surface and is coupled to the active component in the die. A plurality of layers of re-passivation material are on the active surface of the substrate and are used to form a redistribution layer (RDL) on the electrical contact of the die and a plurality of UBMs having different heights on the RDL. Each of the plurality of UBMs and the RDL are in electrical communication with the active component and the passive component in the die. For example, the active component and the passive component receive electrical current through the UBMs and the RDL and the active component and the passive component communicate electrical signals to external electrical components through the RDL and the plurality of UBMs.

[0011] In some embodiments, a first UBM has a first height and a second UBM has a second height, the second height being less than the first height. The second UBM includes a recessed portion that accommodates solder material or conductive material and the first UBM includes a protruding portion that places solder material or conductive material. The first standoff height of the solder material or conductive material and the first UBM is substantially the same as the second standoff height of the solder material or conductive material and the second UBM.

[0012] In some embodiments, a first UBM having a first height is coupled to the RDL, and a recessed portion or opening is aligned with the RDL. The recessed portion or opening is configured to accommodate a solder material or conductive material placed directly on the RDL. In this alternative embodiment, the solder material or conductive material and the first UBM have a first standoff height that is substantially the same as a second standoff height of the solder material or conductive material on the RDL and in the recessed portion or opening.

[0013] In some embodiments, a first UBM is directly coupled to a first contact of the die, and a second UBM is directly coupled to a second contact of the die. In other words, there is no RDL in this alternative embodiment. The first UBM has a first height, and the second UBM has a second height that is less than the first height. The second UBM can have a recessed portion or opening that accommodates a solder material or conductive material. The solder material or conductive material is placed on the first UBM and the second UBM. The first standoff height of the solder material or conductive material and the first UBM is substantially the same as the second standoff height of the solder material or conductive material and the second UBM. BRIEF DESCRIPTION OF DRAWINGS

[0014] In the drawings, like reference numerals identify similar elements or acts throughout the several views. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale.

[0015] Figure 1 is a cross-sectional view of a wafer-level chip-scale package (WLCSP) having a first under bump metal (UBM) with a protruding portion and a second UBM with a recessed portion, in accordance with one or more embodiments;

[0016] Figure 2 is a cross-sectional view of a WLCSP having a first UBM and an opening, in accordance with one or more embodiments;

[0017] Figure 3 is a cross-sectional view of a WLCSP having a first UBM with a protruding portion and a second UBM with a recessed portion that is directly coupled to a contact of a die, in accordance with one or more embodiments;

[0018] Figures 4A-4N is a cross-sectional view illustrating a method of forming a WLCSP, such as the WLCSP shown in Figure 1 is a schematic block diagram illustrating an electronic device including a WLCSP, in accordance with one or more embodiments; and

[0019] Figure 5 is a schematic block diagram illustrating an electronic device including a WLCSP, in accordance with one or more embodiments; and DETAILED DESCRIPTION

[0020] In the following description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments of the present disclosure. However, those skilled in the art will understand that the present disclosure may be practiced without these specific details. In other instances, well-known structures associated with electronic components and semiconductor fabrication techniques have not been described in detail to avoid unnecessarily obscuring the description of embodiments of the present disclosure.

[0021] Unless the context otherwise requires, throughout the following specification and claims, the word “comprising” and its variations (such as “including” and “including”) shall be interpreted in an open inclusive sense, that is, as “including but not limited to”.

[0022] The use of ordinal numbers such as first, second, and third does not necessarily imply the meaning of the sorted order, but can simply distinguish multiple instances of an action or structure.

[0023] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] As described below, the terms "left" and "right" are used only for the purpose of discussion regarding the orientation of components in a discussion based on the diagrams in this disclosure. These terms are not limited to any possible location of explicit, implicit, or inherent disclosure in this disclosure.

[0025] The term "substantially" is used to clarify that there may be subtle differences in the manufacture of WLCSPs in the real world, because it is impossible to make anything exactly the same or identical. The term is not restrictive, as it is only used to clarify the real-world manufacture of WLCSPs. In other words, "substantially" means that there may be some minor variations in practice, because it is impossible to make anything perfect, but rather to make it within acceptable tolerances.

[0026] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural indicators unless otherwise clearly indicated. It should also be noted that the term “or” is generally used to mean “and / or” unless otherwise clearly indicated.

[0027] The present disclosure relates to various embodiments of semiconductor device packages, such as wafer-level chip-scale packages (WLCSPs), that include a die and first and second portions of conductive material on an active surface of the die that have different heights. The first portion has a first height and the second portion has a second height that is less than the first height. Even though the first and second portions have different heights, each of the first and second portions has a point that is furthest from the active surface of the WLCSP that is substantially coplanar in a plane that is substantially parallel to the active surface of the WLCSP. The term "substantially" means that while in preferred embodiments the points can be perfectly aligned, when the WLCSP is manufactured in real-world practice, there can be some variation in the way the points are aligned. In other words, substantially means that there can be some slight variation in actual practice because it is not possible to make anything perfect, but rather to make it within acceptable tolerances.

[0028] While various embodiments are shown and described with respect to wafer-level chip-scale packages (WLCSPs), it will be readily appreciated that embodiments of the present disclosure are not limited thereto. In various embodiments, structures, devices, methods, etc. described herein can be embodied in or otherwise utilized with any suitable type or form of semiconductor package, and can be manufactured utilizing any suitable semiconductor packaging technology.

[0029] Figure 1 is a cross-sectional side view of a WLCSP 100 in accordance with one or more embodiments. The WLCSP includes a die 102, which can be a semiconductor die made of a semiconductor material such as silicon, germanium, gallium arsenide, silicon carbide, etc. The die 102 has a passive surface 101 and an active surface 103, and various active components such as electrical components of one or more integrated circuits, etc. can be formed in the die 102 and can be located at or near the active surface 103. A plurality of contact pads 104 are on the active surface 103 of the die 102. Each respective contact pad of the plurality of contact pads 104 is coupled to a respective active or passive component within the die 102. The contact pads 104 are electrically coupled to the die 102 and can communicate various signals to and from the active components in the die 102, such as power signals, command signals, and instruction signals. The passive surface 101 of the die 102 faces away from the active surface 103 of the die 102.

[0030] A first re-passivation layer 106 is on the active surface 103 of the die 102, and the first re-passivation layer 106 has openings aligned with the contact pads 104. In various embodiments, the first re-passivation layer 106 can be formed of any dielectric or insulating material. These openings allow the contact pads 104 to be coupled to a redistribution layer (RDL) 108 made of a conductive material. The conductive material can be a copper material, a silver material, a gold material, an alloy material, or any other conductive material or combination of conductive materials, as desired. The RDL 108 is on the first re-passivation layer 106 and extends into the first re-passivation layer 106 toward the die 102. The RDL 108 extends into the first re-passivation layer 106 through the openings of the first re-passivation layer 106 to electrically and mechanically couple the RDL 108 to the contact pads 104.

[0031] Each of the contact pads 104 is coupled to a respective portion (e.g., a conductive trace or segment) of the RDL 108. The portions of the RDL 108 are separated from one another in the lateral direction, and in some embodiments, the portions of the RDL 108 can be electrically isolated from one another such that each portion can carry separate signals to and from electrical components of the die 102. Some portions of the RDL 108 can be coupled to multiple ones of the contact pads 104, and some portions of the RDL 108 can be coupled to only one of the contact pads 104. The portions of the RDL 108 that are coupled to the multiple contact pads 104 fill the openings in the first re-passivation layer 106, are coupled to the multiple contact pads 104, and are on the first re-passivation layer 106.

[0032] A second re-passivation layer 110 is on the first re-passivation layer 106 and the RDL 108. The second re-passivation layer 110 includes a plurality of openings that are each aligned with and at least partially expose a respective portion of the RDL 108. In various embodiments, the second re-passivation layer 110 can be formed of any dielectric or insulating material, and in some embodiments, the second re-passivation layer 110 can be formed of the same material as the first re-passivation layer 106.

[0033] The first contact 112 is formed in a first opening of the plurality of openings of the second re-passivation layer 110, and the second contact 117 is formed in a second opening of the plurality of openings of the second re-passivation layer 110. The first contact 112 includes a recessed portion that extends toward the active surface 103 of the die 102 (e.g., the recessed portion of the first contact 112 can extend at least partially into the second opening of the second re-passivation layer 110). The second contact 117 includes a first portion 114 and a second portion 116 on the first portion 114. The first contact 112 and the second contact 117 can be referred to as and are under bump metal (UBM). The second contact 117 is positioned closer to the left side of the die 102, and the first contact 112 is positioned closer to the right side of the die 102. Even though only two contacts are shown in Figure 1 In general, a number of contacts having the structure of the first contact 112, a number of contacts having the structure of the second contact 117, or a number of contacts having different structures can be present on the active surface 103 of the die 102. For example, if the WLCSP 100 has a ball grid array (BGA) solder ball configuration, in general, the various contacts of the WLCSP 100 can have different structures in different locations, such as the structures of the first contact 112 and the second contact 117 or some other contact structure. It can be desirable to have different contacts with different structures in different locations, which will be discussed in more detail below with respect to Figure 5 .

[0034] The second contact 117 has a height hi from a surface of the RDL 108 on which the second contact 117 is located to a surface of the second contact 117 that faces away from the surface of the RDL 108. The first contact 112 has a height h2 from a surface of the RDL 108 on which the first contact 112 is located to a point of the first contact 112 that is farthest from the surface of the RDL 108. The height h2 of the first contact 112 is less than the height hi of the second contact 117.

[0035] A first conductive structure 118 is on the first contact 112 and a second conductive structure 120 is on the second contact 117. The first conductive structure 118 can be referred to as a first solder structure, a first portion of conductive material, or a first portion of solder material. The second conductive structure 120 can be referred to as a second solder structure, a second portion of conductive material, or a second portion of solder material. The first conductive structure 118 and the second conductive structure 120 can be a solder material, a paste material, or some other conductive material configured to couple one electronic component to another electronic component. The second conductive structure 120 has a height h4 extending from a surface of the first portion 114 of the second contact 117 facing away from the active surface 103 of the die 102 to a point of the second conductive structure 120 furthest from the active surface 103 of the die 102. The first conductive structure 118 has a height h3 extending from a surface of the recess of the first contact 112 facing away from the active surface 103 of the die 102 to a point of the first conductive structure 118 furthest from the active surface 103 of the die 102. The height h4 of the second conductive structure 120 is less than the height h3 of the first conductive structure 118.

[0036] While the heights h3, h4 of the first conductive structure 118 and the second conductive structure 120 of conductive material are not equal, the points of the first conductive structure 118 and the second conductive structure 120 furthest from the active surface 103 of the die 102 are coplanar or substantially in a plane substantially parallel to the active surface 103 and the inactive surface 101 of the die 102. The reason these points are coplanar is because the second conductive structure 120 has a first total height h5 (e.g., a height between the highest point of the second conductive structure 120 and the RDL 108) equal to a second total height h6 of the first conductive structure 118 and the first contact 112. That is, the distance between the RDL 108 and the highest point or vertex of each of the first conductive structure 118 and the second conductive structure 120 is substantially equal. It is desirable that the first total height h5 be substantially equal to the second total height h6, however, for brevity and simplicity, the desirability of these substantially equal heights will be discussed in detail later after embodiments have been discussed that do not have these substantially equal heights. Figures 1-3

[0037] Figure 2 FIG. 1 illustrates a WLCSP 100 according to one or more embodiments. The WLCSP 100 includes a die 102 having an inactive surface 101 and an active surface 103 with a plurality of contact pads 104. The plurality of contact pads 104 are coupled to active components within the die 102 and provide power signals, command signals, and instruction signals to the active components of the die 102.

[0038] ​A first re-passivation layer 206 is on the active surface of the die 202, and the first re-passivation layer 206 has openings aligned with the contact pads 204. These openings allow the contact pads 204 to be coupled to a redistribution layer (RDL) 208 made of an electrically conductive material. The electrically conductive material can be a copper material, a silver material, a gold material, an alloy material, or any other electrically conductive material, as desired. The RDL 208 is on the re-passivation layer 206 and extends into the re-passivation layer 206 toward the die 202. The RDL 208 extends into the re-passivation layer 206 through the openings of the re-passivation layer 206 to couple the RDL 208 to the contact pads 204.

[0039] Each respective contact pad 204 of the plurality of contact pads 204 is coupled to a respective portion of the RDL 208. Each respective portion of the RDL 208 is separated from one another in the lateral direction. Some respective portions of the RDL 208 can be coupled to multiple respective contact pads of the plurality of contact pads 204, and some respective portions of the RDL 208 can be coupled to only one respective contact pad of the plurality of contact pads 204. Portions of the RDL 208 fill the openings in the first re-passivation layer 206, are coupled to the plurality of contact pads 204, and are on the first re-passivation layer 206.

[0040] A second re-passivation layer 210 is on the first re-passivation layer 206 and the RDL 208. The second re-passivation layer 210 includes a plurality of openings that are each aligned with and expose a portion of each respective portion of the RDL 208.

[0041] A contact 212 is formed in a first opening of the plurality of openings of the second re-passivation layer 210, which can be referred to as and is a UBM 212. The contact 212 has a height h7 extending from a surface of the respective portion of the RDL 208 on which the contact 212 is mechanically and electrically coupled. The contact 212 extends away from the active surface 203 of the die 202. A first electrically conductive structure 214 is coupled to a surface of the contact 212 that faces away from the active surface 203 of the die 202. The first electrically conductive structure 214 can be referred to as a first solder structure, a first portion of an electrically conductive material, or a first portion of a solder material. The first electrically conductive structure 214 has a height h9.

[0042] The second conductive structure 216 is coupled to a surface of a respective portion of the back die active surface 203 of the RDL 208. The second conductive structure 216 can be referred to as a second solder structure, a second portion of conductive material, or a second portion of solder material. The second conductive structure 216 has a height h8 that is greater than the height h7 of the contact 212 and greater than the height h9 of the first conductive structure 214. The sum of the height h7 of the contact 212 and the height h9 of the first conductive structure 214 is substantially equal to the height h8 of the second conductive structure 216. It is desirable that the height h7 of the contact 212 and the height h9 of the first conductive structure 214 add up to be substantially equal to the height h8 of the second conductive structure 216, however, for brevity and simplicity, these equal height desirabilities will be discussed in more detail after the embodiments in Figures 1-3 have been discussed. Figure 5 It is also desirable that there be a contact with a height h7 and that there be no contact at the respective portion of the RDL 208 where the second conductive structure 216 is coupled to the RDL 208, which will be discussed in more detail with respect to

[0043] Figure 3 FIG. 1 illustrates a WLCSP 100 in accordance with one or more embodiments. The WLCSP 100 includes a die 102 having a passive surface 101 and an active surface 103 with a plurality of contact pads 104. The plurality of contact pads 104 are coupled to active components within the die 102 and the plurality of contact pads 104 provide power signals, command signals, and instruction signals to the active components of the die 102.

[0044] A first re-passivation layer 106 is on the active surface 103 of the die 102 and the first re-passivation layer 106 has openings aligned with the contact pads 104. These openings allow the contact pads 104 to be coupled to a plurality of contacts 111, 112.

[0045] A first portion 108 of the first contact 111 is coupled to a respective contact pad 104 of the plurality of contact pads 104 and a second portion 110 of the first contact 111 is coupled to the first portion 108 of the first contact 111. The first contact 111 can be referred to as a UBM 111 and is a first UBM 111. The first contact 111 has a height h 10 .

[0046] The second contact 312 is coupled to a respective contact pad 304 of the plurality of contact pads 304. The second contact 312 includes a recessed portion that extends toward the active surface 303 of the die 302. The second contact 312 has a height h 11 that extends from a surface of the respective contact pad 304 to which the second contact 312 is coupled to a surface of the second contact 312 that faces away from the active surface 303 of the die 302. The height h 11 of the second contact 312 is less than the height h 10 of the first contact 311. The second contact can be referred to as a UBM 312 and is a second UBM 312.

[0047] Even though only two contacts are shown in Figure 3 , there can be a number of contacts having the structure of the first contact 311, a number of contacts having the structure of the second contact 312, or a number of contacts having a structure that is different from both the structures on the active surface 303 of the die 302 disclosed in Figure 3 . For example, if the WLCSP 300 has a ball grid array (BGA) solder ball configuration, various contacts of the WLCSP 300 in different locations can have a structure that is different from the first contact 311 and the second contact 312. It can be desirable to have different contacts with different structures and heights in different locations, which will be discussed in more detail below with respect to Figure 5 .

[0048] The first conductive structure 314 is on the first contact 311. The first conductive structure 314 can be referred to as a first solder structure, a first portion of conductive material, or a first portion of solder material. The first conductive structure 314 has a height h 13 that extends from a surface of the first portion 308 of the first contact 311 that faces away from the active surface 303 of the die 302 to a point of the first conductive structure 314 that is farthest from the active surface 303 of the die 302 with respect to the first conductive structure 314.

[0049] The second conductive structure 316 is on the second contact 312. The second conductive structure 316 can be referred to as a second solder structure, a second portion of conductive material, or a second portion of solder material. The second conductive structure 316 has a height h 12 that extends from a surface of the recess of the second contact 312 that faces away from the active surface 303 of the die 302 to a point of the second conductive structure 316 that is farthest from the active surface 303 of the die 302 with respect to the second conductive structure 316.

[0050] Although the height h 13 of the first conductive structure 314 of the conductive material is greater than the height h 12are not equal, but the points of the first and second conductive structures 314, 316 that are farthest from the active surface 303 of the die 302 are coplanar in a plane that is substantially parallel to the active surface 303 and the inactive surface 301 of the die 302. As described directly above, the reason these points are coplanar is because the first total height h 14 (e.g., the height between the highest point of the first conductive structure 314 and the respective contact pad 304 to which the first contact 311 is coupled) is equal to the second total height h 15 of the second conductive structure 316 and the second contact 312. That is, the distance between each respective contact pad 304 and the highest point or vertex of the first and second conductive structures 314, 316 is substantially equal. It is desirable that the first total height h 14 is substantially equal to the second total height h 15 However, for the sake of brevity and simplicity, the desirability of these equal heights will be discussed in detail later after various embodiments shown in Figures 1-3 have been discussed.

[0051] The corresponding total heights of the respective solder material and contacts in the various embodiments shown and described with respect to Figures 1-3 are desirable because even if the solder material for each contact has a different solder volume, the total height of the solder material and the contact allows the respective WLCSP to be easily coupled to an external electronic device without any additional components. For example, if the total height of the solder material and the contact on the WLCSP were different, it would be more difficult to mount the WLCSP within an electronic device. This would be more difficult because it is preferred that the active surface of the WLCSP be substantially parallel to the surface on which it is mounted. However, in order for the WLCSP to be substantially parallel to the surface on which it is mounted, additional components or additional layers of material must be provided on the external electronic device to allow the solder material and the contact with the different total heights to be coupled to the external electronic device such that the active surface of the WLCSP is substantially parallel to the surface on which it is mounted.

[0052] Similarly, if the WLCSP is mounted to a printed circuit board (PCB) and the solder material and the contact have different total heights from one another, it would be more difficult to mount the WLCSP to the PCB for the same reasons discussed above.

[0053] When placing a WLCSP on an electronic device, these additional layers of material or additional components that will be added to mount the WLCSP having a total height of the solder material and the contacts to the electronic device different can result in a significant decrease in the allowable tolerances. This decrease in the allowable tolerances makes it more difficult to mount the WLCSP to the electronic device. Accordingly, to facilitate mounting the WLCSP to an external electronic device without providing additional layers of material or additional components, it is desirable to have a total height of the solder material and the contacts that is substantially equal to each other. This substantially equal relationship of the total height results in a substantially same standoff height across the WLCSP when mounting the WLCSP within an electronic device or coupled to a PCB without adding additional layers of material or additional mounting components.

[0054] Figures 4A-4N A method of forming a semiconductor device package, such as a WLCSP similar or identical to the WLCSP 100 shown in Figure 1 Although the method shown in Figures 4A-4N may be described with respect to a WLCSP similar to the WLCSP 100 shown in Figure 1 , it will be readily appreciated that in various embodiments of the present disclosure, the method can be utilized or adapted to form semiconductor device packages having various different structures or features, including, for example, the WLCSP 200, the WLCSP 300 shown in Figure 2 and Figure 3 . Accordingly, for simplicity and brevity, different steps utilized in the method of forming a WLCSP similar or identical to the WLCSP 100 shown in Figure 1 will be discussed as compared to the steps utilized in the method of forming the WLCSP 200, the WLCSP 300 shown in Figure 2 and Figure 3 .

[0055] Figure 4A A die 402 is shown including an active surface 433 and a non-active surface 431. The active surface 433 and the non-active surface 431 face away from each other. A plurality of contact pads 404 are on the active surface 433 of the die 402. Each respective contact pad of the plurality of contact pads 404 is coupled to an active component and a non-active component within the die 402. Although the active component and the non-active component are not shown in the die 402, the active component and the non-active component can include a resistor, a transistor, a sensor, an inductor, a capacitor, an electrical connection, a microelectromechanical system (MEMS), or any other active component and non-active component that can be present within the die 402.

[0056] In Figure 4BIn step 403 illustrated in FIG. 4, a re-passivation or passivation layer 406 is formed on the active surface 433 of the die 402. However, for simplicity and brevity, the layer of material formed on the active surface 433 of the die 402 will be referred to as a first re-passivation layer 406. The first re-passivation layer 406 can be formed by a chemical process, an irradiation process, a vapor deposition process, a deposition process, or any other re-passivation or passivation layer formation technique. The first re-passivation layer 406 is formed to cover the plurality of contact pads 404 on the active surface 433 of the die 402. Although in this embodiment, the re-passivation layer 406 does not extend to the edges or sidewalls of the die 402, in other alternative embodiments, the re-passivation layer 406 can extend to the sidewalls or edges of the die 402. In summary, the re-passivation layer 406 can be an insulating material, a corrosion resistant material, a semiconducting material, a dielectric material, or some other material.

[0057] As Figure 4C As illustrated in FIG. 4, after the step 403 of forming the first re-passivation layer 406, in step 405, an opening 408 is formed in the first re-passivation layer 406. The opening 408 can be formed by selectively removing portions of the first re-passivation layer 406. The portions of the re-passivation layer 406 can be selectively removed, for example, by a chemical etching, a photoresist etching, a wet etching technique, a plasma etching technique, or any other etching technique configured to remove a portion of the first re-passivation layer 406. Alternatively, a removal tool can be utilized instead of an etching technique to form the opening 408 in the first re-passivation layer 406, or some other removal technique can be utilized to remove portions of the first re-passivation layer 406 to form the opening 408.

[0058] If the etching technique is utilized to form the openings 408 in the first re- passivation layer 406, a plurality of resist layers, insulating layers, dielectric layers, semiconductor layers, or sacrificial layers can be stacked on the first re- passivation layer 406 to form the openings 408 and then later removed after the openings 408 are formed. For example, a mask layer can be formed on the first re- passivation layer 406 and a photoresist layer can be formed on the mask layer. The photoresist layer can then be exposed to light or UV light to remove a portion of the photoresist layer to expose a portion of the mask layer. The portion of the exposed mask layer can then be removed or patterned to expose a portion of the re- passivation layer 406. The photoresist layer is then removed and the portion of the first re- passivation layer 406 that was exposed after the photoresist layer was removed can be removed, patterned, or etched to expose a respective contact pad of the plurality of contact pads 404. The removal of this portion of the first re- passivation layer 406 forms the openings 408 aligned with the respective contact pads of the plurality of contact pads 404. Each of the plurality of openings 408 exposes at least one respective contact pad of the plurality of contact pads 404 on the active surface 433 of the die 402 and each of the plurality of openings 408 is aligned with at least one respective contact pad of the plurality of contact pads 404 on the active surface 433 of the die 402.

[0059] In some embodiments, the openings 408 have a width that is less than a width of the contact pads 404. In some embodiments, the openings 408 can have a width that is greater than a width of the contact pads 404 and in other embodiments, the openings 408 can have a width that is substantially equal to a width of the contact pads 404. However, in other alternative embodiments, some of the openings 408 can have a width that is greater than a width of the contact pads 404, some of the openings 408 can have a width that is less than a width of the contact pads 404, and some of the openings 408 can have a width that is substantially equal to a width of the contact pads 404. Accordingly, any combination of openings 408 having varying widths can be utilized to expose each respective contact pad of the plurality of contact pads 404 on the active surface 433 of the die 402.

[0060] After the step 405 of forming the openings 408 in the first re- passivation layer 406 to expose the plurality of contact pads 404, Figure 4DIn step 407 illustrated, a conductive material RDL 410 is formed on a first repassivation layer 406 and a plurality of contact pads 404. The RDL 410 comprises several portions of conductive material. Each corresponding portion of the RDL 410 is coupled to at least one corresponding contact pad among the plurality of contact pads 404. However, corresponding portions of the RDL 410 may be coupled to multiple corresponding contact pads among the plurality of contact pads 404. The RDL 410 extends through and fills the opening 408, allowing the RDL 410 to be coupled to the multiple contact pads 404. Each corresponding portion of the RDL 410 is laterally separated and spaced from the other corresponding portions of the RDL 410 to avoid short circuits or crosstalk between different portions of the RDL 410, thereby ensuring that the active and passive components of the die 402 function correctly.

[0061] like Figure 4E As illustrated, after step 407 where RDL 410 is formed on the first repassivation layer 406, in step 409, a second repassivation layer 412 is formed on the first repassivation layer 406 and RDL 410. Although as... Figure 4E As illustrated, the second repassivation layer 412 does not extend to the edge or sidewall of the die 402 or to the edge and side of the first repassivation layer 406. However, in other embodiments, the second repassivation layer 412 may extend to the sidewall or edge of the die 402, the edge and side of the first repassivation layer 406, or both. In summary, the second repassivation layer 412 may be an insulating material, a corrosion-resistant material, a semiconductor material, a dielectric material, or some other material.

[0062] Similar to the first repassivation layer 406, the second repassivation layer 412 can be formed by chemical processes, irradiation processes, vapor deposition processes, deposition processes, or any other repassivation or passivation layer formation techniques. In some embodiments, the first repassivation layer 406 and the second repassivation layer 412 can be formed from the same material. The second repassivation layer 412 is formed to cover RDL 410.

[0063] like Figure 4FAs illustrated in the middle, after the second re-passivation layer 412 is formed over the RDL 410 and the first re-passivation layer 406 at step 409, in step 411, openings 439 are formed in the second re-passivation layer 410. The openings 439 can be formed by chemical etching, photoresist etching, wet etching techniques, plasma etching techniques, or any other etching technique configured to remove a portion of the second re-passivation layer 412 in a similar manner as discussed above with respect to the first re-passivation layer 406. Alternatively, a removal tool can be utilized instead of an etching technique to form the openings 439 in the second re-passivation layer 412, or some other removal technique can be utilized to remove portions of the second re-passivation layer 412 in a similar manner as discussed above with respect to the first re-passivation layer 406 to form the openings 439. Because the openings 439 in the second re-passivation layer 412 are formed in a similar manner as the openings 408 in the first re-passivation layer 406, the details of forming the second re-passivation layer 412 will not be discussed in further detail for the sake of simplicity and brevity. The removal of the portions of the second re-passivation layer 412 forms the openings 439 aligned with respective portions of the RDL 410. Each respective opening of the plurality of openings 439 exposes a respective portion of the RDL 410 on the active surface 433 of the die 402 and is aligned with the respective portion of the RDL 410 on the active surface 433 of the die 402.

[0064] In some embodiments, the openings 439 have a width that is greater than the width of the contact pads 404 and the width of the openings 408 formed to expose the contacts in step 408. In some embodiments, the width of the openings 439 can be substantially equal to the width of the contact pads 404 or the width of the openings 408, and in another alternative embodiment, the openings 439 can have a width that is less than the width of the contact pads 404 or the width of the openings 408. However, in other alternative embodiments, some of the openings 439 can have a width that is greater than the width of the contact pads 404 and the openings 408, some of the openings 439 can have a width that is less than the width of the contact pads 404 and the openings 408, and some of the openings 439 can have a width that is substantially equal to the width of the contact pads 404 and the openings 408. In other words, any combination of openings 439 having varying widths can be utilized to expose each respective portion of the RDL 410 on the active surface 433 of the die 402.

[0065] After the step 411 in which the openings 439 are formed in the second re- passivation layer 412 to expose portions of the RDL 410, in a step 413, first contact structures 414 are formed in each respective opening 439 in the second re- passivation layer 412. Each respective first contact structure 414 extends into the respective opening 439 in the second re-passivation layer 412 and over a respective portion of the RDL 410. Each first contact structure 414 includes a recessed portion that is aligned with the portion of the RDL 410 to which the first contact structure 414 is coupled. However, in other alternative embodiments of the first contact structure 414, the first contact structure 414 can not have a recessed portion that extends toward the active surface 433 of the die 402. In this embodiment, the first contact structure 414 is formed in an opening 439 that is formed to expose a portion of the RDL 410. Each respective first contact structure 414 is coupled to a respective portion of the RDL 410.

[0066] Each first contact structure 414 includes a portion on a surface of the second re- passivation layer 412 that faces away from the active surface 433 of the die 402. These portions of the first contact structure 414 increase the surface area of the first contact structure 414 to improve electrical communication and physical connection between the first contact structure 414 and the solder material or conductive material, as will be discussed later in Figure 4M and Figure 4N .

[0067] The first contact structures 414 can be formed by a vapor deposition technique, an electroplating deposition technique, or any other deposition technique used to form conductive contact structures. Alternatively, the first contact structures can be formed using a plurality of insulating layers, dielectric layers, semiconductor layers, conductive layers, sacrificial layers, or any other material layers as similarly used to form the openings 408 of the first re- passivation layer 406, as discussed earlier. However, unlike the removal of portions of the first re-passivation layer 406 to form the openings 408, an additive formation technique, which can be one of the deposition techniques discussed earlier, is used in conjunction with these material layers to form the first contact structures 414. Some of the first contact structures 414 can be part of a contact or a complete contact, as will be discussed with respect to Figure 4I . Accordingly, the first contact structures that are complete contacts can be referred to as first contacts 414.

[0068] As Figure 4HAs illustrated in the middle, after the step 413 in which the first contact structures 414 are formed in the openings 439 of the second re-passivation layer 412, in a step 415, a sacrificial layer 416 is formed on the active surface 433 of the die 402. The sacrificial layer 416 is formed to cover some of the first contact structures 414 and leave some of the first contact structures 414 exposed. Openings 418 are formed in the sacrificial layer 416 to expose some of the first contact structures 414. The sacrificial layer can be formed in a similar manner as the first re-passivation layer 406 as discussed above. The openings 418 in the sacrificial layer 416 can be formed in a similar manner as discussed with respect to the openings 408 in the first re-passivation layer 406. The sacrificial layer 416 can be an insulating layer, an oxide layer, a non-conductive layer, a sacrificial re-passivation layer, a sacrificial passivation layer, or some other sacrificial material.

[0069] In some embodiments, the first contact structures 414 covered by the sacrificial layer 416 are first contacts 414, and the first contact structures 414 exposed by the openings 418 in the sacrificial layer 416 are first portions of second contacts 429.

[0070] The openings 418 have a width that is less than a width of the first contact structures 414. The openings 418 expose respective recessed portions of the first contact structures 414. In alternative embodiments, the openings can have a width that is substantially equal to a width of the first contact structures 414, substantially equal to a width of the recessed portions of the first contact structures 414, or less than a width of the recessed portions of the first contact structures 414. In some embodiments, a portion of the sacrificial layer is on a portion of the first contact structures 414 that is on the second re-passivation layer 412.

[0071] After the step 415 in which the sacrificial layer 416 having the openings 418 is formed on the active surface 433 of the die 402, in a step 417, the second contact structures 420 are formed in the openings 418 aligned with the respective first contact structures 414. The second contact structures 420 fill the openings 418 in the sacrificial layer 416. Each respective second contact structure 420 is coupled to at least one respective first contact structure 414 that is exposed through the respective opening 418 in the sacrificial layer 416. The second contact structures 420 can be made of a copper material, a gold material, a silver material, an alloy material, or some other electrically conductive material. The second contact structures 420 can be made of the same electrically conductive material as the first contact structures 414. Each second contact structure 420 is a second portion of a complete second contact 429, and each respective first contact structure 414 coupled to the respective second contact structure is a first portion of the complete second contact 429. Accordingly, the first contact structures 414 and the second contact structures 420 coupled to the first contact structures 414 can be referred to as the second contacts 429. The second contacts 429 can be referred to as (and are) UBMs, external contacts, or any other type of contact used to mount a die within an electronic device, a PCB, or another die.

[0072] In some embodiments, the second contact structures 420 have a width that is less than a width of the first contact structures 414, and the width of the second contact structures 420 is substantially equal to a width of the openings 418. However, in alternative embodiments, the second contact structures 420 can have a width that is substantially equal to or greater than a width of the first contact structures 414.

[0073] In some embodiments, the second contact structures 420 have a surface with a recessed portion that extends toward the active surface 433 of the die 402. However, in alternative embodiments, the second contact structures 420 can have a surface without a recessed portion.

[0074] As Figure 4J As illustrated in FIG. 4B, after the step 417 in which the second contact structures 420 are formed in the openings 418 in the sacrificial layer 416, in a step 419, the sacrificial layer 416 is removed. The sacrificial layer 416 can be removed by a removal tool, which can be a laser removal tool, a cutting removal tool, or some other type of removal tool. Alternatively, the sacrificial layer can be removed by an etching process, which can be a wet etching, a chemical etching, a radiation etching, or some other etching. After the sacrificial layer 416 is removed, the respective first contact structures 414 (i.e., the first contacts 414) covered by the sacrificial layer 416 are again exposed. Alternatively, the sacrificial layer 416 can be a material that degrades when exposed to heat, and can be removed by being exposed to heat.

[0075] After the step 419 in which the sacrificial layer is removed, in step 421 a template 422 is placed on the second re-passivation layer 412, as illustrated in Figure 4K The template includes a first opening 424 aligned with the second contact 429 and a second opening 426 aligned with the first contact 414. The template can be secured in place by a sacrificial adhesive material, a temporary adhesive material, a weak adhesive material, or can be secured in place by a machine. Alternatively, the template 422 can be picked up and secured in place by a pick and place machine.

[0076] After the step 421 in which the template 422 is placed on the second re- passivation layer 412, in step 423 a solder material 428 is formed on the template 422 and fills the first opening 424 and the second opening 426, and then excess solder material is removed by a squeegee 430. The solder material 428 can be a solder paste material, a conductive paste material, a conductive adhesive material, or some other conductive material configured to mount a die within an electronic device, to couple the die to a PCB, or to couple the die to some other external device. The solder material 428 is placed on the template 422 to fill the first opening 424 and the second opening 426. The solder material 428 in the first opening 424 and the second opening 426 covers the second contact 429 and the first contact 414 closer to the right side of the die 402. Excess solder material is placed on the template to fill the first opening and the second opening to increase the likelihood that the solder material will be coupled to the second contact 429 and the first contact 414.

[0077] When the excess solder material 428 is utilized, the excess solder material 428 is removed. The excess solder material 428 is removed by the squeegee 430. The squeegee 430 is pulled or pushed across the surface of the template 422 that is facing away from the active surface 433 of the die 402. As the squeegee 430 is pulled or pushed across the surface of the template 422 that is facing away from the active surface 433 of the die 402, the excess solder material is removed. After the excess solder material 428 is removed, the solder material 428 that remains within the first opening 424 and the second opening 426. The surface of the solder material 428 in the first opening 424 and the second opening 426 that is facing away from the active surface 433 of the die 402 is substantially flush with the surface of the template 422 that is facing away from the active surface 433 of the die 402.

[0078] Once the excess solder material 428 is removed by the squeegee 430, in the next step 425 the solder material 428 in the first opening 424 and the second opening 426 is allowed to solidify before the template 422 is removed.

[0079] After the solder material 428 is placed on the template 422 and excess solder material 428 is removed by the squeegee 430 at step 423, the template 422 is removed from the second passivation layer 412 in step 425. The template 422 can be removed by a pick and place machine that removes the template 422 from the second passivation layer 412. Once the template 422 is removed, the first solder portion 434 is coupled to the first contact 414 and the second solder portion 432 is coupled to the second contact 429. The surfaces of the first solder portion 434 and the second solder portion 432 that are opposite the active surface 433 of the die 402 are substantially coplanar. In other words, the total height of the first contact 414 from the first portion 434 of solder material is substantially equal to the total height of the second contact 429 from the second solder portion 432. The second solder portion 432 has a smaller volume than the first solder portion 434 because the second contact 429 has a larger volume than the first contact 414 and because less solder material 428 is in the first opening 424 than in the second opening 426 when the squeegee 430 removes the excess solder material 428. The surface of the solder material 428 in the first opening 424 and on the second contact 429 that corresponds to the second solder portion 432 is flush with the surface of the solder material 428 in the second opening 426 and on the first contact 414 that corresponds to the first solder portion 434 from the surface of the template 422 that is opposite the active surface 433 of the die 402.

[0080] Because the solder material 428 is allowed to solidify in the first opening 424 and the second opening 426 before the template is removed, the first solder portion 434 and the second solder portion 432 have sides that are transverse to the active surface 433 of the die 402.

[0081] In some embodiments, the second solder portion 432 covers the second contact 429 and the sides of the second contact 429. The first solder portion 434 covers the first contact 414 and the sides of the first contact 414. The second contact 429 extends into the second solder portion 432. The first solder portion 434 extends into the recessed portion of the first contact 414. In alternative embodiments, the second solder portion 432 covers the second contact 429 and has a width that is substantially equal to the width of the second contact 429. In another alternative embodiment, the first solder portion 434 covers the first contact 414 and has a width that is substantially equal to the width of the first contact 414. In yet another alternative embodiment, the second solder portion 432 has a width that is less than the width of the second contact 429 and the first solder portion 434 has a width that is less than the width of the first contact 414.

[0082] After the solder material 428 is solidified to form the first solder portion 434 and the second solder portion 432, and the template 422 is removed in the step 425, in a step 427, the first solder portion 434 and the second solder portion 432 are reflowed to form a first solder bump 438 on the first contact 414 and a second solder bump 436 on the second contact 429. The first solder bump 438 and the second solder bump 436 can be referred to as first and second conductive structures, respectively. The first solder portion 434 and the second solder portion 432 can be reflowed by placing the die in a reflow oven or exposing the solder material to a heat source that will cause reflow of the solder portions 432, 434. The reflow process causes the first solder portion 434 and the second solder portion 432 in Figure 4M to become the first solder bump 438 and the second solder bump 436 as shown in Figure 4N .

[0083] As illustrated in Figure 4N , the first solder bump 438 covers the first contact structure 414 and the second solder bump 436 covers the second contact structure 420. In some embodiments, the first solder bump 438 and the second solder bump 436 leave exposed side surfaces of the first contact structure 414 and the second contact structure 420, and the first solder bump 438 and the second solder bump 436 do not contact the second passivation layer 412. However, in some other embodiments, the first solder bump 438 and the second solder bump 436 can cover the side surfaces of the first contact structure 414 and the second contact structure 420, can be a combination of covering the side walls or leaving exposed side walls of the first contact structure 414 and the second contact structure 420, and can be in direct contact with the second passivation layer 412.

[0084] The above method can be modified to form an embodiment of the WLCSP 200 in Figure 2 by removing the step 413 and instead going from the step 411 to the step 417 to form the UBM 212. Alternatively, the above method can be modified to form an embodiment of the WLCSP 300 in Figure 3 by removing the steps 407, 409, 411 and instead forming the first contact 311 and the second contact 312 on the contact pad 304.

[0085] Figure 5is a block diagram illustrating an electronic device 502 that includes a WLCSP 504, a microprocessor 506 coupled to the WLCSP 504, a memory 508 coupled to the microprocessor 506, and a power supply 510 coupled to the microprocessor 506. The microprocessor 506 receives signals from the WLCSP 504, and the microprocessor 506 sends signals to the WLCSP 504. The microprocessor 506 sends signals to the memory 508 for storage, and the memory 508 sends signals, such as instruction signals, to the microprocessor 506. The power supply 510 supplies power to the microprocessor 506, and the microprocessor distributes the power received from the power supply to other components of the electronic device, such as the WLCSP 504 and the memory 508.

[0086] While the following discussion focuses on embodiments of the WLCSP 100 in Figure 1 the following discussion applies to corresponding components of alternative embodiments of the WLCSP 200, the WLCSP 300 in Figures 2-3 and Figure 4N The following focuses on board-level reliability of the WLCSP 100, the WLCSP 200, the WLCSP 300, and board-level reliability includes resistance to thermal cycling and resistance to failure due to drops. However, board-level reliability can include consideration of other factors that can increase or decrease the likelihood of failure of the WLCSP 100, the WLCSP 200, the WLCSP 300. The following discussion also applies to other alternative embodiments that are not expressly disclosed in the present disclosure but are inherent or implicit in the present disclosure.

[0087] As noted above with respect to Figure 1As discussed, the total height h6 of the first contact 112 and the first conductive structure 118 on the first contact is substantially equal to the total height h5 of the second contact 117 and the second conductive structure 120. However, the height h2 of the first contact 112 is less than the height hi of the second contact 117, and the volume of the first conductive structure 118 is greater than the volume of the second conductive structure 120. The second contact 117, having a greater height hi and a greater volume than the first contact 112, has a greater resistance to thermal cycling than the first contact 112 because less conductive material is used to form the second conductive structure 120 on the second contact 117 as compared to forming the first conductive structure 118 on the first contact 112. The conductive material can be a solder material. Less solder material or conductive material is used to form the second conductive structure 120 as compared to the first conductive structure 118. This reduction in solder material or conductive material reduces the likelihood of failure of the electrical connection due to thermal cycling because solder material or conductive material is more susceptible to failure due to stresses that result from expansion and contraction of the solder material or conductive material due to thermal cycling, meaning that having less solder material or conductive material to form the second conductive structure 120 reduces the chance of failure due to thermal cycling. Accordingly, the greater volume of the second contact 117 as compared to the first contact 112 and the smaller volume of the second conductive structure 120 as compared to the first conductive structure 118 increases the resistance of the second contact 117 and the second conductive structure 120 to thermal cycling when compared to the first contact 112 and the first conductive structure 118.

[0088] The greater volume of the second contact 117 as compared to the first contact 112 increases the electromigration capability of the second contact 117 when compared to the first contact 112. The greater volume of the second contact 117, which can be made of a copper material, a copper alloy, or some other conductive material, reduces the total electrical resistance of the second contact 117 in combination with the second conductive structure 120.

[0089] Due to the increased resistance to thermal cycling, the second contacts 117 are generally positioned at the corner bumps or connections of the WLCSP 100. It is desirable that the increased resistance to thermal cycling due to the second contacts 117 at the corners of the WLCSP 100 because the deformation, contraction, or expansion of the WLCSP 100 and the solder material 428 and their effects are generally greater at the corners of the WLCSP 100 than near the center of the WLCSP 100. Accordingly, this increase in resistance to thermal cycling of the second contacts 117 reduces the likelihood of failure due to thermal cycling in the bump connections at the corners of the WLCSP 100. Failures due to thermal cycling can include cracking in the bump connections, delamination of the bump connections due to expansion, contraction, or deformation of the die or bump connections, or any other form of failure that can result from thermal cycling.

[0090] The second contacts 117 and the second conductive structures 120 form a stronger physical connection with external components than the first contacts 112 and the first conductive structures 118. The connection is stronger because the larger second contacts 117 are made of a physically stronger material than the portion of the conductive material. Accordingly, the larger second contacts 117 and the second conductive structures 120 form a stronger physical connection with external components when compared to the first contacts 112 and the first conductive structures 118.

[0091] While the second contacts 117 can be positioned at the corners of the WLCSP 100, other contacts having the same or similar structure as the second contacts 117 can be positioned anywhere on the WLCSP 100 as desired to reduce the likelihood of connection failure due to thermal cycling. For example, the contacts 212 in Figure 2 the first contacts 311 in Figure 3 may have similar positioning as the second contacts 117 of the WLCSP 100 as discussed earlier.

[0092] While the first contacts 112 have less resistance to thermal cycling, less electromigration, and are physically weaker than the second contacts 117 as discussed above, the first contacts 112 with the first conductive structures 118 have greater resistance to failure due to the WLCSP 100 being dropped when compared to the second contacts 117 and the second conductive structures 120. For example, the drop can result from the WLCSP 100 being dropped while being transported, while being installed within an electronic device, while the WLCSP 100 is undergoing drop testing, or when the WLCSP 100 is subjected to forces and stresses as a result of being dropped, among any other instances.

[0093] The first contact 112 having the first conductive structure 118 is more resistant to drop than the second contact 117 having the second conductive structure 120 because the first conductive structure 118 has a greater volume than the second conductive structure 120. The greater volume of the first conductive structure 118 increases the resistance to drop because the conductive material, which is generally a solder material, has a greater ability to absorb stress and force due to being dropped than the conductive material that makes up the first contact 112 or the second contact 117. In other words, the conductive material of the first conductive structure 118 can deform, expand, and compress with a lower probability of failure than the first contact 112, the second contact 117, or the second conductive structure 120. Because the first conductive structure 118 has a greater volume than the second conductive structure 120, and because of the greater volume, the first conductive structure 118 is more resistant to stress and force due to being dropped than the second conductive structure 120, resulting in a lower probability of failure.

[0094] The first contact 112 having the first conductive structure 118 is generally placed near the center of the WLCSP 100. Although the first contact 112 having the first conductive structure 118 can be positioned near the center of the WLCSP 100, contacts having the same or similar structure as the first contact 112 can be positioned anywhere on the WLCSP 100 as desired to reduce the probability of failure of electrical mounting connections due to drop failure. For example, Figure 2 the second conductive structure 216 in the second contact 212 in Figure 3 the second contact 312 having the second conductive structure 316 in the second contact 312 in Figure 1 may have similar positioning as the first contact 112 having the first conductive structure 118 as discussed above with respect to

[0095] In view of the above discussion, by utilizing contacts having different heights and volumes, in addition to the total height and volume of the combination of the respective contact and its corresponding conductive material portion, the portions of conductive material having different heights and volumes increase the resistance of the respective WLCSP to thermal cycle failure and drop failure of the respective connections. Different combinations of different positions can also maintain desired board level reliability and electromigration. It is desirable that the total height of the respective contacts and respective conductive structures be substantially equal to each other and allow embodiments of the respective WLCSP to be easily mounted to external electronics with proper standoff height.

[0096] The various embodiments described above can be combined to provide further embodiments.

[0097] These and other changes can be made to the embodiments in light of the above detailed description. In general, the described features, structures, or characteristics can be combined in any suitable manner to form yet further embodiments, including in suitable combinations of two or more of the described embodiments. The instant specification provides support for these and other combinations. Accordingly, no limitation is placed on the scope of equivalents inspired by the disclosed embodiments.

Claims

1. An electronic device comprising: a die including an active surface and an inactive surface, the active surface having a plurality of contact pads; a first re-passivation layer on the active surface of the die; a plurality of conductive layers coupled to the plurality of contact pads of the die, the conductive layers being on the first re-passivation layer; a second re-passivation layer on the first re-passivation layer and the plurality of conductive layers; a first contact coupled to one of the plurality of conductive layers, the first contact having a first height, the first contact extending into the second re-passivation layer; a second contact coupled to one of the plurality of conductive layers, the second contact having a second height, the second height being less than the first height, the second contact extending into the second re-passivation layer; and a first conductive structure on the first contact, the first conductive structure having a third height and a first point furthest from the active surface of the die; a second conductive structure on the second contact, the second conductive structure having a fourth height and a second point furthest from the active surface of the die, the fourth height being greater than the third height, the second point being substantially coplanar with the first point.

2. The electronic device of claim 1, wherein: a first total height of the first contact and the first conductive structure extends from a surface of the first contact coupled to the conductive layer to the first point furthest from the active surface of the die; and a second total height of the second contact and the second conductive structure extends from a surface of the second contact coupled to the conductive layer to the second point furthest from the active surface of the die, the second total height being substantially equal to the first total height.

3. The electronic device of claim 1, wherein the second contact includes a recessed portion extending into the second contact toward the active surface of the die.

4. The electronic device of claim 1, wherein: the first conductive structure has the first point furthest from the first contact; and the second conductive structure has the second point furthest from the second contact and substantially coplanar with the first point of the first conductive structure.

5. The electronic device of claim 1, wherein: the fourth height of the second conductive structure is greater than the second height of the second contact; and the third height of the first conductive structure is less than the first height of the first contact.

6. An electronic device comprising: a die having an active surface and an inactive surface; a plurality of contact pads on the active surface of the die; a first re-passivation layer on the active surface of the die; a first conductive layer on the first re-passivation layer and coupled to one of the plurality of contact pads; a second conductive layer on the first re-passivation layer and coupled to one of the plurality of contact pads; a second re-passivation layer on the first re-passivation layer, the first conductive layer, and the second conductive layer; and a first contact coupled to one of the plurality of conductive layers, the first contact having a first height, the first contact extending into the second re-passivation layer; ​ ​ a first contact extending into the second passivation layer and coupled to the first conductive layer, a first solder structure on the first contact, the first solder structure having a first height and a first point furthest from the active surface of the die; and a second solder structure on the active surface of the die, the second solder structure having a second height and a second point furthest from the active surface of the die, the second height greater than the first height, the second point substantially coplanar with the first point, the second solder structure separated from the first contact by the second passivation layer.

7. The electronic device of claim 6, wherein the first contact includes a third height, and the device further includes a second contact having a fourth height, the fourth height less than the third height of the first contact, the second contact physically coupled to the second solder structure.

8. The electronic device of claim 6, wherein: the first contact is physically coupled to the first solder structure, the first contact having a third height, the first contact positioned between the first conductive layer and the first solder structure.

9. A method for manufacturing an electronic device, comprising: forming a first passivation layer on an active side of a die, the first passivation layer covering a plurality of contact pads of the die; forming a plurality of first openings in the first passivation layer, each respective first opening of the plurality of first openings aligned with a respective contact pad of the plurality of contact pads; forming a plurality of first conductive layers in the plurality of first openings and on the plurality of contact pads; forming a second passivation layer on the plurality of first conductive layers and on the first passivation layer; forming a plurality of second openings in the second passivation layer, each respective second opening of the plurality of second openings aligned with a respective first conductive layer of the plurality of first conductive layers; forming a first conductive structure in one of the plurality of second openings and on a respective one of the plurality of first conductive layers, comprising: forming a first contact structure; and forming a first solder structure having a first height, having a first point furthest from the active side of the die, and on the first contact structure; and forming a second conductive structure in another of the plurality of second openings and on a respective other of the plurality of first conductive layers, comprising: forming a second solder structure having a second height and having a second point furthest from the active side of the die, the second height greater than the first height, the second point substantially coplanar with the first point in a plane parallel to the active side of the die; forming the first conductive structure and forming the second conductive structure simultaneously comprising: placing a template on an active side of a die, the template having openings aligned with the first conductive structures and the second conductive structures on the active side of the die; and filling the openings of the template with a conductive material; and removing excess portions of the conductive material on the template to simultaneously form the first solder structures having the first height and the second solder structures having the second height.

10. The method of claim 9, wherein forming the first conductive structure and the second conductive structure further comprises: removing the excess portions of the conductive material on the template by a squeegee.

11. The method of claim 9, wherein: forming the first contact structures includes forming the first contact structures having a third height; and forming the second conductive structures further includes forming second contact structures having a fourth height, the fourth height being less than the third height.

12. The method of claim 11, wherein: forming the second conductive structures includes forming the second solder structures on the second contact structures.

13. The method of claim 11, wherein a first sum of the first height of the first solder structures and the third height of the first contact structures is substantially equal to a second sum of the second height of the second solder structures and the fourth height of the second contact structures.

14. The method of claim 9, further comprising: forming a plurality of second conductive layers in the plurality of second openings and on the plurality of first conductive layers; forming a resist layer on the second re-passivation layer and the plurality of second conductive layers; forming a third opening in the resist layer aligned with one of the plurality of second conductive layers; and forming a third conductive layer in the third opening and on the one of the plurality of second conductive layers.

15. A method for fabricating an electronic device, comprising: forming first conductive structures on an active side of a die, including: forming first contact structures; and forming first solder structures having a first height, having a first point furthest from the active side of the die, and on the first contact structures; and forming second conductive structures on the active side of the die, including: forming second solder structures having a second height, and having a second point furthest from the active side of the die, the second height being greater than the first height, the second point being substantially coplanar with the first point in a plane parallel to the active side of the die; forming the first conductive structures and forming the second conductive structures simultaneously including: placing a template on an active side of a die, the template having openings aligned with the first conductive structures and the second conductive structures on the active side of the die; and filling the openings of the template with a conductive material; and removing excess portions of the conductive material on the template to simultaneously form the first solder structures having the first height and the second solder structures having the second height, wherein: forming the first contact structure includes forming the first contact structure having a third height; and forming the second conductive structure further includes forming a second contact structure having a fourth height on the active side of the die, the fourth height being less than the third height, the method includes: forming a re-passivation layer on a first contact pad and a second contact pad on the active side of the die; forming a first opening in the re-passivation layer on the first contact pad and a second opening in the re-passivation layer on the second contact pad; forming a first contact having a first height on the first contact pad, the first contact being coupled to the first contact pad and the first conductive structure; and forming a second contact having a second height on the second contact pad, the second height being greater than the first height, the second contact being coupled to the second contact pad and the second conductive structure, wherein a sum of the first height of the first conductive structure and the third height of the first contact is substantially equal to a sum of the second height of the second conductive structure and the fourth height of the second contact.

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