Patent Publication Number: US-11658083-B2

Title: Film covers for sensor packages

Description:
BACKGROUND 
     Electrical circuits are formed on semiconductor dies and subsequently packaged inside mold compounds to protect the circuits from damage due to elements external to the package, such as moisture, heat, and blunt force. To facilitate communication with electronics external to the package, an electrical circuit within the package is electrically coupled to conductive terminals. These conductive terminals are positioned inside the package but are exposed to one or more external surfaces of the package. By coupling the conductive terminals to electronics external to the package, a pathway is formed to exchange electrical signals between the electrical circuit within the package and the electronics external to the package via the conductive terminals. 
     SUMMARY 
     In some examples, a sensor package includes a semiconductor die having a sensor; a mold compound covering a portion of the semiconductor die; and a cavity formed in a top surface of the mold compound, the sensor being in the cavity. The sensor package includes an adhesive abutting the top surface of the mold compound, and a semi-permeable film abutting the adhesive and covering the cavity. The semi-permeable film is approximately flush with at least four edges of the top surface of the mold compound. 
     In some examples, a method comprises covering an array of semiconductor dies with a mold compound, the mold compound having an array of cavities in a top surface of the mold compound. Each cavity in the array of cavities is vertically aligned with a sensor of a corresponding semiconductor die in the array of semiconductor dies. The method comprises coupling a semi-permeable film to the top surface of the mold compound using an adhesive. The semi-permeable film covers the array of cavities, and the semi-permeable film has an array of orifices. The method includes singulating the semiconductor dies in the array of semiconductor dies from each other to produce a sensor package. The sensor package includes a portion of the adhesive, a portion of the semi-permeable film, and an orifice of the array of orifices. The orifice exposes the portion of the adhesive to an exterior of the sensor package. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed description of various examples, reference will now be made to the accompanying drawings in which: 
         FIGS.  1 A- 7 D  are perspective, profile, and top-down views of a process flow for manufacturing a sensor package in accordance with various examples. 
         FIGS.  8 A- 19 C  are perspective, profile, and top-down views of another process flow for manufacturing a sensor package in accordance with various examples. 
         FIGS.  20 A- 25 C  are perspective, profile, and top-down views of another process flow for manufacturing a sensor package in accordance with various examples. 
         FIGS.  26 A- 32    are perspective, profile, top-down, and bottom-up views of another process flow for manufacturing a sensor package in accordance with various examples. 
         FIGS.  33 - 36    are flow diagrams of methods for manufacturing sensor packages in accordance with various examples. 
     
    
    
     DETAILED DESCRIPTION 
     Some types of packages are configured to measure various physical properties of an environment, such as temperature, humidity, light, sound, pressure, etc. In many instances, the package includes a sensor that is exposed directly to the environment to be tested. Thus, for example, a package that is configured to measure the temperature of a swimming pool may be positioned in an area of the pool where the sensor will be directly exposed to the pool water. Such packages are referred to herein as sensor packages. 
     Sensor packages contain sensors, but they also contain other circuitry, such as an analog front-end (AFE) circuit, to process the properties of the environment sensed by the sensor. This circuitry cannot be exposed to the environment, as doing so could damage the circuitry and render it inoperable. Accordingly, sensor packages are fabricated so that the sensor is exposed to the environment, but the remaining circuitry of the package is covered by the mold compound of the package. A sensor package may include a cavity in its mold compound, and the sensor is positioned inside this cavity from a top view of the sensor package. 
     Existing designs for sensor packages are unsatisfactory for multiple reasons. One such reason relates to the manner in which sensors in sensor packages are protected from exposure to dust, debris, pollution, and corrosive substances (e.g., flux, solder, cleaning solvents). Sensors are especially vulnerable to such exposure at the time that sensor packages are coupled to printed circuit boards (PCBs), although exposure may happen at any time in the life cycle of a sensor. Such exposure can negatively affect the life and performance of the sensor. To protect sensors from such exposure, existing sensor packages may include a film that permits materials to be sensed (e.g., air for a humidity sensor, pressure sensor, or sound sensor) to pass through the film and that prevents dust, debris, pollution, and corrosive substances from touching the sensor. In some cases, these films cover the sensor permanently, and in other instances, the films are manually removed after the PCB-mounting process is complete. These films may be effective in some instances, but they are applied manually or semi-manually with some assistance from machines. As sensor packages and sensors continue to decrease in size over time, it has become increasingly difficult to manually or semi-manually apply such films accurately. Not only are such films often improperly applied, but even when they are properly applied, the manual or semi-manual technique by which they are applied is time-consuming, expensive, and limited in capacity. 
     This disclosure describes various examples of sensor package manufacturing techniques that overcome the challenges described above. In some examples, the techniques include covering a lead frame strip having multiple semiconductor dies using a mold compound. The techniques further include coupling one or more films to a top surface of the mold compound. The techniques still further include singulating the mold compound to produce a sensor package. The sensor package couples to a portion(s) of the one or more films. The one or more films protect the sensor and the top surface of the mold compound of the sensor package, e.g., from dust, debris, pollution, and/or corrosive substances. The one or more films may be permanent or may be removable. For example, in some applications, the film(s) may remain on the sensor package for the life of the sensor package, continuing to protect the sensor and the top surface of the sensor package while the sensor package remains in use. In other applications, the film(s) may be removed after a dust, debris, pollution, and/or corrosive substance exposure risk has passed, for example, after the sensor package has been coupled to a PCB. 
     By applying the film(s) to the mold compound pre-singulation and then singulating the mold compound to produce individual sensor packages, several advantages are gained. First, the process is more accurate than manual application of films, as relatively large film(s) are applied to relatively large mold compounds, thus reducing or eliminating the small-scale precision work that introduces risk of inaccurate film placement. Second, large groups of sensor packages can be processed relatively quickly, efficiently, and at reduced cost, with minimal human intervention. Third, because the disclosed manufacturing techniques are performed on a large scale, any adhesives that are used (e.g., to attach films to mold compounds) are prevented from excessive drying, thus improving adhesive performance. Examples of such sensor package manufacturing techniques are now described with reference to the drawings. 
       FIGS.  1 A- 7    are perspective, profile, and top-down views of a process flow for manufacturing a sensor package in accordance with various examples.  FIG.  33    is a flow diagram of a method  3300  for manufacturing the sensor packages of  FIGS.  1 A- 7    in accordance with various examples. Accordingly,  FIGS.  1 A- 7  and  33    are now described in tandem. 
     The method  3300  includes covering an array of semiconductor dies with a mold compound ( 3302 ). The mold compound includes an array of sensor cavities in a top surface of the mold compound, with each sensor cavity in the array of sensor cavities vertically aligned with a sensor of a corresponding semiconductor die in the array of semiconductor dies ( 3302 ).  FIG.  1 A  is a perspective view of a carrier  100  supporting a mold compound  102  housing multiple semiconductor dies (not visible in  FIG.  1 A  but visible in  FIG.  1 C  and described below), each semiconductor die having a sensor formed on an active surface of the semiconductor die. The sensors are configured to sense any of a variety of properties, such as humidity, pressure, sound, light, temperature, etc. In some examples, a semiconductor die may have a single sensor, and in other examples, a semiconductor die may have multiple sensors. The remainder of this description assumes that each semiconductor die includes a single sensor, but the techniques described herein may be adapted for applications in which multiple sensors are present on one or more semiconductor dies. The mold compound  102  includes multiple sensor cavities  104 , each sensor cavity  104  containing a different sensor coupled to a different semiconductor die. 
       FIG.  1 B  is a top-down view of the structure of  FIG.  1 A .  FIG.  1 C  is a profile, cross-sectional view of the structure of  FIG.  1 A .  FIG.  1 C  shows multiple semiconductor dies  108 , each semiconductor die  108  having a different sensor  106 . Conductive terminals  110  are positioned on each side of each semiconductor die  108 . The conductive terminals  110  are omitted from the remaining drawings for ease and clarity of explanation, but the conductive terminals  110  are present on each sensor package formed using the techniques described herein so as to facilitate subsequent connections with a PCB. For example, the conductive terminals  110  may be suitable for forming a quad flat no-lead (QFN) style sensor package. 
     The method  3300  comprises coupling a semi-permeable film to the top surface of the mold compound using an adhesive ( 3304 ). The semi-permeable film covers the array of sensor cavities, and the semi-permeable film includes an array of orifices ( 3304 ).  FIG.  2    shows a perspective view of a semi-permeable film  200 . In examples, the semi-permeable film  200  comprises polytetrafluoroethylene (PTFE). In other examples, the semi-permeable film  200  comprises expanded PTFE or micro-porous PTFE formed from sintering. In examples, the permeability of the semi-permeable film  200  ranges from 100 nanometers to 10 microns, with greater permeability being advantageous because it allows faster gas exchange rates across the membrane while lesser permeability offers better liquid ingress protection under high pressure. A permeability greater than this 100 nm to 10 micron range, however, can result in excessive liquid ingress and a permeability less than this range may result in inadequately slow gas exchange. The semi-permeable film  200  may have any suitable dimensions, including length, width, and thickness.  FIG.  3    is a perspective view of the structure of  FIG.  1 A , but with the addition of an adhesive  300  on a top surface of the mold compound  102 . In examples, the adhesive  300  includes acrylates or adhesion-modified polymers, although stronger or weaker adhesives and different types of adhesives are contemplated. In examples, the adhesive  300  has an adhesive strength ranging from 0.88 N/mm 2  to 1.81 N/mm 2 . In some examples, a stronger adhesive strength (e.g., at least 1.2 N/mm 2 ) for the adhesive  300  is used, because in such examples the semi-permeable film  200  may remain permanently coupled to the mold compound  102  using the adhesive  300  for the lives of the sensors  106 . In examples, such a strong adhesive strength may also be beneficial during manufacture, as insufficient adhesive strength for the adhesive  300  may result in slippage or movement of the semi-permeable film  200  during, e.g., singulation. This may be particularly problematic if the semi-permeable film  200  is patterned, as in examples described below. 
       FIG.  4 A  is a perspective view of a patterned version of the semi-permeable film  200 . Specifically, the semi-permeable film  200  may include optional orifices  402 . In examples, when the semi-permeable film  200  is coupled to the top surface of the mold compound  102  using the adhesive  300  and the mold compound  102  has been singulated into individual sensor packages, each orifice  402  is positioned closest to pin  1  of the corresponding sensor package relative to the other pins of that sensor package. In this way, the orifice  402  of a sensor package identifies pin  1  of the sensor package. In examples, the orifices  402  are triangular. In examples, the orifices  402  are circular. In some examples, after the semi-permeable film  200  is coupled to the top surface of the mold compound  102  and the mold compound  102  is singulated, each orifice  402  occupies a corner of the top surface of the corresponding sensor package (e.g., after singulation, the orifice  402  on a sensor package is not circumscribed by the semi-permeable film  200 ), and in other examples, the orifices  402  do not occupy a corner of the top surface of the corresponding sensor package (e.g., after singulation, the orifice  402  on a sensor package is circumscribed by the semi-permeable film  200 ). In examples, orifices  402  that do not occupy a corner of the top surface of a corresponding sensor package may result in semi-permeable films  200  that are more easily and quickly aligned with the top surface of the mold compound  102  than would be the case with orifices  402  that do occupy a corner of the top surface of a corresponding sensor package, due to the precise alignment associated with corner orifices  402 . In addition, in some examples, a stronger adhesive (e.g., greater than or equal to the minimum adhesive strength provided above) may be used when orifices  402  should have precision alignment, for example, when orifices  402  occupy corners of the top surfaces of corresponding sensor packages. The orifices  402  may be formed using any suitable technique, such as laser, die-cut, etc.  FIG.  4 B  is a top-down view of the structure of  FIG.  4 A . 
       FIG.  5 A  is a perspective view of the semi-permeable film  200  coupled to the top surface of the mold compound  102  using the adhesive  300 . As shown, the semi-permeable film  200  covers the sensor cavities  104  the sensors  106  within the sensor cavities  104 , as well as portions of the top surface of the mold compound  102 . In this example, the orifices  402  are aligned in a manner such that after singulation, each orifice  402  is located in a corner of a top surface of a corresponding sensor package. The adhesive  300  is exposed through the orifices  402 , as shown.  FIG.  5 B  is a top-down view of the structure of  FIG.  5 A . 
     The method  3300  includes singulating the semiconductor dies in the array of semiconductor dies from each other (e.g., singulating the mold compound) to produce multiple sensor packages ( 3306 ). The sensor package includes a portion of the adhesive, a portion of the semi-permeable film, and an orifice of the array of orifices, with the orifice exposing the portion of the adhesive to an exterior of the sensor package ( 3306 ).  FIG.  6 A  is a perspective view of an example post-singulation sensor package  600  produced using the example method  3300 .  FIG.  6 B  is a top-down view the sensor package  600 . As shown in both  FIGS.  6 A and  6 B , a portion of the semi-permeable film  200  couples to a top surface of the sensor package  600  using a portion of the adhesive  300 . Further, as shown, the adhesive  300  and the semi-permeable film  200  are approximately flush (i.e., exactly flush or within 1 mm of being flush) with each edge of the top surface of the sensor package  600 . In some examples, the adhesive  300  and the semi-permeable film  200  are approximately flush with at least four edges of the top surface of the sensor package  600  (e.g., the mold compound  102 ). In some examples, the adhesive  300  and the semi-permeable film  200  are approximately flush with at least three, at least two, or at least one edge of the top surface of the sensor package  600 . The approximately flush alignment of the adhesive  300  and/or the semi-permeable film  200  with the edges of the top surface of the sensor package  600  (e.g., the mold compound  102 ) is evidence of use of the method  3300  to manufacture a sensor package. Manual or semi-manual techniques for applying films to individual sensor packages post-singulation will not produce such flush alignments. Coupling of the semi-permeable film  200  to the mold compound  102  and subsequent singulation, however, will produce such flush alignments, and for this reason the presence of such alignments is evidence of the use of the method  3300  described herein. Stronger adhesives  300  having the minimum adhesive strength range mentioned above may facilitate such alignments pre- and post-singulation by preventing or mitigating slippage. 
     As explained above, various advantages are realized by application of the method  3300 . These advantages may be most pronounced when relatively large numbers of sensor packages are manufactured in parallel, e.g., when the mold compound  102  described above covers more rather than fewer semiconductor dies. In such cases where multiple or large scales of sensor packages are simultaneously produced using the method  3300 , precision coverage of the sensors  106  by the semi-permeable film  200  is achieved by the act of package singulation rather than manual or semi-manual alignment of a film on an individual sensor package. Accordingly, although these advantages of the method  3300  may be realized with any number of semiconductor dies, the advantages may be more pronounced when the semiconductor dies are arranged in such a pattern and have such a number that there are more semiconductor dies bounded on all sides by other semiconductor dies than there are semiconductor dies not bounded on all sides by other semiconductor dies. Stated another way, the advantages of the method  3300  may be more pronounced when the number of semiconductor dies along the perimeter of the group of dies is less than the number of semiconductor dies not along the perimeter of the group of dies (e.g., a square composed of 2500 dies, with 198 dies on the perimeter and 2,302 interior dies). This is because, when the semi-permeable film  200  is approximately the same size as the group of dies to be processed, proper alignment of the semi-permeable film  200  may be more difficult to achieve for the dies along the perimeter of the group of dies than for the group of dies not along the perimeter. Misalignments are more readily detectable for dies along the perimeter of the group, whereas misalignment for dies in the interior area of the group becomes irrelevant post-singulation. For groups of dies that have fewer interior dies and more dies along the perimeter of the group (e.g., a square of four dies with four perimeter dies and no interior dies), a larger semi-permeable film  200  may be used, so that precise alignment of the semi-permeable film  200  with the edges of the mold compound  102  covering the semiconductor dies is irrelevant post-singulation.  FIG.  7 A  illustrates the case where improper alignment of the semi-permeable film  200  on a mold compound  102  covering four semiconductor dies produces poor results. In the example of  FIG.  7 A , only one semiconductor die  702  (on the bottom right) is fully covered by the semi-permeable film  200  and will result in a post-singulation sensor package with proper alignment of the semi-permeable film  200  with the edges of the top surface of the sensor package.  FIG.  7 B  illustrates the case where improper alignment of the semi-permeable film  200  on a mold compound  102  covering a larger number of semiconductor dies produces good results for the interior dies post-singulation. In the example of  FIG.  7 B , many semiconductor dies  702  are fully covered by the semi-permeable film  200  and will result in post-singulation sensor packages with proper alignment of the semi-permeable film  200  with the edges of the top surface of the sensor packages.  FIG.  7 C  illustrates the case where a large semi-permeable film  200  on a mold compound  102  covering a smaller number of semiconductor dies  702  produces good results for all of the dies post-singulation. In the example of  FIG.  7 C , all four semiconductor dies  702  are fully covered by the semi-permeable film  200  and will result in post-singulation sensor packages with proper alignment of the semi-permeable film  200  with the edges of the top surface of the sensor packages.  FIG.  7 D  is a perspective view of the sensor package  600  coupled to a PCB  700 . Conductive terminals and solder connections are omitted for clarity and ease of explanation. 
       FIGS.  8 A- 19 B  are perspective, profile, and top-down views of another process flow for manufacturing a sensor package in accordance with various examples.  FIG.  34    is a flow diagram of a method  3400  for manufacturing the sensor packages of  FIGS.  8 A- 19 B  in accordance with various examples. Accordingly,  FIGS.  8 A- 19 B and  34    are now described in tandem. 
     The method  3400  includes providing a first film having a first surface, the first surface having multiple rows of a first adhesive ( 3402 ). The method  3400  also includes coupling a second film to the first surface of the first film using the multiple rows of the first adhesive ( 3404 ).  FIG.  8 A  is a perspective view of a structure that may be identical to the structure of  FIG.  1 A , with numerals  800 ,  802 , and  804  corresponding to numerals  100 ,  102 , and  104 , respectively.  FIG.  8 B  is a top-down view of the structure of  FIG.  8 A , with the numeral  806  corresponding to numeral  106  in  FIG.  1 B . Accordingly, the description provided above for  FIGS.  1 A and  1 B  also apply to  FIGS.  8 A and  8 B . 
       FIG.  9    is a perspective view of a non-permeable film  900 . In examples, the non-permeable film  900  comprises polyimide. In other examples, the non-permeable film  900  comprises silver epoxy-based materials, anisotropic conductive films and pastes, etc. The dimensions of the non-permeable film  900 , including length, width, and thickness, may vary as may be suitable.  FIG.  10 A  is a perspective view of a film  1000 . In examples, the film  1000  comprises plastic (e.g., high-density polyethylene), although other materials, such as silicone-coated kraft paper, also may be used. Adhesive  1002  is applied to the film  1000 . In examples, the adhesive  1002  is applied in multiple rows along a length of the film  1000 , as shown. Other arrangements are contemplated, for example, the adhesive  1002  may be applied in multiple rows along a width of the film  1000 . In examples, the adhesive  1002  comprises acrylates and adhesion-modified polymers customized to the surface properties of interest. In examples, the adhesive  1002  has an adhesive strength ranging from 0.88 N/mm 2  to 1.81 N/mm 2 , and in some examples, the adhesive  1002  has an adhesive strength of at least 1 N/mm 2 . These ranges are significant for reasons described below, e.g., insufficient adhesive strength may result in films such as films  900  and  1000  becoming separated.  FIG.  10 B  is a top-down view of the structure of  FIG.  10 A . As shown in  FIGS.  11  and  12   , the films  900 ,  1000  are then coupled together using the adhesive  1002 . In examples, alternatives may be used in lieu of an adhesive, for example, a thermal, laser, or chemical bonding technique may be used to couple the films  900 ,  1000  together so that the areas of the films  900 ,  1000  are fused together in the same areas as with the adhesive  1002  and so that the fused portions of the films  900 ,  1000  have the same physical dimensions as the adhesive  1002 . 
     The method  3400  includes applying a second adhesive to a top surface of a mold compound ( 3406 ). The mold compound covers multiple semiconductor dies and includes multiple sensor cavities in the top surface of the mold compound, where each of the multiple sensor cavities is vertically aligned with a sensor of a corresponding one of the multiple semiconductor dies ( 3406 ).  FIGS.  13 A and  13 B  show perspective and top-down views of a structure produced by step  3406 . The structure of  FIGS.  13 A and  13 B  are identical to the structure of  FIGS.  8 A and  8 B , except with the addition of an adhesive  1300 . In examples, the adhesive  1300  is the same as the adhesive  300  described above, and thus is not described again here. 
     The method  3400  comprises coupling the second film to the top surface of the mold compound using the second adhesive, with the second film covering the multiple sensor cavities ( 3408 ).  FIG.  14 A  is a perspective view of the structure of  FIG.  12    coupled to the top surface of the mold compound  802  ( FIG.  13 A ) using the adhesive  1300  ( FIG.  13 A ). As shown, the non-permeable film  900  abuts the adhesive  1300 , and the film  1000  faces away from the adhesive  1300 .  FIGS.  14 B and  14 C  provide profile and top-down views of the structure of  FIG.  14 A . 
     The method  3400  includes singulating the mold compound to produce a sensor package, where the sensor package is coupled to a portion of the second film and to a portion of the first film ( 3410 ).  FIG.  15 A  is a perspective view of the structure of  FIG.  14 A , except that a singulation process has been performed to separate the semiconductor dies from each other and to produce multiple sensor packages  1500 . The singulation may be performed using any suitable technique, including mechanical sawing, laser sawing, etc.  FIG.  15 B  is a profile view of the structure of  FIG.  15 A , and  FIG.  15 C  is a top-down view of the structure of  FIG.  15 A . In examples, the films  900 ,  1000  are approximately flush with the one, two, three, four, or more edges of the top surface of the corresponding sensor package  1500 . Considerations in achieving such flush alignments of films  900 ,  1000  and edges of the top surface of the corresponding sensor package  1500  are similar to those provided above with respect to the method  3300  and thus are not repeated here. 
     The method  3400  includes coupling the sensor package to a PCB ( 3412 ).  FIGS.  16 A,  16 B, and  16 C  show perspective, profile, and top-down views of the sensor package  1500  coupled to a PCB  1700 . Although the conductive terminals on the sensor package  1500 , solder connections, etc. are not expressly shown for convenience and clarity, as explained above, the process of coupling a sensor package to a PCB involves dust, debris, pollution, corrosive cleaning solvents, etc. The non-permeable film  900  protects the sensor package  1500 , and particularly the sensor  806  inside the sensor cavity  804 , from such deleterious substances during the PCB mounting process. 
     The method  3400  includes using the portion of the first film to remove the portion of the first film and the portion of the second film from the sensor package ( 3414 ).  FIGS.  17 A,  17 B, and  17 C  depict perspective, profile, and top-down views of step  3414 . Only some of the film  1000  is coupled to the non-permeable film  900 , due to the arrangement of the adhesive  1002  in rows, as described above. The remainder of the film  1000  is not coupled to the non-permeable film  900 . Accordingly, the non-coupled area of the film  1000  may function as a tab that can be lifted and grasped to peel both the film  1000  and the non-permeable film  900  off of the top surface of the sensor package  1500  (e.g., by a human or by a pick-and-place tool). Because part of the film  1000  is coupled to the non-permeable film  900  using a strong adhesive  1002  as described above, the connection between the films  900 ,  1000  is sufficiently strong to withstand the forces applied when the films  900 ,  1000  are pulled off of the sensor package  1500 . In addition, the adhesive  1300  is weaker than the adhesive  1002 , and thus the non-permeable film  900  is weakly coupled to the top surface of the sensor package  1500  relative to the strength of the adhesive  1002  between the films  900 ,  1000 .  FIGS.  18 A,  18 B, and  18 C  are perspective, profile, and top-down views of the films  900 ,  1000  being lifted off of the sensor package  1500 .  FIGS.  19 A,  19 B, and  19 C  are perspective, top-down, and profile views of the sensor package  1500  without the films  900 ,  1000 . Although not expressly shown, a portion of the adhesive  1300  may remain on the top surface of the sensor package  1500  as residue. 
     The adhesive  1002  may have certain qualities that facilitate the performance of the method  3400 , and in particular, the removal of the films  900 ,  1000  in step  3414 . For example, if the area of coupling between the films  900 ,  1000  is not sufficiently large, then when the film  1000  is pulled to remove the films  900 ,  1000 , the film  1000  may separate from the film  900 , leaving the film  900  coupled to the sensor package  1500 . To prevent this, in examples each row of adhesive  1002  is sufficiently wide so as to form a large coupling area between the films  900 ,  1000 . In examples, the width of each row of adhesive  1002  may range between 5 millimeters and 30 millimeters. A row wider than this range may inappropriately increase costs and reduce the portion of the film  1000  available for gripping during removal of the films  900 ,  1000 , and a row narrower than this range may provide inadequate adhesion between films  900 ,  1000 . 
     In addition, the benefits of a sufficiently wide row of adhesive  1002  may be negated if the row is not properly aligned with a row of semiconductor dies when the film  1000  is being coupled to the mold compound  802 . For example, the film  1000  or a row of adhesive  1002  on the film  1000  may be so misaligned relative to a corresponding row of semiconductor dies that, after singulation, some sensor packages  1500  will have films  900 ,  1000  with little or no adhesive in between them. Even slight angular misalignments may become pronounced if the film  1000  and/or mold compound  802  is sufficiently long. To mitigate such risks, in some examples the lengths of the film  1000  and/or mold compound  802  may be limited, or extra precautions may be taken to mitigate misalignments of the rows of adhesives  1002 . 
       FIGS.  20 A- 25 C  are perspective, profile, and top-down views of another process flow for manufacturing a sensor package in accordance with various examples.  FIG.  35    is a flow diagram of a method  3500  for manufacturing the sensor packages of  FIGS.  20 A- 25 C  in accordance with various examples. In  FIGS.  20 A- 25 C and  35   , tabs similar to those described above with reference to  FIGS.  8 A- 19 B and  34    are produced, but in a different manner. Accordingly,  FIGS.  20 A- 25 C and  35    are now described in tandem. 
     The method  3500  includes coupling a lengthwise portion of a compliant member to a first surface of a film using a first adhesive ( 3502 ). The method  3500  also includes applying a second adhesive to a top surface of a mold compound ( 3504 ). The mold compound covers multiple semiconductor dies and includes multiple sensor cavities in the top surface of the mold compound, with each of the multiple sensor cavities vertically aligned with a sensor of a corresponding one of the multiple semiconductor dies ( 3504 ).  FIG.  20 A  is a perspective view of the structure of  FIG.  1 A , with numerals  2000 ,  2002 , and  2004  corresponding to numerals  100 ,  102 , and  104 , respectively.  FIG.  20 B  is a top-down view of the structure of  FIG.  20 A , with sensors  2006  visible in the sensor cavities  2004 . The sensors  2006  are similar to the sensors  106  of  FIG.  1 B .  FIG.  21    is a perspective view of a non-permeable film  2100 , such as the non-permeable film  900  of  FIG.  9   .  FIG.  22 A  is a perspective view of the structure of  FIG.  20 A , but with the addition of an adhesive  2200 . The adhesive  2200  is similar to the adhesive  300  shown in  FIG.  3   .  FIG.  22 B  is a top-down view of the structure of  FIG.  22 A .  FIG.  23 A  is a perspective view of the non-permeable film  2100  having lengthwise portions  2302  of multiple compliant members  2300  coupled to the non-permeable film  2100  as shown. In examples, the lengthwise portions  2302  couple to the non-permeable film  2100  using a high strength adhesive, such as the adhesive  1002  described above. In examples, the description provided above for the adhesive  1002  also applies to the adhesive used to couple the lengthwise portions  2302  to the non-permeable film  2100 . Because the compliant members  2300  are compliant, portions  2304  of the compliant members  2300  that are not directly coupled to the non-permeable film  2100  using adhesive may be bent or folded at an approximate right angle with reference to the lengthwise portions  2302 , as shown. Such a bend or fold produces a tab that may later be grasped (e.g., by a human hand or a pick-and-place tool) to remove the compliant member  2300  and the non-permeable film  2100  from a sensor package. Alternatives to adhesives include thermal, laser, and chemical bonding techniques.  FIGS.  23 B and  23 C  are profile and top-down views, respectively, of the structure of  FIG.  23 A . 
     The method  3500  comprises coupling a second surface of the film to the top surface of the mold compound using the second adhesive, the film covering the multiple sensor cavities ( 3506 ).  FIG.  24    is a perspective view of the structure of  FIG.  23 A  coupled to the structure of  FIG.  22 A . Specifically, a bottom surface of the non-permeable film  2100  is coupled to the top surface of the mold compound  2002  using the adhesive  2200 . 
     The method  3500  includes singulating the mold compound to produce a sensor package, the sensor package coupled to a portion of the film and to a portion of the compliant member ( 3508 ).  FIG.  25 A  is a perspective view of a sensor package  2500  comprising the mold compound  2002  and having coupled thereto the non-permeable film  2100  and the compliant member  2300 . The non-permeable film  2100  covers at least the sensor cavity  2004  and sensor  2006  of the sensor package  2500 .  FIG.  25 B  is a top-down view of the sensor package  2500 , and  FIG.  25 C  is a profile view of the sensor package  2500 . 
     The method  3500  includes coupling the sensor package to a PCB ( 3510 ). The non-permeable film  2100  protects at least the sensor cavity  2004  and the sensor  2006  from debris, dust, pollution, corrosive substances, etc. during the PCB mounting process. After the sensor package  2500  has been coupled to a PCB, the method  3500  comprises using the portion of the compliant member to remove the portion of the film and the portion of the compliant member from the sensor package ( 3512 ). Thus, the portion  2304  may be grasped and pulled to remove both the compliant member  2300  and the non-permeable film  2100  from the sensor package  2500 . Because the compliant member  2300  couples to the non-permeable film  2100  using a stronger adhesive than the adhesive used to couple the non-permeable film  2100  to the mold compound  2002 , pulling on the compliant member  2300  causes both the compliant member  2300  and the non-permeable film  2100  to detach from the sensor package  2500 . The considerations described above for the adhesive  1002  (e.g., width of adhesive, alignment of adhesive with reference to rows of semiconductor dies) with reference to  FIGS.  8 A- 19 B and  34    apply to the adhesive used to couple the compliant member  2300  to the non-permeable film  2100 , and thus are not repeated here. In examples, the compliant member  2300  has a stiffness ranging from 0.2 Gigapascals (GPa) to 3 GPa. A stiffer compliant member  2300  may fail to adequately mitigate mechanical stress and may increase the possibility of damage during the removal process, while a less stiff compliant member  2300  may provide inadequate grip during the removal process. 
       FIGS.  26 A- 32    are perspective, profile, top-down, and bottom-up views of another process flow for manufacturing a sensor package in accordance with various examples.  FIG.  36    is a flow diagram of a method  3600  for manufacturing the sensor packages of  FIGS.  26 A- 32    in accordance with various examples. Accordingly,  FIGS.  26 A- 32  and  36    are now described in tandem. 
     The method  3600  includes coupling multiple flags to a first surface of a film ( 3602 ). The method  3600  also includes applying an adhesive to a top surface of a mold compound ( 3604 ). The mold compound covers multiple semiconductor dies and includes multiple sensor cavities in the top surface of the mold compound, with each of the multiple sensor cavities vertically aligned with a sensor of a corresponding one of the multiple semiconductor dies ( 3604 ).  FIG.  26 A  is a perspective view of a structure that is the same as the structures of  FIG.  1 A , with numerals  2600 ,  2602 , and  2604  corresponding to numerals  100 ,  102 , and  104 , respectively.  FIG.  26 B  is a top-down view of the structure of  FIG.  26 A , with sensors  2606  inside the sensor cavities  2604 . The sensors  2606  are the same as the sensors  106  shown in  FIG.  1 B .  FIG.  27    is a top-down view of a carrier  2700  (e.g., a paper carrier) having positioned thereupon multiple flags  2702  (composed of, e.g., wax paper or PTFE). In examples, the flags  2702  have a triangular shape, for instance when the flags  2702  are intended for subsequent positioning in a corner of a top surface of a sensor package, as described below. However, other shapes are contemplated and included in the scope of this disclosure, such as rectangles, semi-rectangles, semi-circles, etc. Such shapes may be better suited to placement in areas other than corners of the top surfaces of sensor packages, and, consequently, flags  2702  with such shapes may be positioned differently on the carrier  2700 . The flags  2702  may be sticky (or have an adhesive applied) on one surface, for example, the surface facing away (not touching) the carrier  2700 . In examples, an adhesive strength of the flags  2702  may range from 0.88 N/mm 2  and 1.81 N/mm 2 , with some examples having a minimum adhesive strength of 1.2 N/mm2. An adhesive strength below these ranges may produce insufficient adhesion to prevent detachment of the flags  2702 , while an adhesive strength above these ranges may be unnecessarily expensive or cumbersome to use during manufacture.  FIG.  28 A  is a perspective view of the structure of  FIG.  26 A , but with the addition of an adhesive  2800 . In examples, the adhesive  2800  corresponds to the adhesive  300  described above.  FIG.  28 B  is a top-down view of the structure of  FIG.  28 A .  FIG.  29 A  is a perspective, top-down view of a non-permeable film  2900 , which is the same as the non-permeable film  2100  described above, both without and with the flags  2702  coupled thereto. In examples, the flags  2702  are coupled to the non-permeable film  2900  by laying the non-permeable film  2100  on top of the carrier  2700 , thus causing the sticky flags  2702  to couple to the non-permeable film  2900  as shown.  FIG.  29 B  is a perspective, bottom-up view of the structures of  FIG.  29 A . 
     The method  3600  includes coupling the multiple flags and the first surface of the film to the top surface of the mold compound using the adhesive, where the film covers the multiple sensor cavities ( 3606 ).  FIG.  30 A  is a perspective view of the structure of  FIG.  29 A  (including the flags  2702 ) coupled to the structure of  FIG.  28 A . As shown, the non-permeable film  2900  covers the sensor cavities  2604  and the sensors  2606  inside the sensor cavities  2604 .  FIG.  30 B  is a top-down view of the structure of  FIG.  30 A . 
     The method  3600  includes singulating the mold compound to produce a sensor package, where the sensor package is coupled to one of the multiple flags and to a portion of the film ( 3608 ).  FIG.  31 A  is a perspective view of a sensor package  3100  having the non-permeable film  2900  coupled to a top surface of the sensor package  3100  using the adhesive  2800 . A flag  2702  is positioned in a corner of the top surface of the sensor package  3100 , as shown.  FIG.  31 B  is a top-down view of the structure of  FIG.  31 A . 
     The method  3600  includes coupling the sensor package to a PCB ( 3610 ) and using the one of the multiple flags to remove the portion of the film from the sensor package ( 3612 ).  FIG.  32    is a perspective view of the sensor package  3100  coupled to a PCB  3200 , with conductive terminals, solder connections, etc. omitted for clarity and ease of explanation. The mounting of the sensor package  3100  may expose the sensor  2606  to dust, debris, pollution, corrosive substances, but the non-permeable film  2900  covers and thus protects the sensor  2606  and the sensor cavity  2604  from such harmful exposures. After the sensor package  3100  is coupled to the PCB  3200 , however, the flag  2702  may be used to remove both the flag  2702  and the non-permeable film  2900  from the sensor package  3100 , as shown. Specifically, the flag  2702  may be used to remove the flag  2702  and the non-permeable film  2900  because it is less firmly coupled to the adhesive  2800  than the non-permeable film  2900 . As a result, the flag  2702  is lifted off of the adhesive  2800  with relative ease, and the flag  2702  may then be grasped and pulled (e.g., by hand or a pick-and-place tool) to remove both the flag  2702  and the non-permeable film  2900  from the sensor package  3100 . 
     In examples, the flag  2702  is sized to be large enough so that it can be grasped with relative ease. Conversely, the flag  2702  should not be so large that an adhesive seal does not form between the flag  2702  and the sensor cavity  2604 . On the contrary, a seal is desirable between the flag  2702  and the sensor cavity  2604  so that there are no vulnerable ingress points for dust, debris, pollution, corrosive substances, etc. to enter the sensor cavity  2604  and damage the sensor  2606 . Accordingly, in some examples, the flag  2702  has an area approximately equivalent to the horizontal cross-sectional area of the sensor cavity  2604 . In some examples, an area of the flag  2702  ranges from 0.5 mm 2  to 1 mm 2 . In some examples, to ensure an adequate seal between the flag  2702  and the sensor cavity  2604 , the shortest distance between the flag  2702  and the sensor cavity  2604  is at least 1 mm. 
     In addition, the flag  2702  should be aligned with an edge of a top surface of the sensor package  3100 . Otherwise, the flag  2702  will be of diminished use in lifting the non-permeable film  2900  off of the sensor package  3100 , or in some cases, portions of non-permeable film  2900  may become attached to the sensor package  3100  without also being coupled to the flag  2702 , making such portions of non-permeable film  2900  difficult to remove from the sensor package  3100 . Thus, care should be taken to facilitate proper alignment of the flag  2702  with the edge of the top surface of the sensor package  3100 . In the event that a relatively small degree of misalignment is still present after the non-permeable film  2900  has been coupled to the mold compound  2602 , the singulation process may be adjusted to ensure that the flags  2702 , post-singulation, are present on the edges of the top surfaces of the sensor packages  3100 . 
     In general, each of the example methods described above produces a film that covers at least a sensor cavity of a sensor package or, in examples, an entire top surface of a sensor package. Because these films protect from exposure to debris, dust, pollution, corrosive substances, etc., removal of the films after PCB mounting reveals areas of the sensor packages that are free of damage from such exposure. In examples, the areas of the sensor packages free of damage from such exposure are commensurate with the coverage provided by the corresponding films. Thus, in examples where a film covers an entire top surface of a sensor package, the entire top surface of the sensor package may be free from evidence of exposure to damaging substances. Such an area that is free from damage due to corrosive and other harmful substances may be approximately flush with one, two, three, four, or more edges of the top surface of the sensor package. Such flush alignment with the edges of the top surface of the sensor package are possible with the methods described herein because the bounds of film protection are determined by the singulation process and not by the ability of a human to accurately and precisely position a protective film on a sensor package. Other patterns evidencing protection from damaging substances are possible and are included in the scope of this disclosure. 
     In the foregoing discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus mean “including, but not limited to . . . .” Also, the term “couple” or “couples” means either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections. Similarly, a device that is coupled between a first component or location and a second component or location may be through a direct connection or through an indirect connection via other devices and connections. An element or feature that is “configured to” perform a task or function may be configured (e.g., programmed or structurally designed) at a time of manufacturing by a manufacturer to perform the function and/or may be configurable (or re-configurable) by a user after manufacturing to perform the function and/or other additional or alternative functions. The configuring may be through firmware and/or software programming of the device, through a construction and/or layout of hardware components and interconnections of the device, or a combination thereof. Unless otherwise stated, “about,” “approximately,” or “substantially” preceding a value means +/−10 percent of the stated value. 
     The above discussion is illustrative of the principles and various examples of the present disclosure. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. The following claims should be interpreted to embrace all such variations and modifications.