IMAGE SENSOR PACKAGES AND RELATED METHODS

An image sensor package may include an image sensor die; an electromagnetic radiation transmissive cover coupled over the image sensor die; and a dam between the image sensor die and the electromagnetic radiation transmissive cover, the dam including a colored additive. The dam may form a space between the image sensor die and the electromagnetic radiation transmissive cover.

BACKGROUND

1. Technical Field

Aspects of this document relate generally to semiconductor device packages. More specific implementations involve packages for image sensor semiconductor devices.

Various semiconductor packages have been devised to allow for formation of electrical interconnects between a semiconductor die and a motherboard or circuit board to which the semiconductor packages are attached. Other semiconductor packages work to provide mechanical support to a semiconductor die. Some semiconductor packages work to help prevent damage to the semiconductor die from humidity or shock and vibration.

SUMMARY

An image sensor package may include an image sensor die; an electromagnetic radiation transmissive cover coupled over the image sensor die; and a dam between the image sensor die and the electromagnetic radiation transmissive cover, the dam including a colored additive. The dam may form a space between the image sensor die and the electromagnetic radiation transmissive cover.

Implementations of an image sensor package may include one, all, or any of the following:

The colored additive may make the dam optically opaque to one or more wavelengths of electromagnetic radiation detected by the image sensor die. Package.

The colored additive may make the dam optically opaque to ultraviolet light wavelengths.

The colored additive may make the dam optically opaque to infrared light wavelengths.

The colored additive may make the dam optically opaque to visible light wavelengths.

The dam may fixedly couple the image sensor die and the electromagnetic radiation transmissive cover together.

The package may include a substrate coupled to the image sensor die.

The package may include an adhesive material that fixedly couples the image sensor die, the dam, and the electromagnetic radiation transmissive cover together.

Implementations of a method of forming an image sensor package include providing an image sensor die; forming a dam on an electromagnetic radiation transmissive cover; placing the electromagnetic radiation transmissive cover over the image sensor die; fixedly coupling the image sensor die to the electromagnetic radiation transmissive cover by curing a material of the dam; and preventing one or more wavelengths of light from passing through the dam using a colored additive included in the dam.

Implementations of a method of forming an image sensor package may include one, all, or any of the following:

The method may include coupling a substrate to the image sensor die.

The method may include applying a mold compound to the image sensor die, the dam, and the electromagnetic radiation cover.

The colored additive may make the dam optically opaque to ultraviolet light wavelengths.

The colored additive may make the dam optically opaque to infrared light wavelengths.

The colored additive may make the dam optically opaque to visible light wavelengths.

Implementations of a method of forming an image sensor package may include providing an image sensor die; forming a dam on an electromagnetic radiation transmissive cover; applying an adhesive material to the image sensor die; placing the electromagnetic radiation transmissive cover over the image sensor die; fixedly coupling the image sensor die to the electromagnetic radiation transmissive cover by curing the adhesive material; and preventing one or more wavelengths of light from passing through the dam using a colored additive included in the dam.

Implementations of a method of forming an image sensor package may include one, all, or any of the following:

The method may include coupling a substrate to the image sensor die.

The method may include applying a mold compound to the image sensor die, the dam, and the electromagnetic radiation cover.

The colored additive may make the dam optically opaque to one of infrared light wavelengths or ultraviolet light wavelengths.

Curing the adhesive material further may include only thermally curing the adhesive material.

The colored additive may make the dam optically opaque to visible light wavelengths.

DESCRIPTION

This disclosure, its aspects and implementations, are not limited to the specific components, assembly procedures or method elements disclosed herein. Many additional components, assembly procedures and/or method elements known in the art consistent with the intended image sensor packages will become apparent for use with particular implementations from this disclosure. Accordingly, for example, although particular implementations are disclosed, such implementations and implementing components may comprise any shape, size, style, type, model, version, measurement, concentration, material, quantity, method element, step, and/or the like as is known in the art for such image sensor packages, and implementing components and methods, consistent with the intended operation and methods.

Referring toFIG.1, a cross sectional view of an implementation of an image sensor package2is illustrated. In this implementation, an image sensor die4is coupled to substrate6through a die attach/die bonding material8. In this implementation the substrate8includes a plurality of solder balls attached thereto and so this particular image sensor package2is a ball grid array (BGA) package. Electrical connections between die pads (not visible inFIG.1) on the image sensor die4and corresponding pads on the substrate8are formed using wirebonds10. Electromagnetic radiation transmissive cover12is attached to the image sensor die4over the wirebonds10and pads using adhesive material14which also forms a spacer or dam that creates an air gap16. A black layer/light block layer18is present between the adhesive material14and the electromagnetic radiation transmissive cover12and works to prevent undesired electromagnetic radiation of one or more wavelengths to scatter from the wirebonds/pads and be received by the pixels of the image sensor die4. A mold compound is also applied around the edge of the package to protect the wirebonds and further secure the joint between the electromagnetic radiation transmissive cover12, the image sensor die4, and the adhesive material14. This type of image sensor package can be referred to as a wire-in-dam package where the adhesive material acts both as the dam and adhesive and the wirebonds/bond wires are embedded in the material.

In various image sensor packages with this structural design, the adhesive material is applied in a liquid/flowable form so as to flow around the wirebonds without causing voids and then is cured to harden it and form a secure bond between the electromagnetic radiation transmissive cover12and the image sensor die4. In some implementations, the adhesive material is cured to a first tacky B-stage using ultraviolet light to ensure that the joint between the electromagnetic radiation transmissive cover12and the image sensor die4is sufficiently strong before the package2is heated in a thermal curing step to complete the final curing of the adhesive material to a hardened C-stage. Without the use of the ultraviolet light curing process, during the thermal curing process bubbles, voids, or a separation between the electromagnetic radiation transmissive cover and/or the image sensor die may take place, which can cause immediate failures or longer-term reliability problems.

Because the black layer18is present directly above the adhesive material14, the ability of ultraviolet light oriented top down to expose the adhesive material14is essentially eliminated, and so the ultraviolet light used to cure the adhesive material14is that which comes from each side of the package, which provides attenuated irradiation intensity. Furthermore, observations of location specific failures of wirebonds have indicated that the adhesive material14is unevenly cured around the perimeter of the image sensor die4, creating locations where ionic contaminants like chlorine in the uncured adhesive material14have the ability to migrate to the wirebond joint itself and participate in corrosion reactions prior to and after operation. Higher voltage pads appear to be more sensitive to this corrosion effect due to the higher electric field involved in these joints.

Eliminating the black layer18would permit more even curing of the adhesive material14, but unfortunately, would result in an increase in light scattering defects in the images produced by the image sensor4caused by light reflected from the wirebonds and pads in the otherwise optically transparent material of the dam. Thus, in the structure of this particular package design, a black layer18that is as wide as or wider than the adhesive material14is used to minimize the number of possible light scattering defects. However, a black layer of this size around the perimeter of the electromagnetic radiation transmissive cover also minimizes the amount of ultraviolet light available to cure the adhesive material14.

Referring toFIG.2, another implementation of an image sensor package20is illustrated. In this implementation, a dam22is located between image sensor die24and electromagnetic radiation transmission cover26. In this implementation, no black layer is present and the dam22is located between the wirebonds28and the pixel array30of the image sensor die24. In this implementation, the dam22includes a colored additive that makes the material of the dam optically opaque to one or more wavelengths of electromagnetic radiation that is detectable by the pixel array30of the image sensor die24. In some implementations, the colored additive may make the dam22optically opaque to ultraviolet light wavelengths. In other implementations, the colored additive may make the dam22optically opaque to infrared light wavelengths. In yet other implementations, the colored additive may make the dam22optically opaque to visible light wavelengths. In yet other implementations, the colored additive may make the dam22optically opaque to any combination of the wavelengths of ultraviolet light, infrared light, visible light, or all of the foregoing. For example, where the colored additive turns the color of the dam22visibly black, this may be sufficient for the dam22to prevent transmission of ultraviolet, infrared, and visible light through the material of the dam22.

The particular color of the colored additive may be a function of the particular wavelength of electromagnetic radiation that is desired to be blocked/absorbed. In particular implementations, the colored additive may turn the color of the material of the dam22, by non-limiting example, black, blue, red, purple, green, gray, opaque white, or any other desired color capable of blocking/absorbing the desired wavelength(s) of electromagnetic radiation. The colored additive may be added during manufacture of the material of the dam in various system and method implementations to create material for specific image sensor packages designed to receive and process specific wavelengths of electromagnetic radiation.

Because the dam22is located between the wirebonds28and pads and the pixel array30, reflected electromagnetic radiation from the wirebonds28and pads is blocked from being received by the pixel array by the material of the dam22. In this implementation, a higher dam may be more effective in blocking reflected electromagnetic radiation in combination with the particular color of the colored additive used. The effectiveness may also increase where an electromagnetic radiation opaque mold compound32is used to cover the wirebonds28and the edges/sidewalls of the electromagnetic radiation transmissive cover26, dam22, and image sensor die24. This helps ensure that the only light that enters the material of the electromagnetic radiation transmissive cover26is reflected at a fairly high angle relative to the surface of the pixel array30and thus is now unlikely to be able to reach the pixel array30.

This ability of the dam with the colored additive to block reflected light from the wirebonds and pads means that the issues of ultraviolet cure of an adhesive material are eliminated. In this particular implementation, no adhesive material is used as the material of the dam22itself is what is used to form the fixed bond between the electromagnetic radiation transmissive cover26and the image sensor die24. Because of this, corrosion of wirebonds caused by ion migration in incompletely cured adhesive material can also be eliminated. Like the image sensor package implementation ofFIG.1, the illustrated image sensor package20also includes a substrate34. However, in some implementations, a substrate may not be included. Various methods of forming image sensor packages like those disclosed here will be discussed in this document.

Referring toFIG.3, an implementation of an image sensor die36is illustrated following bonding/attaching to a substrate38and completion of formation of wirebonds40between pads on the image sensor die36and the substrate38. Here a die attach/die bonding material42is used to form the bond between the image sensor die36and the substrate38. The substrate38at this point is illustrated without solder balls as these will be added in a later processing step.

Referring toFIG.4, an implementation of an electromagnetic radiation transmissive cover44is illustrated following formation of a dam46thereon. The dam46includes a colored additive like any disclosed in this document. The dam46can be formed using, by non-limiting example, a photolithography/etching process, a dispensing process, a screen printing process, a stenciling process or another process consistent with the particular material of the dam itself. In various implementations, the material of the dam46may include, by non-limiting example, an epoxy, a resin, a polymer, any combination thereof, or any other material capable of forming a fixed bond between the material of the electromagnetic radiation transmissive cover44and the image sensor die36. While the cross sectional view inFIG.4shows the dam46on two sides of the electromagnetic radiation transmissive cover44, it is understood that the dam46is formed around the entire perimeter of the electromagnetic radiation transmissive cover44so as to form a seal with the image sensor die36.

Referring toFIG.5, the image sensor die36is illustrated following placing of the electromagnetic radiation transmissive cover44over it with the dam46contacting both. In this situation, in particular method implementations, the material of the dam46may be cured to a B-stage where it has sufficient stiffness and stickiness/tackiness to adhere to the image sensor die36to retain alignment during subsequent processing while forming air gap48. Note that the position of the dam46on the electromagnetic radiation transmissive cover44is designed so that the dam46rests between the wirebonds40and the pixel array50of the image sensor die36.

Referring toFIG.6, the image sensor die36is illustrated following thermal curing of the material of the dam46to form a fixed bond between the image sensor die36and the electromagnetic radiation transmissive cover44(to a C-stage, depending on the material of the dam46). Following the thermal curing, a mold compound52has been applied around the sidewalls/edges of the electromagnetic radiation transmissive cover44, image sensor die36, and the dam46. The mold compound46also encloses the wirebonds40and bond wires54. The image sensor package implementation illustrated inFIG.6also shows the substrate38following a ball drop/ball attach operation in which a plurality of solder balls56have been attached to pads in the substrate38. While the use of balls is illustrated in the ball grid array image sensor package implementation of56, in other implementations no balls may be used and the package may employ just pads (as in a land grid array package design), leads, or pins (as in a pin grid array package).

The image sensor package implementation ofFIG.6, which employs the material of the dam46itself to form the bond between the electromagnetic radiation transmissive cover44and the image sensor die36, does not utilize any separate adhesive material. Thus, since the material of the dam46is thermally cured only when reaching the C-stage, any issues with incomplete ultraviolet light curing when the electromagnetic radiation transmissive cover44are avoided. Because of this, this image sensor package implementation may see no wirebond corrosion while avoiding image defects caused by scattered light from the wirebonds/bond wires/pads. In various implementations, while the presence of an air gap48is illustrated in the package implementation ofFIG.6, the foregoing method implementation could also be used in gapless image sensor packages where a material of a desired refractive index is applied to the electromagnetic radiation transmissive cover44prior to placing of the cover over the image sensor die36.

Referring toFIG.7, another implementation of an image sensor die58is illustrated after bonding/attaching to substrate60using die attach/bonding material62. Wirebonds64with bond wires66have also been formed between corresponding pads on the image sensor die58and the substrate60. Referring toFIG.8, an implementation of an electromagnetic radiation transmissive cover68is illustrated following formation of a dam70thereof. The dam70includes a colored additive which may be any disclosed in this document. In this method implementation, the material of the dam70has been fully cured (C-stage) as the material of the dam70is not used as the sole bonding/attaching material between the electromagnetic radiation transmissive cover68and the image sensor die58. The dam70may be formed using any process previously disclosed in this document with the addition that instead of curing to a tacky stage (B-stage), the curing processed used takes the material of the dam70to a fully cured stage (C-stage).

Referring toFIG.9, the image sensor die58is illustrated following application of an adhesive material72thereto between the wirebonds64and the pixel array74of the image sensor die58. In this method implementation, the adhesive material72is one that is thermally cured only and since it is designed to bond to the material of the dam70and to the image sensor58rather than to the electromagnetic radiation transmissive cover68, the need for the adhesive material72to be cured to a B-stage prior to the thermal cure step may be eliminated, as the adhesive material72needs to yield around the material of the dam70when the dam70is pressed down into it.

Referring toFIG.10, the dam70is illustrated following placing of the electromagnetic radiation transmissive cover68over the image sensor58and thermal curing of the adhesive material72which is no longer visible in this view. An air gap76is present between the electromagnetic radiation transmissive cover68and the image sensor58. The ability to use adhesive material72to secure the dam70to the image sensor58may allow for accurate processing during thermal curing without creating voids or bubbles due to the low amount of adhesive material72needed to complete the formation of the bond. As previously discussed, while an air gap76is illustrated inFIG.10, in other implementations a gapless image sensor may be formed by adding a material of a desired refractive index over the pixel array74of the image sensor die58after application of the adhesive material72and before placing of the electromagnetic radiation transmissive cover68thereon.

Referring toFIG.11, the image sensor die58is illustrated following application of mold compound78around the sidewalls/edges of the electromagnetic radiation transmissive cover68, dam70, and image sensor die58. Balls80have also been attached to pads on the substrate60using any process disclosed in this document (though balls may not be used in other implementations in favor of any other interconnect solution disclosed herein). Where the mold compound78is also electromagnetic radiation optically opaque to the wavelength of electromagnetic radiation the pixel array74is designed to receive, the placement of the dam70between the wirebonds64and the pixel array74ensures minimal reflected light can encounter the pixel array74. In this image sensor package implementation, because the adhesive material72is only thermally cured, the issue of ultraviolet light curing with the adhesive material used in the image sensor package ofFIG.1is also eliminated. Also, because of the presence of the dam70, a much smaller amount of adhesive material relative to the implementation ofFIG.1is needed to complete the formation of a fixed bond between the electromagnetic radiation transmissive cover and the image sensor die which aids in the thermal curing process.

In places where the description above refers to particular implementations of image sensor packages and implementing components, sub-components, methods and sub-methods, it should be readily apparent that a number of modifications may be made without departing from the spirit thereof and that these implementations, implementing components, sub-components, methods and sub-methods may be applied to other image sensor packages.