Contact spring application to semiconductor devices

A contact spring applicator is provided which includes an applicator substrate, a removable encapsulating layer and a plurality of contact springs embedded in the removable encapsulating layer. The contact springs are positioned such that a bond pad on each contact spring is adjacent to an upper surface of the removable encapsulating layer. The contact spring applicator may also include an applicator substrate, a release layer, a plurality of unreleased contact springs on the release layer and a bond pad at an anchor end of each contact spring. The contact spring applicators apply contact springs to an integrated circuit chip, die or package or to a probe card by aligning the bond pads with bond pad landings on the receiving device. The bond pads are adhered to the bond pad landings. The encapsulating or release layer is then removed to separate the contact springs from the contact spring applicator substrate.

TECHNICAL FIELD

The present disclosure relates to semiconductor devices, solid state devices, sensors and actuators that utilize spring contacts and more particularly to the application of the spring contacts to these devices.

BACKGROUND

Metal spring contacts may be used for electrically connecting integrated circuit chips or dies to circuit boards or other devices and may also be used as probe needles on a probe card. Spring contacts allow for reduced pitch, and thus, smaller devices. Spring contacts and methods of forming them are known in the art.

Spring contacts may be formed by depositing a release layer on a substrate or some other underlying layer. In this approach, layers of engineered spring metal are deposited onto the release layer and conductive bond pads and patterned. The release layer is then etched away to release a free end of the spring which curls up and away from the substrate. Another approach involves overplating or cladding the released spring contact.

The method described above requires the spring contact to be formed on the wafer as part of the wafer manufacturing process, which requires the sputtering of metals not normally used in the manufacturing process.

Anisotropic Conductive Film (ACF) tape separates the application of conductive contacts from the chip manufacturing process. ACF tape has limitation as to how small a pitch can be used by the chip. Smaller pitch sizes may lead to short circuiting within the tape between adjacent landings. Also, ACF tape is not compliant and is not easy to rework.

SUMMARY OF THE DISCLOSURE

A contact spring applicator has a substrate, a removable encapsulating layer and a plurality of released spring contacts embedded in the encapsulating layer. Each contact spring is positioned to locate a bond pad on an anchor end of the contact spring adjacent to an upper surface of the encapsulating layer. A free end of each contact spring is located near the substrate.

The contact spring applicator may be made by forming a handle substrate and sequentially depositing a handle release layer, a bond pad metallization layer, a spring release layer and a spring metal layer on the handle substrate. The spring metal layer is patterned to form unreleased contact springs. Then the bond pad metallization layer and spring release layer are patterned to form a bond pad and to release the spring contacts. A wax encapsulating layer may be formed on a contact spring applicator substrate. The contact springs and bond pads on the handle substrate are embedded in the wax encapsulating layer such that the bond pads are adjacent to an upper surface of the wax encapsulating layer. The handle release layer is then removed to remove the handle release layer and the handle substrate from the contact springs and bond pads.

A contact spring applicator may also have an applicator substrate, a release layer, a plurality of patterned unreleased contact springs and a bond pad on an anchor end of each contact spring.

DETAILED DESCRIPTION

It is often desirable to make springs on input/output ports of integrated circuits (IC) in order to use the spring to electrically connect to other devices. However, the spring manufacturing process can be incompatible with the IC manufacturing process. Therefore, it would be helpful to decouple the spring fabrication process from the IC manufacturing process and then bond the springs to the ICs after IC manufacture. Also, it would be helpful to have a spring manufacturing process that is independent of the IC manufacturing process because spring can then be placed on a large variety of ICs from different IC manufacturers.

This disclosure describes means of separating the IC manufacturing process from the spring manufacturing process through the use of a contact spring applicator. The contact spring applicator allows for the formation of the spring contacts to be separated from the manufacturing of an integrated circuit or die. A plurality of contact springs are contained on the applicator. After the chip, die or package is separately manufactured, bond pads on the contact springs are fused to select contact pads on the chip, die or package, and the applicator material is removed leaving the contact springs on the chip, die or package.

FIG. 1is a cross-sectional view of a portion of a contact spring applicator20. The applicator20includes a substrate22an encapsulating layer24and a plurality of contact springs26embedded in the encapsulating layer. Each contact spring26is positioned to have an anchor end28and a bond pad30attached to the anchor end with the bond pad adjacent to an upper surface32of the encapsulating layer24. The free end34of the contact spring26is positioned near the substrate.

The substrate22may be made from a flexible sheet and/or tape or may be made from a rigid material, including but not limited to silicon substrate or a circuit board. The encapsulating layer24may be a sacrificial layer which can later be removed without damaging the pads, springs and substrate. For example, a meltable material may be used as the encapsulating layer24and may be melted to release the substrate22from the contact springs26after the contact springs have been applied. An example of such a meltable material is wax.

FIGS. 2-4are cross-sectional views showing a method of manufacturing the contact spring applicator20. A handle substrate36is deposited. A handle release layer38is deposited on the handle substrate36. A bond pad metallization layer40is deposited on the handle release layer38. A spring release layer42is deposited on the bond pad metallization layer40. A spring metal layer44is deposited on the spring release layer42.

The spring metal layer44is patterned to create spring contacts26. The spring release layer and the bond pad metallization layer are patterned to create bond pad30and release the free end34of the contact spring26. The contact spring26may then be overplated, if desired.

A removable encapsulating layer24is deposited on the applicator substrate22. In one embodiment, the removable encapsulating layer is a wax that can be melted at around 110° C., but crystallizes into a solid mass at room temperature. The wax may also be dissolved in solvents such as acetone. The plurality of contact springs26on handle substrate36are then embedded in the removable encapsulating layer24with the bond pad30adjacent to an upper surface32of the removable encapsulating layer24.

The handle release layer38and handle substrate36are then removed from the spring release layer42leaving the plurality of contact springs26embedded on the contact spring applicator20, resulting in the structure shown inFIG. 1.

The handle release layer38may be a crystalbond wax layer. A solvent such as acetone may then be used to dissolve the handle release layer38to remove the handle release layer and the handle substrate36.

The handle release layer38may also be a thermal release material or tape. The thermal release material is the heat-activated to remove the handle release layer38and the handle substrate36.

The handle release layer may also be an ultraviolet (UV) release material. The UV release material is then activated by applying ultraviolet light to remove the handle release layer38and the handle substrate36.

FIG. 5is a cross-sectional view of another contact spring application120. The applicator120includes a substrate122, a release layer124and a plurality of patterned spring metal126formed on the release layer. This spring metal is designed with a stress gradient so that later, when the substrate122, onto which the spring is deposited, is removed, the spring tip will release and move down toward where the substrate was. This is in contrast to the stress gradient shown inFIG. 3, which directs the spring tip to move up away from the substrate122when released. Bond pads130are formed on each patterned spring metal126.

The substrate122may be made from a flexible sheet and/or tape or may be made from a rigid material, including but not limited to a silicon substrate or a circuit board. The substrate122has a plurality of contact springs126spaced to be fused to a plurality of bond pad landings on an integrated circuit, chip, die or package. The contact springs126may also be utilized as probe needles on a probe card.

The release layer124may be made from a crystalbond wax, a thermal release material or tape, an ultraviolet (UV) release tape or silicon. When the release layer124is made from silicon, the substrate122and release layer124may be removed from the patterned spring metal126by etching the silicon with xenon diflouride or some other appropriate etchant.

FIGS. 6-9are cross-sectional views showing methods of applying spring contacts using the spring contact applicators20and120. Referring toFIGS. 6-7showing spring contact applicator20, each bond pad30is aligned with chip pads52on the device50receiving the contact springs26. Examples of device50include but are not limited to an integrated circuit, an optoelectronic device, a sensor, an actuator, a meme device, all of which are on substrates such as silicon, printed circuit board, plastic, glass or polymer. The plurality of bond pads30are adhered to the plurality of bond pad landings52. The device50, pad52, pad30and spring26are then separated from the substrate22by removing the removable encapsulating layer24. Any residue of the encapsulating layer24may then be cleaned off of the contact spring26and device50.

Referring toFIGS. 8-9showing spring applicator120, the plurality of bond pads130are aligned with a plurality of bond pad landings52on device50. The release layer124is then removed to separate the contact springs126from the substrate122and to release the contact springs126. Note that the spring tips on spring applicator120rise out of the plane, toward where the substrate122was and away from the device50.

The release layer124may be a crystalbond was layer. A solvent such as acetone may then be used to dissolve the crystalbond wax layer124to separate and release the contact springs126.

The release layer124may also be a thermal release material or tape. The thermal release material124is then activated by applying heat to separate and release the contact springs126.

The release layer124may also be an ultraviolet (UV) release material. The UV release material124is then activated by applying ultraviolet light to separate and release the contact springs126.

The release layer may also be a sacrificial layer such as titanium, oxide and silicon which may be removed by etching or some other process.