Spatial light modulator including a VLSI chip and using solder for horizontal and vertical component positioning

A liquid crystal spatial light modulator, comprising;

• a rectangular substrate member having a generally flat upper surface,
• a four-sided semiconductor chip of a size smaller than said substrate member, said semiconductor chip having a plurality of liquid crystal modulating circuits thereon, said semiconductor chip having a generally flat upper surface and a generally flat lower surface,
• a first plurality of solder joints mounting said semiconductor chip generally centered on said upper surface of said substrate member in a manner such that four edge portions of said substrate member extend beyond said four sides of said semiconductor member, said semiconductor member being mounted in spaced relation to said upper surface of said substrate member with said lower surface of said semiconductor chip being spaced above said upper surface of said substrate member,
• a rectangular cover glass of generally the same size or a larger size than said substrate member, said cover glass having a generally flat lower surface,
• liquid crystal cavity spacer means,
• a second plurality of solder joints mounting said cover glass on said four edge portions of said substrate member with said liquid crystal spacer means confined between said lower surface of said cover glass and said upper surface of said semiconductor chip, to thereby define a liquid crystal cavity between said upper surface of said semiconductor chip and said lower surface of said cover glass, and
• a liquid crystal layer in said liquid crystal cavity.

A method of making a liquid crystal spatial light modulator, comprising the steps of;

• providing a substrate member having a first and a second pattern of solder wettable pads on an upper surface thereof,
• providing a semiconductor chip having an upper surface, having at least one liquid crystal modulating circuit means thereon, and having a third pattern of solder wettable pads on a lower surface,
• said first and third pattern of solder wettable pads being of generally identical physical configuration,
• positioning said semiconductor chip above said substrate member with said first and third pattern of solder wettable pads generally in alignment,
• providing a first plurality of solder joints between said semiconductor chip and said substrate member, and in general alignment with said first and third pattern of solder wettable pads,
• heating said first plurality of solder joints such that solder reflow forces produce a desired alignment of said semiconductor chip to said substrate member, and such that said first plurality of solder joints operate to support said semiconductor chip above said upper surface of said substrate member,
• providing a cover glass having a fourth pattern of solder wettable pads on a lower surface thereof,
• said second and fourth pattern of solder wettable pads being of generally identical physical configuration,
• positioning said cover glass above said substrate member with said second and fourth pattern of solder wettable pads generally in alignment,
• providing a second plurality of solder joints between said cover glass and said substrate member, and in general alignment with said second and fourth pattern of solder wettable pads,
• providing a plurality of spacer means intermediate said cover glass and said upper surface of said semiconductor chip,
• heating said second plurality of solder joints such that solder reflow forces produce a desired alignment of said cover glass to said substrate member, and such that said solder reflow forces operate to force said cover glass downward onto said spacer means, so as to establish a liquid crystal cavity between said lower surface of said cover glass and said upper surface of said semiconductor chip, and
• injecting a liquid crystal material into said liquid crystal cavity.

A spatial light modulator, comprising;

• a substrate member having a first, second and third pattern of solder wettable pads on an upper surface thereof,
• a semiconductor chip having an upper surface, having a plurality of liquid crystal modulating circuits on said upper surface, having a like plurality of liquid crystal modulator pads on said upper surface, said modulator pads being arranged in a pixel pattern to define a pixel configuration for said spatial light modulator, each of said modulator pads being connected to be controlled by one of said liquid crystal modulating circuits, said semiconductor chip having a lower surface, and said semiconductor chip having a fourth and a fifth pattern of solder wettable pads on a lower surface,
• said second and fourth pattern of solder wettable pads being of generally identical physical configuration,
• said third and fifth pattern of solder wettable pads being of generally identical physical configuration,
• said semiconductor chip being positioned above said substrate member with said second and fourth pattern of solder wettable pads generally in alignment, and with said third and fifth pattern of solder wettable pads generally in alignment,
• a first plurality of solder joints between said semiconductor chip and said substrate member, and in general alignment with said second and fourth pattern of solder wettable pads,
• a second plurality of solder joints between said semiconductor chip and said substrate member, and in general alignment with said third and fifth pattern of solder wettable pads,
• a cover glass having a sixth pattern of solder wettable pads on a lower surface thereof,
• said first and and sixth pattern of solder wettable pads being of generally identical physical configuration,
• said cover glass being positioned above said substrate member with said first and sixth pattern of solder wettable pads generally in alignment,
• a third plurality of solder joints between said cover glass and said substrate member, and in general alignment with said first and sixth pattern of solder wettable pads,
• a plurality of individual spacers intermediate said cover glass and said upper surface of said semiconductor chip, and
• a liquid crystal intermediate said cover glass and said upper surface of said semiconductor chip.

A method of making a spatial light modulator, comprising the steps of;

• providing a generally rectangular substrate member having a generally flat and horizontal upper surface of a given area,
• providing a generally rectangular semiconductor chip having an upper horizontal surface of an area less than said given area, having a lower horizontal surface of said area less than said given area, and having at least one liquid crystal modulating circuit means,
• positioning said semiconductor chip above said substrate member,
• providing a first plurality of solder joints between said semiconductor chip and said substrate member, said first plurality of solder joint being of a relatively small size diameter,
• providing a second plurality of solder joints between said semiconductor chip and said substrate member, said second plurality of solder joint being of a relatively medium size diameter,
• heating said first and second plurality of solder joints such that solder reflow forces produce horizontal alignment of said semiconductor chip and said substrate member, and such that said first and second plurality of solder joints support said lower surface of semiconductor chip above said upper surface of said substrate member,
• providing a cover glass, said cover glass having a generally flat and horizontal lower surface of generally said given area,
• positioning said cover glass above said substrate member,
• providing a third plurality of solder joints of relatively large diameter between said cover glass and said substrate member,
• providing a plurality of vertical spacers intermediate said lower surface of said cover glass and said upper surface of said semiconductor chip,
• heating said third plurality of solder joints such that solder reflow forces produce alignment of said cover glass and said substrate member, and such that said solder reflow forces force said cover glass downward onto said vertical spacer, so as to establish a liquid crystal cavity between said lower surface of said cover glass and said upper surface of said semiconductor chip, and
• injecting liquid crystal into said liquid crystal cavity.