Texas Instruments Corporation

Harold T Kelleher

David W West

Paul R Moehle

Gijsbert Willem Lokhorst

The invention is a method for making a lead frame (,) having fine pitched lead frame leads (,). A first side of the lead frame material is etched to for the lead frame and define the lead frame leads and die pad, but the etch process does not etch completely through the lead frame material. The partially etched first side is then covered with a tape (,) or layer of photoresist (,). The second side of the lead fame material is then etched to complete the lead frame. The lead frame may then be plated.

Method of forming lead frames with preformation support

A leadframe (10) for diverting current to an adjacent conductor (55) when a current in the leadframe (10) exceeds a predetermined level includes a first portion (12) for carrying a chip (13) in which an integrated circuit has been constructed. A second portion (20) is connected to receive a current that flows through at least a portion of the integrated circuit. The second portion (20), which may include a bimetallic portion (40,41), is physically deformed by the current and is located to contact the adjacent conductor (55) when the current reaches the predetermined magnitude.

Deformable leadframe for overcurrent protection

This invention relates to a process for strengthening the adhesive bond between a lead frame and a plastic mold compound (350). The process involves plating the lead frame with a copper strike and selectively exposing the copper strike to an oxidizing agent to form a layer of cupric oxide (CuO) (318). Such lead frames are fitted with chips (324) and then encapsulated in the plastic mold compound (350), whereby the adhesive bond forms directly between the layer of CuO (318) and the plastic mold compound (350). A lead frame produced by this process may include a plurality of leads (310) having lead ends (312) and lead fingers (314) and a die pad (320) having a layer of CuO (318). The die pad (320) is encased by a plastic mold compound (350) which forms an adhesive bond directly with the layer of CuO (318). This layer (318) may have a thickness in a range of about 5 to 50.mu. inches (12.7 to 127 .mu.cm). Lead ends (312 ) and lead fingers (314) may be spot-plated with silver or palladium.

Method of forming lead frame with strengthened encapsulation adhesion

A method of providing selective silver plating to a lead frame structure 10 performs the silver plating operation prior to etching the lead frame, thereby avoiding mechanical damage to the lead frame during plating, and producing finished silver spots 24 on the top surface of the lead frame only, with no plating on the gauge. The disclosed method includes the steps of applying a layer of photoresist 42 to a surface of a sheet of lead frame material 40, exposing areas of the photoresist such as to define selected regions 44, developing the photoresist 42 to uncover the lead frame material 40 at the selected regions 44, and plating the surface of the sheet defined by the layer of photoresist 42 with an electrically conductive material 46. The method further includes subsequent steps of stripping the layer of photoresist 42 from the surface, applying a layer of a second photoresist 50 to the plated surface, exposing areas of the second layer of photoresist 50 such as to define an unexposed lead frame pattern, the selected regions 44 corresponding to electrical contact locations on the lead frame pattern, and developing the photoresist 50 to uncover exposed regions 52 of the sheet of lead frame material 40. The method includes a final step of etching the sheet 40 to remove material from regions 52 uncovered by the second photoresist layer 50.

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Attleboro, MA, United States of America

Harold T Kelleher