Light source and technique for mounting light emitting diodes

• US 5,475,241 A
• Filed: 10/27/1993
• Issued: 12/12/1995
• Est. Priority Date: 08/20/1992
• Status: Expired due to Fees

• Current Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Fajardo, Thomas, Kreger, Jerry D., Smith, Trevor J., Uebbing, John, Harrah, Shane
• Primary Examiner(s): Jackson, Jerome
• Assistant Examiner(s): Kelley, Nathan K.
• Application Number:
  US08/119,913
• Time in Patent Office: 776 Days
• Field of Search: 257/99, 257/88, 257/91, 257/100, 257/703, 257/92, 257/773
• US Class Current: 257/99
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 33/00 Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof H10K50/00 takes precedence; devices consisting of a plurality of semiconductor components formed in or on a common substrate and including semiconductor components having potential barriers, specially adapted for light emission H01L27/15; semiconductor lasers H01S5/00
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/385 the electrode extending at least partially onto a side surface of the semiconductor body
• CPC Class Codes: H01L 33/40 Materials therefor
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: Y10T 156/1768 Means simultaneously conveying plural articles from a single source and serially presenting them to an assembly station
• CPC Class Codes: Y10T 29/53191 Means to apply vacuum directly to position or hold work part
• CPC Class Codes: Y10T 29/53261 Means to align and advance work part

Abstract

A light emitting diode has both end faces metallized and is mounted on a substrate with the light emitting junction perpendicular to the substrate. The electrically conductive ends are electrically bonded to conductive areas on the substrate by solder or conductive adhesive. LED dice can be placed on the substrate by temporarily attaching the dice to a tape which has been wrapped around a knife edge. The dice tilt as the tape wraps around the edge and are picked off one at a time by a vacuum collet while temporarily supported by a movable finger, and then transferred by the vacuum collet to a substrate. A similar method may be used for placing semiconductor dice on a substrate without the tilting of dice around the edge. In another embodiment, an array of LEDs can be assembled in windows through a metallized plastic tape which is bonded to a foundation with additional metallized leads.

Claims

1. A light source having end faces parallel to a semiconductor junction and side faces normal to the junction comprising:

a substrate;

a light emitting diode having a light emitting junction perpendicular to the substrate and having an electrically conductive layer at each end face of the light emitting diode which is parallel to the junction; and

means for mounting the light emitting diode on the substrate with the junction perpendicular to the substrate and the electrically conductive layers in electrical contact with conductive areas on the substrate wherein at least one of the conductive layers on an end face of the light emitting diode comprises a metal pad covering less than the entire end face of the light emitting diode for emission of light through the end face and having an edge adjacent to a side face of the light emitting diode, the metal pad comprising a stripe extending between opposite side faces of the light emitting diode and perpendicular to the substrate.

2. A light source comprising:

a substrate;

a light emitting diode having a light emitting junction perpendicular to the substrate;

a non-conductive layer for reflection on a face of the light emitting diode parallel to the junction;

a metal layer over the non-conductive layer;

at least one hole through the non-conductive layer for electrical contact between the metal layer and the light emitting diode; and

means for mounting the light emitting diode on the substrate with the junction and the metal layer perpendicular to the substrate, the metal layer being in electrical contact with a conductive area on the substrate.

3. A light source comprising:

a substrate comprising;

a first plurality of electrically conductive areas formed on the substrate for electrical connection between a light emitting diode and an external circuit,

an insulating layer over at least a portion of the conductive areas, and

a hole through the insulating layer for electrical contact;

a light emitting diode having a light emitting junction perpendicular to the substrate and having a first electrically conductive layer on an end face of the light emitting diode parallel to the junction and a second electrically conductive layer on an opposite end face of the light emitting diode parallel to the junction;

means for mounting the light emitting diode on the substrate with the junction perpendicular to the substrate and the electrically conductive layers in electrical contact with the conductive areas through the hole;

a non-conductive layer formed over the substrate and covering at least a portion of the first conductive areas;

a second plurality of electrically conductive areas formed on the non-conductive layer;

wherein the insulating layer covers at least a portion of the second plurality of electrically conductive areas;

a plurality of holes through the insulating and non-conductive layers, each hole overlying such a second conductive area on the non-conductive layer and also overlying a first conductive area formed on the substrate; and

a light emitting diode mounted in each hole with a light emitting junction perpendicular to the substrate, each light emitting diode comprising a metal layer on each of a pair of end faces parallel to the junction, the metal layer on one end face being in electrical contact with a first conductive area on the substrate and the metal layer on another end face being in electrical contact with a second conductive area on the non-conductive layer.

4. A light source as recited in claim 3 wherein the first plurality of conductive areas comprises a plurality of parallel conductive stripes formed on the substrate and the second plurality of electrically conductive areas comprises a plurality of parallel metal traces formed on the insulating layer, the traces being orthogonal to the stripes on the substrate.