United States Patent [19]
`Thome
`
`4,032,963
`[11]
`[45] June 28, 1977
`
`[54] PACKAGE AND METHOD FOR A
`SEMICONDUCTOR RADIANT ENERGY
`EMITTING DEVICE
`[75] Inventor: Gene P. Thome, Scottsdale, Ariz.
`[73] Assignee: Motorola, Inc., Schaumburg, Ill.
`[22] Filed:
`May 5, 1976
`[21] Appl. No.: 683,552
`Related U.S. Application Data
`f63) Continuation of Ser. No. 502,582, Sept. 3, 1974,
`abandoned.
`[52] U.S. Cl. ................................... 357/72; 357/70;
`357/74; 174/52 PE; 29/588; 264/272;
`264/135; 357/17
`-
`[51] Int. Cl.”.................. H01L 23/28; H01L 23/02;
`H01L 23/12
`[58] Field of Search .................. 357/17, 69, 72, 74,
`357/70; 174/52 PE; 264/135, 272; 29/588
`References Cited
`UNITED STATES PATENTS
`i? 1959 Corbitt et al. ................. 174/52 PE
`2,870,287
`3,609,475 9/1971
`Kaposhilin ........................... 357/72
`3,622,419 1 1/1971 London et al. ......
`......... 357/72
`3,689,804 9/1972 Ishihama et al. .............. 174/52 PE
`
`[56]
`
`3,706,840 12/1972 Moyle et al. ...................... 264/272
`3,739,241
`6/1973 Thillays ............................... 357/72
`3,742,599 7/1973 Desmond et al. ................... 29/588
`3,760,237 9/1973 Jaffe .................................... 357/72
`3,764,862 10/1972 Jankowski ........................... 357/72
`3,805,347 4/1974 Collins et al. ....................... 357/72
`3,820,237 6/1974 Effer .................................... 29/588
`3,855,606 12/1974.
`Schobel ............................... 357/72
`Primary Examiner—William D. Larkins -
`Assistant Examiner—Gene M. Munson
`Attorney, Agent, or Firm—Kenneth R. Stevens
`[57]
`ABSTRACT
`Method and structure for encapsulating or providing a
`package for a light emitting semiconductor device in
`order to prevent package failure due to chemical con
`taminants. A light emitting semiconductor chip is con
`nected to terminal leads having sharp angular portions.
`The device and the sharp angular portions are coated
`with a resilient elastomeric resin material inner core.
`An outer core comprising an acrylic or polycarbonate
`plastic material is injection molded over the inner core
`so as to leave exposed terminal leads for interconnec
`tion to electrical substrates such as cards or printed
`circuit boards.
`
`2 Claims, 4 Drawing Figures
`
`
`
`VIZIO 1021
`
`

`
`U.S. Patent
`
`June 28, 1977
`
`4,032,963
`
`IO
`
`ATTACHING
`LIGHT
`EMITTING
`CHIP
`
`|NNER
`COAT|NG OF
`CHIP AND
`LEADS
`
`MOLDING
`OUTER SHELL
`
`F’g /
`
`
`
`
`
`Fig 3
`
`VIZIO 1021
`
`

`
`1
`
`-
`
`ergy.
`
`4,032,963
`2
`solvent cleaner, but the package was damaged. More
`over, it was found that if non-injection molding tech
`PACKAGE AND METHOD FOR A
`niques were employed to form the polycarbonate or
`SEMICONDUCTOR RADIANT ENERGY EMITTING
`acrylic package, then these latent package stresses
`DEVICE
`were often avoided. This latter solution of course suf
`This is a continuation of application Ser. No. 502,582
`fers in that it loses all of the batch processing, time, and
`filed Sept. 3, 1974, now abandoned.
`cost advantages associated with injection molding.
`BACKGROUND OF THE INVENTION
`Further, during the analysis of the apparent mecha
`nisms leading to package failures resulting from the
`1. Field of the Invention
`release of latent internal stresses, it was found that
`This invention relates to method and structure for
`minimal package damage was experienced even using
`packaging a semiconductor device, and more particu
`injection molding techniques when the lead structure
`larly a semiconductor device for emitting radiant en
`was constituted by non-angular straight portions. Thus,
`2. Description of the Prior Ar
`it has been theorized that the creation of these latent
`In the past, thermosetting and thermoplastic materi
`stresses are further aggravated by the existence of
`15
`sharp structural angular lead edges.
`als, such as acrylics or polycarbonates, have been em
`ployed to encapsulate light emitting diode semiconduc
`SUMMARY OF THE INVENTION
`tor devices. Normally, a plurality of light emitting di
`odes are electrically bonded to respective lead pairs on
`It is therefore an object of the present invention to
`provide a package or encapsulating technique for radi
`a lead frame structure. After the device bonding opera
`20
`ant emitting or light emitting semiconductor devices
`tion the entire lead frame structure is inserted in an
`which maintains the light transmitting qualities and
`injection molding apparatus and all of the devices are
`encapsulated by employing injection molding tech
`package structural integrity when subjected to poten
`niques. Thereafter, each of the lead pairs are then sepa
`tial chemical contaminants, such as, a solvent cleaner.
`Another object of the present invention is to provide
`rated from the overall lead frame structure for use in
`25
`a reliable package for a light emitting semiconductor
`interconnection substrates, such as, cards or boards.
`device which can be formed by batch processing and
`This batch processing reduces cost and simplifies han
`dling during the overall encapsulating or packaging
`injection molding techniques.
`A further object of the present invention is to provide
`process.
`a light integrity encapsulating package for radiant or
`Normally, when the separate devices are used on
`30
`light emitting semiconductor devices which require
`cards or boards it is necessary to connect the exposed
`electrically conductive angular terminals leads.
`terminal leads to other circuitry and soldering is often
`the preferred technique. However, the overall solder
`In accordance with the aforementioned objects, the
`ing technique requires that the in situ soldered light
`present invention provides method and structure for
`encapsulating a radiant energy emitting semiconductor
`emitting semiconductor device be rinsed and cleaned
`chip by completely coating the chip and all angular
`by using a suitable solvent in order to remove the solder
`edge portions of the terminal leads with a resilient,
`flux.
`This procedure causes a totally unexpected problem
`rubber-like silicone resin inner encapsulating core and
`then completely covering the inner core with an outer
`in that while the overall packaged light emitting device
`encapsulating radiant energy transmitting core by in
`was virtually indestructible during normal lifetime us
`40
`jection molding of a plastic material.
`age, the exposure of the packaged device to solvents in
`many instances completely destroyed the integrity of
`DESCRIPTION OF THE DRAWINGS
`the injected molded outer package producing internal
`FIG. 1 illustrates the basic process steps required for
`cracks or a “fried marble” appearance. Naturally,
`these defects completely destroyed the requisite light 45 forming the light emitting diode encapsulated package.
`transmitting qualities of the package.
`FIG. 2 illustrates a lead frame structure, partially
`broken away, showing the beginning and ending termi
`Although the phenomena is not completely under
`nal pairs and having light emitting semiconductor chips
`stood, the injection molding of an acrylic or polycar
`bonate plastic material over the light emitting device
`attached thereto.
`-
`apparently creates latent stresses in the device pack
`FIG. 3 illustrates a specific lead pair location broken
`50
`away from the structure of FIG. 2 with the light emit
`age. These latent stresses are released when exposed to
`ting diode chip and all the sharp angular edge portions
`certain solvents causing package damage.
`One obvious suggested solution is to increase the
`of the terminal leads covered with a resilient rubber
`strength of the acrylic or polycarbonate material in
`like silicone resin material for forming an inner encap
`sulating core.
`order to allow it to withdstand the exposure to certain
`55
`FIG. 4 illustrates the structure of FIG. 3 after being
`chemical solvents. However, this solution has its draw
`completely covered with an outer encapsulating radi
`backs when applied to light emitting diode devices. The
`ant energy transmitting core by injection molding of a
`addition of strengthening material to the acrylic or
`plastic material, but prior to its separation from the
`polycarbonate material detracts from the light or radi
`ant energy transmitting qualities of the cured material.
`lead frame structure illustrated in FIG. 2.
`In looking at the prior art, it is found that elastomeric
`DESCRIPTION OF THE PREFERRED
`resilient silicone resins have been employed to protect
`EMBODIMENTS
`semiconductor devices per se. That is, the silicone
`Now referring to the Figures, FIG. 1 illustrates the
`resins provide both mechanical and device protection
`basic process steps required for protecting the light
`to the semiconductor device. However, with respect to
`65
`emitting semiconductor chip package. At 10, a plural
`the problem leading to the present invention, the semi
`ity of chips are bonded or attached to lead frame termi
`conductor device was in itself undamaged by the re
`nal locations by suitable means such as wire bonding,
`lease of these package stresses upon contact with the
`
`10
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`35
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`60
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`VIZIO 1021
`
`

`
`4,032,963
`3
`What is claimed is:
`soldering, etc. A lead frame structure 12 is illustrated in
`1. Structure for protecting a semiconductor chip
`FIG. 2 and shows the first and last terminal pair sites 14
`capable of emitting radiant energy comprising:
`and 16. Light emitting semiconductor chips 18 and 20
`a. a pair of continuous, separated electrically con
`are attached to the planar terminal locations associated
`ducting beam leads each having elongated portions
`with terminal pairs 14 and 16, respectively.
`and each terminating at their respective same ends
`At 12, each of the terminal pair locations are coated
`in a pair of chip terminal locations angularly dis
`with a resilient, rubber-like silicone resin for forming
`posed to its respective elongated portion;
`an inner core 20 as illustrated in FIG. 3. The inner core
`b. a semiconductor chip electrically coupled to said
`20 completely covers the light emitting semiconductor
`pair of chip terminal locations;
`chip and all the sharp angular edge portions of the
`c. a solid injection molded outer plastic acrylic or
`terminal leads 22 and 24. One suitable silicone resin
`polycarbonate housing material having side, top
`material is known as DC-R6103 supplied by the
`and bottom surfaces surrounding the semiconduc
`At 30, the structure illustrated in FIG. 3 is then sub
`tor chip and extending downwardly from the semi
`jected to an injection molding operation in order to
`conductor chip;
`form an outer cured plastic core 32 which completely
`d. a plurality of surfaces forming angles with respect
`surrounds the inner core 20. In the preferred embodi
`to each other comprising substantial portions of
`ments, the material used to form the outer core 32
`comprises thermosetting or thermoplastic acrylic or
`said pair of leads and the semiconductor chip lo
`cated within said outer plastic housing and at least
`polycarbonates having the desired radiation transmit
`one of said angles being disposed on each of said
`ting qualities and characteristics compatible with the
`20
`elongated portions;
`particular radiant energy being emitted by the semicon
`e. an encapsulating layer entirely covering the entire
`ductor light emitting device. One suitable material for
`semiconductor chip and all said angular surfaces
`forming the outer core 32 is an acrylic thermoplastic
`constituted by portions of said pair of leads and the
`material known as V8-11 supplied by the Roman Haas
`semiconductor chip and extending downwardly at
`Company.
`25
`least to the outer plastic housing bottom surface;
`Once the encapsulated device 34 is separated from
`f. said encapsulating layer being in direct contact
`the lead frame structure 36 it is then connected to
`with internal portions of said outer plastic housing
`interconnection substrates, such as, printed circuit
`for protecting said outer plastic housing from stress
`boards, cards, etc. by soldering. The use of chemicals
`releasing chemicals;
`such as perchlorothylene to dissolve solder fluxes after
`g. said encapsulating layer comprising a material
`soldering the device 34 in situ does not damage the
`more resilient than said outer plastic housing; and
`structural and light transmitting integrity of the outer
`h. said outer plastic housing and said encapsulating
`core 32. Thus, the inner core 20 protects the outer core
`layer comprising material for transmitting radiant
`32 from the release of latent stresses due to contact
`energy emitted by the semiconductor chip.
`with chemical contaminants.
`2. Structure for protecting a semiconductor chip
`Although specific materials have been designated for
`capable of emitting radiant energy as in claim 1
`the inner core material, outer core material, and the
`wherein:
`chemical solvent contaminant it is to be realized that
`a. said encapsulating layer comprises a resilient elas
`numerous other compounds and chemical materials
`may be readily substituted or provide the same effect
`tomeric resin material.
`and result as those examples specifically taught herein.
`* #:
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`VIZIO 1021