Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal
Reexamination Certificate
2002-08-20
2003-07-29
Fahmy, Wael (Department: 2814)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
C438S106000, C438S082000, C438S098000, C362S249070
Reexamination Certificate
active
06599768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light emitting device, and more particularly to a chip-type package for high power III-V compound semiconductor light emitting diodes.
2. Description of the Prior Art
A first explanatory conventional chip-type light emitting diode (LED) device is disclosed in U.S. Pat. No. 6,345,903 B1. FIG.
1
. herein shows a structure of the light emitting assembler
10
the patent disclosed. The LED
22
having an electrode formed on the bottom surface is adhered to a first metal contact
13
by silver paste or a solder layer
20
. The other electrode of the LED chip
22
formed on the upper surface thereof is bonded to the other first metal electrode
14
by a conductive wire
23
. Both of the first metal contacts
13
,
14
are formed on an upper surface of a glass fiber substrate
12
and are connected to the second metal contacts
33
,
34
on the bottom surface thereof by though holes
40
, which have a conductive plating layer
41
formed thereon.
Enclosing each of the LED chips is a corresponding reflective frame
17
in a form of a reflective frame assembler. The reflective frame
17
has an inclined inner periphery surface in a conic form, which has the function to reflect the light emitted by the LED chip thereby causing the light to converge in an upward direction. A first transparent resin encapsulating layer
15
is then refilled the reflective frame
17
so as to protect the LED chip
22
and the conductive bonding wire
23
.
Above the first resin encapsulator
15
is a second resin encapsulator
27
formed by injecting the resin into a mask mold
28
which has a plurality of semi-sphere concaves formed therein so as to form lens
29
for converging the light. After the resin encapsulator is cured, the mask mold
28
is then removed (not shown). Finally the LED assemble substrate is then saw from the cut line
42
, which is along the center line of the through hole
40
.
The surface mounted of the LED package in the first embodiment is for LED chip having two electrodes, respectively, on the upper and bottom surface. Thus, the light emitted is blocked by the upper electrode. Moreover, the base substrate
12
is an insulator, so that a through hold plating layer
41
is demanded to connect the first metal contacts
13
,
14
on the upper surface and the second metal contacts
33
,
34
on the bottom surface. The heat irradiated by the LED
22
can only be dissipated through the metal contacts
13
,
33
, and the through hole plating layer
41
since the LED
22
, is encapsulated by resin
15
. Consequently, bad heat dissipation capability of the substrate assembler is result.
The second explanatory conventional chip-type light emitting diode (LED) device is a flip-chip type disclosed in U.S. Pat. No. 6,396,082 B1, as shown in
FIG. 2
The LED flip-chip
79
with a transparent substrate upward is fixed on a glass epoxy substrate
72
, which has a through hole
75
formed therein directly above the LED chip
79
and two metal contacts
73
,
74
on the upper surface
76
a
thereof extended to the lower surface
76
b
. The through hole
75
is filled with a transparent resin layer
77
. Two metal electrodes
83
,
84
on the upper surface of the LED
79
are respectively, bonded to the metal contacts
73
,
74
by conductive wires
85
,
86
. The LED chip
79
and the conductive wires
85
,
86
are then protected by a transparent sealing body
88
. Finally, the glass epoxy substrate
72
is then upside down mounted onto a motherboard
91
by inserting the sealing body
88
into a hole
92
of the motherboard
91
.
Since the LED is upside down and light irradiated is upward through the through hole
75
without blocking by any metal electrodes
83
,
84
, an excellent light emission efficiency is thus anticipated. However, owing to the insulating base substrate
72
, the heat irradiated by the LED
79
can only be dissipated through the metal contacts
73
,
74
, since the LED
79
, is encapsulated by resin
77
too. Consequently, heat dissipation capability of the substrate assembler as previous embodiment is result. The output power of LED is limited and a high power LED can't be obtained without further improvement.
An object of the present invention is thus to propose a method and structure about surface mounting for a high power LED.
SUMMARY OF THE INVENTION
The present invention discloses two surface mount techniques for high power LED chips. In the first preferred embodiments, the LED chip having two electrodes formed on the same side is mounted onto an electric & thermal conductive substrate. The method comprises the following steps:
At first the base-substrate is cut or sawed or patterned to form a plurality of trenches. The trenches are then filled with spin on glass (SOG) or polyimide or BCB (B-staged bisbenzocyclobutene; BCB) layer. Thereafter, first metal contacts are formed on the upper surface of the base substrate. For every two metal contacts, respectively, at left hand side and right hand side of each trench function to support two electrodes of the LED chip. Next, the base-substrate is then back-side milling until at least the bottom of the trenches are exposed. Afterward, second metal contacts are formed on the milled surface. The second metal contacts on the right hand side and left hand side of each trench are formed for connecting external electrodes.
Subsequently, a reflective frame assembler is adhered to the upper surface of the base-substrate. The reflective frame assembler has a plurality of reflective frame, and each of them corresponding to a LED chip.
After that, the LED chip is up-side down placed within the reflective frame and with its p-type electrode and n-type electrode mounted on a pair of the first metal contacts with solder ball or solder layer. Finally, the LED chip is sealed and protected by transparent resin or epoxy. The upper portion of the reflective frame can be optionally formed with lens shaped so as to converge the light.
The method according to the second preferred embodiment is for LED chip with two electrodes, respectively, on the different sides of the LED.
The processes are as follows:
Firstly, the conductive base-substrate is formed with a plurality of trenches therein. The trenches are then filled with SOG or polyimide. Thereafter, first metal contacts are formed on the upper surface of the base substrate. It is noted that each two first metal contacts, one on the left hand side of the trench is for connecting a bottom electrode and the other one at the right hand side is for bonding a conductive wire. Hence, the metal contacts at left hand side and right hand side of each trench are not necessary to have equal area. Next, the base-substrate is then back-side milling until at least the bottom of the trenches are exposed. Afterward, second metal contacts are formed on the milled surface. The second metal contacts on the right hand side and left hand side of each trench are formed for connecting external electrodes.
Subsequently, a reflective frame assembler is adhered to the upper surface of the base-substrate. The reflective frame assembler has a plurality of reflective frame, and each of them corresponding to a LED chip. It is noted that the central position of the reflective frame is substantially aligned with one first metal contact, which is located at the central position of the reflective frame.
After that, the LED chip is placed within the reflective frame and with bottom electrode thereof attaching the first metal contact with solder ball or solder layer, wherein the first metal contact is approximately at the central position of the reflective frame.
Subsequently, a conductive wire is bonded to the upper electrode of the LED chip and the other first metal bonding electrode. Finally, the LED chip is sealed and protected by transparent resin or epoxy. The upper portion of the reflective frame can be optionally formed with lens shaped so as to converge the light.
REFERENCES:
patent: 6130111 (2000-10-01), Ikuina et al.
paten
Fahmy Wael
Trinh (Vikki) Hoa B.
Troxell Law Office PLLC
United Epitaxy Co., Ltd.
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