JPH10189643A - High-speed and selective heating of integrated circuit package assembly using tungsten halogen light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device of a structure, wherein as a semiconductor chip and a lead frame come into contact with each other, the chip is selectively heated in comparison with the lead frame, by a method wherein a heat source is provided so that heat energy in a specified wavelength range is fed to a semiconductor die and the lead frame which are arranged adjacent to each other. SOLUTION: In a device of a structure, wherein a semiconductor die 20 is selectively heated in comparison with a lead frame 24 during a wire-bonding process, the die 20 is arranged adjacent to the lead frame 24. A heat source 28 is provided, which feeds simultaneously heat energy in the extent of a wavelength of about 0.5μm to about 2μm to the die 20 and the lead frame 24, so as to heat the die 20 to a fully high temperature for wire-bonding as the lead frame 24 is maintained in a non-oxidized state. Moreover, a wire-bonding means for bonding wires to the die 20 is provided. For example, one comprising a non-focal tungsten halogen lamp is used as the heat source 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for rapidly heating selected portions of an integrated circuit package assembly, and more particularly, to a method for heating a selected portion of an integrated circuit package assembly while the entire region receives heat-generating radiation from a heat source. In connection with such heating using a heat source capable of selectively heating the portion, the heat source is preferably a tungsten halogen light source.

[0002]

BACKGROUND OF THE INVENTION In the manufacture of semiconductor devices and especially integrated circuits, a semiconductor chip is required to have approximately 20
It is desirable to heat to a temperature in the range of 0 ° C to 300 ° C. Further, the leadframe to be bonded is kept at a much lower temperature than the chip, and it is desirable that this lower temperature be low enough to minimize oxidation of the leadframe, which is typically copper. Normally, the oxidation of the lead frame depends on the wettability of the solder.
It is clear that the problem arises. This problem has existed in the prior art because the mechanism used to heat the semiconductor chip, typically a heater block or hot plate, also supports the lead frame and is non-thermal selective. Therefore, both the chip and the lead frame are heated together to almost the same high temperature as a single unit, that is, the temperature required for bonding to the chip. Thus, it is apparent that an apparatus that selectively heats a semiconductor chip compared to a lead frame while the chip and the lead frame are in contact with each other is highly desirable.

[0003]

SUMMARY OF THE INVENTION In accordance with the present invention, the above-mentioned problems of the prior art have been minimized, and certain components within a region are selectively heated at a much faster rate than the rest of the region. , Defocused or unfocused
2.) An apparatus and process for delivering thermally induced radiation is provided. By using non-focal heat-induced radiation, the need for a focusing device is reduced and the radiation traverses the entire area without requiring precise positioning, since the nature of the material receiving the radiation determines the temperature of its heating. Enable. For example, if the semiconductor chip heats up much faster than the copper-based lead frame prior to wire bonding, this allows wire bonding between the chip and the lead frame without excessively heating the lead frame. . The same type of operation is also useful when replacing the lead frame with tape with conductors on for standard tape automated bonding (TAB), where the tape degrades at normal wire bonding temperatures and It is best to heat the metal lead portions and the chip on the tape adjacent to the chip, excluding the tape itself, because it affects the electrical properties. The tape may be between the chip and the circuit board.

[0004] When a heat source provides non-focal thermal energy radiation in the range of about 0.5 microns to about 2 microns, some materials, such as chips, may be heated at a much faster rate than other materials, such as leadframe materials. It has been measured to rise. This is because leadframes, which are typically copper, heat up quickly when the thermal energy emission is greater than 2 microns and slowly increase when the thermal energy is in the range of about 0.5 microns to about 2 microns. Chip materials, which are typically silicon, germanium or III-V or II-VI compounds, cause a rapid temperature rise when the thermal energy is in the range of about 0.5 microns to about 2 microns. . Therefore, about 0.5
A heat source that provides at least a substantial portion of its thermal energy in the range of microns to about 2 microns selectively heats the semiconductor material as compared to a lead frame. The amount of energy required, ranging from about 0.5 microns to about 2 microns, depends on the required heating temperature difference and how fast this temperature difference is achieved. Therefore, about 0.5
A heat source that provides a substantial portion of its thermal energy in the range of microns to about 2 microns is required according to the present invention. Standard tungsten halogen light sources typically provide a substantial portion of their thermal energy in the range of about 0.5 microns to about 2 microns.

[0005] Briefly, the foregoing relates to lead frames and chips, and is accomplished by providing a base and placing the lead frame and chips thereon in a standard relationship to one another. A heat source of the type described above desirably has a reflector that directs most of the radiation to the desired area and then directs that heat to the leadframe and chip. The chip is heated to the required bonding temperature, after which the bonding takes place, while the lead frame is kept below the temperature of the chip and sufficiently low to avoid excessive oxidation. The heat source is turned off after the bonding has taken place.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings conceptually illustrate a heating device for a semiconductor die and an associated lead frame according to the present invention.

The drawings conceptually illustrate a novel optical heating apparatus and method used in connection with bonding wires between pads on a semiconductor chip and a lead frame. In FIG. 1, a silicon semiconductor die 20 is placed on a chip pad 26 together with a lead frame 24. Examples of lead frame materials include copper alloy, alloy 4
2, including palladium plated copper and nickel plated copper. An optical heat source 28, typically a heat source as described in the application above, can be used herein, and this heat source is incorporated herein by reference. Optical heat source 28 generates substantial radiation in the range of 0.5 to 2 microns, which energy is used to heat leadframe 24 and die 20.

[0008] With copper-based leadframes and conventional die sizes, this heating device is particularly advantageous because the leadframe 24 remains much cooler than the die 20 during die heating. For example, exposure to optical heat source 28 for one minute heats die 20 to about 200 ° C., but heats lead frame 24 only to about 125 ° C. Thus, the optical heat source 28 selectively heats the die 20.
The main thermal transition is caused by radiation and the temperature response of the die is advantageously a slow transient. The temperature profile is
It can be easily controlled during cure by varying the current through lamp 28. However, in the prior art heater block method, the thermal transition is by conduction and is a step function, such as a temperature response. Heat remaining in the heater block prevents rapid cooling, thereby causing further oxidation of the leadframe material. Fast optical response can result in fast thermal response.

Preferably, the optical heat source 28 is a lamp of the type that emits near-infrared light. Exemplary lamps include tungsten and xenon incandescent halogens.
Lamp included. The wavelength of near infrared light ranges from about 0.5 microns to about 2.0 microns. Silicon chip 20 has good absorption in the near infrared spectrum. For example, the energy of tungsten halogen light is absorbed more by the silicon chip 20 than by the lead frame 24, which has a higher incidence of reflection than the chip 20. The silicon chip 20 is radiatively heated to a temperature higher than the lead frame 24 by selective heating. Thereafter, wire bonding is performed while the chip is heated relative to the lead frame.

The reflector 30 emits unfocused radiation to the lamp 2.
8 to lead frame 24. This radiation is preferably sent across the width of the leadframe to generate uniform heat. Light spreads over the leadframe area as opposed to being focused on the semiconductor chip. Optionally, via a lead finger cutout (not shown) in leadframe 24, a porous tip
Dry air 32 exiting outlet 34 via pad 26 may flow over die 20. The purge air 32
It is capable of flowing over the die 20 and through a lead frame 24 closer to the end of the die 20, substantially increasing outgassing or similar evacuation effects. The intensity (power) of the lamp 28 may be controlled by a rheostat 36 or SCR, which may in turn be controlled by a computer, which is optionally programmed. This has the advantage of profiling the lamp power with an immediate energy response or turning it on and off, unlike prior art heater blocks, where an effective profile is not possible during snap cure due to its thermal mass. To be possible. Instantaneous lamp power adjustment helps the energy profile.

Although the present invention has been described with reference to certain preferred embodiments, various modifications and combinations will be apparent to those skilled in the art. It is therefore intended that the appended claims encompass any such modifications and combinations.

With respect to the above description, the following section is further disclosed. (1) An apparatus for selectively heating a semiconductor die compared to a lead frame during a wire bonding step,
A semiconductor die disposed adjacent to the leadframe, and the semiconductor die heated to a temperature sufficiently high for wire bonding while maintaining the leadframe in a substantially non-oxidized state. A heat source that supplies a majority of its thermal energy in the range of about 0.5 microns to about 2 microns in conjunction with thermal energy greater than 2 microns and less than 0.5 microns to simultaneously direct the heat to the leadframe; Wire bonding means for bonding a wire to the die.

(2) The apparatus according to item 1, wherein the heat source includes a non-focal lamp. 3. The apparatus of claim 1, further comprising a rheostat coupled to the non-focal heat source for controlling an amount of heat generated by the heat source. The apparatus of claim 2, further comprising a rheostat coupled to the non-focal heat source for controlling an amount of heat generated by the heat source. The apparatus of claim 1, further comprising a computer coupled to the heat source for controlling a current to the heat source. The apparatus of claim 2, further comprising a computer coupled to the heat source for controlling a current to the heat source.

(7) A method for selectively heating a semiconductor die compared to a lead frame during a wire bonding step, wherein a semiconductor die disposed adjacent to the lead frame is disposed, and the semiconductor die is disposed at a position larger than 2 μm and 0 mm. In connection with thermal energy less than 0.5 microns, heat having a majority of its thermal energy in the range of about 0.5 microns to about 2 microns was provided to maintain the leadframe in a substantially non-oxidized state. Directing the heat to the semiconductor die and the lead frame simultaneously to bond the wire to the heated die so as to heat the semiconductor die to a sufficiently high temperature for wire bonding.

(8) The method according to item 7, wherein the optical heat source includes a non-focal lamp. 9. The method of claim 7, further comprising controlling an amount of heat generated by the heat source. The method of claim 8, further comprising the step of controlling the amount of heat generated by the heat source. The method of claim 7, further comprising the step of computer-controlling the amount of heat generated by the heat source. (12) The method according to (8), further comprising the step of computer-controlling the amount of heat generated by the heat source.

(13) The method according to item 11, wherein the control by the computer is programmed control. (14) The method according to paragraph 12, wherein the control by the computer is a programmed control.

(15) Structures capable of absorbing heat radiation in the range of 0.5 to 2 microns, as compared to adjacent structures that have much less ability to absorb heat radiation in the range of 0.5 to 2 microns. Is selectively heated, wherein 0.
First to absorb thermal radiation in the 5 to 2 micron range
Providing a first structure capable of absorbing thermal radiation in the range of 0.5 to 2 microns disposed adjacent to a second structure much less than the second structure, wherein the first structure is greater than 2 microns and 0.5 microns Providing a heat source that supplies a majority of that thermal energy in the range of about 0.5 to about 2 microns, in conjunction with lesser thermal energy, sending the heat to the first and second structures simultaneously; Structure sufficiently high and the second
Heating to a temperature much higher than the structure of the first structure, allowing a predetermined function to be performed with the first structure while keeping the second structure below a predetermined temperature, and performing the function. Method.

(16) The method according to paragraph 15, wherein the optical heat source includes a non-focal lamp. (17) The method according to paragraph 15, further comprising a step of controlling an amount of heat generated by the heat source. (18) The method according to (16), further comprising controlling an amount of heat generated by the heat source. (19) The method according to paragraph 15, further comprising providing a computer for controlling the heat source. 20. The method of claim 16, further comprising providing a computer for controlling the heat source.

(21) A method and apparatus for selectively heating a structure 20 capable of absorbing thermal radiation in the range of 0.5 to 2 microns as compared to an adjacent structure 24, comprising: A first structure capable of absorbing thermal radiation in the range of 0.5 to 2 microns is located adjacent to a second structure that has less ability to absorb thermal radiation in the range of 0.5 to 2 microns. . A non-focal heat source 28 that provides a majority of its thermal energy in the range of about 0.5 to about 2 microns in relation to thermal energy greater than 2 microns and less than 0.5 microns provides the first and second structures with At the same time, heat is sent to the first structure while keeping the second structure below a predetermined temperature.
The first structure is heated sufficiently high to a higher temperature than the second structure so that a predetermined function can be performed with the second structure. The function is then performed. The heat source is
It is desirable to include a non-focal tungsten halogen lamp.

RELATED APPLICATIONS The present invention is related to US patent application Ser. No. 08 / 255,197, filed Jun. 7, 1994,
The application and all prior art described therein are incorporated herein by reference.

[Brief description of the drawings]

FIG. 1 conceptually illustrates a heating device for a semiconductor die and an associated lead frame in accordance with the present invention.

[Explanation of symbols]

 Reference Signs List 20 semiconductor die 24 lead frame 26 chip pad 28 optical heat source 30 reflector 32 dry air 34 exhaust port 36 rheostat

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Robo One Taiwan Taipei, Taiwan. Road section 2,23F, 216

Claims (2)

[Claims] 1. An apparatus for selectively heating a semiconductor die during a wire bonding process as compared to a lead frame, the semiconductor die being disposed adjacent to the lead frame, and the lead frame being substantially non-conductive. More than 2 microns and less than 0.5 microns to direct the heat to the semiconductor die and the lead frame simultaneously to heat the semiconductor die to a sufficiently high temperature for wire bonding while maintaining the oxidized state An apparatus comprising: a heat source that supplies a majority of its thermal energy in the range of about 0.5 microns to about 2 microns in relation to thermal energy; and wire bonding means for bonding a wire to the die. 2. A method for selectively heating a semiconductor die during a wire bonding process as compared to a lead frame, comprising: placing a semiconductor die disposed adjacent to the lead frame, wherein the semiconductor die is greater than 2 microns. Providing heat having a majority of its thermal energy in the range of about 0.5 microns to about 2 microns, with respect to thermal energy less than 5 microns, while maintaining the leadframe in a substantially non-oxidized state Directing the heat to the semiconductor die and the leadframe simultaneously to heat the semiconductor die to a sufficiently high temperature for wire bonding, and bonding a wire to the heated die.