JP4002736B2 - Mask sheet for assembling semiconductor device and assembling method of semiconductor device - Google Patents

Description

【００２８】
【発明の効果】
本発明のマスクシートは、上記の構成を有するから、耐熱性に優れ、ダイアタッチ材のキュア時の熱履歴でも分解物の揮発量が少なく、リードフレームが汚染されることがないため、金ワイヤーによる半導体チップとリードフレームの高接続信頼性を得ることができる。また、リードフレームの反りが少ないため、位置決め不良を起こし難い。更には封止樹脂がマスクテープから漏れる「モールドフラッシュ」も押さえることができ、接着剤の糊残りを抑制するため安定してＱＦＮ等の半導体パッケージを生産することができる。したがって、本発明のマスクシートを使用することにより、効率よく半導体装置を組み立てることが可能になる。
【図面の簡単な説明】
【図１】 リードフレームにマスクシートを接着した状態を示す断面図である。
【図２】 半導体チップを搭載して金ワイヤで接続した状態を示す断面図である。
【図３】 樹脂封止した状態を示す断面図である。
【図４】 マスクシートを剥がした状態を示す断面図である。
【図５】 半導体装置を個片化した状態を示す断面図である。
【符号の説明】
１…リードフレーム、２…接着剤層、３…耐熱フィルム、４…金ワイヤー、５…半導体チップ、６…樹脂封止剤。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device assembly mask sheet used for masking a lead frame from a sealing resin when a semiconductor chip is mounted on a metal lead frame and sealed with a resin to assemble a semiconductor device. The present invention relates to a method for assembling a semiconductor device.
[0002]
[Prior art]
With the spread of portable personal computers and mobile phones, electronic devices are required to be further reduced in size, thickness and functionality. In order to realize this requirement, it is indispensable to reduce the size and increase the integration of electronic components, but further requires a high-density mounting technology for electronic components. Therefore, instead of the peripheral mounting type such as the conventional QFP (Quad Flat Package) and SOP (Small Outline Package), a surface mounting type called CSP (Chip Size Package) has attracted attention as an IC package capable of high-density mounting. ing. Among them, in particular, the type called QFN (Quad Flat Non-Lead) can be manufactured by conventional lead frame, wire bonding, resin sealing (molding) technology and equipment, and is mainly less than 100 pins. Used to make small terminal type packages. This QFN is manufactured as follows. That is, a mask sheet is attached to one side of the lead frame, a semiconductor chip is mounted on the opposite side, and the lead and the chip are connected by a gold wire. Next, after sealing with resin, the mask sheet is peeled off and finally separated into pieces.
[0003]
[Problems to be solved by the invention]
Conventionally, a mask sheet in which a heat-resistant film is coated with an acrylic pressure-sensitive adhesive or a rubber pressure-sensitive adhesive mainly composed of rubber such as natural rubber or SBR is used. However, in the case of an acrylic adhesive, in the die attach process for joining a semiconductor chip to a lead frame, it begins to decompose by heat, and the decomposed product contaminates the lead frame, causing defective gold wire bonding, and resin. In the sealing (molding) step, there is a problem that “mold flash”, which is a phenomenon in which the sealing resin protrudes from the external connection lead portion, occurs due to weak adhesion with the lead frame. In the case of rubber-based adhesives, the adhesive strength to the sealing resin and / or leads is strong, making it difficult to remove the mask sheet from the package, so the rubber-based adhesive remains on the lead frame. ”Occurs and the lead frame is deformed.
[0004]
The present invention has been made for the purpose of solving the above-described problems in the prior art. That is, an object of the present invention is to provide a mask sheet capable of stably producing a semiconductor package such as QFN by suppressing protrusion of a resin sealing agent and adhesive residue of an adhesive during assembly of a semiconductor device. It is in. Another object of the present invention is to provide a method for efficiently assembling a semiconductor device using such a mask sheet.
[0005]
[Means for Solving the Problems]
In the manufacturing process of the QFN package, the mask sheet is peeled off from the lead frame after being exposed to the environment at 150 to 180 ° C. for 1 to 6 hours in the die attach process and the resin sealing process. Heat resistance at is the most important property. As a result of intensive studies, the present inventor has found that a material that can withstand the above environment can be obtained by producing a mask sheet using a specific heat-resistant film and a silicone-based pressure-sensitive adhesive, thereby completing the present invention. It came to.
[0006]
That is, the semiconductor device assembly mask sheet of the present invention is for releasably bonding to a lead frame, has a glass transition temperature of 150 ° C. or higher, and a linear expansion coefficient of 10 to 50 ppm at 150 to 200 ° C. An adhesive layer made of a silicone-based pressure-sensitive adhesive is provided on a heat-resistant film at / ° C., and the weight loss when heated at 180 ° C. for 1 hour is 5% or less.
[0007]
In the mask sheet of the present invention, as the silicone-based pressure-sensitive adhesive, those having polydimethylsiloxane as the main component and those having polyalkylalkenylsiloxane and polyalkylhydrogensiloxane as the main components are preferable.
[0008]
The method for assembling a semiconductor device of the present invention includes: bonding an adhesive sheet to a lead frame; mounting the semiconductor element on a lead frame to which the adhesive sheet is adhered; connecting the semiconductor element and the lead frame with a gold wire; Resin sealing is performed with a sealing agent, and then the pressure-sensitive adhesive sheet is peeled off. The mask sheet is used as the pressure-sensitive adhesive sheet.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The mask sheet for a semiconductor device of the present invention comprises a heat-resistant film and an adhesive layer as a support, and the heat-resistant film has a glass transition temperature (Tg) of 150 ° C. or higher and a line at 150 to 200 ° C. Those having an expansion coefficient of 10 to 50 ppm / ° C. are used. When manufacturing a semiconductor device such as QFN, the mask sheet is exposed to an atmosphere of 150 to 180 ° C. in a die attach process, a wire bonding process, a resin sealing process, and the like, but when the heat-resistant film reaches a glass transition temperature Tg or higher. Since the coefficient of linear expansion increases rapidly, the difference in thermal expansion from the lead frame made of metal increases. In that case, warpage occurs due to the difference in thermal expansion between the heat-resistant film and the lead frame when the temperature is returned to room temperature, and this causes warpage after the die attach process, which is a resin sealing that is a subsequent process. In the process, there is a problem that the lead frame cannot be set on the positioning pins of the mold, resulting in misalignment. Therefore, the Tg of the heat resistant film needs to be 150 ° C. or higher, and is preferably 180 ° C. or higher. Moreover, the linear expansion coefficient in 150-200 degreeC of a heat-resistant film is 10-50 ppm / degreeC, It is especially preferable that it is 15-40 ppm / degreeC. Specific examples of the heat resistant film satisfying these heat resistance include films of polyimide, polyamide, polyether sulfone, polyphenylene sulfide, polyether ketone, polyether ether ketone, triacetyl cellulose, and the like.
[0010]
The linear expansion coefficient of the heat-resistant film in the present invention can be determined as follows. That is, after the heat-resistant film is heated at 200 ° C. for 1 hour, the heated heat-resistant film is cut into 5 × 25 mm and mounted on TMA (Thermal Mechanical Analyzer, manufactured by Vacuum Riko Co., Ltd .; TM9300). Next, the elongation of the sample when the temperature is increased from 150 to 200 ° C. at a temperature increase rate of 3 ° C./min with a load of 1 g can be obtained by the following formula.
Linear expansion coefficient = ΔL / L · Δt
[ΔL: length of sample, (length at 200 ° C.−length at 150 ° C.)
L: Original length of sample Δt: Measurement temperature difference (200 ° C.-150 ° C.)]
[0011]
The adhesive layer in the mask sheet of the present invention, like the heat resistant film, has little change in decomposition, deterioration, etc. with respect to the thermal history in the die attach process, wire bond process, and resin sealing process, and stable adhesive strength. It is necessary to have Further, in order for the mask sheet to be peelable from the lead frame, it is necessary that the adhesive strength of the adhesive layer on the mask sheet to the heat-resistant film is higher than the adhesive strength to the resin sealant and the lead frame. The silicone-based pressure-sensitive adhesive can satisfy such requirements and form an adhesive layer that can withstand the above-mentioned environment.
[0012]
Silicone pressure-sensitive adhesives are divided into a curing reaction form, an organic peroxide curing type using a peroxide, and an addition reaction type using a platinum catalyst. The organic peroxide is a radical residue in the reaction process. Since a low molecular organic substance is generated and the lead frame is contaminated, an addition reaction type silicone pressure-sensitive adhesive is preferably used in the present invention. Specific examples of the silicone-based pressure-sensitive adhesive include those having polydimethylsiloxane as a main component and those having polyalkylalkenylsiloxane and polyalkylhydrogensiloxane as main components. Furthermore, for example, there can be mentioned those obtained by bonding a silicone raw rubber mainly composed of polyorganosiloxane and a silicone resin mainly composed of trimethylsiloxysilicic acid.
[0013]
In addition, the silicone-based pressure-sensitive adhesive may contain an inorganic or organic filler for the purpose of adjusting the thermal expansion coefficient, thermal conductivity, surface tack, and adhesion control. As the inorganic filler, pulverized silica, fused silica, alumina, titanium oxide, beryllium oxide, magnesium oxide, calcium carbonate, titanium nitride, silicon nitride, boron nitride, titanium boride, tungsten boride, silicon carbide, titanium carbide, Zirconium carbide, molybdenum carbide, mica, zinc oxide, carbon black, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, antimony trioxide or those whose surfaces are treated with a trimethylsiloxyl group, etc. Examples of the filler include polyimide, polyamideimide, polyetheretherketone, polyetherimide, polyesterimide, nylon, and silicone. The blending amount of these fillers is in the range of 1 to 500 parts by weight, preferably 3 to 200 parts by weight, and more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the silicone resin constituting the adhesive layer. .
[0014]
As a method of laminating an adhesive layer on a heat-resistant film, a casting method in which a silicone pressure-sensitive adhesive solution is directly applied on the heat-resistant film and dried, and a silicone pressure-sensitive adhesive solution is once applied on a releasable film. A laminating method is used in which the applied adhesive layer is applied and dried, and the formed adhesive layer is transferred onto a heat-resistant film. Generally the film thickness of an adhesive bond layer is set to the range of 1-30 micrometers.
[0015]
A protective film can be provided on the adhesive layer as necessary. As the protective film, a film having releasability, for example, a film of polyester, polyethylene, polypropylene, polyethylene terephthalate, or the like, and a film whose surface is subjected to a release treatment with a silicone resin or a fluorine compound can be used.
[0016]
The adhesive layer in the mask sheet of the present invention needs to have a weight loss of 5% or less when heated at 180 ° C. for 1 hour, preferably 3% or less. If the weight loss exceeds 5%, the lead frame is contaminated by the decomposed material of the adhesive layer, particularly in the die attach process, which causes a problem of poor connection of gold wires.
[0017]
A method for assembling a semiconductor device of the present invention will be described with reference to the drawings. 1 to 5 are schematic cross-sectional views for explaining a method of assembling a semiconductor device. First, the mask sheet of the present invention in which an adhesive layer made of a silicone pressure-sensitive adhesive is formed on a heat-resistant film on one side of the lead frame 1 is formed by, for example, pressing the mask sheet under heating and curing the silicone pressure-sensitive adhesive. The heat resistant film 3 is bonded to the lead frame 1 through the adhesive layer 2 (FIG. 1). Next, the semiconductor chip 5 is mounted on the opposite surface of the lead frame, and the lead and the semiconductor chip are connected by the gold wire 4 (FIG. 2). After resin sealing with the resin sealant 6 (FIG. 3), the mask sheet is peeled off from the lead frame (FIG. 4), and finally cut into individual pieces (FIG. 5).
[0018]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.
[Example 1]
(Preparation of coating solution for adhesive layer formation)
A mixed solution of polyalkylalkenylsiloxane and polyalkylhydrogensiloxane (X40-3103, manufactured by Shin-Etsu Chemical Co., Ltd.) and a platinum catalyst solution (PL50T, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed at a weight ratio of 100: 1.
(Manufacture of mask sheet)
As a support, a polyimide film (thickness 25 μm) having a Tg of 490 ° C. and a linear expansion coefficient of 12 ppm / ° C. of 150 to 200 ° C. is used, and the thickness after drying the adhesive layer forming coating solution thereon Was applied to a thickness of 8 μm and dried at 160 ° C. for 15 minutes to obtain a mask sheet. The weight loss of the mask sheet adhesive layer when heated at 180 ° C. for 1 hour was measured and found to be 0.8%.
[0019]
[Example 2]
(Preparation of coating solution for adhesive layer formation)
Polydimethylsiloxane (KR120, manufactured by Shin-Etsu Chemical Co., Ltd.) and benzyl peroxide (Nyver B, manufactured by NOF Corporation) were mixed at a weight ratio of 100: 1.
(Manufacture of mask sheet)
As a support, a polyimide film (thickness 25 μm) having a Tg of 490 ° C. and a linear expansion coefficient of 12 ppm / ° C. of 150 to 200 ° C. is used, and the thickness after drying the adhesive layer forming coating solution thereon Was applied to a thickness of 8 μm and dried at 160 ° C. for 15 minutes to obtain a mask sheet. The weight loss of the mask sheet adhesive layer when heated at 180 ° C. for 1 hour was measured and found to be 1.2%.
[0020]
[Comparative Example 1]
(Preparation of coating solution for adhesive layer formation)
Isocyanate (Coronate L-40, manufactured by Nippon Polyurethane Co., Ltd.) was mixed with acrylic copolymer (SK Dyne 1131B, manufactured by Soken Chemical Co., Ltd.) at a weight ratio of 100: 1.
(Manufacture of mask sheet)
As a support, a polyimide film (thickness 25 μm) having a Tg of 490 ° C. and a linear expansion coefficient of 12 ppm / ° C. of 150 to 200 ° C. is used, and the thickness after drying the adhesive layer forming coating solution thereon Was applied to a thickness of 8 μm, dried at 100 ° C. for 5 minutes, and then allowed to stand at 30 ° C. for 7 days to prepare a mask sheet. The weight loss of the mask sheet adhesive layer when heated at 180 ° C. for 1 hour was measured and found to be 5.6%.
[0021]
[Comparative Example 2]
(Preparation of coating solution for adhesive layer formation)
An epoxy resin (Epicoat 828, manufactured by Yuka Shell Co., Ltd.), an epoxy curing agent (Resitop PSM4261, manufactured by Gunei Chemical Co., Ltd.), and an acrylonitrile-butadiene copolymer (Nippol 1001, manufactured by Nippon Zeon Co., Ltd.) in a weight ratio of 40:30: 30 mixed.
(Manufacture of mask sheet)
As a support, a polyimide film (thickness 25 μm) having a Tg of 490 ° C. and a linear expansion coefficient of 12 ppm / ° C. of 150 to 200 ° C. is used, and the thickness after drying the adhesive layer forming coating solution thereon Was applied to a thickness of 8 μm and dried at 130 ° C. for 5 minutes to prepare a mask sheet. The weight loss of the mask sheet adhesive layer when heated at 180 ° C. for 1 hour was measured and found to be 3.8%.
[0022]
[Comparative Example 3]
(Preparation of coating solution for adhesive layer formation)
A mixed solution of polyalkylalkenylsiloxane and polyalkylhydrogensiloxane (X40-3103, manufactured by Shin-Etsu Chemical Co., Ltd.) and a platinum catalyst solution (PL50T, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed at a weight ratio of 100: 1.
(Manufacture of mask sheet)
As a support, a polyethylene terephthalate film (thickness 25 μm) having a Tg of 73 ° C. and a linear expansion coefficient of 150 to 200 ° C. of 60 ppm / ° C. (thickness: 25 μm) is used. Was applied at a thickness of 8 μm and dried at 130 ° C. for 5 minutes to prepare a mask sheet. The weight loss of the mask sheet adhesive layer when heated at 180 ° C. for 1 hour was measured and found to be 0.8%.
[0023]
In addition, the measurement of the weight reduction | decrease of the adhesive bond layer in the mask sheet produced in the said Example 1 and 2 and Comparative Examples 1-3 was performed as follows.
Each adhesive layer forming coating solution used in Examples 1 and 2 and Comparative Examples 1 to 3 was applied to a release-treated polyethylene terephthalate film, and each Example and Comparative Example were produced under the same conditions. After drying, the adhesive layer was peeled off from the polyethylene terephthalate film, and only the adhesive layer was measured with a differential thermal balance (TG / DTA320, manufactured by Seiko Instruments Inc.) at 180 ° C. for 1 hour to measure the weight loss rate. did.
[0024]
(Warpage characteristic evaluation)
The QFN lead frame (Au—Pd—Ni plated Cu lead frame, 8 × 32 matrix arrangement, package size) having an outer dimension of 200 × 60 mm was used for the mask sheets prepared in Examples 1 and 2 and Comparative Examples 1 to 3 above. 5 × 5 mm, resin-sealed area 180 × 40 mm), and cut into the size of the QFN lead frame to prepare a film laminate. This film laminate was used as a warpage characteristic evaluation sample.
The evaluation sample was placed on a horizontal table with the mask sheet surface facing upward, and the height of the edge warp was measured by Z-axis coordinate measurement with a digital measurement microscope (Olympus: STM-UM). The results are shown in Table 1.
[0025]
(Wire bond property)
The QFN lead frame (Au—Pd—Ni plated Cu lead frame, 8 × 32 matrix arrangement, package size) having an outer dimension of 200 × 60 mm was used for the mask sheets prepared in Examples 1 and 2 and Comparative Examples 1 to 3 above. 5 × 5 mm, resin sealing area 180 × 40 mm). Then, an aluminum vapor-deposited dummy chip (3 × 3 mm, thickness 0.4 mm) was bonded to the die pad part of the lead frame with an epoxy die attach material, and temperature: 180 ° C., frequency with a wire bonder (FB131, manufactured by Kaijo Corporation) : 60 kHz, load: 150 gf, time: 10 ms / pin The lead-side adhesion failure number when the lead pin tip and the dummy chip were connected with a gold wire was confirmed. The results are shown in Table 1.
The numerical values in the table indicate the number of defective connections in 256 packages.
[0026]
(Mold flash)
The wire-bonded lead frame is transferred with an epoxy sealing resin (o-cresol novolac epoxy, filler amount 85% by weight) under conditions of temperature: 180 ° C., pressure: 10 MPa, time: 3 minutes. Molded). Thereafter, the mask sheet was peeled from the resin encapsulated material, and the mask sheet surface of the resin encapsulated material was observed, and the number of packages in which the sealing resin leaked to the lead pins was confirmed. The results are shown in Table 1. The numerical values in the table indicate the number of defects in 256 packages due to leakage of the sealing resin.
In the mask sheets of Examples 1 and 2, there was no adhesive residue on the adhesive layer when the mask sheet was peeled from the resin encapsulant.
[0027]
[Table 1]

[0028]
【The invention's effect】
Since the mask sheet of the present invention has the above-described configuration, it has excellent heat resistance, the volatilization amount of the decomposition product is small even in the heat history when the die attach material is cured, and the lead frame is not contaminated. Therefore, high connection reliability between the semiconductor chip and the lead frame can be obtained. Further, since the lead frame is less warped, it is difficult to cause positioning failure. Furthermore, the “mold flash” in which the sealing resin leaks from the mask tape can be suppressed, and a semiconductor package such as QFN can be stably produced in order to suppress adhesive residue. Therefore, it becomes possible to assemble a semiconductor device efficiently by using the mask sheet of the present invention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a state in which a mask sheet is bonded to a lead frame.
FIG. 2 is a cross-sectional view showing a state in which semiconductor chips are mounted and connected with gold wires.
FIG. 3 is a cross-sectional view showing a resin-sealed state.
FIG. 4 is a cross-sectional view showing a state where a mask sheet is peeled off.
FIG. 5 is a cross-sectional view showing a state where a semiconductor device is separated into pieces.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lead frame, 2 ... Adhesive layer, 3 ... Heat-resistant film, 4 ... Gold wire, 5 ... Semiconductor chip, 6 ... Resin sealing agent.

Claims (4)

An adhesive layer made of a silicone-based pressure-sensitive adhesive is provided on a heat-resistant film having a glass transition temperature of 150 ° C. or higher and a linear expansion coefficient of 10 to 50 ppm / ° C. at 150 to 200 ° C., and at 180 ° C. for 1 hour. A mask sheet for assembling a semiconductor device, which is detachably bonded to a lead frame, wherein the weight loss when heated is 5% or less. 2. The mask sheet for assembling a semiconductor device according to claim 1, wherein the silicone-based pressure-sensitive adhesive contains polydimethylsiloxane as a main component. 2. The mask sheet for assembling a semiconductor device according to claim 1, wherein the silicone-based pressure-sensitive adhesive mainly comprises polyalkylalkenylsiloxane and polyalkylhydrogensiloxane. A pressure-sensitive adhesive sheet is pressure-bonded to the lead frame, a semiconductor element is mounted on the lead frame to which the pressure-sensitive adhesive sheet is adhered, the semiconductor element and the lead frame are connected by a gold wire, and then resin sealing is performed with a resin sealant in the mold, Thereafter, in the method of assembling a semiconductor device by peeling off the adhesive sheet, the mask sheet according to claim 1 is used as the adhesive sheet.

Images