JP3204142B2 - Semiconductor device manufacturing method and lead frame - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device and a lead frame, and more particularly to a lead frame (LF) -BGA (Ball Grid Array).
Related to the manufacture of packaging for electronic devices.

[0002]

2. Description of the Related Art In recent years, LF-BGA has been developed. FIG. 4 is a plan view of a conventional LF-BGA. FIG. 5 is a cross-sectional view of a conventional LF-BGA. In these figures, the LF-BGA has a structure in which a lead frame 9 and a wiring board 2 are connected. Usually, in a semiconductor maker who has assembled a semiconductor package using a conventional lead frame, such a structure is convenient.
BGA is being widely used. That is, since the wiring board 2 is attached to the center of the lead frame 9 with the adhesive 11, a normal wire bonder can be used for wire bonding as it is.

A polyimide film tape 6 on which a wiring pattern 10 made of copper or the like has already been formed is usually bonded to a lead frame 9 with an epoxy-based adhesive 11. The lead frame 9 is usually made of Fe-4
2 wt% Ni alloy: made of 42 alloy. In FIG. 4, four BGAs are connected to the lead frame 9, but FIG. 5 shows a state in which the four BGAs are separated from the lead frame 9 on which the semiconductor element is mounted.

Conventionally, the lead frame of LF-BGA is
The ball terminal 5 was attached after mounting the semiconductor element. Further, the adhesive 22 for mounting a semiconductor element was applied by a dispenser immediately before mounting in a die mounter for mounting a semiconductor element.

[0005]

However, a problem in the above-described manufacturing process is that the heating for forming the ball terminals 5 after mounting the semiconductor element causes the lead frame 9 and the polyimide film tape 6 to be in contact with each other. There are interfacial peeling of the adhesive 11 between them, interfacial peeling between the sealing resin 3 and the polyimide film tape 6, and generation of cracks in the sealing resin 3.

In the LF-BGA, a part of the lead frame becomes a stiffener and a die pad, and is finally cut off from the lead frame one by one after the package is completed to be a product. Conventionally, a solder ball terminal is mounted on a semiconductor device and sealed with a resin, before cutting individual pieces from the lead frame 9,
Alternatively, it was formed after cutting individual pieces. In each case, the above-mentioned problems of interface peeling and cracking were serious because the reflow was performed to form the solder ball terminals 5.

For this reason, when a semiconductor device is manufactured by attaching a wiring board, a terminal, a semiconductor element, or the like to a lead frame and sealing it with a resin, a thermal stress is not applied to the semiconductor element, and the wiring board is peeled off. In addition, there is a demand for a method of manufacturing a semiconductor device and a lead frame that prevent the occurrence of interface peeling or cracking of a sealing resin.

[0008]

SUMMARY OF THE INVENTION Accordingly, a method of manufacturing a semiconductor device according to the present invention is directed to a method of manufacturing a semiconductor device by mounting a wiring board, a ball terminal, and a semiconductor element on a lead frame and sealing the resin with a resin. , Above lead frame
Then, before attaching the semiconductor element and the wiring board, the ball terminals are attached to the wiring board.

Thus, before the semiconductor element and the wiring board are attached to the lead frame, the ball terminals are connected to the wiring board (for example, a printed circuit board using any one of polyimide resin, epoxy resin, ceramic, etc. , TA
(B tape or a flexible printed circuit board) by heat treatment or the like, so that the heat at this time does not cause thermal stress on the semiconductor element, and the heat also causes peeling of the adhesive between the lead frame and the wiring board. Not
Since no thermal stress is applied to the sealing resin, no interface peeling or cracking of the sealing resin occurs. In addition, since the ball terminals are attached without attaching the semiconductor element, the attachment is easy.

The lead frame according to the present invention is a lead frame before a semiconductor element is mounted, and has a wiring board on which ball terminals are already mounted.

Here, it is necessary to attach the ball terminals before attaching the wiring board to the lead frame, whereby the peeling between the wiring board and the lead frame can be eliminated, and the ball terminals can be heat treated. The semiconductor element is not damaged by heat at the time of attachment, and there is no fear that interface peeling or cracking of the sealing resin occurs. In addition, since the ball terminals are attached in a state where the semiconductor element is not attached, the attachment is easy. Furthermore, by attaching an adhesive for attaching the semiconductor element to the lead frame, the semiconductor element maker is released from the trouble of attaching the adhesive when attaching the semiconductor element.

Further, in the method of manufacturing a semiconductor device according to a reference example of the present invention, instead of mounting a ball terminal, a metal foil for forming a wiring pattern is partially protruded to form a protruding terminal. This eliminates the need for heat treatment for forming the protruding terminals, which greatly simplifies the manufacturing process, does not apply thermal stress to the semiconductor element, peels off the wiring substrate, peels off the interface of the sealing resin, There are no cracks.

Further, in the lead frame as a reference example of the present invention, a protruding terminal made of a metal foil for forming a wiring pattern is attached instead of the ball terminal. Thus, it is not necessary to perform a heat treatment for forming the protruding terminals, and the protruding terminals can be formed only by mechanical processing. Therefore, the production becomes easy, and the problem of peeling or cracking does not occur.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a lead frame is attached before solder ball terminals are mounted on a semiconductor element. By doing so, the problem of any package cracks and interfacial delamination is eliminated. Heretofore, this concept has not been implemented due to concerns about contamination of solder ball terminals and thermal damage in later assembly steps.
However, this concept has been made possible by optimizing the assembly conditions of the semiconductor device.

In FIG. 2, the lead frame is formed by punching and punching a die or the like.
And the outer leads 12 are formed, and the inner leads 13 and the outer leads 12 are formed in advance on the lead frame itself. This is because the outer leads 12 correspond to BGA ball terminals, and the inner leads 13 correspond to BGA wiring boards. However, in the case of the BGA, the following considerations are required to attach solder ball terminals first.

(1) It is necessary to take measures to prevent the gold plating of the tape from being contaminated by reflow when forming the ball terminals of the solder.
Gold plating is applied to the inner lead of the tape to a thickness of about 1.0 μm on a nickel plating base of a thickness of about 0.5 μm for connection with an electrode formed of aluminum vapor-deposited wiring of the semiconductor element. . If this is contaminated in the heating step of forming the solder ball terminals in advance, a failure occurs in the wire bonding connection with the electrode formed of the aluminum deposited wiring of the semiconductor element.

However, it has been found that, in the step of cleaning the flux used for mounting the solder ball terminals, the plating contaminated by the vapor of the flux can be completely cleaned. That is, the components included in the flux are rosin, higher alcohol, wax, petroleum-based solvent, paraffin-based hydrocarbon, surfactant, amine-based chelate activator and a trace amount of chlorine compound. Thus, the generated vapor is somewhat corrosive and contains organic volatile components, thus contaminating the gold-plated surface. However, it has been found that a contaminant film can be removed by selecting an aqueous or solvent-based cleaning agent that can sufficiently wash in accordance with the used flux.

(2) In wire bonding, it is necessary that the solder ball terminals do not melt at the bonding temperature. This problem is solved by using a high-temperature solder ball terminal such as 3.5 Ag-Sn (melting point 220 ° C.) instead of a eutectic composition (Sn—37 wt% Pb; melting point 180 ° C.) for the solder ball terminal. . Further, even when a eutectic solder ball terminal is used, the problem can be solved by setting the wire bonding temperature to less than 180 ° C.

(3) Further, it is necessary to take care that melting of the solder ball terminals does not occur in sealing after wire bonding. However, this problem has no problem at all because the usual epoxy-based sealing resin is cured at 120 ° C. Also, by attaching the adhesive for mounting the semiconductor element together with the ball terminals in advance at the stage of the lead frame, the semiconductor assembly maker is released from the trouble of handling the adhesive as a material.

The main point of this embodiment is that the wire bonding structure B in which the lead frame and the wiring board are bonded to each other is used.
In GA, a ball terminal is formed on a wiring board before assembly. This solves the problem of interface delamination and package cracking. Furthermore, after attaching the ball terminals to the wiring board by heat treatment, this wiring board is adhered and attached to the lead frame,
This prevents the adhesion between the lead frame and the wiring substrate from being peeled off by the heat.

FIG. 1 is a cross-sectional view of an LF-BGA according to a first embodiment. TAB (Ta
A 400-pin flexible wiring board manufactured on a peAutomated Bonding tape manufacturing line was attached to the lead frame 9. The TAB tape production line can form fine wiring by a continuous winding method, and has recently been applied to various fields of flexible wiring substrates.

The material of the polyimide film tape 6 is 5
0 μm thick polyimide resin film, TAB
Widely used for tape. Wiring pattern 10
Was used as an electrolytic copper foil having a thickness of 18 μm. After the wiring pattern 10 is formed by photochemical etching, the wiring pattern 10 is printed on the entire surface except for a wiring portion for wire bonding the solder resist 23 and a portion for forming a ball terminal. Further, gold plating having a thickness of 1.0 μm was applied on a nickel base layer of 0.5 μm to a portion for forming a lead portion to be wire-bonded and a portion for forming a ball terminal.

In the present embodiment, the lead frame 9 is manufactured by selecting 42 alloy (Fe-42 wt% Ni) having a thickness of 0.2 mm. The lead frame 9 was manufactured by punching using a die, but the die pad on which the semiconductor element 1 was mounted was pressed down by half the thickness of the semiconductor element. This is to facilitate wire bonding.

As the adhesive 11, an epoxy adhesive was used. Thereafter, the ball terminals 5 of eutectic solder of Sn-37% by weight Pb were mounted on pads for forming ball terminals of the polyimide film tape 6, and then placed in a 235 ° C. reflow furnace for 5 minutes. The actual temperature of the polyimide film tape 6 is 230 ° C., and the heating time at the actual temperature of 230 ° C. is 30 seconds because the 5 minutes include the preheating time. During this time, the solder melts and the ball terminals 5 are soldered to the pads. This pad has
A rosin-based flux is applied in advance, and the solder ball terminals 5 and the pads are wet-spread and connected by the action of the flux. After forming the ball terminals, the polyimide film tape 6 was washed with an aqueous detergent containing a surfactant. By this washing, the wiring pattern 10 for wire bonding of the polyimide film tape 6 which was partially contaminated by evaporation of the flux was washed, and it became clear that there was no problem in the wire bonding property.

After the formation of the solder ball terminals, an epoxy adhesive 22 previously formed into a tape having a thickness of 100 μm is punched on a die pad for mounting the semiconductor element on a die pad for forming the area of the semiconductor element using a die. Was. The application temperature is 150 ° C. and the time is 1 second. This adhesive 22
Is a tape using a bisphenol A type base polymer having relatively low corrosiveness and having dicyandiamide as a latent curing agent, and the curing initiation temperature is 170 ° C. The effective storage period for maintaining the adhesive reaction of the adhesive 22 is 6
Since this is a month, the semiconductor element 1 may be adhesively mounted after the adhesive tape is attached.

A polyimide film tape 6 with an adhesive to which a solder ball terminal is attached is adhered to the lead frame 9, and the 400-pin semiconductor element 1 is mounted on a semiconductor element mounting die pad to which an adhesive 22 is attached. The semiconductor package was completed by mounting. Since the curing start temperature of the adhesive 22 was 170 ° C., the lead frame 9 was placed on a stage at 175 ° C., and after mounting the semiconductor element 1, the pressure was maintained for 5 seconds. As a result, the epoxy resin adhered the semiconductor element 1 to the die pad of the lead frame 9 while starting the curing reaction. Thereafter, in order to completely cure the epoxy resin, it was stored in an oven at 175 ° C. for 1 hour.

Next, at a stage temperature of 175 ° C., 25 μm
The aluminum electrode of the semiconductor element 1 was bonded to the gold-plated wiring pattern 10 of the polyimide film tape 6 with a gold bonding wire 4 having a diameter of 5 mm. Since the temperature is 175 ° C., the solder ball terminal 5 having a eutectic composition having a melting point of 180 ° C. does not melt at all. However, since the temperature condition is lower by 30 ° C. than the normal temperature of 190 ° C., the ultrasonic output applied to the bonding tool is set to 1.5 times the conventional one.

Next, sealing was performed using a liquid epoxy-based sealing resin 3. A dispenser was used for this sealing. Since the curing temperature of the liquid sealing resin 3 was 150 ° C. and the curing time was 2 hours, no melting of the solder occurred. Conventionally, solder ball terminals were formed after this. However, in the present embodiment, since the ball terminals have already been formed before the semiconductor element is mounted, this is a completed product.

[Second Embodiment] In the second embodiment, a copper alloy containing 0.5% of Fe is used for the lead frame 9 in the configuration of the above-described first embodiment. In this case, nickel is easily discolored, so nickel plating is applied
m.

[Third Embodiment] In the third embodiment, an adhesive film having silver particles contained in an adhesive 22 for attaching a semiconductor element and having conductivity is used. This adhesive 22 was tape-processed so that the silver-containing paste could be easily pasted, and a commercially available adhesive was used.

"Fourth Embodiment": The fourth embodiment is different from the first embodiment in that, instead of the polyimide film tape, a PCB (PCB) manufactured in a printed circuit board manufacturing process is used. Printed Circuit
Board). This wiring board is a glass epoxy resin substrate having a thickness of 0.2 mm, and has a copper foil layer having a thickness of 18 μm.

Fifth Embodiment: The fifth embodiment is different from the first embodiment in that the flexible wiring layer is formed by using an FPC (Flexible Print).
ed Circuit). In this case, unlike the TAB line, there is an advantage that a wide tape material can be selected and manufactured, and the price can be reduced. T
The AB line has a limit of 70 mm width, but the FPC line is usually manufactured with a width of 200 mm.

"Sixth Embodiment": In the sixth embodiment, a copper metal ball is used for a ball terminal in the configuration of the first embodiment. To connect the ball terminals, use P
(b) A solder paste containing 10% by weight of a flux is partially printed on a ball mounting land of the polyimide film tape 6 using a metal mask, and then a copper metal ball is mounted, and this is placed in a reflow furnace maintained at a temperature of 260 ° C. I passed. This copper ball terminal was connected to the copper wiring land of the polyimide film tape 6 by the action of the flux and the solder paste.

"Seventh Embodiment": In the seventh embodiment, a fluorine-modified epoxy resin is used as the adhesive 22 for attaching the semiconductor element in the structure of the first embodiment. did. This epoxy resin is VitonG
It is a compound obtained by mixing a fluorine elastomer of F with an epoxy resin, and has been developed to impart toughness to the resin, and has excellent heat resistance and durability in adhesive bonding.

Eighth Embodiment: In the eighth embodiment, thermoplastic polyimide is used for the adhesives 11 and 22 in the configuration of the first embodiment. Since this polyimide is thermoplastic, it has the characteristic that it can be reversibly bonded any number of times without the need for a curing agent. As the thermoplastic polyimide, one obtained by lowering the Tg of a normal linear polyimide to 270 ° C. depending on the composition of the diamine was used. Specifically, it is TPI (trade name) manufactured by Mitsui Toatsu. The bonding temperature to the polyimide film tape 6 is 280 ° C.
Therefore, the ball terminal was a copper metal ball. In this case, a high-temperature solder of Pb-5% by weight Sn was used to connect the copper metal balls. In this solder system, the solidus temperature is 300 ℃
It has sufficient heat resistance.

"Ninth Embodiment": In the ninth embodiment, a high-temperature solder ball of Sn-3.5 Ag weight% is used as the solder ball terminal in the configuration of the first embodiment. It was used. The solder balls had a heat resistance of 225 ° C. of solidus, and could be wire-bonded at 200 ° C.

[Tenth Embodiment] The tenth embodiment is an example of a flip chip BGA, and FIG. 3 is a structural diagram of the flip chip BGA. A flip chip with gold micro-bumps of 400 pins was manufactured and mounted on a wiring board on which ball terminals were formed in advance. That is, a bump 25 having a height of 20 μm was formed on the semiconductor element 1 by an electroplating method. This is because a plating solution is sprayed onto an aluminum electrode formed on a surface of the semiconductor element 1 and exposed from a passive film made of a polyimide resin via a UBM (Under Barrier Metal) for controlling an interlayer diffusion reaction. This is a method of forming protrusions by performing electroplating of gold while gold.

A large amount of epoxy resin-based conductive paste is applied to the tip of the wiring pattern 10 of the wiring board 2 (wiring board on which a solder ball terminal of Sn-37% by weight Pb is already mounted) facing the position of the bump 25. Coated by point dispenser. The epoxy resin is a conductive epoxy resin in which dicyandiamine is used as a latent curing agent in bisphenol A type and silver particles having a diameter of 50 μm are mixed in order to impart conductivity. After storing for one month in this state, the semiconductor element 1 on which the gold bump was formed was
The printed circuit board was mounted on the wiring board 2 with the conductive paste 26 applied side down. The mounting method is such that the positions of the bumps 25 and the conductive paste applied portion of the wiring board 2 are mutually recognized by a CCD.
According to a flip chip mounter equipped with a camera.

After mounting the semiconductor element, the entire wiring board 2 is
The conductive paste 26 was cured by placing it in a constant temperature bath at 70 ° C. Although the ball terminal of the 63/37 eutectic solder of Sn-Pb was attached to the wiring board 2, the melting of the solder ball terminal did not occur. "Eleventh embodiment": In the eleventh embodiment, ceramic wiring is used for the wiring board 2 in the configuration of the above-described second embodiment. Ceramics have features of being superior in heat resistance as compared with plastic wiring boards, and of easily forming multilayer wiring.

"Twelfth Embodiment": In the twelfth embodiment, the solder ball terminals are formed by a solder paste printing reflow method in the configuration of the first embodiment. In this method, a ball terminal is formed by printing a solder paste thickly on a circular land of a wiring pattern forming a solder ball terminal without using a solder ball terminal, and then reflow-melting the solder paste. . The solder paste was printed using a metal mask having a thickness of 0.3 mm. Reflow was performed at 250 ° C. for 5 minutes.

(Effect of Embodiment of the Present Invention): According to the above embodiment of the present invention, after the solder ball terminals 5 are attached to the wiring pattern of the polyimide film tape 6 by heat treatment, the adhesive 11 The polyimide film tape 6 is bonded to the lead frame 9 to which the semiconductor element 1 is attached.
, And wire sealing is performed to seal the resin, so that heat during the mounting of the ball terminals 5 does not give thermal stress to the semiconductor element 1, and this heat is applied between the polyimide film tape 6 and the lead frame 9. Does not cause peeling of the adhesive, and does not give thermal stress to the sealing resin 3, so that the conventional interface peeling of the sealing resin 3 and generation of cracks can be eliminated.

Also, in manufacturing a flip chip BGA mounted on a lead frame, ball terminals 5 are attached to the wiring board 2 in advance by heat treatment, and then the semiconductor element 1 is mounted.
Is attached to the wiring board 2, so that the heat generated when the ball terminals 5 are attached does not give thermal stress to the semiconductor element 1, and also does not give thermal stress to the underfill material 24 and the conductive paste 26. Therefore, there is no occurrence of interface peeling or cracking.

With the above effects, the ball terminal 5
The productivity of the mounting process can be improved, the yield loss of the BGA package can be reduced, and the reliability of the BGA package can be improved.

(Other Embodiments) It is to be noted that an adhesive 22 for attaching a semiconductor element is attached in advance at the stage of the lead frame before attaching the semiconductor element 1 of the lead frame 9, so that a semiconductor element assembly manufacturer Then, the trouble of handling the adhesive as a material is released.

Instead of mounting the solder ball terminals 5, a protruding terminal may be formed by partially projecting a metal foil (for example, a copper foil) for forming a wiring pattern of a wiring board. For this purpose, for example, a copper foil of the wiring board may be pushed into the projection processing hole of the board and protruded out of the substrate to form a projection terminal, or the copper foil may be bent to form a projection terminal. According to this, since it is not necessary to perform a heat treatment for forming the terminals, there is no influence of thermal stress, and the manufacturing process is simplified.

[0046] Furthermore, as a wiring board, when using TAB tape, it is also preferable pasting separately stiffener for reinforcement of the tape. Further, by forming a feed hole for conveyance in the above-described lead frame, it is possible to easily perform mechanical conveyance. The ball terminal may be a conductive ball terminal formed by plating a plastic ball with copper, tin, or the like. further,
The wiring may be a metal foil made of copper and a copper alloy, or a vapor-deposited thin-film conductive circuit.

[0047]

As described above, according to the method of manufacturing a semiconductor device of the present invention, the ball terminals are attached to the wiring board before the semiconductor element and the wiring board are attached to the lead frame, so that the ball terminals can be heated or the like. The heat at the time of attachment prevents peeling between the lead frame and the wiring board, and does not cause interface peeling or cracking of the sealing resin.

In the lead frame of the present invention, since the wiring board on which the ball terminals are mounted is mounted, the ball terminals can be easily mounted.
Even when a semiconductor element is later attached or resin-sealed, no interface peeling or cracking occurs.

[Brief description of the drawings]

FIG. 1 is a sectional view of an LF-BGA according to a first embodiment of the present invention.

FIG. 2 is a structural diagram of a lead frame for explaining the present embodiment.

FIG. 3 is a flip chip BG according to a tenth embodiment;
It is a structural diagram of A.

FIG. 4 is a structural diagram of a conventional LF-BGA.

FIG. 5 is a cross-sectional view of a conventional LF-BGA.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor element 2 wiring board 3 sealing resin 4 bonding wire 5 ball terminal 6 polyimide film tape 9 lead frame 10 wiring pattern 11, 22 adhesive 14 die pad 23 solder resist 24 underfill material 25 bump

Continued on the front page (72) Inventor Shoji Niizawa 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Inside the Hitachi Research Co., Ltd. (72) Inventor Kazuhisa 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable, Ltd. Inside the System Materials Research Laboratory (72) Inventor Yasuharu Kameyama 3550 Kida Yomachi, Tsuchiura-shi, Ibaraki Hitachi Systems, Ltd. System Materials Research Laboratory (56) References JP-A-7-283336 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 23/50 H01L 23/12

Claims (6)

(57) [Claims] 1. A method of manufacturing a semiconductor device by mounting a wiring board, a ball terminal, and a semiconductor element on a lead frame and sealing the resin with a resin, wherein the semiconductor element and the wiring board are mounted on the lead frame. A method of manufacturing a semiconductor device, comprising: attaching the ball terminals to the wiring board before attaching. 2. A lead frame before mounting a semiconductor element, wherein the wiring has ball terminals already mounted.
A lead frame to which a substrate is attached. 3. Oite the lead frame according to claim 2, wherein,
A lead frame further provided with an adhesive for attaching a semiconductor element. 4. The lead frame according to claim 2, wherein
Oite, lead frame can be characterized being further the wiring installation of reinforcing member for reinforcing the substrate or formation of the feed holes for conveyance,. 5. The lead frame according to claim 2 , wherein said wiring board is a printed circuit board using any one of polyimide resin, epoxy resin and ceramic , or a TAB tape or a flexible printed circuit board. A lead frame, comprising: 6. The lead frame according to claim 2 , wherein said ball terminals are Sn-Pb-based eutectic solder ball terminals, Pb-Sn-based high-temperature solder ball terminals, and Sn-Ag-based. A lead frame, which is one of a high-temperature solder ball terminal and a conductive ball terminal plated with plastic.