JP5290792B2 - Manufacturing method of optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical module that is improved in wire bonding durability and also improved in yield and reliability, and to provide the optical module manufactured by the method. <P>SOLUTION: The method of manufacturing the optical module 30 includes a step (Fig.4(b)) of forming a bump 32a on a chip of a driver IC 32, a step (Fig.4(d)) of sticking a mask tape 90 on the entire surface of a high-frequency signal line 36 to mask it, a step (Fig.4(e)) of supplying an NCP resin 93 to a mounting region of the driver IC, a step (Fig.4(f)) of curing the NCP resin 93 while heating and bonding a plurality of electrodes etc., on a module substrate 33 and the bump 32a using a bonder 95, a step (Fig.4(h)) of carrying out post-curing, a step (Fig.4(g)) of peeling the mask tape 90, and a step of connecting a plurality of high-frequency signal lines 36 and a VCSEL array 31 by a wire 37. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method of manufacturing an optical module by mounting an IC on a substrate by flip chip bonding, and in particular, an optical module using a resin material that hardens the resin together with bumps after the resin is first supplied to the substrate. The present invention relates to an optical module manufacturing method suitable for manufacturing the optical module and an optical module manufactured by the method.

Conventionally, for example, a technique disclosed in Patent Document 1 is known for flip chip bonding (FCB). In this prior art, solder bumps are formed on the electrodes of the semiconductor device, the bumps are reflow-bonded to the electrodes on the substrate, and a resin is poured into the gap between the semiconductor device and the substrate to be cured. To implement.
Further, after the resin is first supplied to the substrate, the resin is cured together with the bump connection, and a material such as NCP (Non-Conductive Paste) resin is used as a material for mounting the semiconductor device on the substrate by FCB. Are known. A resin such as an NCP resin is a liquid sealing material that has improved the curability at high temperature, supplied the material to the substrate first, and then given the reactivity that can be cured simultaneously with the connection of the bumps.

JP 2001-148404 A

  By the way, an IC mounted on a substrate by an FCB and an optical element array mounted on the substrate are provided, and a signal is transmitted between the IC and each optical element of the optical element array by a plurality of transmission lines formed on the substrate. In an optical module that is transmitted through a plurality of wires connecting the transmission line and each optical element, the plurality of transmission lines are shortened as much as possible (for example, 500 μm or less for 10 Gbps transmission and 1 mm or less for 5 Gbps transmission). Is desirable.

  Thus, a resin such as NCP resin can be used to manufacture an optical module in which a plurality of transmission lines connected to the optical element array by wires are close to the IC mounting area, because the process can be shortened. It is conceivable to mount the IC by FCB using IC. In this method, it is difficult to supply a necessary amount of resin such as NCP resin on the substrate by coating or the like. For this reason, there is a possibility that a part of the resin flows (spreads) and adheres on the transmission line at the time of bonding or subsequent post-curing due to variations in the amount of resin supplied. If the resin adheres to the transmission line in this way, the variation causes a problem such as an increase in transmission characteristics between channels, a failure to obtain necessary transmission characteristics, and an increase in product-to-product variation, resulting in poor yield. . Moreover, although the transmission line and the optical element array are connected by a wire, the wire bonding strength (wire pull strength) at the connecting portion is lowered, and the reliability of the optical module is lowered.

  The present invention has been made in view of such a conventional background, and has been manufactured by an optical module manufacturing method and a method for improving wire bonding resistance, improving yield and improving reliability. An object is to provide an optical module.

  In order to solve the above problems, a first aspect of the present invention includes an IC flip-chip mounted on a substrate and an optical element array mounted on the substrate, and each optical element of the IC and the optical element array In the method of manufacturing an optical module in which signals are transmitted via a plurality of transmission lines formed on the substrate and a plurality of wires connecting the transmission lines and the optical elements, A first step of forming bumps on an IC chip; a second step of masking at least the plurality of transmission lines with a masking means; and a third step of supplying resin to a region of the substrate where the IC is mounted. A fourth step of bonding the electrode on the substrate and the bump of the IC by heating using a bonder and simultaneously curing the resin; and reheating the bonding portion of the electrode on the substrate and the bump. A fifth step of performing post cure, a sixth step of removing the mask means before or after the fifth step, a step of connecting the plurality of transmission lines and the optical element array with wires, It is characterized by providing.

  Here, the resin takes the process of curing the resin together with the bump connection after the material is first supplied to the substrate, and is highly curable at high temperature, and is cured simultaneously with the connection between the electrode and the bump on the substrate. It is a liquid sealing material to which the reactivity which complete | finishes is provided. Examples of such a liquid sealing material include resins such as NCP (Non-Conductive Paste) resin and ACP (Anisotropic Conductive Paste) resin.

  According to this configuration, before supplying the resin to the substrate in the third step, at least a plurality of transmission lines are masked and protected by the mask means. For this reason, even if a part of the resin flows and spreads out of the IC mounting area at the time of bonding in the fourth step or subsequent post-cure due to variations in the amount of resin supplied, the resin is It is possible to prevent the mask from adhering to the top. As a result, it is possible to prevent the occurrence of problems such as the loss of necessary transmission characteristics due to the resin adhering to the transmission line, and the yield is improved. Further, although the transmission line and the optical element array are connected by a wire, the wire bonding strength (wire pull strength) at the connection portion is improved, and the reliability of the optical module is improved.

In another aspect of the present invention, in the second step, a mask tape having at least heat resistance capable of withstanding heating in the fourth step is used as the mask means, and the mask tape is used at least in the plurality of transmission lines. It is affixed on the top.
According to this configuration, the mask tape can prevent the resin from adhering to the transmission line.

  Another aspect of the present invention is characterized in that the mask tape is a tape using a siloxane-free acrylic adhesive in the glue part.

  According to this configuration, since the mask tape is a tape using a siloxane-free acrylic adhesive in the glue part, there is no generation of low-molecular siloxane, and the insulator generated by the low-molecular siloxane is the optical element array. It is possible to prevent problems such as contact failure due to adhering to a plurality of transmission lines connected by wires.

  According to a second aspect of the present invention, an array of electrodes for bonding and an IC to be connected to the array of electrodes are arranged close to each other, and the IC is fixed on a substrate with an adhesive resin. The module is characterized in that an end portion of the resin exuded when the IC is fixed is substantially parallel to the electrode row.

  According to this configuration, in a state where the mask tape is removed, the boundary line on the side facing the plurality of transmission lines of the resin is a straight boundary line by the side surface of the mask tape. For this reason, when positioning a wire bonding apparatus with respect to each transmission line and wire bonding each transmission line and each optical element, the apparatus is accurately positioned with respect to each transmission line and each optical element. Can do. Thereby, each transmission line and each optical element can be connected by the wire of the same line length, and there is no variation between channels and an optical module with good transmission characteristics can be realized.

ADVANTAGE OF THE INVENTION According to this invention, the optical module which improved the wire-bonding tolerance, and aimed at the improvement of a yield and reliability can be implement | achieved.

The disassembled perspective view which shows schematic structure of the parallel optical transmission apparatus in which an optical module is used. FIG. 2 is a view showing a part of the optical module shown in FIG. 1 and a perspective view showing a state where a driver IC is mounted on a module substrate. The perspective view which shows the state in which the driver IC and the VCSEL array were mounted on the module substrate. (A)-(g) is process drawing for demonstrating the manufacturing method of the optical module which concerns on one Embodiment of this invention. FIG. 3 is a plan view showing a module substrate of the optical module shown in FIG. The top view which shows a part of optical module in the top view which shows the state before peeling a mask tape and connecting a VCSEL array and a some high frequency signal wire with a wire. The figure which shows a part of optical module produced without masking, and is a top view which shows the state before connecting a VCSEL array and a some high frequency signal wire with a wire. The top view of the connection state of IC using wire bonding connection.

Before describing a method for manufacturing an optical module according to an embodiment of the present invention, a schematic configuration of a parallel optical transmission device using the optical module will be described with reference to FIGS.
As shown in FIG. 1, the parallel optical transmission device 1 includes an electric board 10, an electric pluggable socket 20, an optical module 30, a pressing plate 40, an optical connector 50, and an optical component 60. For example, the parallel optical transmission device 1 converts an electrical signal into an optical signal, and the optical signal is transmitted in parallel through a plurality of channels, for example, 12 channels (12 ch) through 12 optical fibers (10 Gbps / 1 ch × This is a parallel optical transmission device for transmission (12-channel transmission).

  Therefore, as shown in FIGS. 2 and 3, the optical module 30 of the parallel optical transmission device 1 includes a VCSEL array (optical element array) composed of a plurality of (in this example, 12) surface emitting semiconductor laser elements (VCSEL). ) 31, a driver IC (electronic element) 32 that drives each VCSEL of the VCSEL array 31, and a module substrate 33 on which the VCSEL array 31 and the driver IC 32 are mounted. A noise removing capacitor 35 is mounted on the module substrate 33.

  As shown in FIGS. 2 and 3, the VCSEL array 31 is disposed in a hole 91 described later formed in the module substrate 33. The driver IC 32 is mounted on the module substrate 33 by flip chip bonding (FCB). The module substrate 33 includes a plurality of sets (12 sets, 24 sets in this example) of high-frequency signal lines 36 which are transmission lines that electrically connect the VCSEL array 31 and the driver IC 32 to each other. Is formed. These high-frequency signal lines (transmission lines) 36 and each VCSEL of the VCSEL array 31 are electrically connected by wires 37 (see FIG. 3). Thus, the VCSEL array 31 and the driver IC 32 are electrically connected by a plurality of sets (12ch) of high-frequency signal lines 36 and wires 37, and the high-frequency signal lines 36 and wires 37 of each set (ch) are connected. A drive signal (differential signal) is supplied from the driver IC 32 to each VCSEL of the VCSEL array 31.

  A plurality of electrical terminals and a wiring pattern (not shown) connected to each electrical terminal are formed on the front and back surfaces of the electrical substrate 10. The wiring pattern is a signal line for supplying a differential signal from the outside to the driver IC 32. In order to control the driver IC 32, a plurality of sets (12 sets) of high-frequency signal lines including two signal lines as one set. A plurality of control signal lines and a plurality of monitor signal lines are formed. In addition, as a plurality of electrical terminals, terminals connected to 12 sets of high-frequency signal lines, respectively, 12 sets (12ch) of signal input / output terminals, each having two terminals, and connected to a plurality of control signal lines A plurality of terminals and a plurality of terminals connected to the plurality of monitor signal lines are formed.

  The optical module 30 is mounted in the module receiving recess 21 (see FIG. 1) of the electric pluggable socket 20 that is positioned on the electric substrate 10 and fixed with screws. When the optical module 30 is mounted in the module housing recess 21 and the plate 40 pressed from above the module cover 34 is fixed to the electrical pluggable socket 20 with screws, each electrical terminal of the optical module 30 and each electrical terminal of the electrical substrate 10 are Are electrically connected via a plurality of connection terminal portions 22 of the electric pluggable socket 20. The plurality of connection terminal portions 22 are spring-like terminals configured such that when a predetermined pressing force is applied, a coil-like spring portion (not shown) contracts to electrically connect the upper contact pin and the lower contact pin. It is.

  As shown in FIG. 1, the optical connector 50 includes a tape fiber 51 in which a plurality (12 in this example) of optical fibers are arranged in a row, and a connector (ferrule) 52 that holds the plurality of optical fibers. And an optical component 60 that bends light (optical signal) emitted from each VCSEL of the VCSEL array 31 in a vertical direction by 90 degrees and optically couples the light to each end face of a plurality of optical fibers. The connector part 52 is a multi-core ferrule connector (MT connector). The tape fiber 51 is connected to another optical connector 53 and transmits optical signals in parallel with the optical module 30.

  As the mask tape 90, a siloxane-free mask tape is preferably used. The authors tested the strength of IC wire bonding when using multiple tapes, such as polyimide tapes using polyimide adhesives and polyimide tapes using acrylic adhesives, as mask tape candidates. The experiment was repeated, and as a result, it was discovered that sufficient bonding strength can be easily obtained when using a siloxane-free polyimide tape.

(One Embodiment of Manufacturing Method)
Next, an embodiment of the method for manufacturing the optical module 30 described in FIGS. 1 to 3 will be described with reference to FIGS.
FIG. 5 is a plan view showing a module substrate of the optical module shown in FIG. 2, and shows an IC mounting area and a mask area using a mask tape.

  As shown in FIG. 5, on the module substrate 33, in addition to the above-described plural sets (12 sets, 24 sets in this example) of the high-frequency signal lines 36, a VDD terminal 71 electrically connected to the driver IC 32, 72, a GVD terminal 80 electrically connected to the driver IC 32, and a ground pattern 81 are formed. Each high-frequency signal line 36 is electrically connected to a plurality of signal input / output terminals provided on the driver IC 32 side when the driver IC 32 is mounted by FCB (FCB mounting).

  On the module substrate 33, a plurality of sets (12ch) of high frequency signal lines 38 for supplying differential signals to the driver IC 32 and a plurality of lines 38a for supplying control signals to the driver IC 32 are provided. An uppermost line 39 a of the control signal line 39 is formed. The uppermost line 38a of each high-frequency signal line 38 is electrically connected to a plurality of signal input / output terminals provided on the driver IC 32 side when the driver IC 32 is FCB-mounted. Similarly, the uppermost line 39a of each control signal line 39 is also electrically connected to a plurality of control signal input terminals provided on the driver IC 32 side.

The manufacturing method of the optical module 30 described above includes the following steps.
(First Step) A large number of bumps 32a are formed on the chip (IC chip) of the driver IC 32 shown in FIG. 4A (see FIG. 4B).
Thereafter, the chip 32a is turned over (see FIG. 4C).

  (Second Step) A siloxane-free mask tape 90 as a mask means is applied to the entire surface of at least a plurality of high-frequency signal lines (transmission lines) 36, and the entire surface is masked with the mask tape 90 (FIG. 4D). reference).

  At this time, the mask tape 90 is affixed to a location where wire bonding of a plurality of high-frequency signal lines (transmission lines) 36 is performed, for example, as indicated by a broken line in FIG. The method of applying the mask tape is not limited to this, and the mask tape may be attached so as to cover the electrodes (signal lines) that may be covered by the resin oozing.

(Third Step) Resin such as NCP resin 93 is supplied to the region 32A (see FIG. 5) where the driver IC is mounted on the module substrate 33 (see FIG. 4E).
In FIG. 5, a region 94 indicated by a thick alternate long and short dash line indicates a region where the NCP resin 93 is applied.

(Fourth Step) Using the bonder 95, a plurality of electrodes and a plurality of signal lines on the module substrate 33 and a plurality of bumps 32a of the driver IC are joined by heating, and at the same time, the NCP resin 93 is cured (FIG. 4F). )reference).
The heating temperature at this time is, for example, 200 ° C., and the heating time is, for example, 4 seconds.

(Fifth Step) Post-cure is performed by reheating the joints between the electrodes and signal lines on the module substrate 33 and the bumps 32a (see FIG. 4H).
The heating temperature at this time is 165 ° C., for example, and the heating time is 60 minutes, for example.

  (Sixth Step) The mask tape 90 is peeled off and removed before or after the fifth step (see FIG. 4G).

  (Seventh Step) After removing the mask tape 90, the entire surfaces of the plurality of high-frequency signal lines 36 are cleaned by plasma cleaning.

(Eighth Step) The VCSEL array 31 is mounted in the hole 91 (see FIG. 3).
(9th process) The some high frequency signal wire | line 36 and each VCSEL of the VCSEL array 31 are joined by the wire 37 (refer FIG. 3).
Through the above steps, the optical module 30 as shown in FIG. 3 is manufactured.

According to the manufacturing method which concerns on one Embodiment, there exist the following effects.
Before supplying the NCP resin 93 to the module substrate 33 in the third step, at least a plurality of high-frequency signal lines 36 are masked and protected by the mask tape 90. For this reason, even when a part of the NCP resin 93 flows and spreads outside the IC mounting area at the time of bonding in the fourth step or subsequent post-curing due to variations in the supply amount of the NCP resin 93, etc. The mask tape 90 can prevent the NCP resin 93 from adhering to the plurality of high-frequency signal lines 36. As a result, it is possible to prevent the NCP resin 93 from adhering to the plurality of high-frequency signal lines 36 and preventing the required transmission characteristics from being obtained, thereby improving the yield.

-A normal electrode (signal line) surface can be easily obtained by using a siloxane-free mask tape, and wire bonding characteristics are improved.
A plurality of high-frequency signal lines 36 and the VCSEL array 31 are connected by wires 37, but the wire bonding strength (wire pull strength) at the connection portion is improved, and the reliability of the optical module is improved.

  In the optical module 30 manufactured by the manufacturing method according to the above embodiment, as shown in FIG. 6, the plurality of high-frequency signal lines 36 of the NCP resin 93 in the state where the mask tape 90 is removed in the sixth step. A boundary line 93 a on the side facing the line is a straight boundary line by one side surface of the mask tape 90. Since the resin on the transmission line can be in a straight line, the transmission line characteristics can be made constant, and variations between channels can be eliminated. This also allows each high-frequency signal line 36 and each VCSEL array to be connected by a wire 37 having the same line length, thereby realizing an optical module 30 with good transmission characteristics.

  On the other hand, when the entire surface of the plurality of high-frequency signal lines 36 is not masked with the mask tape 90, the side of the NCP resin 93 facing the plurality of high-frequency signal lines 36 as shown in FIG. Boundary line 100 meanders irregularly and adheres to the surface of the high-frequency signal line 36. In this case, when the wire bonding apparatus is positioned with respect to the high-frequency signal line 36 to wire-bond each high-frequency signal line 36 and each VCSEL array, the NCP resin 93 whose boundary lines 100 meander irregularly becomes an obstacle, The device cannot be accurately positioned with respect to each high-frequency signal line 36 and each VCSEL array. As a result, the high-frequency signal lines 36 and the VCSEL arrays cannot be connected by the wires 37 having the same line length, and transmission characteristics are deteriorated.

In addition, this invention can also be changed and embodied as follows.
In the above-described embodiment, the mask tape 90 is used as the mask unit. However, instead of the mask tape 90, the entire surface of the plurality of high-frequency signal lines 36 is printed with a liquid resin such as a solder resist. However, the present invention can also be applied to a manufacturing method using this as a mask means.

  In the above embodiment, a transmission optical module having a function of converting an electrical signal into an optical signal has been described. However, the present invention can also be applied to a reception optical module having a function of converting an optical signal into an electrical signal. It is. In this configuration, a TIA (Transimpedance Amplifier) function that uses a photodiode array having a plurality of photodiodes as a plurality of optical elements and converts the output current of each photodiode into a voltage and amplifies it instead of the driver IC 33 as an electronic element. An amplification IC provided with

  An example in which the present invention is applied to an IC for wire bonding connection is shown in FIG. In this case, a resin end portion 100 is defined in the electrode array 60 substantially parallel to the arrangement direction. As a result, the bonding portions on the electrodes can be set in a line as indicated by the dotted line 50, and the electrical environment can be made uniform.

30: Optical module 35: Capacitor 31: VCSEL array (optical element array)
32: Driver IC (electronic element)
33: Module substrate,
50: Contact line 60: Electrode (signal line)
71, 72: Power supply terminal (VDD terminal)
80: Ground terminal (GVD terminal)
81: Ground pattern 91: Hole 93: Resin 100: End of resin oozing

Claims (4)

An IC that is flip-chip mounted on a substrate and an optical element array that is mounted on the substrate,
A signal is transmitted between the IC and each optical element of the optical element array via a plurality of transmission lines formed on the substrate, and a plurality of wires connecting the transmission line and the optical elements. In the method of manufacturing an optical module to be transmitted,
A first step of forming bumps on the IC chip;
A second step of masking with a mask means before Symbol plurality of transmission lines,
A third step of supplying a resin to a region where the IC is mounted on the substrate;
A fourth step of bonding the electrode on the substrate and the bump of the IC by heating using a bonder and simultaneously curing the resin;
A fifth step of performing post-cure by reheating the joint between the electrode on the substrate and the bump;
A sixth step of removing the mask means before or after the fifth step,
The optical element array is disposed in a hole formed in the substrate,
The said mask means masks so that the edge by the side of the said some transmission line of the said hole may be covered with the said some transmission line .   In the second step, a mask tape having at least heat resistance capable of withstanding the heating in the fourth step is used as the mask means, and the mask tape is pasted on at least the plurality of transmission lines. The manufacturing method of the optical module of Claim 1.   The method of manufacturing an optical module according to claim 2, wherein the mask tape is a tape using a siloxane-free acrylic adhesive in a glue portion. The optical module according to any one of claims 1 to 3, wherein, in the fourth step, an end portion of the resin oozing is substantially parallel to the row of the plurality of transmission lines. Manufacturing method .

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