JP2014204083A - Wiring board and board generation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board capable of ensuring a wiring space on the board, and to provide a board generation method.SOLUTION: A wiring board 1 has a plurality of electrodes 2A, 2B, and a wiring 4 for plating. A wire can be bonded to the electrodes 2A, 2B. The wiring 4 for plating is used for plating the electrodes 2A, 2B, and are electrically connected with the electrodes 2A, 2B, respectively. The wiring 4 for plating is branched (4b and 4c) corresponding to the electrodes 2A, 2B, on the electrodes 2A, 2B side from a branch point 42. After subjected to plating, the wiring 4 for plating can be cut between (44A, 44B) the branch point 42 of the wiring 4 for plating and the electrodes 2A, 2B.

Description

  The present invention relates to a wiring substrate and a substrate generation method, and more particularly to a wiring substrate and a substrate generation method in which wiring is formed on the substrate.

  For example, a die (circuit element) is bonded to a bonding pad with a bonding wire on a BGA (Ball grid array) substrate or the like, and the bonding pad needs to be covered with plating or the like. If the wiring provided for the plating process remains, the remaining wiring becomes a stub wiring (unnecessary branch wiring).

  If the stub wiring is connected to the signal wiring for transmitting the signal, there is a risk of degrading the signal quality. For example, a part of the signal enters the stub wiring, the stub is reflected at the open end, and superimposed on the original signal, there is a possibility that the signal quality is deteriorated. Further, there is a possibility that an EMI (Electro Magnetic Interference) problem that the stub wiring transmits and receives noise occurs. Further, if the stub wiring remains for each bonding pad, many stub wirings are arranged on the substrate, so that the wiring space on the substrate is compressed.

Documents related to techniques for reducing the effects of stubs are disclosed.
For example, Patent Document 1 is a printed wiring board that includes a wiring layer having at least a three-layer structure and uses a via hole to form a transmission line that spans a plurality of the wiring layers, and the via hole has wiring layers on both surfaces. Except for those that connect each other, the side of the wiring layer to be connected is not the wiring layer on the surface, and is electrically connected to the resistance element arranged in the immediate vicinity of the hole end on that side, thereby A printed wiring board that prevents deterioration of a signal waveform due to a stub is disclosed.

  Further, in Patent Document 2, in the bus line, in the bus line wiring portion to which the stub line is connected, the stub line is shortened to reduce the reflection noise by narrowing the bus line wiring interval. A bus wiring method on a printed wiring board is disclosed in which crosstalk noise is reduced by increasing the wiring interval between bus lines in a bus line wiring portion without line connection.

  Further, in Patent Document 3, it is possible to immediately commercialize by cutting and forming the plating line at the time of design. Since galvanic corrosion does not occur by cutting the plating line, the copper plating layer is constant during half etching. A BGA package and a method for manufacturing the same are disclosed.

  Further, in Patent Document 4, when forming a circuit pattern, a plating pattern for connecting a plurality of contact terminals is formed, and the surface of the contact terminals is subjected to electroplating treatment by supplying power from the plating pattern, Thereafter, a method of plating the contact terminal portion of the printed wiring board is disclosed in which the plating pattern is fused by an electric current.

JP 2007-317716 A JP-A-11-168266 Japanese Patent No. 4387336 Japanese Patent Publication No. 61-46996

  In the techniques disclosed in Patent Documents 1 to 4 described above, the wiring space on the substrate may be compressed. In particular, in Patent Document 4, after the electroplating process is performed on the contact terminal surface by supplying power from the plating pattern for connecting the contact terminals, the plating pattern is only melted by current. Not all the patterns are removed. Therefore, even in Patent Document 4, the wiring space on the substrate is not ensured.

  An object of the present invention is to solve such a problem, and it is an object of the present invention to provide a wiring board and a board generation method capable of securing a wiring space on the board.

  The wiring board according to the present invention includes a plurality of electrodes to which wires can be joined, and a plating wiring that is used to perform plating on the electrodes and is electrically connected to each of the plurality of electrodes. The wiring for plating has one or more branch points, and the wiring for plating branches from the branch point on the side of the plurality of electrodes corresponding to the plurality of electrodes, and the wiring for plating is After the plating process is performed, it is configured to be cut between the branch point of the plating wiring and the plurality of electrodes.

  The substrate generation method according to the present invention is electrically connected to each of a plurality of electrodes to which wires can be joined, has one or more branch points, and the plurality of electrode sides from the branch points correspond to the plurality of electrodes. A plating wiring branching on the substrate, a step of plating each of the plurality of electrodes using the plating wiring, a branching point of the plating wiring, and the step Cutting between the plurality of electrodes.

  ADVANTAGE OF THE INVENTION According to this invention, the wiring board which can ensure the wiring space on a board | substrate, and a board | substrate production | generation method can be provided.

It is a figure which shows the wiring board concerning embodiment of this invention. 1 is a diagram showing a wiring board according to a first exemplary embodiment; FIG. 3 is a diagram illustrating the wiring board according to the first embodiment and is an enlarged view illustrating details of a portion surrounded by a broken line A in FIG. 2. FIG. 4 is a diagram illustrating the wiring board according to the first embodiment and is a cross-sectional view taken along line AA in FIG. 3. In the wiring board concerning Embodiment 1, it is a figure which shows the state by which the wiring for plating was cut | disconnected. 3 is a flowchart showing a method for generating a wiring board according to the first exemplary embodiment; It is a figure which shows the wiring board concerning a comparative example.

[Outline of Embodiment of the Present Invention]
Prior to the description of the embodiment, the outline of the embodiment according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a wiring board 1 according to an embodiment of the present invention. As shown in FIG. 1, the wiring substrate 1 includes a plurality of electrodes 2 </ b> A and 2 </ b> B and plating wiring 4. The electrodes 2A and 2B can join wires. The plating wiring 4 is used for plating the electrodes 2A and 2B, and is electrically connected to the electrodes 2A and 2B, respectively.

The plating wiring 4 has one or more branch points 42. The plating wire 4 branches (4b and 4c) from the branch point 42 on the electrodes 2A and 2B side corresponding to the electrodes 2A and 2B. The plating wiring 4 is configured to be cut between the branching point 42 of the plating wiring 4 and the electrodes 2A and 2B (44A and 44B) after the plating process is performed.
According to the wiring board 1 according to the embodiment of the present invention, a wiring space on the board can be secured.

[Embodiment 1]
Hereinafter, embodiments will be described with reference to the drawings. FIG. 2 is a plan view showing the wiring board 100 according to the first embodiment. The wiring substrate 100 is a BGA substrate used in, for example, LSI (Large Scale Integration). The wiring substrate 100 has a substrate body 102 on which circuit elements and the like are arranged. The substrate body 102 is made of an insulator such as a resin.

  A plurality of bonding pads 120 as electrodes are arranged on the substrate body 102. For example, the bonding pad 120 is disposed near the center of the substrate body 102. At least one of the bonding pads 120 is provided with conductive wiring (not shown in FIG. 2). Details will be described later.

  FIG. 3 is an enlarged view showing details of a portion surrounded by a broken line A in FIG. 4 is a cross-sectional view taken along line AA in FIG. Hereinafter, when a plurality of constituent elements such as the bonding pads 120 </ b> A to 120 </ b> E are generically described, they may be simply referred to as bonding pads 120, for example.

  The substrate body 102 is composed of, for example, a plurality of wiring layers 102a, 102b, and 102c. A die 110 such as a circuit element is disposed on the wiring layer 102 a of the substrate body 102. Further, bonding pads 120 </ b> A to 120 </ b> E that are electrodes are disposed on the wiring layer 102 a of the substrate body 102. The bonding pads 120A, 120B, and 120C are electrically connected with signal wirings 122A, 122B, and 122C for transmitting signals, respectively. The signal wiring 122 is made of a conductor material such as copper foil.

  A bonding wire 112 which is a wire is bonded to the die 110. By bonding the bonding wire 112 to the bonding pad 120, the die 110 is bonded to the substrate body 102. Here, when the bonding pad 120 and the bonding wire 112 are bonded, the bonding pad 120 needs to be plated with a metal for the surface corrosion resistance and bonding stability. This plating process will be described later.

  The substrate body 102 is provided with via holes 104A, 104B, and 104C that electrically connect the wiring layers 102a, 102b, and 102c to each other. A signal wiring 122A is electrically connected to the wiring layer 102a side of the via hole 104A. A signal wiring 122B is electrically connected to the wiring layer 102a side of the via hole 104B. A signal wiring 122C is electrically connected to the wiring layer 102a side of the via hole 104C.

  Further, as shown in FIG. 4, the signal wiring 124A is electrically connected to the wiring layer 102c side of the via hole 104A. The signal wiring 124A is electrically connected to a ball pad 130A disposed in the wiring layer 102c. The solder ball 132A is bonded to the wiring layer 102c by the ball pad 130A.

  That is, the bonding pad 120A is electrically connected to the solder ball 132A via the signal wiring 122A, the via hole 104A, the signal wiring 124A, and the ball pad 130A. Similarly, the bonding pad 120B is electrically connected to an electrode or the like provided in the wiring layer 102b or 102c through the signal wiring 122B and the via hole 104B. Similarly, the bonding pad 120C is electrically connected to an electrode or the like provided in the wiring layer 102b or 102c through the signal wiring 122C and the via hole 104C.

  On the wiring layer 102 a of the substrate body 102, a plating wiring 140 used for plating the bonding pad 120 is disposed. The plating wiring 140 is made of a conductor material such as copper foil, for example. The plating wiring 140 has a main line 140a, branch lines 140b to 140i, branch points 142a to 142d, and cutting portions 144A to 144E. As shown in FIGS. 3 and 4, the plating wiring 140 is disposed from the bonding pad 120 toward the outside of the substrate body 102.

  The main line 140a of the plating wiring 140 is branched into branch lines 140b and 140c at a branch point 142a. The branch line 140b branches into a branch line 140d and a branch line 140e at a branch point 142b. The branch line 140c branches into the branch line 140f and the branch line 140g at the branch point 142c. The branch line 140g branches into a branch line 140h and a branch line 140i at a branch point 142d.

  The cutting portion 144 (first portion) is formed narrower than the other portions (main line 140a and branch lines 140b to 140i) of the plating wiring 140 and the signal wirings 122 and 124. The cutting portion 144A is provided at the end of the branch line 140f, for example. The cutting part 144B is provided at the end of the branch line 140d. The cutting portion 144C is provided at the end of the branch line 140h. The cutting portion 144D is provided at the end of the branch line 140e. The cutting part 144E is provided at the end of the branch line 140i.

  The cutting portion 144A is electrically connected to the via hole 104A. The cutting part 144B is electrically connected to the via hole 104B. The cutting portion 144C is electrically connected to the via hole 104C. Further, the cutting portion 144D is electrically connected to the bonding pad 120D. The cutting part 144E is electrically connected to the bonding pad 120E. That is, the cutting parts 144A to 144E are electrically connected to the bonding pads 120A to E, respectively. That is, the plating wiring 140 is configured to branch correspondingly to the bonding pad 120 on the bonding pad 120 side from the branch point 142.

Here, when a current is passed through the wiring, Joule heat is generated in the wiring. Due to this Joule heat, the temperature of the wiring rises. When the temperature rise of the wiring reaches the limit temperature, the wiring is cut.
Further, assuming that the resistance value of the wiring is R [Ω], the current flowing through the wiring is I [A], and the current flowing time is t [seconds], the Joule heat Q [J] generated in the wiring is Q = RI ² It is represented by t. That is, the temperature rise at a portion having a large resistance value is larger than the temperature rise at another portion. Further, when the cross-sectional area of the wiring is S [m ² ], the length is l [m], and the resistivity is ρ [Ωm], R = ρ * l / S. That is, the resistance value at a portion having a small cross-sectional area is larger than the resistance value at another portion. Therefore, the temperature rise at a location where the cross-sectional area is small is greater than the temperature rise at other locations.

  Here, as described above, the cutting portion 144 is formed to be narrower than other portions of the plating wiring 140 (the main line 140a and the branch lines 140b to 140i) and the signal wirings 122 and 124. That is, when a current is passed through the cutting portion 144, the temperature rises more than the other portions of the plating wiring 140 (main line 140a and branch lines 140b to 140i) and the signal wirings 122 and 124. The temperature rises due to heat and reaches the limit temperature earlier than other parts. Note that when the cut portion 144 is cut, no current flows, so the signal wirings 122 and 124 do not reach the limit temperature.

  Therefore, as shown in FIG. 5, the plating wiring 140 is cut at the cutting portion 144. As a result, the electrical connection between the plating wiring 140 and the bonding pad 120 is interrupted. Moreover, since the cutting part 144 is cut, it is possible to prevent a signal from each of the bonding pads 120A to 120E from being short-circuited. Before the cutting part 144 is cut, the bonding pads 120A to 120E are electrically connected to each other. Therefore, when the wiring board 100 is shipped in this state, for example, a signal transmitted through the signal wiring 122A is short-circuited to the signal wiring 122B. However, since the cutting portion 144 is cut, such a signal short-circuit does not occur.

  FIG. 6 is a flowchart illustrating a method for generating the wiring board 100 according to the first embodiment. First, the plating wiring 140 is installed on the substrate body 102 (S102). At this time, the plating wiring 140 is installed so as to be electrically connected to the bonding pad 120. For example, the cutting portion 144 of the plating wiring 140 may be bonded to the via hole 104 that is electrically connected to the bonding pad 120 like the bonding pad 120A. Further, the cutting portion 144 of the plating wiring 140 may be directly bonded to the bonding pad 120 like the bonding pad 120D.

  Next, a plating process is performed on the bonding pad 120 using the plating wiring 140 (S104). Specifically, the plating is performed on the bonding pad 120 by supplying power to the bonding pad 120 through the plating wiring 140 to perform the electrolytic plating process. Note that the cutting portion 144 is configured not to be cut during the plating process. In other words, the cross-sectional area of the cutting portion 144 is set so that the current value flowing through the cutting portion 144 during the plating process does not reach the limit temperature.

  Next, the cutting portion 144 of the plating wiring 140 is cut (S106). Specifically, the cutting unit 144 is cut by passing a current through the cutting unit 144. As a result, the wiring board 100 is generated as shown in FIG. 5, and the wiring board 100 is shipped in the state shown in FIG. Note that the current value flowing through the cutting portion 144 is set to be larger than the current value used for the plating process.

  Specifically, for example, when a current flows between the end E of the main line 140a of the plating wiring 140 and the via hole 104A, a current flows through the cutting portion 144A, so that the cutting portion 144A is cut as described above. Is done. In addition, when a current is passed between the end E of the main line 140a of the plating wiring 140 and the ball pad 130A or the solder ball 132A, a current flows through the cutting portion 144A, so that the cutting portion 144A is cut.

  Similarly, for example, when a current flows between the end E of the main line 140a of the plating wiring 140 and the via hole 104B, a current flows through the cutting portion 144B, so that the cutting portion 144B is cut. Further, for example, when a current flows between the end E of the main line 140a of the plating wiring 140 and the via hole 104C, a current flows through the cutting portion 144C, so that the cutting portion 144C is cut.

  Further, for example, when a current flows between the end E of the main line 140a of the plating wiring 140 and the bonding pad 120D, a current flows through the cutting portion 144D, and thus the cutting portion 144D is cut. Similarly, for example, when a current flows between the end E of the main line 140a of the plating wiring 140 and the bonding pad 120E, a current flows through the cutting portion 144E, so that the cutting portion 144E is cut.

  As a method of flowing a current through the cutting unit 144, for example, a device such as a voltage / current generator having two probes having a potential difference is used. When one of the probes is brought into contact with the end E of the main wire 140a of the plating wiring 140 and the other probe is brought into contact with the via hole 104 or the like, a current flows through the cut portion 144. Thus, the cutting part 144 can be easily cut only by passing a current through the cutting part 144.

  This probe contact operation may be performed manually by an operator or automatically by mechanization. Further, the probe may be brought into contact with both ends of each cutting portion 144. Further, a dedicated contact point for cutting the plating wiring 140 may be provided on the wiring board 100. This contact point is configured to be electrically connected to each end of each cutting portion 144. And the cutting part 144 can be easily cut | disconnected by pinching each contact point with each of two clamps instead of a probe.

  For example, the contact point connected to the end E of the main line 140a of the plating wiring 140 is sandwiched by one clamp, and the other clamp is sandwiched by the contact points connected to the bonding pads 120A to 120E, so that The cutting parts 144A to 144E can be cut.

[Comparative example]
FIG. 7 is a diagram showing a wiring board 200 according to a comparative example with the first embodiment. The wiring board 200 includes a board body 102 as with the wiring board 100 according to the first embodiment. Bonding pads 120 </ b> A to 120 </ b> E are arranged on the substrate body 102 as in the first embodiment.

  Similarly to the first embodiment, the substrate body 102 is provided with via holes 104A, 104B, and 104C that electrically connect the wiring layers 102a, 102b, and 102c to each other. The via hole 104A and the bonding pad 120A are electrically connected via a signal wiring 122A. The via hole 104B and the bonding pad 120B are electrically connected via the signal wiring 122B. The via hole 104C and the bonding pad 120C are electrically connected via a signal wiring 122C.

  Here, in the comparative example, the plating treatment of the bonding pads 120A to 120E is performed using separate plating wirings 240A to 240E. Here, the plating wirings 240A to 240E are not connected. Further, unlike the first embodiment, the plating wiring 240 does not have the cutting portion 144.

  The plating wiring 240A is electrically connected to the via hole 104A. The plating wiring 240B is electrically connected to the via hole 104B. The plating wiring 240C is electrically connected to the via hole 104C. The plating wiring 240D is electrically connected to the bonding pad 120D. The plating wiring 240E is electrically connected to the bonding pad 120E. The bonding pads 120A to 120E are plated using the plating wirings 240A to 240E, respectively.

  Here, the wiring board 200 is shipped without disconnecting the electrical connection between the bonding pads 120A to 120E and the plating wirings 240A to 240E. The plating wiring 240 is an unnecessary wiring after the plating process is completed. That is, the plating wiring 240 is a stub wiring. In addition, depending on the scale of the wiring substrate 200, the plating wiring 240 has a length of several centimeters, and there is a possibility that the signal quality is deteriorated as described below.

For example, a part of the signal transmitted through the signal wiring 122 </ b> A enters the plating wiring 240 </ b> A and causes signal reflection at the end of the plating wiring 240. Therefore, as described above, the signal quality may be deteriorated. Further, the plating wiring 240 may cause radio interference by transmitting and receiving noise.
Furthermore, since the plating wirings 240A to 240E are separately installed on the substrate body 102 corresponding to the bonding pads 120A to 120E, the wiring space on the substrate body 102 is compressed.

  On the other hand, in the first embodiment, as shown in FIG. 5, the plating wiring 140 is not electrically connected to the bonding pad 120, the signal wiring 122, and the via hole 104. Accordingly, it is possible to suppress the deterioration of signal quality and the occurrence of radio interference as described above. Further, since the plating wiring 140 is configured to be branched from the main line 140a via the branch point 142, there is a space as shown by broken lines B1 and B2 in FIG. Therefore, a wiring space is secured as compared with the comparative example shown in FIG.

[Modification]
Note that the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, the wiring method of the plating wiring 140 according to the first embodiment can be applied to a wiring arranged in the inner layer (for example, the wiring layer 102 b) of the substrate body 102.

  An inspection may be performed before shipping a wiring board using a circuit arranged in an inner layer. For example, a debug circuit may be incorporated in the inner layer of the substrate body. Since the circuit (internal circuit) incorporated in the inner layer is incorporated in the substrate, it can be undisclosed to the user. Further, the function of the internal circuit can be made unrecoverable by removing the parts used for the inspection or providing an external circuit at the probe point. However, by mounting components again and accessing the probe point, the function of the internal circuit can be restored relatively easily, and therefore the internal circuit can be estimated.

  On the other hand, the internal circuit is wired like the plating wiring 140 according to the first embodiment, the cutting part is provided at an arbitrary location, and the cutting part can be cut by flowing current to the internal circuit after the inspection. it can. As a result, the electrical connection of the internal circuit is interrupted, making it difficult to restore the function of the internal circuit. Therefore, the confidentiality of the internal circuit is maintained and the tamper resistance is improved.

In the first embodiment, the bonding pads 120, the via holes 104, and the number of branch points 142 of the plating wiring 140 may be any number.
Further, the cutting portion 144 may not be provided at the end of the plating wiring 140 (branch line 140f or the like). In other words, the signals transmitted through the bonding pads 120 </ b> A to 120 </ b> E need not be short-circuited and may be provided on the bonding pad 120 side from the branch point 142. On the other hand, the length of the stub wiring is shorter when it is provided at the end of the plating wiring 140.

DESCRIPTION OF SYMBOLS 1 Wiring board 2A, 2B Electrode 4 Plating wiring 42 Branch point 100 Wiring board 102 Board | substrate body 102a, 102b, 102c Wiring layer 104 Via hole 110 Die 112 Bonding wire 120 Bonding pad 122 Signal wiring 124A Signal wiring 130A Ball pad 132A Solder Ball 140 Plating wiring 140a Main line 140b to 140i Branch line 142 Branch point 144 Cutting part

Claims (6)

A plurality of electrodes capable of joining wires;
A plating wire that is used to perform plating on the electrode and is electrically connected to each of the plurality of electrodes;
The wiring for plating has one or more branch points, and the wiring for plating branches from the branch point to the plurality of electrodes, corresponding to the plurality of electrodes,
The said wiring for plating is comprised so that a cutting | disconnection is possible between the branch point of the said wiring for plating, and these electrodes after a plating process is given. The wiring board according to claim 1, wherein the first portion of the plating wiring that can be cut is provided at an end of the plating wiring. The wiring board according to claim 1, wherein a resistance value of a first portion of the plating wiring that can be cut is larger than a resistance value of a portion different from the first portion. Multiple layers,
One or more via holes for electrically connecting the plurality of layers to each other;
A signal wiring for transmitting a signal between at least one of the plurality of electrodes and the via hole;
The wiring board according to claim 1, wherein the plating wiring is connected to the via hole. The wiring board according to any one of claims 1 to 4, wherein the plating wiring is installed from the plurality of electrodes toward the outside of the wiring board. A plating wiring that is electrically connected to each of a plurality of electrodes to which wires can be joined, has one or more branch points, and the plurality of electrode sides branch from the branch points corresponding to the plurality of electrodes. Installing on the substrate;
Performing a plating process on each of the plurality of electrodes using the plating wiring;
A step of cutting between a branch point of the plating wiring and the plurality of electrodes.

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