JPH08264938A - Printed wiring board,and method for connecting its contacting pad with plated bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent short-circuit of contact pads in a plating process and to eliminate additional processes by electrically connecting a plating bar and a conducting track and a contact pad and a conducting track by a conducting via. SOLUTION: This device is constituted of contact pads 22 and 23 arranged on the surface of a wiring board at an interval and a printed wiring board 12 having a plating bar. In a conducting track in the printed wiring board 12, the first end part is positioned at the plating bar, and the second end part is positioned at the contact pads 22 and 23. They are located at the plating bar and the contact pads 22 and 23. The plating bar and an inner track 34 are electrically connected by a first conducting via 40 extending between the plating bar and the first end part of the inner track 34. The inner track 34 and the contact pads 22 and 23 are electrically connected by the second conducting via 40 extending between the contact pads 22 and 23 and the second end part of the inner track 34.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates generally to printed wiring boards, and more particularly to a method of plating contact pads on a printed wiring board.

[0002]

Printed Wiring Boards (PWBs), also known as printed circuit boards, are widely used in the electronics industry to connect the individual components of electronic devices together. Typical printed wiring board (PW
B) can consist of one or more layers of metal circuit paths or conductors bonded to an insulating substrate. The circuit paths or conductors are typically thin copper strips and the insulating substrate is typically composed of glass reinforced epoxy, although other materials can be utilized. Depending on the complexity of the electronic circuit, the PWB can be single-sided or double-sided, or it can be composed of multiple layers of circuit paths or conductors, such as a multi-layer PWB. Complex electronic circuits are usually not short-circuited and
Double-sided or multi-layer PW that allows printed circuit paths to cross each other without the need for additional special jumpers
B is required. The materials used to manufacture PWBs as well as the PWB manufacturing process are well known, for example, Electroni, which is incorporated herein by reference.
c Materials Handbook, Volu
me 1-Packaging, (ASM Inter
national, Materials Park, O
H44073, 1989) pp. It is described in detail in numerous technical documents such as 505-603.

[0003] PWBs can be connected to each other and to various other electrical components by individual wires or ribbon wire bundles that are soldered directly to the PWB, but usually one or more PWBs. It is more convenient to provide a plurality of contact pads located adjacent the edges of the. The contact pads are designed to be aligned with the contacts of the mating mating connector, thus allowing the PWB to be connected to external circuitry or devices simply by inserting the PWB into the mating mating connector. To ensure a reliable, low resistance electrical connection, it is common to plate both the PWB contact pads and the contacts in the mating connector with gold or a hard gold alloy. Gold, which is a precious metal, has excellent corrosion resistance, and its small contact resistance is maintained indefinitely.

The electroplating process is generally a PWB.
Used to apply a compatible gold alloy coating to the contact pads of the. However, since the electroplating process requires a certain potential between the object to be plated and the electroplating solution, all contact pads of the PWB should be electroplated to a compatible voltage potential if they are to be plated. Must be connected to each other.

FIG. 1 illustrates a general method of electrically connecting the contact pads to each other in preparation for plating. Essentially, the printed wiring board B has a circuit area C and a waste (was
te) Region W is included. In the circuit area C, a plurality of contact pads P and a plurality of circuit paths or conductors (not shown) necessary to connect various electrical components (not shown) which are later mounted on the wiring board B to each other. Can be included. In the waste area W, a plating tie bar or a plating bar electrically connected to the end E of each contact pad P by a thin conductor strip or track T arranged on the surface of the wiring board B. ) PB can be included. A suitable voltage source (not shown) is then connected to the plating bar PB to bring each contact pad P to the proper potential required for electroplating. When the plating process is completed, the waste area W of the wiring board B is normally removed by routing to expose the new edge L.

While the above methods for plating contact pads are widely used, they are not without drawbacks. For example, one of the drawbacks is that when the waste area is removed by the router, the underlying conductor, copper, which comprises the contact pad, is exposed. Over time, the exposed copper of the contact pads may result in oxidation, which may compromise the integrity of the overlying gold plating. In the extreme, oxidation of the underlying copper can strip the overlying gold plating, which, of course, will significantly reduce contact pad reliability. Another drawback is that the router used to separate the waste area from the circuit area can also cause a short circuit between adjacent contact pads. That is, the copper of the forgeable material contact pad is drawn along the cutting path by the router bit a sufficient distance to contact the exposed copper or gold plating of the adjacent contact pad. The routing process can also lift the copper contact pads off the substrate, which can, at best, cause contact reliability problems and, in the worst case, damage the wiring board.

In FIG. 2, the contact pad P is a tie for plating.
An alternative method of connecting to the bar PB is shown. In this alternative method, all of the contact pads P are first connected to each other by a plurality of lateral tracks T. The contact pad P is then connected to the plating tie bar PB by a single track S. While this method has been used, it again suffers from all of the same problems as the method shown in FIG. Furthermore, this method also has the drawback of requiring a secondary drilling step after the plating step to cut the lateral tracks T between adjacent contact pads P.

Therefore, there remains a need for contact pad and plating bar connection methods that avoid the drawbacks of current methods. By such a method, a reliable contact pad is obtained and the gold plating is stripped from the pad, or
It should be minimized to the extent that it can be compromised. The improved method should also eliminate the problems associated with removing waste areas, such as shorts between contact pads or lift of the contact pads from the wiring board. is there. An improved method in a conventional PWB manufacturing process without the need for additional materials or process steps and without resorting to secondary drilling steps to destroy any unwanted connections. If practicable, another advantage can be realized.

[0009]

SUMMARY OF THE INVENTION It is possible to solve the problems described above, prevent short-circuiting of contact pads in a plating process, and obtain a highly reliable printed wiring board and contact pad connecting method without additional steps.

[0010]

An apparatus for later exposing the copper of a contact pad or contacting a plating bar without the need to rework the plating of the contact pad comprises:
It can consist of a printed wiring board with contact pads and plated bars spaced on the surface of the wiring board. The conductive tracks in the printed wiring board have a first end located near the plating bar and a second end located near the contact pad. A first conductive via extending between the plating bar and the first end of the inner track electrically connects the plating bar and the inner track. A second conductive via extending between the contact pad and the second end of the inner track electrically connects the inner track and the contact pad.

The method of electrically connecting the contact pad and the plated bar includes the steps of providing a conductive track inside the printed wiring board and a first conductive portion between the plated bar and the first end of the internal track. A conductive via may be provided, and a second conductive via may be provided between the contact pad and the second end of the inner track.

An important advantage associated with the inner tracks and conductive vias is that after the plating process, it allows the waste portion of the wiring board to be removed without exposing the copper under the contact pads. Is. Therefore, the copper that makes up the contact pad does not oxidize and avoids all the drawbacks associated therewith. Another advantage is that you can remove the waste of the wiring board without touching the edges of the contact pad, which can lift the contact pad from the wiring board or create a short circuit between adjacent contact pads. There is no nature. Yet another advantage is
It is possible to provide the inner tracks in the appropriate inner layer and at the same time place other conductors elsewhere in the inner layer, thus eliminating the need for additional process steps. . Similarly, connecting inner tracks to plating bars and contact pads during the same process steps required to provide other conductive vias between conductors on the inner layer of the wiring board and conductors on the outer surface. It is possible to provide conductive vias.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus 10 for contacting the plating bar 18 without the need to later expose the copper of the contact pad or to rework the plating of the contact pad is best seen in FIGS. As can be seen, a printed wiring board or PWB 1 having a circuit area 32 and a disposal area 14 is provided.
It can be composed of two. Printed wiring board 12
A plurality of contact pads 22 and a circuit area 32 of
Later mounted on PWB12 and soldered to the conductor,
It includes a plurality of circuit paths or conductors (not shown) needed to connect various electronic components (not shown) that will complete the electronic circuit. The waste area 14 of the PWB 12 will later serve as a connection point for the voltage source (not shown) needed to carry out the electroplating of the contact pads 22, or a plating tie bar or plating. -It is composed of a bar 18. As described in more detail below,
The waste area 14 is separated from the circuit area 32 along the line 16 so that the line 16 becomes the new edge of the printed wiring board or PWB 12.

Electroplating the contact pads 22 with a suitable material, such as gold or a gold alloy, connects each contact pad 22 to the plating bar 18 and further
The bar 18 must be connected to the appropriate electroplating voltage source. In one preferred embodiment, each contact pad 22 is P
It is electrically connected to the plating bar 18 by a conductor or track 34 inside the WB 12. But plating
Although the bars 18 and contact pads 22 are located on the outer surface 36 of the PWB 12, the tracks 34 are internal to the PWB 12, so a set of conductive vias 40 are used to define each inner track 34 and plated bar 18 and The contact pads 22 are connected.

All of the contact pads 22 are internal tracks 3
4 and conductive vias 40 connected to the plating bar 18, it is possible to immerse a portion of the PWB containing the contact pads 22 in a suitable electrical plate solution (not shown) containing, for example, gold or a gold alloy. It will be possible. It is then possible to establish a compatible voltage potential between the contact pad 22 and the electroplating solution by connecting a suitable electroplating voltage source (not shown) to the plating tie bar 18. When the plating process is complete, it is possible to remove the PWB 12 from the electroplating solution and remove the waste area 14 of the PWB 12 by routing along line 16, for example. As a result, line 16 becomes PWB12.
Becomes the new edge of. However, the new edge 16
Located near the end 20 of the contact pad 22, but the end 2
There is no contact with 0, and thus the end 20 of the pad 22 remains covered by the protective layer of gold plating 42, as best shown in FIG.

An important advantage of the present invention is that the end 20 of the contact pad 22 is prevented from being exposed after removal of the waste portion 14 of the PWB 12. As a result, the copper that makes up the contact pad 22 does not have to oxidize and avoids all the drawbacks associated therewith. Another advantage is that during the routing process the ends 20 of the contact pads 22 are
Since the router bit (not shown) does not touch the edge, there is no possibility that the bit will be dragged along the edge 20 of the contact pad 22, resulting in the contact pad 22 being lifted from the wiring board or adjacent to it. This means that there is no possibility of a short circuit occurring between the contact pads 22.

Still another advantage relates to the structure of this printed wiring board. For example, in most cases the printed wiring board 12 will consist of a multilayer printed wiring board with at least one internal layer, but PWB1
2 can be composed of many internal layers. It is then possible to provide the inner track 34 in a suitable inner layer while at the same time placing other conductors elsewhere in the inner layer. Similarly, PWB12
Of the inner track 34 and the plating bar 18 and contact pads 22 during the same process steps required to provide other conductive vias between the conductors of the inner layer and the outer surface 36. It is possible to provide a sex via 40. Therefore, it is possible to provide the inner track 34 and the conductive via 40 without requiring additional process steps. The present invention also eliminates the need for secondary drilling steps to break unwanted contact between contact pads.

Referring now to FIGS. 3-6, apparatus 10 for later exposing contact pad copper or contacting plating bar 18 without requiring reworking of contact pad plating. Will be described in detail. As mentioned above, the printed wiring board (PWB) 12 can be constructed from a multilayer printed wiring board that is comprised of one or more internal layers 50, 52 of circuit paths or conductors, as best seen in FIG. is there. Such a multilayer printed wiring board is manufactured by first manufacturing a plurality of single-sided wiring boards (not shown) in which conductors are appropriately routed. Methods for manufacturing single sided circuit boards are well known in the art (eg, Electronic Mater).
ials Handbook, Vol. 1-Pakag
ing, pp 505-506). next,
Each one of the individual wiring boards (not shown) is stacked by stacking various one-sided wiring boards, one on top of the other, and pressing each other with a suitable binder (not shown). To form a single unitary wiring board with a plurality of internal circuit paths or conductor layers 50, 52 (FIG. 4). Stacking and bonding methods for single sided circuit boards to provide a multilayer wiring board are also well known in the art. The multi-layer printed wiring board 12 shown in FIGS. 3 to 7 is made up of such multi-layered individual wiring boards that have already been stacked and joined, and is represented herein by the singular.

Next, referring to FIG. 3, the printed wiring board 12 further includes a circuit portion 32 and a discard portion 34. In the circuit area 32 of the printed wiring board 12, a plurality of contact pads 22 and various electronic components (not shown) that will be mounted on the PWB 12 and soldered to conductors to complete an electronic circuit later are formed. It includes multiple circuit paths or conductors (not shown) required for connections. The printed circuit board 12 is further illustrated in FIGS.
It is also possible to construct additional contact pads 23 located on opposite or lower surfaces 44 of PWB 12, as best seen in FIG. The waste area 14 of the PWB 12 will later serve as a connection point for the voltage source (not shown) necessary to carry out the electroplating of the contact pads 22, 23, the plating tie bar. Alternatively, it is composed of a plating bar 18.

Plating bar 18 and contact pads 22, 2
3 are electrically connected by a plurality of inner tracks 34 and conductive vias 40. Methods for forming conductive vias are well known in the art. The inner track 34 is one or more of the inner layers 50, 52 that make up the PWB 12, as best seen in FIG.
Can be placed at. Providing the inner track 34 on any single inner layer 50 or on several inner layers 50, 52 is primarily a matter of overall circuit complexity, as well as for all of the tracks 34 on a given layer. It depends on whether enough space is available. Therefore, the present invention should not be considered limited to any particular configuration of inner track 34 in 50 single layers or 50, 52 multilayers.

The conductive inner tracks 34 can be constructed from copper conductors and, as best seen in FIGS. 4 and 5, the plating bar 18 and contact pads 2 are shown.
Aligned with 2, 23. However, it should be noted that the materials that make up the conductors of the PWB, such as the conductive inner tracks 34, the contact pads 22 and the plating bars 18, are not limited to copper, but may be aluminum, silver, gold, etc. It can be composed of any of a wide range of conductive materials.
However, copper is by far the most common material used for PWB conductors. In a preferred embodiment, the inner layer 50,
It is possible to form inner tracks 34 in inner layers 50, 52 at the same time that other circuit paths or conductors are placed in 52. After fabrication of the inner layer 50 or layers 50, 52, a single unitary PWB 12 is formed by pressing them together with a suitable binder (not shown) in a manner well known in the art.

The conductive vias 40 connecting the inner track 34 to the plating bar 18 and the contact pads 22, 23 are:
As best seen in FIG. 5, the same used to provide the other conductive vias (not shown) needed to connect the circuit conductors of inner layer 50 to the circuit conductors of upper surface 36 and lower surface 44. Provided between process steps. In one preferred embodiment, vias 40 may comprise through vias that extend through PWB 12 as best seen in FIG. Although there are many processes for forming such conductive through vias, the through vias 40 include the plating bar 18, one end 46 of the inner track 34, and P.
It may be formed by drilling a hole completely through the WB 12 and through the lower surface 44 of the PWB 12 to an optional opposed plating bar 19. The inner track 34 and plating bar 1 are then plated by plating the inside of the holes with a conductive material utilizing any one of several plating processes.
It is possible to electrically connect 8 and 19. The conductive through vias 40 connecting the other end of the inner track 34 and the contact pads 22, 23 can be formed in a similar manner.

Once the conductive vias 40 have been formed, the contact pads 22, 23 can be plated in the conventional manner. For example, a suitable electroplating solution (not shown)
Dip the contact pads 22 and 23 into the
A voltage source (not shown) can be connected between the bars 18. Upon completion of the plating process, each contact pad 22, 23 is encapsulated by a thin layer 42 of plating material, such as a gold alloy, as best seen in FIG.
sulated). The thin layer 42 also covers the ends 20, 21 of each contact pad 22, 23 to prevent oxidation due to exposure to the atmosphere. Further, a suitable device (not shown), such as a router, can be utilized to remove the waste area 14 of the PWB 12 and expose a new edge 16. The edges 16 may be chamfered to remove sharp edges and prevent the PWB 12 from tearing. The ends 20, 21 of the contact pads 22, 23 are not exposed by the routing process and remain protected by the thin layer 42 of plating material. Of course, PW
The upper surface 36 and lower surface 44 of B12 remain electrically connected to each other by through vias 40, as best seen in FIG.

In FIG. 7, upper surface 136 and lower surface 1
A plurality of blind vias 1 capable of keeping 44 contact pads 122, 123 electrically isolated.
Another embodiment utilizing 40, 141 is shown at 110. That is, the embodiment 110 shown in FIG. 7 electrically couples the plating bar 118 and the contact pads 122 of the upper surface 136 to the upper inner track 134 located in the upper inner layer 150. Via 140
It consists of Another pair of blinds
Via 141 has plated bar 119 and lower surface 144.
Used to electrically connect the contact pads 123 of the lower inner track 135 to the lower inner track 135 disposed in the lower inner layer 152. Blinds such as vias 140 and 141
The use of vias includes contact pads 122 on the top surface 136.
Are electrically isolated from the contact pads 123 on the lower surface 144 and nevertheless lower surface 144
The advantage is that it can be kept connected to the plating bar 119.

It will be apparent to those skilled in the art that the present invention disclosed herein is capable of various alternative implementations and includes various alternative embodiments in addition to the limitations of the prior art.

Although the embodiments of the present invention have been described in detail above, the respective embodiments of the present invention will be listed below. (1) Contact pads (22) and plating bars (18) located on the outer surface (36) of the printed wiring board (12)
In the method for electrically connecting the printed wiring board (1
2) Inside, a conductive track (34) is formed, the conductive track being near the first end (46) located near the plating bar (18) and near the contact pad (22). Having a second end located (48) and forming a conductive via (40) between the plating bar (18) and the first end (46) of the conductive track (34). A conductive via (40) electrically connects the plating bar (18) and the conductive track (34), the contact pad (22) and the second end of the conductive track (34). (4
Forming a second conductive via (40) between
The conductive vias (40) of (1) electrically connect the contact pads (22) and the conductive tracks (34) to the contact pads of the printed wiring board and the plating bar. (2) The printed wiring board (12) is a multilayer printed wiring board having at least one internal layer (50), and the step of forming the conductive tracks (34) inside the printed wiring board (12) is The connection method according to (1) above, which is performed at the time of forming a conductor for the layer (50). (3) The step of forming the first and second conductive vias (40) is carried out while the other via of the printed wiring board (12) is conducting. (1) or (2) The connection method described. (4) In a printed wiring board having two opposing surfaces (36, 44), two opposing surfaces (36, 4)
4) a first contact pad (22) arranged on one side,
A first plating bar (18) disposed on one of the two opposing surfaces (36,44), a first conductive track (34) provided inside the printed wiring board, and a conductive layer. The track (34) comprises a first end (46) located near the plating bar (18) and a second end (48) located near the contact pad (22). One plating bar (18) and first conductive track (3)
4) extending between the first ends (46) of the first plating
A first conductive via (40) electrically connecting the bar (18) and the first conductive track (34), a first contact pad (22) and a first conductive track (34). A printed wiring comprising a second conductive via (40) extending between the second ends (48) and electrically connecting the contact pads (22) and the first conductive tracks (34). Board (12). (5) The printed wiring board (12) comprises a multilayer printed wiring board having at least one inner layer (50),
The printed wiring board (1) according to the above (4), characterized in that the conductive tracks (34) of (1) are arranged in the inner layer (50).
2). (6) The first contact pad (22), the first plating bar (18) and the first conductive track (34) are made of copper, as described in the above item (4) or (5). Printed wiring board (12). (7) The first and second conductive vias (40) are connected to the printed wiring board (12) and the respective first contact pads (2).
2), the first plating bar (18) and the through via extending through the first conductive track (34), which are characterized in the above (4), (5), (6). Printed wiring board (12). (8) The first and second conductive vias (40) are blind.
(4), (5), characterized in that it is composed of vias,
The printed wiring board (12) according to (6) or (7). (9) In a method of plating a contact pad (22) arranged on an outer surface (36) of a printed wiring board (12), a first end portion (46) located near a plating bar (18). A second end (48) located near the contact pad (22), the first end (46) being electrically connected to the plating bar (18) by a first conductive via (40). A conductive track (34) having a second end (48) connected to the contact pad (22) by a second conductive via (40) is provided inside the printed wiring board (12) for contact. The pad (22) is electrically connected to a plating bar (18) disposed at a distance from the contact pad (22), and the contact pad (22) is immersed in an electroplating solution containing a plating material to form a plating plate. Apply a voltage source between the bar (18) and the electroplating solution Continue to the plating material is deposited on the surface of the contact pads (22), a plating method comprised of retrieving the contact pads (22) from the plating solution. (10) Furthermore, the disposal area (3) of the printed wiring board (12)
The plating method according to the above item (9), characterized in that it comprises a step of removing 6) and that the disposal area (36) includes a plating bar (18).

[0027]

As described above, according to the present invention, it is possible to prevent a short circuit of a contact pad or the like and accurately perform a plating process, and then easily discard a discard area such as a bar used for plating. It is possible.

[Brief description of drawings]

FIG. 1 is a partial plan view of a printed wiring board showing a configuration for connecting a contact pad to a plating bar.

FIG. 2 is a partial plan view of a printed wiring board showing another configuration for connecting the contact pad to the plating bar.

FIG. 3 is a partial plan view of a printed wiring board that is an embodiment of the present invention.

FIG. 4 is an enlarged perspective view of FIG.

5 is a sectional view taken along line 5-5 of FIG.

FIG. 6 is a partial cross-sectional view of FIG. 5, which is plated.

FIG. 7 is a cross-sectional view of a printed wiring board that is another embodiment of the present invention.

[Explanation of symbols]

12: Printed wiring board, 14: Disposal area 18: Plating bar, 22, 23, 122, 123:
Contact pad 32: Circuit area, 34: Inner track 40: Via, 50, 52: Inner layer 118, 119: Plating bar, 140, 141: Blind via 150, 152: Inner layer

Claims (3)

[Claims] 1. A method of electrically connecting a contact pad disposed on an outer surface of a printed wiring board and a plating bar, wherein a conductive track is formed inside the printed wiring board, and the conductive track is formed. A first end located near the plating bar and a second end located near the contact pad, the plating bar comprising a first end of the conductive track. A conductive via is formed between the contact pad and the second end of the conductive track, the conductive via electrically connecting the plating bar and the conductive track. A second conductive via is formed therebetween, the second conductive via electrically connecting the contact pad and the conductive track, and a contact pad of a printed wiring board and a plating bar. Connect How to. 2. A printed wiring board having two opposing surfaces, a first contact pad disposed on one of the two opposing surfaces and a first contact pad disposed on one of the two opposing surfaces. Plating bar, a first conductive track provided inside the printed wiring board, the conductive track, a first end located near the first plating bar, and the contact. A second end located near the pad, extending between the first plating bar and the first end of the first conductive track, the first plating bar and A first conductive via electrically connecting the first conductive track; extending between the first contact pad and a second end of the first conductive track; Electrically connecting the first conductive track Printed circuit board composed of a second conductive via. 3. A method of plating a contact pad located on the outer surface of a printed wiring board, comprising: a first end located near the plating bar and a second end located near the contact pad. With a first end at the first
A conductive track electrically connected to the plating bar by a conductive via of, and having a second end connected to the contact pad by a second conductive via, inside the printed wiring board, The contact pad and the plating bar disposed at a certain distance from the contact pad are electrically connected, and the contact pad is immersed in an electroplating solution containing a plating material to form the plating bar and the electroplating solution. A plating method comprising connecting a voltage source between the electrodes to deposit a plating material on the surface of the contact pad, and removing the contact pad from a plating solution.