JP2008085001A - Printed wiring board and electronic device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board which can avoid a solder wetting failure between a conductor layer of the printed wiring board and an electrode such as a lead of an electronic component with an excellent reliability in electric connection and with an eco-friendly environment even if an oxide of the lead-free solder is present on the surface of the solder when an electronic component is mounted to be electrically connected by flow soldering using a lead-free solder; and also to provide an electronic device having the printed wiring board. <P>SOLUTION: The printed wiring board has an electrically-insulating substrate, an electrically-conductive conductor layer formed on the surface of the substrate, and a solder resist part formed on a part of the surface of the substrate and on a part of the surface of the conductor layer. A soldered conductor layer is provided independently of the conductor layer having an electronic component mounted thereon in a flow soldering direction and in the vicinity of a tip of the printed wiring board having a flow soldering surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a printed wiring board in which electronic components are soldered and electrically connected, and an electronic apparatus having the printed wiring board.

Printed wiring boards used in various electronic devices are generally assembled after soldering and mounting electronic components on a conductor layer that conducts electricity formed on the surface of an insulating base material. Conventionally, the solder used for this soldering is so-called lead solder composed of tin and lead, and the molten solder adheres to the electrodes such as leads of electronic parts and the conductor layer of the printed wiring board and solidifies. Various electronic components are fixed on the printed wiring board.

However, in recent years, from the viewpoint of global environmental protection, electronic component mounting using so-called lead-free solder that does not contain lead, which is a heavy metal hazardous substance, has been adopted in the manufacture of electronic devices. Generally, the composition of lead-free solder is classified into tin + silver, tin + copper, tin + zinc and the like. And, for example, in the tin + silver-based lead-free solder, the melting point reaches 220 ° C., which is about 40 ° C. higher than the melting point of the conventional lead solder. Lead-free solder is becoming mainstream (see, for example, Patent Documents 1-3).

JP 2002-111189 A JP 2003-142810 A JP 2002-096163 A

However, when lead-free solder is used in the flow soldering method, which is a soldering method in which a printed wiring board carrying electronic components is in contact with the molten solder surface that is continuously flowing and circulating, lead-free solder flows and circulates. At the time of falling, the atmosphere is entrained, and the pump shaft of the circulating motor pump rotates in the molten solder, so that a large amount of lead-free solder oxide is generated.

The generation amount of the oxide of the lead-free solder is proportional to the content of tin, and the lead-free solder is about 1.8 to 2.0 times as compared with the case where the lead solder is used. When this lead-free solder oxide is present on the surface of the molten solder and is in contact with the printed wiring board, solder such as poor lead-free solder wetting between the conductor layer of the printed wiring board and the electrodes of the electronic component leads, etc. This is a concern that induces attachment defects and impairs the reliability of electronic devices using printed wiring boards.

Therefore, the present invention solves the above problems, and when an electronic component is soldered and mounted electrically by a flow soldering method using lead-free solder, an oxide of lead-free solder exists on the surface of the molten solder. Even in the state, the printed wiring board and the printed wiring which are excellent in the reliability of the electrical connection without causing the solder wettability between the conductor layer of the printed wiring board and the electrode such as the lead of the electronic component, etc., and friendly to the global environment An object is to provide an electronic device having a plate.

The invention described in claim 1 of the present invention is a printed wiring board that is electrically connected by soldering and mounting an electronic component by a flow soldering method using lead-free solder, a substrate having electrical insulation, It has a conductor layer that conducts electricity formed on the surface of the base material, and a solder resist portion formed on the surface of the base material and a part of the surface of the conductor layer, and has a flow soldering direction and flow soldering. The printed wiring board has a configuration in which a solder-attached conductor layer independent of the conductor layer on which the electronic component is mounted is provided in the vicinity of the front end portion of the printed wiring board on the surface.

According to a second aspect of the present invention, in the printed wiring board according to the first aspect, the solder-attached conductive layer independent of the conductive layer is mounted on the printed wiring board main body after soldering and mounting and before assembling the electronic device. It has the structure which consists of a printed wiring board provided in the discard board | substrate divided | segmented and removed.

Invention of Claim 3 of this invention is an electronic device which has a printed wiring board which solders and mounts an electronic component by the flow soldering method using lead-free solder, and is electrically connected, The said printed wiring The board includes a base material having electrical insulation, a conductor layer for conducting electricity formed on the surface of the base material, and a solder resist portion formed on the surface of the base material and a part of the surface of the conductor layer. A printed wiring having a solder-attached conductor layer independent of the conductor layer on which the electronic component is mounted in the flow soldering direction and in the vicinity of a tip portion of the printed wiring board on the flow soldering surface It has the structure which consists of an electronic device which has a board.

According to a fourth aspect of the present invention, in the electronic device according to the third aspect, the printed wiring board has the solder-attached conductor layer independent of the conductor layer mounted after soldering and before assembling the electronic device. It has the structure which consists of an electronic device which has the printed wiring board provided in the discard board | substrate divided | segmented and removed from the printed wiring board main body.

According to the present invention, even in the state where the lead-free solder oxide is present on the surface of the molten solder, the solder-attached conductor layer provided near the tip portion of the printed wiring board attaches and removes the lead-free solder containing the oxide, A clean lead-free molten solder surface makes it possible to achieve a good solder wetting state between the conductor layer of the printed wiring board and the electrodes of the electronic component, resulting in a global environment with excellent electrical connection reliability. A gentle printed wiring board and an electronic device having the printed wiring board can be provided.

The invention described in claim 1 of the present invention is a solder-attached conductor that is electrically independent from a conductor layer on which an electronic component is mounted in the flow soldering direction and in the vicinity of the tip portion of the printed wiring board on the flow soldering surface. Even when the lead-free solder oxide is present on the surface of the molten solder, the solder-attached conductor layer provided near the tip portion of the printed wiring board adheres the lead-free solder containing the oxide. Lead-free solder that is removed and cleaned can realize a good solder wet condition between the conductor layer of the printed wiring board following the solder-adhered conductor layer and the electrode such as the lead of the electronic component. It is possible to provide a printed wiring board having excellent electrical connection reliability without inducing defects.

The invention described in claim 2 of the present invention is a conductor layer of a printed wiring board that follows a solder-attached conductor layer by a lead-free solder in a clean state by a configuration in which the solder-attached conductor layer independent of the conductor layer is disposed on the substrate. A good solder wetting condition between the lead and the electrodes of the electronic component and at the same time, lead-free solder containing oxide is attached and removed. It becomes possible to divide and remove from the printed wiring board main body before assembly, and it is possible to provide a printed wiring board for electronic equipment with higher reliability.

The invention described in claim 3 of the present invention is a solder attachment that is electrically independent from the conductor layer on which the electronic component is mounted in the flow soldering direction and in the vicinity of the tip portion of the printed wiring board on the flow soldering surface. By configuring a printed wiring board with a conductor layer, even if lead-free solder oxide is present on the surface of the molten solder, the solder-attached conductor layer provided near the tip of the printed wiring board is oxidized first. Lead-free solder containing objects is attached and removed, and the lead-free solder in a clean state achieves a good solder wet condition between the conductor layer of the printed wiring board following the solder-attached conductor layer and the electrode such as the lead of the electronic component It is possible to provide an electronic apparatus having a printed wiring board with excellent electrical connection reliability.

According to a fourth aspect of the present invention, the conductor layer of the printed wiring board following the solder-adhered conductor layer is formed by a lead-free solder in a clean state by a configuration in which the solder-attached conductor layer independent of the conductor layer is disposed on the substrate. A good solder wet state between the lead and the electrodes of the electronic component and at the same time, lead-free solder containing oxide is attached and removed. It becomes possible to divide and remove from the printed wiring board main body before assembly, and it is possible to provide an electronic device having a printed wiring board with higher reliability.

(Example 1)
Embodiment 1 of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram of a printed wiring board in Embodiment 1 of the present invention. Hereinafter, the same components are given the same reference numerals, and the description of the reference numerals in each drawing is omitted. In FIG. 1, 11 is a printed wiring board, 11a is a main body of the printed wiring board, 13 is a solder-attached conductor layer, 15 is a conductor layer, 16 is a component hole, and 17 is a base material having electrical insulation.

2 is a cross-sectional view of the printed wiring board (XY portion in FIG. 1) in Embodiment 1 of the present invention. In FIG. 2, 14 is a solder resist portion, 15a is a conductor layer made of copper foil, and 15b is a conductor layer made of copper plating.

FIG. 3 is a solder resist diagram according to the first embodiment of the present invention. FIG. 4 is an example in which a solder resist portion is formed on the solder adhesion conductor layer in Example 1 of the present invention to limit the solder adhesion portion. In FIG. 4, reference numeral 14a is a solder resist diagram for limiting lead-free solder containing oxides attached to the solder-attached conductor layer.

FIG. 5 shows an example in which the solder adhesion portion is limited by etching when forming the conductor layer without forming the solder resist portion in Example 1 of the present invention. In FIG. 5, reference numeral 13 a denotes a solder attachment that limits the solder attachment portion 13 by an etching process when forming the conductor layer 15 without forming the solder resist portion 14 a that limits the lead-free solder containing oxide attached to the solder attachment conductor layer. It is a conductor layer.

FIG. 6 is a conceptual diagram showing a flow soldering method using lead-free solder in Example 1 of the present invention. In FIG. 6, 20 is a lead-free solder, 20a is a lead-free solder containing an oxide attached to a solder-attached conductor layer, 21 is a solder bath, 30 is an electronic component, and 30a is a lead of the electronic component.

The printed wiring board in the flow soldering method using the lead-free solder constituted as described above will be described below.

First, prior to the production of the printed wiring board 11, when the conductor layer 15 of the printed wiring board 11 is designed by design means such as CAD, the solder-adhered conductor layer 13 as shown in FIG. The main body 11a of the printed wiring board near the tip portion of the printed wiring board 11 on the flow soldering surface and in the flow soldering direction in the electronic component 30 mounting process in the flow soldering using the lead-free solder 20 with a width of 0 mm It is designed by arranging and applying to a portion independent of the conductor layer 15.

Next, the solder resist portion 14 is arranged and designed on the surface of the conductor layer 15 including the designed solder adhesion conductor layer 13 and the base material 17 having electrical insulation. The solder resist portion 14a for limiting the lead-free solder containing oxides attached to the solder-attached conductor layer as shown in FIG. 3 so that the solder resist portion 14 can be placed on the solder-attached conductor layer 13 at the time of placement and design. It is also possible to limit the solder adhesion part 13 by forming the solder adhesion part 13a by the etching process at the time of forming the conductor layer 15 without forming the solder resist part 14a as shown in FIG. It is also possible.

A production tool such as a production master film created based on the artwork master designed as described above is prepared, and production of the printed wiring board 11 is started. First, a base material 17 (for example, a glass cloth base material epoxy resin copper-clad laminate) having an electrical insulating property in which a conductor layer 15a composed of copper foil serving as a base of a conductor layer is disposed on both surfaces thereof has a predetermined size. Into a panel for manufacturing.

A plurality of the manufacturing panels are stacked, and a predetermined diameter and a predetermined number of holes to be used as a reference hole and a component hole 16 of the printed wiring board 11 are processed using an NC drilling machine, a drill bit, and the like, and then panel plating is performed. A conductor layer 15b constituted by copper plating is formed on the entire surface of the manufacturing panel including the hole wall processed by the method. The manufacturing panel in which the conductor layer 15b is formed by copper plating is then laminated with a photosensitive dry film on both sides and exposed to ultraviolet rays through the prepared manufacturing master film, followed by development, photosensitive drying. An etching resist is formed by a film.

In the manufacturing panel on which the etching resist is formed, the portion of the conductor layer 15 where the etching resist is not formed is chemically etched by a chemical solution such as cupric chloride, that is, etched, and after the etching resist is peeled off, electrical insulation is performed. 1 is formed on a conductive layer 15a made of copper foil serving as a wiring circuit and on a conductive layer 15b made of copper plating on the surface of the base material 17 having the property. . The manufacturing panel in which the conductor layer 15 and the solder-attached conductor layer 13 are formed has a solder resist portion 14 formed on the surface thereof. Simultaneously with the formation of the solder resist portion 14, it is possible to form a solder resist portion 14a for limiting the solder adhesion portion 13 as shown in FIG.

Next, the outer shape of the manufacturing panel is processed by a die or a drill bit, and as shown in FIG. 1, an electronic component is provided in the flow soldering direction and in the vicinity of the tip portion of the printed wiring board 11 on the flow soldering surface. The printed wiring board 11 provided with the solder adhesion conductor layer 13 independent of the conductor layer 15 to be mounted is completed.

Next, after the surface-mounted component is mounted on the completed printed wiring board 11, the electronic component 30 having the lead 30a is inserted into the component hole 16 and conveyed to the flow soldering process. The conveyed printed wiring board 11 is soldered and mounted by a flow soldering method using lead-free solder 20 in a flow soldering process. The printed wiring board 11 is applied with a preflux on its surface, and after drying, as shown in FIG. 6, the solder-attached conductor layer 13 is transported to the solder bath 21 at the top, first, in the solder-attached conductor layer 13, The printed wiring board 11 following the solder-adhering conductor layer 13 is formed by adhering the lead-free solder 20a containing oxide present on the surface of the jet of the molten lead-free solder 20 to form a molten lead-free solder 20 surface in a clean state. Soldering is performed between the conductor layer 15 of the main body 11 a and the electrodes such as the leads 30 a of the electronic component 30.

By this operation, the solder-attached conductor layer 13 provided in the vicinity of the tip portion of the printed wiring board 11 can attach and remove the lead-free solder 20a containing the oxide, thereby realizing a clean lead-free solder 20 surface. It is possible to realize a good solder wet state between the conductor layer 15 of the main body 11a of the printed wiring board 11 following the solder-attached conductor layer 13 and the electrodes such as the leads 30a of the electronic component 30. Thereafter, the printed wiring board 11 on which the electronic component 30 is soldered and mounted is incorporated into an electronic device such as a television receiver through a predetermined inspection process.

According to the present embodiment, the number of defects in soldering can be reduced by about 50% as compared with the conventional printed wiring board not provided with the solder adhesion conductor layer 13, and a nitrogen gas filling device is used in combination with the atmosphere. The soldering atmosphere can be reduced by about 97% by controlling the oxygen concentration to about 50 ppm.

In the present embodiment, the printed wiring board 11 is a double-sided through-hole printed wiring board, but it goes without saying that the same effect can be obtained even if it is a single-sided printed wiring board or a multilayer printed wiring board. Further, in the process of producing a small variety of printed circuit boards, since the printed wiring board 11 is small, there is a time gap until the next lot is soldered, during which solder oxide is easily generated. The invention can be a particularly effective means.

Furthermore, although a television receiver is taken as an example of an electronic device, the present invention is not limited to the above-described embodiment, and is not limited to this, but other types of electronic devices such as a personal computer and a machine. The printed wiring board of the present invention can be applied to any machine controller and other types of electronic equipment, that is, any electronic equipment using a printed wiring board on which electronic components are soldered and mounted. it can.

(Example 2)
Embodiment 2 of the present invention will be described below with reference to the drawings. In addition, the same structure as Example 1 is provided with the same code | symbol, and description of a code shall be abbreviate | omitted.

FIG. 7 is a conceptual diagram of the printed wiring board 11 according to the second embodiment of the present invention. In FIG. 7, 12a, 12b and 12c are discarded substrates provided integrally attached to the outer periphery of the printed wiring board main body 11a, and 13a, 13b and 13c are formed on each discarded substrate 12a, 12b and 12c. The solder-attached conductor layers 18a, 18b and 18c are V-cut portions for dividing the discarded substrates 12a, 12b and 12c.

FIG. 8 is a conceptual diagram showing a flow soldering method using lead-free solder in Example 2 of the present invention.

The printed wiring board in the flow soldering method using the lead-free solder constituted as described above will be described below.

First, prior to the production of the printed wiring board 11, when the conductor layer 15 of the printed wiring board 11 is designed by design means such as CAD, the solder-attached conductor layers 13a, 13b and 13c as shown in FIG. Waste soldering board in the vicinity of the tip part of the printed wiring board 11 on the flow soldering surface in the flow soldering direction in the electronic component 30 mounting process in the flow soldering using the lead-free solder 20 with a width of 0 to 3.0 mm Design by arranging and applying to 12a, 12b and 12c. Next, the conductor layer 15 including the designed solder adhesion conductor layers 13a, 13b, and 13c is arranged and designed.

When the solder resist portion 14 is arranged and designed, a solder resist portion 14a as shown in FIG. 4 is formed so as to be placed on the solder-attached conductor layer 13 in the same manner as in the first embodiment. 5 and 13c can be limited. Further, as shown in FIG. 5, the solder adhesion portions 13a, 13b and 13c are formed only on the conductor layer 15 by the etching process when forming the conductor layer 15 without forming the solder resist portion 14a. It is also possible to limit.

A production tool such as a production master film created based on the artwork master designed as described above is prepared, and production of the printed wiring board 11 is started. The following processes are the same as those in the first embodiment, and the printed wiring board is disposed on the discarded boards 12a, 12b and 12c in the flow soldering direction as shown in FIG. The printed wiring board 11 provided with the solder adhesion conductor layers 13a, 13b and 13c independent of the main body 11a is completed.

Next, after the surface-mounted component is mounted on the completed printed wiring board 11, the electronic component 30 having the lead 30a is inserted into the component hole 16 and conveyed to the flow soldering process. The conveyed printed wiring board 11 is soldered and mounted in the flow soldering step by the flow soldering method using the lead-free solder 20 in the same manner as in the first embodiment. The printed wiring board 11 is provided with a preflux on the surface, and after drying, as shown in FIG. 8, the solder-attached conductor layers 13a, 13b and 13c are transported to the solder bath 21 at the head, and first, the discarded boards 12a, 12b And the lead-free solder 20a containing oxide existing on the surface of the lead-free solder 20 jetted by the solder-attached conductor layers 13a, 13b and 13c provided on the lead-free solder 12c, and the surface of the molten lead-free solder 20 in a clean state The solder is applied between the conductor layer 15 of the main body 11a of the printed wiring board 11 and the electrodes such as the leads 30a of the electronic component 30 following the solder-attached conductor layers 13a, 13b and 13c.

With this operation, the solder-attached conductor layers 13a, 13b, and 13c provided on the discarded substrates 12a, 12b, and 12c in the vicinity of the tip portion of the printed wiring board 11 attach and remove the lead-free solder 20a containing oxide, and are in a clean state. The surface of the lead-free solder 20 can be realized, and the lead of the electronic component 30 and the conductor layer 15 of the main body 11a of the printed wiring board 11 following the solder-attached conductor layers 13a, 13b and 13c provided on the discarded substrates 12a, 12b and 12c. It becomes possible to realize a good solder wet state between the electrodes such as 30a. The printed wiring board 11 on which the electronic component 30 is mounted by soldering is subjected to a predetermined inspection process, and is disposed on the printed wiring board 11 to divide the discarded substrates 12a, 12b and 12c to which the lead-free solder 20a containing oxide is attached. , Removed and incorporated into electronic equipment.

According to this example, as in Example 1, the number of defects in soldering defects can be reduced by about 50% compared to a conventional printed wiring board not provided with a solder-adhering conductor layer. By using a gas filling device in combination and controlling the soldering atmosphere to an oxygen concentration of about 50 ppm, an effect of reducing about 97% can be obtained. In addition, since the solder-attached conductor layer provided on the discarded substrate to which the lead-free solder containing oxide is adhered can be divided and removed together with the discarded substrate, a more reliable electronic device can be realized.

The present invention is useful when applied to a soldering mounting between a conductor layer of a printed wiring board and an electrode such as a lead of an electronic component by a flow soldering method using lead-free solder.

The conceptual diagram of the printed wiring board in Example 1 of this invention. The cross-sectional enlarged view of the printed wiring board (XY part in FIG. 1) in Example 1 of this invention. The soldering resist figure in Example 1 of this invention. The figure which shows the example which formed the solder resist part in the solder adhesion conductor layer in Example 1 of this invention, and limited the solder adhesion part. The figure which shows the example which limited the solder adhesion part by the etching at the time of formation of a conductor layer, without forming the soldering resist part in Example 1 of this invention. The conceptual diagram which shows the flow soldering method using the lead-free solder in Example 1 of this invention. The conceptual diagram of the printed wiring board in Example 2 of this invention. The conceptual diagram which shows the flow soldering method using the lead-free solder in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Printed wiring board 11a Printed wiring board main body 12a Discard substrate 12b Discard substrate 12c Discard substrate 13 Solder adhesion conductor layer 13a Solder adhesion conductor layer 13b Solder adhesion conductor layer 13c Solder adhesion conductor layer 14 Solder resist conductor 14a Lead-free solder containing oxide Solder resist portion 15 for limiting conductor layer 15a Conductor layer 15b constituted by copper foil Conductor layer 16 constituted by copper plating Component hole 17 Base material 18a having electrical insulation V-cut portion 18b for separating discarded substrate V-cut portion 18c for dividing the discarded substrate V-cut portion 20 for dividing the discarded substrate 20 Lead-free solder 20a Lead-free solder 21 containing oxide adhering to the solder-attached conductor layer Solder bath 30 Electronic component 30a Electronic component lead

Claims (4)

In a printed wiring board that is electrically connected by soldering and mounting electronic components by a flow soldering method using lead-free solder, the base material having electrical insulation is electrically connected to the electricity formed on the surface of the base material. And a solder resist portion formed on the surface of the base material and a part of the surface of the conductor layer, and in the flow soldering direction and in the vicinity of the tip portion of the printed wiring board on the flow soldering surface. A printed wiring board comprising a solder-attached conductor layer independent of the conductor layer on which an electronic component is mounted. 2. The printed wiring board according to claim 1, wherein the solder-attached conductive layer independent of the conductive layer is provided on a discarded board that is separated and removed from the printed wiring board main body after assembly by soldering and before assembly of the electronic device. An electronic apparatus having a printed wiring board that is electrically connected by soldering and mounting an electronic component by a flow soldering method using lead-free solder, the printed wiring board comprising a base material having electrical insulation, It has a conductor layer that conducts electricity formed on the surface of the base material, and a solder resist portion formed on the surface of the base material and a part of the surface of the conductor layer, and has a flow soldering direction and flow soldering. An electronic apparatus having a printed wiring board, wherein a solder-attached conductor layer independent of the conductor layer on which the electronic component is mounted is provided in the vicinity of a tip portion of the printed wiring board on the surface. 4. The printed wiring board according to claim 3, wherein the solder-attached conductive layer independent of the conductive layer is provided on a discarded board that is separated and removed from the printed wiring board main body after mounting by soldering and before assembly of the electronic device. Electronic device having a printed wiring board.

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