JPH0710977U - Dummy land for bridge prevention - Google Patents

Abstract

(57) [Abstract] [Purpose] This is a dummy land that prevents a bridge that solder sticks across narrow lands when soldering a printed circuit board by the flow method, and a bridge that changes depending on the soldering conditions It can be installed according to the location. [Structure] In the dummy land 1 of the present invention, a sticking agent 3 such as an adhesive or an adhesive is applied to one surface of a copper foil 2, and a release paper 4 is stuck thereon.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a material that does not generate a bridge between adjacent lands when a printed circuit board is flow-soldered.

[0002]

[Prior art]

 There are a trowel method, a reflow method, and a flow method as a method for soldering a printed circuit board.

In the troweling method, an operator holds the soldering iron in one hand and the wire soldering in the other hand, puts the wire soldering on the soldering portion, and applies the soldering iron from the top of the soldering iron. This is a method of soldering by melting the solder. This trowel method is extremely poor in productivity because soldering is performed at each soldering portion. Therefore, the troweling method is used today for the soldering of post-mounting parts and for repairing soldering defects such as bridges and unsolders generated by other soldering methods.

In the reflow method, a solder paste is printed and applied to a soldering part of a printed circuit board by a screen or a metal mask, or a discharge is applied by a dispenser, and then a reflow furnace, an infrared irradiation device, a laser irradiation device, a high temperature steam device. It is a method of soldering by heating with a heating device such as. This method is excellent in productivity because the solder paste can be applied to a large number of soldering points in a rational manner, but the solder paste is expensive because it takes time to prepare the solder paste. However, since the solder paste application device and heating device are also expensive, they are not suitable for inexpensive home appliances.

The flow method is a method of collectively soldering with an automatic soldering device. As shown in FIG. 5, the automatic soldering device is equipped with a processing device such as a fluxer F, a preheater H 2, a jet solder bath S, and a cooler C, and the soldering is performed in the direction of arrow A. The flux is applied to the printed circuit board P by a fluxer, preheated by a preheater, solder is attached by a jet solder bath, and cooled by a cooler. This flow method is extremely productive because it allows soldering at a large number of soldering points by passing the printed circuit board through an automatic soldering device once, and the solder used here is It is inexpensive because it does not take time and effort like solder paste. Therefore, the flow method is most commonly used for soldering printed circuit boards used in home appliances such as televisions, videos and radios.

[0006]

[Problems to be solved by the device]

 By the way, recent home appliances tend to be light, thin, short, and small, so many electronic components are mounted on this printed circuit board at high density, and the land spacing for soldering electronic components is also very narrow. ing. When a printed circuit board with a narrow land interval is soldered by the flow method, a large number of so-called "bridges", in which solder is attached to adjacent lands, will occur. If a printed circuit board has a bridge, the electric circuit will be short-circuited and will not function as an electric product at all, resulting in a defective product.

Therefore, the printed circuit board soldered by the flow method must be inspected for bridging after soldering. Although this inspection was performed visually by the operator, it was a very tiring task for the operator because there were many soldering points and they were small and the solder was shiny and difficult to see.

If the inspected printed circuit board had a bridge, the operator had to correct the bridge with a soldering iron. In this modification work, the bridge is melted with a soldering iron and the excess solder attached to the land is attached to the soldering iron and removed.However, even if the bridge is melted, another solder is attached near the land where the bridge is formed. Since the lands were close to each other, the molten solder sometimes adhered to another land and formed a bridge there.

Although the flow method is superior to other soldering methods in terms of productivity and economy, it also has a problem that bridges often occur, and many of these solutions have been solved. Has been desired by users of.

Conventionally, as a solution to the bridge in the flow method, a land having a large area has been formed in the vicinity of the land. This large land has nothing to do with the mounting of electronic components and is merely for preventing bridges, and is called a "dummy land".

If dummy lands are installed in the vicinity of a large number of lands that are in close proximity to each other, a large amount of a large amount of land will be produced immediately after the printed circuit board immersed in the molten solder comes out of the molten solder during soldering by the flow method. Molten solder adheres to the lands and bridges between adjacent lands. However, if there is a dummy land in the vicinity of this, a large amount of the molten solder that has adhered is pulled by the dummy land having a large area and no bridge is formed.

In the conventional dummy land, assuming a location where a bridge is generated from the stage of designing a printed circuit board, the dummy land has been installed on the printed circuit board in advance at that location. In other words, the dummy land was installed from the beginning like other lands, and the position of the dummy land could not be changed.

[0013]

[Problems to be solved by the device]

 By the way, in the flow method, in order to maximize the soldering condition of the printed circuit board, the conditions such as the jet flow state of the jet solder, the flux coating state on the fluxer, the traveling speed of the printed circuit board, the traveling direction of the printed circuit board, etc. can be changed appropriately ing. If the conditions change in this way, the location of the bridge will naturally change. Generally, a bridge is likely to occur on the last land in the printed circuit board traveling direction, so a dummy land is installed near the last land at the stage of designing the printed circuit board. However, it may be necessary to change the traveling direction of the printed circuit board depending on the engagement state of the transfer claws during soldering. If the running direction of the printed circuit board is changed in this way, the dummy lands previously installed on the printed circuit board will lose their effect.

Therefore, it is desirable to install the dummy land in a place where bridging is likely to occur depending on the soldering conditions. However, as described above, the conventional dummy land was originally installed on the printed circuit board. And, it was not useful for eliminating the bridge. An object of the present invention is to provide a dummy land that can be appropriately installed in a place where bridging is likely to occur even if the soldering conditions and the running direction of the printed circuit board change.

[0015]

[Means for Solving the Problems]

 The present invention is a dummy land for a printed circuit board, characterized in that a heat-resistant adhesive is applied to one surface of a copper foil, and release paper is attached to the adhesive.

The adhesive of the present invention may be a peelable pressure-sensitive adhesive or an adhesive that is difficult to peel off. After soldering, the dummy land using adhesive can be removed if it interferes with the electrical circuit or if it is not aesthetically pleasing, and the dummy land using adhesive has dummy land remaining. However, if there is no problem, remove the trouble of peeling and leave it as it is.

The heat-resistant adhesive material used for the dummy land of the present invention comprises an acrylic resin as a main component, and a heat resistance-imparting component such as a silicon-acrylic copolymer contained in or copolymerized with the acrylic resin. Resin-based materials are suitable.

Epoxy resin is suitable as the adhesive used for the dummy land of the present invention.

The copper foil used in the present invention may have any thickness, but a thickness that is easy to handle for cutting and pasting is appropriately selected. The easy-to-handle copper foil thickness is 0.03 to 0. About 5 mm is suitable.

[0020]

【Example】

 FIG. 1 is a front sectional view of a dummy land of the present invention. The dummy land 1 of the present invention comprises a copper foil 2, an adhesive 3 and a release paper 4.

A release paper 4 is attached to the copper foil 2 via a fixing agent 3. Release paper is attached to the adhesive, but when peeled off, it is easily peeled off from the adhesive. The release paper used in the present invention is preferably a paper laminated with polyethylene, coated with silicon, and then heat-treated.

The dummy land of the present invention may have a sheet shape as shown in FIG. 2, a tape shape as shown in FIG. 3, or a pellet shape as shown in FIG. Cut sheet-shaped and tape-shaped dummy lands into appropriate sizes and attach them near the land where bridges are likely to occur. Further, since the pellet-shaped dummy land is simply peeled off from the release paper and attached to the printed circuit board, there is no need to cut it.

Next, the installation of the dummy land of the present invention and the state where the printed circuit board is free of the bridge during soldering will be described.

FIG. 6: A large number of lands 5 a and 5 b are installed on the printed circuit board P. Holes are bored in these lands, and leads 6 of electronic parts are inserted into the holes. Figure 7: When the printed circuit board P is run in the direction of arrow A, a bridge is likely to occur between the land 5a, which is the last in the running direction, and the land 5b that is close to it. , Stick the dummy land 1 of the present invention further behind it. This dummy land 1 must be larger than the area of the land 5a. FIG. 8: After the dummy land 1 is attached to the printed circuit board P, when the molten solder bath S of the automatic soldering device of FIG. 5 is passed, the molten solder 7 is immediately between the lands 5b and 5a and the dummy land 1. Adheres across. FIG. 9: However, since the molten solder is drawn toward the larger amount, among the molten solder deposited across the lands 5a and 5b, first, the molten solder deposited on the land 5b but the dummy land 1 and the land It is pulled toward 5a, and the gap between land 5a and land 5b is cut. FIG. 10: Next, of the molten solder adhered across the land 5a and the dummy land 1, the molten solder of the land 5a is drawn by the molten solder 7 of the dummy land 1, and the molten solder between them is cut.

When sticking the dummy land to the printed circuit board, if the dummy land has a large sheet shape or a long tape shape, simply peel off the copper foil from the release paper, then cut it into appropriate sizes with scissors and stick it. That's a simple task. In addition, the pellet type can prevent the bridge of the printed circuit board by the simpler work of peeling it off from the release paper and attaching it.

[0026]

[Effect of device]

 The dummy land of the present invention can be attached in the vicinity of the bridging point even if the bridging point changes due to changes in the soldering conditions of the printed circuit board. It is versatile in that it can prevent the occurrence of.

[Brief description of drawings]

FIG. 1 is a side sectional view of a bridge preventing dummy land of the present invention.

FIG. 2 is a perspective view of a sheet-shaped dummy land for bridge prevention according to the present invention.

FIG. 3 is a perspective view of a tape-shaped bridge-preventing dummy land of the present invention.

FIG. 4 is a perspective view of a pellet-like dummy land for preventing bridges of the present invention.

FIG. 5 is a schematic view of an automatic soldering device.

FIG. 6 is a plan view of the printed circuit board before a dummy land is installed.

FIG. 7 is a plan view of the printed circuit board after the dummy land is installed.

FIG. 8 is a diagram illustrating a state of the bridge immediately after leaving the molten solder bath.

FIG. 9 is a diagram illustrating a state in which a bridge is broken.

FIG. 10 is a diagram illustrating a state in which a bridge is completely cut off.

[Explanation of symbols]

 1 Dummy land 2 Copper foil 3 Adhesive 4 Release paper 5a, 5b Land 7 Molten solder

Claims (6)

[Scope of utility model registration request] 1. A dummy land for bridge prevention, characterized in that a heat-resistant adhesive is applied to one surface of a copper foil, and release paper is attached to the adhesive. 2. The dummy land for bridge prevention according to claim 1, wherein the copper foil has a sheet shape. 3. The bridge preventing dummy land according to claim 1, wherein the copper foil has a tape shape. 4. The bridge preventing dummy land according to claim 1, wherein the copper foil has a pellet shape. 5. The dummy land for bridge prevention according to claim 2, wherein the adhesive is a peelable adhesive. 6. The dummy land for bridge prevention according to claim 2, wherein the adhesive is an adhesive that is difficult to peel off.