JPH01170090A - Soldering - Google Patents

Abstract

PURPOSE:To prevent a chip component from deviating in position and uprising by a method wherein a dam formed of a material which is hard to get wet with a soldering flux is provided surrounding a soldering land. CONSTITUTION:A dam 4 formed of a material which is mutually insoluble in a flux contained in a soldering paste and hard to spread wetting is provided to a boundary between a solder resist 5 and a soldering land 3 both formed on a base material 6, and a soldering paste is localized on the soldering land 3. Therefore, when a chip component or others are soldered onto a printed wiring board through a flow or a reflow soldering, an adverse effect caused by flux which flows out of the soldering land 3 can be prevented. By these processes, a chip component and the like are prevented from deviating in position and uprising, so that a non-defective soldered product can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the formation of soldering lands on a printed wiring board suitable for reflow soldering surface-mounted chip-like components such as resistors and capacitors to the printed wiring board. Regarding the method.

[Conventional technology]

Hybrid Circuit Vol. 9 (January 1986), pages 9 to 12, describes how to solder surface mount components such as resistors and capacitors onto a conventional printed wiring board.
Page (Hybrid C1rcuits No. 9 (J
annual 1986) pp9-123,
An infrared reflow soldering method is discussed.

Also, Electronic Packaging and Production Vol. 25, No. 2 (February 1985), pages 96 to 99 (E 1 electronic packaging and production)
ng & Production vol, 25. No
, 2 (February 1985) pp96-9
9) discusses the problems of wave soldering technology for surface mount components.

These conventional methods of soldering surface mount components on a printed wiring board include lands for lead soldering of surface mount chip components on a printed wiring board, such as a wiring circuit board formed by etching a copper-clad laminate. A commonly used method is to surround the land with a solder resist and then solder surface-mounted components to the land. This solder resist is adapted for use in flow soldering, and is often made of an insulating organic film material that must be at least compatible with the flux so that the flux spreads uniformly over the entire surface during soldering. , etching followed by printing, photopolymerization, or heat curing. However, this solder resist is also used in reflow soldering, which is one of the causes of the following soldering defects.

In other words, in many methods of reflow soldering chip components, solder paste is supplied onto the reflow soldering land using a print or dispenser, and after the chip component is mounted, the paste is melted using an appropriate heating method and soldered. It's a method. In this method, in addition to being caused by non-uniform temperatures and non-uniform solder supply amounts, flux in the paste flows out around the lands to be soldered. For this reason, solder is drawn to this, causing the chip components to be misaligned as shown in Figure 5, and furthermore, the solder is soldered to only one side of the bidirectional land first, as shown in Figure 4. However, there was a problem in that a defect occurred in which the chip component stood up.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional technology, the solder resist and flux are compatible.

This promotes the flow of flux onto the solder resist, which may attract solder and cause the chip-shaped components to shift, or the chip may be soldered to only one side of the bidirectional land in advance. There was a problem in that defects such as shaped parts standing up occurred.

An object of the present invention is to solder surface-mounted chip-like components to a printed wiring board or the like.

The present invention relates to a method for soldering surface-mounted components onto a printed wiring board without causing defects such as misalignment of chip-shaped components or rising of chip-shaped components.

[Means for solving problems]

The object of the present invention is to prevent the flux in the solder paste from forming at the boundary between the solder resist formed on the base material and the soldering land when reflow soldering chip-like components onto a printed wiring board or the like. We provide a weir body made of compatible materials that do not spread easily.
By localizing the solder paste onto the soldering lands.

achieved.

Note that one solution to the problem is to replace the entire solder resist with a material that is incompatible with flux, but this is limited only to reflow soldering applications.

However, in general, a process that uses flow soldering in combination is required, so as a solution that does not directly affect flow soldering, localized soldering, in which the solder paste described above is localized on the soldering land, is used. We need a method.

[For production]

The barrier body provided between the soldering land and the solder resist localizes the flux component, which melts at a low temperature by heating the solder paste and begins to foam and spread, onto the soldering land on the inner periphery of the barrier body. make it exist Furthermore, when the solder alloy is heated to a temperature at which it melts, the flux of the molten solder remains on the inner periphery of the weir, so that the solder is not drawn outside the land. Figure 5 is.

This shows a case in which flux flows out of the soldering land when there is no conventional barrier, and the solder is pulled in this direction, causing the chip-shaped component to shift its position. In extreme cases, the chip-shaped component can stand up. It shows. Therefore, it is necessary to prevent the flux from flowing onto the solder resist, and in the soldering method of the present invention, the weir body provided on the soldering land exhibits an extremely effective effect.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in more detail based on the drawings.

(Example 1) FIG. 1 is a plan view showing an example of the configuration when chip-shaped components are soldered onto the printed wiring board of the present invention.
The figure is a side view showing the side of FIG. 1.

In the figure, a bidirectional land 3 made of copper foil formed on a base material 6 of a printed board is surrounded by a solder resist 5. This solder resist 5 may overlap the two-way land 3. The present invention includes a weir body 4 made of a material that is difficult to get wet with flux at these boundaries so as to surround the two-way land 3. are doing. The electrode 2 of the chip-shaped component 1 is naturally mounted within the weir body 4. Considering the manufacturing process of copper-clad laminates, we adopted a method of resist printing and printing and supplying the barrier body after curing, and urethane was used as the material for the barrier body, taking into consideration the heat resistance and insulation properties of reflow soldering. Paint was used.

Of course, if these required characteristics are satisfied,
The material for the weir body is not limited to urethane paint.

(Embodiment 2) As another embodiment of the present invention, as shown in FIG. 3, the weir body 8 is constructed of a metal material that is difficult to get wet with solder or flux by a method of individually surrounding the tops of the two-way lands 3. ing. As a result of considering the possibility of supplying such a material by plating after the copper foil etching process, it was found that nickel plating containing boron was suitable. The reason for this is that a film with a high boron concentration is formed on the nickel plating surface, which prevents the flux from getting wet.

What are the effects of using a metal material for the weir body 8?

It has the advantage that its electrical conductivity does not adversely affect the performance of the printed wiring board.

Furthermore, it goes without saying that in the method of the first embodiment, it is also effective to construct a weir body that individually surrounds the two-way land 3.

〔Effect of the invention〕

As explained in detail above, in the method of reflow or flow soldering of chip components etc. on a printed wiring board of the present invention, troubles such as leakage of flux outside the soldering land are prevented, and as a result, chip components etc. It is possible to prevent positional displacement and rise after soldering, and a defect-free soldered product can be obtained.

In addition, in the soldering method of the present invention, the defect rate for rising of chip components, which was approximately 0.15% in the conventional method, can be reduced to 0.01% or less. In addition, the flux content in solder paste is generally 7 to 1 (wt,%), but since a large amount flows out onto the solder resist, in conventional methods, it is difficult to use an excess amount than is necessary for soldering. The viscosity of the solder paste decreases when the amount of flux is large, so conventional methods have problems with viscosity adjustment and stability, and drips are likely to occur after supplying the solder paste.1 stick According to an example of the method of the invention, it was possible to reduce the flux from 10 wt% to about 7 wt%, and it was possible to obtain a high-quality soldered product without any blemishes.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration when chip-shaped components are soldered onto a printed wiring board in Embodiment 1 of the present invention, FIG. 2 is a side view showing the side view of FIG. 1, and FIG. FIGS. 4 and 5 are a plan view showing the arrangement of soldering lands and dams of a chip-shaped component in Example 2 of the invention, and FIGS. 4 and 5 are explanatory diagrams showing soldering defects of a conventional chip-shaped component. DESCRIPTION OF SYMBOLS 1... Chip-shaped component, 2... Electrode, 3... Bidirectional land, 4... Weir body, 5... Solder resist,
6... Base material, 7... Solder, 8... Weir body, 9...
··flux. Broom 1st time 2nd Broom 5th time!・-Chimisaki Pubushi-91s & 2- Electrode 3-m-Two-way land 7---ttAJtε゛9----7 Fu Nogu person

Claims (3)

[Claims] 1. In the method of soldering the above-mentioned surface-mounted components by forming a plurality of soldering lands, which are areas for soldering surface-mounted components, on the printed wiring board, one or more soldering lands are formed for the above-mentioned soldering lands. A weir body that surrounds the plurality of soldering lands and is made of soldering flux and a material that is difficult to wet is provided near the periphery of the soldering lands to prevent soldering of the surface mount components. A soldering method characterized by: 2. The soldering method according to claim 1, wherein the soldering method is a flow or reflow soldering method. 3. 3. The soldering method according to claim 1, wherein the weir body is made of a urethane resin or a nickel alloy containing boron.