JPS60149190A - Chip part for soldering printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to chip components for printed wiring board soldering, and particularly to chip components that are electrical components having leadless electrodes mounted on printed wiring boards with high packaging density. This invention relates to a solder land and a solder wetting prevention film provided on the upper surface that is not soldered to prevent solder bridges from occurring between the electrodes of adjacent chip components when the mounted chip component is soldered.

In general, printed wiring boards are made by etching copper foil pasted onto the surface of a laminate to form a circuit pattern according to an electrical circuit, and to which electrical components such as resistors and capacitors can be attached. To attach these electrical components, their terminals are soldered to the lands of the circuit pattern.

In this case, the circuit pattern is formed on the opposite side of the printed wiring board to which the electrical components are attached, and the circuit pattern is formed on the opposite side of the printed wiring board to which the electrical components are attached. There is a so-called planar mounting type with a land.

In this planar mounting, chip components of electric elements are mounted on printed wiring boards such as thick film IC circuit boards and copper-clad laminates. This printed wiring board is
For example, as shown in Fig. 1, soldering made of copper foil on board a is formed with lands 1 and 1', lands 2 and 2°, and lands 3 and 3' in pairs, and the other boards are An insulating coating film 4 is provided on the surface. On the other hand, the chimp part is shaped like a rectangular parallelepiped, and the four peripheral surfaces and end faces of both ends are electrodes. In order to solder this chip component to the printed wiring board, flow soldering is used.

As shown in Figure 2, 1) the printed wiring board is carried into an automatic chip component mounting device, and 2) for example, when soldering this printed wiring board, an adhesive is applied to the insulating coating between lands 1 and 1'. The adhesive is applied using a screen printing method or a dispenser method, then the chip parts are supplied and held in place with this adhesive, and then the chip parts are temporarily fixed by heating or irradiating ultraviolet rays to harden the adhesive. Attach electrical parts with lead terminals as necessary.

■Then, for automatic soldering, turn the printed wiring board upside down, carry it into the equipment, apply fluffx, and apply this fluffx so that the chip components come into contact with the molten solder spouted from the solder supply device. 1. Solder the electrodes of the chip components in the specified manner. It is soldered to l. This soldered state is
As shown in FIG. 3, the solder adheres only to the electrodes made of metal materials and the solder joints because they wet the lands well, but the manner in which the solder adheres is different on both sides and on the top surface of the electrodes. This is because molten solder is supplied between both sides of the electrode and the end surface of the land, so this molten solder wets the electrode and the land well, so the intermediate part between the two forms a concave shape on the contact side of the two. In contrast to the concave shape, molten solder wetted on the top surface of the electrode spreads only on this top surface, and its surface tension causes it to curl up and protrude at the edges. When this happens, the mounting density of chip components increases, and the soldering shown in Figure 1 is performed using lands 1°2.3 and 1.
For example, the distance between ゛, 2°, and 3゛ is 0.5 u.
When the size becomes small, the molten solder protruding from each electrode of adjacent chip components comes into contact with each other and creates a solder bridge.

If this happens, a short circuit will occur, resulting in defective soldering, which will require manual correction later. Since this reduces work efficiency, it has been desired to improve it.

Therefore, in the past, when chip components are soldered onto a printed wiring board, especially when the packaging density is high, solder bridges may occur between the electrodes of adjacent components, which requires a lot of effort to correct. In order to improve the problem of soldering, we provide an electrical component for soldering on a printed wiring board, which has a solder wetting prevention film that repels solder on the top surface of the chip component, thereby reducing the formation of solder bridges. be.

In the present invention, the solder wetting prevention film refers to a coating film that repels molten solder without getting wet when soldering, and a commonly used solder resist can also be used for this. For example, solder resist 5R-31G, solder resist 5R-51G manufactured by Tamura Kaken Co., Ltd.
7r tocoat υSR-IG, 7t tocoat USR-
2G and Photocoat USR-3G are exemplified.

More preferably, a silicone-based or fluorine-based surfactant such as silicone oil, silicone-based polymer, fluorinated silicone oil, fluorinated silicone resin, or fluorinated hydrocarbon-containing polymer is added to the solder resist. . Examples of the surfactant composition include the following.

Silicon-based Po1on L, Po1on T, KPO3, KS-7
00, KS-701, MS-707, MS-705F,
MS-706, KS-709, MS-709S, M
S-711゜KSX-712, MS-62P, KS-
62M, KS-64,5ilicolube G-4
30+ 5ilicolube G-54(L 5il
Icolube G-541 or higher manufactured by Shin-Etsu Chemical Co., Ltd.

5ll-200, 5H-210, 5H-1109, 5R
-3109,5H-3107,5H-8011,FS-
1265,5yli-off23. DCpan Gla
ze 620 or higher Manufactured by Toray Silicon ■.

Fluorine-based Guifree MS-443, MS-543, MS-743
, MS-043, ME-413, ME-810 and above Daikin Industries type.

Florado FC-93, FC-95, PC-98, FC
-129,FC-134゜FC-430,FC-431
, PC-721 and above are manufactured by Sumitomo 3M.

Sumiflunon FP-81, FP-81R, FP-82,
PP-84C, FP-84R, FP-86 and above are manufactured by Sumitomo Chemical Co., Ltd.

7 o ySR-100, 5R-100X or higher Manufactured by Kiyomi Kagaku Co., Ltd.

The surface tension of these surfactant compositions is, for example, 6 to 20 dyn/c+n (according to the Dunoy method described below). Other surfactants having such surface tension or compositions of mixtures of the above-mentioned surfactants and other surfactants can also be used. These surfactants include not only polymeric surfactants but also low molecular surfactants.

The above-mentioned surfactant composition is a surfactant or a mixture of the surfactant and a solvent, but a mixture of the surfactant of these compositions and/or another surfactant with a solvent may also be used. Diluted versions of the above surfactant compositions may also be used. As a solvent for this purpose, a solvent that dissolves or disperses the surfactant and imparts coating properties is used. This solvent is preferable because it evaporates after coating and eliminates the stickiness of the film left behind. Other properties of this solvent include:
It is preferable that the above composition be able to wet the printed wiring board surface well when it is applied. As such,
1,1.1 A halogenated hydrocarbon solvent such as 1-lychloroethane is preferred.

The surfactant concentration of the above surfactant composition is
: 0.1 to 5% by weight for In-type, 0.01 to 2% by weight for Fluorine-based
Weight percent is preferred.

In order to form the above solder wetting prevention film, it may be formed by applying only the above surfactant composition or a solder resist containing this surfactant composition or this surfactant composition. In either case, a resin or a material containing a lubricant or other additives that become slicker after film formation can be used. Among these, those containing resin are also useful in reducing the stickiness of low-molecular surfactants.

The above-mentioned composition used when forming the solder wetting prevention film of the present invention is applied to the upper surface of the electrode of the chip component. This coating method includes spraying, brushing, a method of jetting the coating material and bringing the printed wiring board into contact with it,
There are methods such as scraping off the coating material adhering to the roll with a doctor knife and applying it to the upper surface of the chip component, foaming the coating liquid and bringing the upper surface of the electrode of the chip component into contact with the bubbles, and screen printing. This coated material is
It is dried by an appropriate means. This forms a film.

The chip component with the solder wetting prevention film formed on the electrode in this way is soldered as shown in Figure 1. At this time, the top surface of the electrode of the chip component is repelled from the molten solder, so this part Do not touch the same soldered part of the adjacent WB product with the beam.

Next, an embodiment of the present invention will be described based on FIGS. 4 and 5 while referring to FIGS. 1 and 2.

Example 1 In FIG. 4, a square chip resistor 11 (length 3.2
Electrodes 1 at both ends of mm, width 1.6fi, thickness 0.5M)
A paint having the following composition was applied to 1a11a by brushing and dried to form a solder wetting prevention film 12 with a thickness of 104 m. Fifty similar chip resistors having such a solder wetting prevention film formed thereon are prepared. On the other hand, for similar soldering in which the spacing of L in Fig. 1 is 0°511 m, a printed wiring board having 50 sets of lands is prepared, and the above-mentioned chip components are soldered to this printed wiring board by the process shown in Fig. 2. I attached it. As a result, soldering was performed as shown in FIG. 5, and not a single solder bridge was observed.

For comparison, a chip component without a solder wetting prevention film provided on the upper surface of the electrode was soldered in the same manner as above, and 21 solder bridges were observed.

In addition, although the anti-solder film was formed on the entire upper surface of the chip component in the above example, it may be formed by printing only on the upper surface of the electrode. Furthermore, a solder prevention film may be formed on both sides of the electrode, and in this case, it is possible to further reduce bridging defects.

As explained above, according to the present invention, since a solder wetting prevention film is provided on the unsoldered upper surface of the electrode of an electrical component, even when the electrical component is soldered to a printed wiring board with high mounting density, adjacent components It is possible to eliminate the occurrence of solder bridges between the electrodes. For this reason,
Soldering electrical parts not only reduces defects, but also
It also saves the trouble of manually correcting defective products, contributing to improved production efficiency.

[Brief explanation of the drawing]

Figure 1 is a plan view showing a part of a printed wiring board to which chip components are soldered, Figure 2 is an explanatory diagram showing the mounting process using a chip component mounting device and the soldering process using jet soldering, and Figure 3 is a conventional diagram. FIG. 4 is a perspective view of a chip component according to an embodiment of the present invention, and FIG. It is an explanatory view of a part of the soldered state. In the figure, 111' is a soldering land, 11 is a chip resistor, and 12 is a solder wetting prevention film. January 14, 1980 Patent applicant Ginya Ishii Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] (1) When soldering printed wiring boards, electrical components with leadless electrodes are soldered to lands.
A chip component for soldering on a printed wiring board, characterized in that a solder wetting prevention film is provided on at least the upper surface of the electrode on the side opposite to the side in contact with the soldering land.