CN1080082C - Printed circuit board - Google Patents

Abstract

In order to reliably absorb and hold the extruded solder when the chip component is fixed, the printed circuit board provided by the present invention includes a substrate for fixing the chip component, an electrode island welded to the electrode part of the chip component with solder, and a The solder absorbing island protrudes slightly below the chip components, and there is a specific gap between the solder absorbing island and the electrode island. The present invention provides a printed circuit board in which the upper part of the wiring pattern is used as a solder absorbing island, a solder mask is covered on an area other than the area corresponding to the solder absorbing island and an electrode island, and the solder absorbing island is provided with through holes.

Description

A printed circuit board

The present invention relates to a printed circuit board on which electrode portions and electrode islands of chip components are connected.

Chip components including resistors and capacitors used to form a specific circuit are fixed on a printed circuit board with a specific wiring diagram in advance, and are connected to the electrode islands on the printed circuit board substrate by reflow soldering.

1A to 1C are cross-sectional views illustrating connection states of a conventional printed circuit board and chip components, respectively.

As shown in FIG. 1A, a conventional printed circuit board 1 includes an insulating substrate 2 mainly made of glass epoxy resin, an electrode portion 11 of a chip component 10 formed on this substrate 2 and electrodes connected to the electrode portion with solder 12. island3.

Parts of the electrode islands 3 other than their upper parts on the substrate 2 are covered with a solder mask 4 which does not adhere to the solder 12 .

In order to fix the chip component 10 on the above-mentioned printed circuit board, use, for example, a screen printing process, apply a certain amount of solder paste 12 on the electrode island 3, and then use a suction chuck (not shown) to clamp it. Alignment of specific chip components 10 with electrode islands 3 is maintained.

Next, as shown in FIG. 1B , the chip component 10 is pressed against the substrate 2 , and the electrode portion 11 of the chip component 10 is pushed down into the solder paste 12 .

In this way, almost the lower half of the electrode portion 11 of the chip component 10 is buried in the solder paste 12 , and the chip component 10 is fixed on the substrate 2 due to the viscosity of the solder paste 12 .

In this case, the solder 12 spreads out on the electrode island 3 and enters the underside of the chip component 10 .

Next, the printed circuit board 1 on which the chip component 10 is fixed is passed through a reflow furnace or similar equipment (not shown), so that the solder 12 is melted, as shown in FIG. The electrode islands 3 are bonded together by solder 12 .

The solder 12 is preheated (eg, to a temperature of about 120° to 160°) in a reflow furnace before being melted to achieve sufficient diffusion and bonding.

Due to the preheating, the viscosity of the solder 12 decreases, and the solder 12 fully spreads on the electrode island 3 and also permeates to the bottom of the chip component 10 .

After preheating, reheating (eg, to a temperature of approximately 200° C. to 240° C.) completely melts the solder 12 .

Through this step of heating, the electrode portion 11 of the chip component 10 is welded to the electrode island 3 of the printed circuit board, and at the same time, the solder 12 that has entered the bottom of the chip component 10 is also melted to form a solder ball 12a.

The solder balls 12 a are separated from the solder 12 on the electrode island 3 and remain on the solder mask 4 .

However, the solder balls 12a shown in FIG. 1c not only affect the appearance of the soldering surface layer, but also cause short circuits between wire ends of other chip components, for example, because the solder balls remain outside the electrode island 3, and when the substrate 2 touches When vibration or torsion occurs, the solder balls will easily peel off and cause the above-mentioned short circuit.

Such solder balls can greatly impair the reliability of electronic devices.

The first object of the present invention is to provide a printed circuit board comprising a substrate for fixing a chip component and an electrode island existing on the substrate connected to the electrode portion of the chip component with solder, wherein the solder absorbing island is provided, on the chip component There is a specific gap between the electrode island and the electrode island, so that the solder protrudes slightly from the underside of the chip component fixed on the substrate.

A second object of the present invention is to provide a printed circuit board on which a specific wiring pattern is provided on a substrate located under a chip component to be fixed, a portion of the wiring pattern is used as a solder absorbing island, and on the substrate other than Areas other than those corresponding to the solder absorbing islands and electrode islands are covered with a solder mask that does not adhere to the solder.

A third object of the present invention is to provide a printed circuit board in which perforations of a specific depth are arranged in solder absorbing islands.

In the printed circuit board according to the present invention, the solder absorbing islands are provided with a certain gap from the electrode islands, so that solder is crushed and extruded from the electrode islands to be in contact with the solder absorbing islands when chip components are mounted.

When the solder melts, due to the surface tension and cohesive force of the solder, the solder that has been in contact with the solder-absorbing island is separated into: those on the electrode island side and those on the solder-absorbing island side, and the solder is positioned on the solder-absorbing island in a connected state .

Since the wiring pattern is formed on the substrate under the chip components to be fixed, the portion of the wiring pattern is used as a solder absorbing island, and the wiring pattern can be used not only for signal conduction but also for absorbing extruded solder.

In this case, by covering the area of the substrate with a solder mask that does not adhere to the solder except the area corresponding to the solder absorbing island and the electrode island, the molten solder must be separated without sticking to the solder mask. film and is attached and positioned over solder absorbing islands.

Due to capillary action when the solder melts, the solder that has been extruded from the electrode island is drawn to the solder-absorbing island and introduced into the perforations provided in the solder-absorbing island.

Therefore, increasing the force that pulls the solder that has extruded from the electrode islands to the solder absorbing islands prevents the solder from forming balls.

1A to 1C are cross-sectional views illustrating examples of conventional printed circuit boards having electrode islands, respectively;

2A to 2B are respectively schematic diagrams illustrating a printed circuit board of a first embodiment of the present invention; FIG. 2A is a perspective view and FIG. 2B is a plan view.

3A to 3C are respectively cross-sectional views illustrating the steps of a chip element connection process.

4A to 4C are respectively rough plan views illustrating an example of a printed circuit board as a second embodiment of the present invention on which wiring diagrams with solder absorbing regions are provided; and

5A and 5B are schematic plan views illustrating an example of a printed circuit board having solder absorbing through holes according to a third embodiment of the present invention, respectively.

Preferred embodiments of the printed circuit board according to the present invention will be described below with reference to the accompanying drawings. A schematic diagram for illustrating a printed circuit board according to the present invention is shown as a perspective view of FIG. 2A and a plan view of FIG. 2B.

Specifically, according to the printed circuit board 20 of the present invention, it is intended to form a specific circuit by using solder to fix chip components 30 including resistors and capacitors, and it mainly includes a substrate 22 for fixing chip components 30, and is fixed on the substrate with solder. The electrode islands 23a and 23b where the electrode portions 31a and 31b of the chip component 30 on 22 are connected together and the solder absorbing islands 25a and 25b residing near the electrode islands 23a and 23b.

The areas on the substrate 22 except the upper parts of the electrode islands 23a and 23b and the solder absorbing islands 25a and 25b are covered with a solder mask 24 that does not adhere to solder to prevent electrical shorts caused by solder adhering to other areas.

In one structure, the solder absorbing islands 25a and 25b are arranged with a certain gap d between the electrode islands 23a and 23b, and the solder absorbing islands protrude slightly beyond the underside of the chip component 30 to be fixed.

This gap d is set to a distance (for example, about 0.2mm) that makes the solder coated on the electrode islands 23a and 23b absorb with the solder when the solder is extruded from the electrode islands 23a and 23b due to fixing the chip component 30. The islands 25a and 25b are in contact, and the molten solder can be separated into the electrode islands 23a and 23b sides and the solder absorbing islands 25a and 25b due to the surface tension and cohesive force of the solder during chip component 30 soldering.

The connection state of the printed circuit board 20 according to the present invention will be described with reference to the sectional views shown in FIGS. 3A to 3C.

As shown in FIG. 3A , a specific amount of solder paste 32 a and 32 b is coated on the electrode islands 23 a and 23 b provided on the substrate 22 of the printed circuit board 20 .

In this structure, a chip component 30 held by a suction chuck (not shown) is placed over the electrode islands 23a and 23b.

Then, as shown in FIG. 3B, the chip component 30 is pressed onto the substrate 22 so that almost the lower half of the electrode portions 31a and 31b are buried in the solder paste 32a and 32b.

In this case, the solder pastes 32 a and 32 b are squeezed so as to squeeze out of the electrode islands 23 a and 23 b and also squeeze into the underside of the chip component 30 .

The extruded solder 32a and 32b spreads out on the solder mask 24 on the substrate 22 so as to contact (or reach the vicinity of) the solder absorbing islands 25a and 25b.

As shown in FIG. 3C, the printed circuit board on which the chip component 20 is mounted is passed through a reflow furnace to subject the printed circuit board to preheating and main heating to melt the solders 32a and 32b.

After preheating, the viscosity of the solder 32a and 32b that has been extruded and extruded from the electrode islands 23a and 23b is reduced, so even when the solder has reached the vicinity of the solder absorbing islands 25a and 25b, the solder 32a and 32b are the same as the solder. The absorption islands 25a and 25b are in contact.

The solders 32a and 32b are completely melted by the main heating, and are separated into the side of the electrode islands 23a and 23b and the side of the solder absorbing islands 25a and 25b due to the surface tension and cohesive force of the solder.

In other words, the solders 23a and 23b enter a vapor phase state to increase its surface tension, that is, its adhesion to metal (so-called solder wettability) and thus the solders 32a and 32b are separated to bond to the electrode islands 23a and 23b side and solder absorbing islands 25a and 25b sides. Since the solder mask 24 does not adhere to the solders 32a and 32b, it acts as a boundary.

By cooling and solidifying the solder 32a and 32b under this condition, the electrode portions 31a and 31b of the chip component 30 and the electrode islands 23a and 23b of the printed circuit board 20 are soldered, and the separated solder 32a and 32b are positioned on the solder absorption island 25a and 25b.

Therefore, the solder 32a and 32b that have been extruded from the electrode islands 23a and 23b are positioned on the solder absorbing islands 25a and 25b without becoming balls and remaining on the solder mask 24, and even when vibration or torsional force acts on the It will not peel off easily when it is on the substrate 2.

The reason why two solder absorbing islands 25a and 25b are provided between the two electrode islands 23a and 23b as shown in FIG. The sides are extruded.

A second embodiment of the present invention will be described below with reference to FIGS. 4A to 4C.

In the example shown in FIG. 4A, solder absorbing islands 45a and 45b are shown respectively provided with a minimum required area sufficient to absorb solder 32a and 32b extruding from electrode islands 43a and 43b (see FIG. 3B).

Provided that these solder-absorbing islands have an area sufficient to absorb and hold the extruded solder 32a and 32b (see FIG. 3B) as described above, although the solder-absorbing islands 45a and 45b can be provided in any shape, the solder-absorbing islands 45a and 45b The gap d between electrode islands 43a and 43b should also be maintained at a certain distance as described above.

In other words, maintaining this gap d enables the extruded solders 32a and 32b (see FIG. 3B) to contact and to be separated into electrode islands 43a and 43b side and solder absorbing islands 45a and 45b sides, thereby preventing solder from bridging between electrode islands 43a and 43b and solder absorbing islands 45a and 45b after soldering.

In the example shown in Figure 4B, on the substrate 42, a specific connection pattern 46 is provided between the two electrode islands 43a and 43b below the fixed chip element 50 (seeing the dotted line at 2 points in the figure). Portions of 46 serve as both solder absorbing islands 45a and 45b.

In addition, regions other than regions corresponding to the solder absorbing islands 45a and 45b and the electrode islands 43a and 43b are covered with a solder mask 44 for preventing unnecessary solder adhesion.

The wiring pattern 46 is entirely covered with the solder mask 44 as a common signal transmission line in a conventional example.

In this embodiment, by opening the solder mask 44 on the portion of the wiring pattern 46 corresponding to the solder absorbing islands 45a and 45b, the wiring coil 46 can be used for signal transmission and for bonding extrusion from the electrode islands 43a and 43b. Out of the solder 32a and 32b (see Figure 3B).

When the wiring pattern 46 is provided below the chip component 50 to be fixed, by opening the solder mask 44 on the corresponding area, even if no new solder absorbing islands 45a and 45b are additionally provided, the part of the wiring pattern 46 is Can be used as solder absorbing islands 45a and 45b.

The example shown in Figure 4c is a combination of the above two examples (shown in Figures 4A and 4B), where the part of the wiring diagram 46 is used as solder absorbing islands 45a and 45b, which have absorbing solder extruded from the electrode islands 43a and 43b, respectively. The minimum required area of the solder 32a and 32b out.

Also, the solder mask 44 is opened on corresponding areas above the solder absorbing islands 45a and 45b.

Therefore, the gap between the electrode islands 43a and 43b and the solder absorbing islands 45a and 45b can be reliably adjusted, and the wiring pattern 46 can be used for signal transmission and absorbing solder.

As a third embodiment according to the present invention, solder absorbing islands 55 a and 55 b are provided with perforations 57 a and 57 b according to an example of FIGS. 5A and 5B .

Specifically, FIG. 5A shows an example in which through-holes 57a and 57b are provided near the centers of solder absorbing islands 55a and 55b, respectively, and FIG. 5B shows that the part of the wiring diagram 56 is used as solder absorbing islands 55a and 55b, and a hole is provided in the center thereof. Examples of perforations 57a and 57b.

As described above, by providing the solder absorbing islands 55a and 55b, when the solder melts, the solder 32a and 32b extruded from the electrode islands 53a and 53b can be separated and adsorbed on the electrode island 53a due to the surface tension and cohesive force of the solder. and 53b sides and solder absorbing islands 55a and 55b sides.

At this time, the through holes 57a and 57b having a certain depth are provided in the solder absorbing islands 55a and 55b, so the solder absorbed on the solder absorbing islands 55a and 55b is pulled into the through holes 57a and 57b.

In other words, drawing the solder into the through holes 57a and 57b increases the solder absorbing capacity and solder pulling force of the solder absorbing islands 55a and 55b, so that the solder extruded from the electrode islands 53a and 53b must be separated and connected.

In addition, as the solder is drawn into the through-holes 57a and 57b, the amount of solder remaining on the surfaces of the solder-absorbing islands 55a and 55b and solder balls are prevented from forming thereon. Sufficient force to absorb the extruded solder can thus be obtained.

The depth of the perforations 57a and 57b can be half thickness or full perforation, depending on the solder absorption capacity.

As described above, the printed circuit board according to the present invention provides the following effects.

The printed circuit board according to the present invention is provided with solder absorbing islands to reliably absorb and hold solder extruded from the electrode islands.

Also, the wiring diagram section serves as a solder absorbing island. Therefore, there is no need to provide additional solder absorbing islands, and at the same time, the perforated solder absorbing islands are configured to enhance the solder absorbing force and ensure reliable absorption and retention of solder.

Therefore, even when stress such as vibration or torsion is applied to the substrate, the extruded solder does not peel off easily and electrical reliability of the printed circuit board can be improved.

Therefore, by using the above-mentioned printed circuit board, the present invention can provide highly reliable electronic equipment.

Claims (5)

1. circuit board comprises:

A substrate;

On described substrate, be provided with one or more electrode islands; With

Be located on the described substrate, leave one or more absorptions island of described electrode islands preset distance;

Can be fixed on circuit block on the described substrate by immobilization material, make the electrode and the described electrode islands of parts contact, and unnecessary immobilization material is stayed on the described absorption island, it is characterized in that described circuit board comprises a plurality of immobilization material suckings that leave described one or more electrode islands.

2. circuit board as claimed in claim 1 is characterized in that, extend by described substrate in described hole.

3. circuit board as claimed in claim 1 or 2 is characterized in that, described immobilization material sucking is on described one or more absorptions island.

4. circuit board as claimed in claim 3 wherein is provided with described immobilization material sucking according to described circuit board wiring pattern.

5. as claim 1 or 4 described circuit boards, it is characterized in that at least one described immobilization material sucking is set at the either side that connects described electrode islands circuit.

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