JPH11150359A - Method of pre-coating electrode land with solder and screen suitable therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method of comparatively easily and accurately pre-coating the faces of all electrode lands with a proper amount of solder and a screen suitable therefor. SOLUTION: A method of pre-coating electrode lands with solder is carried out through a manner where cream solder As is supplied inward between the electrode lands 2 so as to be filled into each space between the electrode lands 2 being lower than the tops of the lands 2 taking factors such as the height and width of the electrode land 2, a space between the electrode lands 2 formed on an electronic circuit board 1, and the surface tension and wetting spredability of solder S used for pre-coating into consideration, thereafter hot air is made to blow against the electrode lands from obliquely above with an air blower 30 from a direction vertical to the longer direction of the electrode lands 2 to melt cream solder filled in between the electrode lands 2 for pre-coating the surfaces of the electrode lands 2 with the solder S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a narrow pitch type such as a TCP (Tape Carrier Package) type used for a CPU (Central Processing Unit) of a computer.
A solder for pre-coating solder on the plurality of electrode lands of the electronic circuit board on which a plurality of electrode lands are formed corresponding to the narrow pitch and multi-pin for surface mounting a multi-pin surface-mounted semiconductor integrated circuit device. The present invention relates to a precoating method and a screen suitable for the method.

[0002]

2. Description of the Related Art First, a method of surface-mounting a surface-mount type semiconductor integrated circuit device (hereinafter simply referred to as "semiconductor device") having a narrow pitch and multi-pin electrodes on a current electronic circuit board will be described. FIG. 8 shows a part of a current electronic circuit board, FIG. 8A is a plan view thereof, and FIG. 8B is an enlarged sectional view taken along line AA of FIG.

Conventionally, a TCP (Tape Carrier Package) type used for a CPU of a computer, for example, Pentiu
The electronic circuit board 1 for surface-mounting a semiconductor device on which a multi-pin electrode having a narrow pitch of 0.25 mm and 320 pins as shown in FIG. In addition, as shown in FIG. 8, according to the number and position of the narrow pitch multi-pin electrodes of the semiconductor device,
For example, the width W is 0.127 mm, the length L is 2 mm, the height H (the depth of the groove between the electrode lands 2) is 10 μm, and the pitch P
Is 0.25 mm, a plurality of electrode lands 2 are formed on the surface of a substrate 3 made of synthetic resin, and the surface of each electrode land 1 is previously coated with solder S (hereinafter, referred to as “pre-coat”). I have. FIG. 8A shows only a plurality of electrode land groups corresponding to multi-pin electrodes formed on two adjacent sides of the semiconductor device, and a plurality of electrode land groups corresponding to the other two sides are omitted. I refuse that.

The electronic circuit board 1 thus pre-coated is usually supplied from a board maker to an assembling maker. In the assembling maker, not only the various electronic components but also the semiconductor device and the semiconductor device are provided at predetermined positions by a component mounting apparatus. The surface is mounted on the land 2 and reflowed and soldered collectively. However, it is difficult to correctly solder each of the narrow-pitch, multi-pin electrodes of the semiconductor device to the electrode lands 2 at predetermined positions on the electronic circuit board 1. In some cases, soldering failure may occur, for example, soldering may be performed over two. If a soldering failure of the semiconductor device occurs, the semiconductor device must be removed and soldered again accurately. In this case, the electronic circuit board 1
It is necessary to remove all the solder S adhering to the surface of all the electrode lands 2 to which the above semiconductor device was soldered, and to re-apply an appropriate amount of the solder S to all the electrode lands 2 appropriately. is there.

[0005]

As a method of pre-coating the solder, there is a method of pre-coating the solder so as to form a bump by using a dedicated screen of a CSP (Chip Size Package). Pitch is a relatively wide 0.5-0.8 mm pitch, and TC
It is difficult to apply the present invention to a semiconductor device having a narrow-pitch, multi-pin electrode of 0.25 mm pitch or less such as P.
There is also a method of pre-coating the solder using a screen having a single character opening. However, since the single character opening solves the problem of solder detachment, it has a narrow pitch of 0.25 mm or less and a multi-pin. In a semiconductor device having electrodes, there is a problem that solder adheres between adjacent electrode lands and so-called bridges are easily generated. Furthermore, there is a method of directly embedding solder between the electrode lands. However, it is very difficult to supply an appropriate amount of solder and embed the solder so as not to protrude outside between the electrode lands. Also, when pre-coating is performed in an atmosphere of a normal reflow furnace with the amount of solder embedded as described above, a bridge is likely to occur in many cases. Current technology has various problems as described above.

An object of the present invention is to solve these problems and to provide a method for precoating solder on an electrode land which is relatively simple and can accurately precoat an appropriate amount of solder on the surface of all electrode lands. The purpose of the present invention is to obtain a suitable screen.

[0007]

Therefore, in the present invention,
Pre-coating solder for pre-coating solder on the plurality of electrode lands of an electronic circuit board on which a plurality of electrode lands are formed corresponding to the narrow pitch / multi-pin so that a semiconductor device having a narrow pitch / multi-pin can be surface-mounted. In the method,
Considering the height and width of the electrode lands, the width of the gap between the electrode lands, the surface tension of the solder to be precoated, and the spreadability of the solder, cream solder is applied between the electrode lands, and Toward the inner side, it is supplied so as to be buried shorter than the length of each of the electrode lands, and thereafter, from obliquely above the surface of the buried cream solder, and in the longitudinal direction of the cream solder and each of the electrode lands. Hot air is blown from a direction perpendicular to the electrode lands to melt each of the buried cream solders, so that the solder swells on the surface of each of the electrode lands, and pre-coats the electrode lands. The problem has been solved by adopting a method.

A screen suitable for use in the method of pre-coating solder on the electrode lands is a thin screen having a narrow pitch and a large number of pins.
A plurality of electrode lands for pre-coating solder on a plurality of electrode lands corresponding to a narrow pitch multi-pin electrode present on each side of the semiconductor device of the electronic circuit board on which a plurality of electrode lands are formed corresponding to the number of pins. A screen in which an opening is formed, wherein each of the openings faces an inner side of the plurality of electrode lands, has an opening width shorter than a length of each of the electrode lands, and is provided on one side of the semiconductor device. The object is achieved by a structure in which a single-character opening is formed across the plurality of electrode lands corresponding to the existing narrow pitch multi-pin electrodes.

Therefore, the method of pre-coating solder on electrode lands and the screen suitable for use in the method according to the present invention have good cream solder removability and can accurately pre-coat each electrode land with an optimal amount of solder. Can be.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for pre-coating solder on an electrode land and a screen suitable for use in the method according to the present invention will be described with reference to the drawings. FIG. 1 is a front perspective view of a precoating screen according to an embodiment of the present invention suitable for use in the method for precoating solder on an electrode land of the present invention. FIG. 2 is a perspective view of a squeegee used with the precoating screen shown in FIG. FIG. 3 is a partial plan view of the electronic circuit board showing the partial electrode lands with the semiconductor device removed, and FIG. 4 is a view of the pre-coating screen shown in FIG. 1 on the electronic circuit board shown in FIG. FIG. A shows a plan view, and FIG. B shows A-A of FIG.
FIG. 5 is an enlarged cross-sectional view on line A. FIG. 5 is a view illustrating a method of pre-coating solder on electrode lands according to the present invention, in which cream solder is embedded between some electrode lands formed at a narrow pitch. FIG. 6 is a cross-sectional view taken along line AA of the electronic circuit board shown in FIG. 5 in a state where a precoating screen is mounted, and FIG. 7 is a view showing the electrode land of the present invention. FIG. 4 is a cross-sectional side view showing a relationship between an air blower and an electronic circuit board at a stage of blowing hot air in the solder precoating method.

First, a precoating screen (hereinafter simply referred to as "screen") of the present invention of one embodiment shown in FIG. 1 will be described. The screen 10 is slightly wider than the dimensions of the semiconductor device to be remounted, has an area which does not adversely affect other electronic components (not shown) mounted around the screen, and is provided in a horizontal state. A quadrangular flat screen main body 11, side plates 12 and 13 having the same shape and the same height and formed in parallel to each other perpendicularly to the screen main body 11 from both side surfaces of the screen main body 11, and other screen main bodies 11 Screen body 1 from one side full width
1 and a back plate 14 having the same height as the side plates 12 and 13 and a top plate of the side plates 12, 13 and 14 and being laid over the side plates 12, 13 and the back plate 14.
And a support plate 15 to which a handle 16 is fixed. The side plates 12 and 13 and the back plate 14 serve as protective covers when the semiconductor device is remounted, so as not to adversely affect the electronic components existing around the semiconductor device to be remounted. Things.

The screen main body 11 has a plurality of single-character openings 17 formed in accordance with the type of the semiconductor device. For example, in the case of a DTCP type semiconductor device, two openings 17 opposed to a narrow pitch multi-pin electrode group derived from two sides of the package of the semiconductor device are Q
In the case of a TCP-type semiconductor device, four openings 17 are formed opposite to a narrow-pitch, multi-pin electrode group derived from four sides of the package of the semiconductor device as shown in the figure. As shown in FIG. 3, the position where each of the openings 17 is formed is on the inner side 2B side of each of the electrode lands 2 of the plurality of electrode lands formed on the electronic circuit board 1 (see FIG. 3A). The electrode land 2 shown in FIG. The opening width Wa of each opening 17 is shorter than the length L of each of the electrode lands. In the present embodiment, the opening width Wa corresponds to a half length.
Has been selected. In addition, the opening length La of each opening 17 is a length extending over the plurality of electrode land groups existing on one side of the semiconductor device to be mounted.

The opening width Wa of the openings 17 is selected in consideration of the height H and width W of the electrode lands 2, the width of the gap between the electrode lands 2, the surface tension of the solder to be precoated, the spreadability of the solder, and the like. Is done.

FIG. 2 shows a squeegee 20 for embedding cream solder using the screen 10 between the electrode lands 2. The squeegee 20 has a hardness of 60, for example.
The squeegee body 21 is made of urethane rubber and has a rectangular shape and a handle 22 fixed to the back of the squeegee body 21. The width Wb of the squeegee body 21 is the opening length L of the screen 10.
The width is slightly longer than a.

Next, referring to FIGS. 5 to 7, a method of pre-coating solder on electrode lands according to the present invention, in which cream solder is pre-coated on all electrode lands 2 using the screen 10 and the squeegee 20 will be described. . First, the surface of each electrode land 2 of the electronic circuit board 1 from which the semiconductor device has been removed and the solder remaining between the electrode lands 2 are removed with a solder wick or the like, and the surfaces of all the electrode lands 2 are smoothed. Next, as shown in FIG.
The screen 10 is brought into close contact with all the electrode lands 2 and positioned so that each of the opening portions 17 of 0 is opened in the inner portion 2B of the electrode land 2 of each electrode land group. Next, an appropriate amount of cream solder is scooped using the squeegee 20 shown in FIG. 2, and the scooped cream solder Sa is printed on the screen 10 set on the electronic circuit board 1 as described above. And as shown in FIG.
The cream solder Sa is embedded between the electrode lands 2 on the inner side of the above. In this case, excess cream solder Sa, particularly cream solder Sa adhered to the surface of each electrode land 2, is scraped off with a squeegee 20 so that cream solder Sa does not exist on the surface of each electrode land 2 (FIG. 6). When the embedding of the cream solder Sa is completed as described above, the screen 10 is then lifted upward so as not to be displaced in the horizontal direction, and removed from the electronic circuit board 1.

Then, as shown in FIG. 7, the electronic circuit board 1 in which cream solder Sa is embedded between the electrode lands 2
Hot air is blown from the oblique direction at an acute angle α °, for example, at an angle of 40 ° to 70 °, and perpendicular to the longitudinal direction of each electrode land 2 using the air blower 30. By blowing hot air from an oblique direction, the cream solder Sa buried between the electrode lands 2 is melted, and is applied to the surface of each electrode land 2 by the force of the hot air and the surface tension and wet spreadability of the molten solder Sa. The molten solder S rides over, and the surfaces of all the electrode lands 2 are coated with the solder S.

Next, all the multi-pin electrodes of the semiconductor device are aligned with the all-electrode lands 2 for the semiconductor device on which the solder S is pre-coated in this manner, and the pre-coated solder S is melted by thermocompression bonding to form the semiconductor device. Solder. As described above, the amount of solder pre-coated on each of the electrode lands 2 is determined by changing the opening width Wa of the opening 17 of the screen 10 to the height H and the width W of the electrode lands 2, the interval between the electrode lands 2, and the pre-coating. It is an appropriate amount due to the selection in consideration of the surface tension of the solder to be tried, the spreadability of the solder, etc.
Therefore, when the solder S is melted and the semiconductor device is remounted, the solder does not protrude to the adjacent electrode lands 2 and a bad phenomenon such as a bridge does not occur.

[0018]

As is apparent from the above description, according to the solder precoating method of the present invention, an appropriate amount of cream solder can be embedded between the electrode lands by setting the width of the opening formed in the screen. Yes, therefore, when hot air is blown, no solder remains between each electrode land,
Moreover, since an appropriate amount of solder can be optimally pre-coated on the surface of each electrode land, the semiconductor device can be remounted in a good and extremely simple manner. Further, since the opening of the screen is formed in a single character, the cream solder can be easily removed between the electrode lands and can be easily embedded.
As described above, the present invention has many excellent effects.

[Brief description of the drawings]

FIG. 1 is a front perspective view of a precoating screen according to an embodiment of the present invention suitable for use in a method for precoating solder on an electrode land of the present invention.

FIG. 2 is a perspective view of a squeegee used with the precoat screen shown in FIG.

FIG. 3 is a partial plan view of the electronic circuit board showing a partial electrode land in a state where the semiconductor device is removed.

4 shows a state in which a part of the screen for precoating shown in FIG. 1 is provided on the electronic circuit board shown in FIG. 3, FIG. A is a plan view thereof, and FIG. It is an expanded sectional view on the -A line.

FIG. 5 is a view for explaining a method of pre-coating solder on an electrode land according to the present invention, showing a state in which cream solder is embedded between a part of electrode lands formed at a narrow pitch and electrode lands. It is a top view of a circuit board.

6 is a cross-sectional view of the electronic circuit board shown in FIG. 5 along a line AA in a state where a precoating screen is mounted.

FIG. 7 is a cross-sectional side view showing a relationship between an air blower and an electronic circuit board in a step of blowing hot air in a method of precoating solder on an electrode land according to the present invention.

FIG. 8 shows a part of a working electronic circuit board,
FIG. A is a plan view thereof, and FIG. B is an enlarged cross-sectional view taken along line AA of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic circuit board, 2 ... Electrode land, 2B ... Inner part of electrode land 2, 3 ... Substrate, 10 ... Screen for precoating of one embodiment of the present invention, 11 ... Screen body, 17 ...
Opening, 20 squeegee, 21 squeegee body, 30
Air blower, Sa: cream solder, S: solder

Claims (2)

[Claims] 2. The electronic circuit board according to claim 1, wherein said plurality of electrode lands are formed so as to correspond to said narrow-pitch, multi-pin surface-mounted semiconductor integrated circuit device. In a solder precoating method of precoating solder on an electrode land, the height and width of the electrode land, the width of the gap between the electrode lands, the surface tension of the solder to be precoated, the spreadability of the solder, Between each of the electrode lands, and nearer to the inner side of each of the electrode lands, supply so as to be buried shorter than the length of each of the electrode lands, and thereafter, at an angle to the surface of the buried cream solder. Hot air is blown from above and from a direction perpendicular to the longitudinal direction of the cream solder and each electrode land, and the embedded cream solder is melted to melt the respective solders. It was Moriagara solder on the surface of the electrode lands, solder pre-coating method to the electrode lands, characterized in that the precoat. 2. The surface mounting method for an electronic circuit board on which a plurality of electrode lands are formed corresponding to the narrow pitch multi-pins so that a surface mounting type semiconductor integrated circuit device with a narrow pitch multi-pins can be surface-mounted. A screen having a plurality of openings for pre-coating solder on a plurality of electrode lands corresponding to a narrow pitch multi-pin electrode group present on each side of the semiconductor integrated circuit device. The narrow-pitch multi-pin electrode having an opening width shorter than the length of each of the electrode lands and facing one side of the surface-mounted semiconductor integrated circuit device. A screen for pre-coating solder on electrode lands, wherein the screen is formed with a single-character opening astride the plurality of electrode land groups corresponding to the above.