JPH09130028A - Mask for solder printing and liquid crystal display device mounting printed circuit board manufactured by using the mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high quality printing of a solder film by eliminating repetive operation of the solder printing. SOLUTION: Thickness of a solder printing mask 5 to form by printing a solder film to mount by the soldering the lead pins of electronic parts 11, 12, 13, 14 on the printed wiring of a printed circuit board 1 for mounting electronic devices such as a liquid crystal display device, etc., is locally changed depending on the size of pitch of the lead pins 11a, 12a, 13a of the electronic parts to be mounted in the vicinity of the electronic parts and the printed wiring for mounting the electronic parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device incorporating a solder printing mask and a printed circuit board manufactured using the same, and more particularly, controlling the thickness of a solder film to cause insulation failure between wirings. The present invention relates to a solder printing mask in which a short circuit defect is eliminated and a liquid crystal display device incorporating a printed circuit board manufactured using the same.

[0002]

2. Description of the Related Art Liquid crystal display devices, video cameras, and other electronic devices have a strong need for smaller size and lighter weight, and accordingly, small electronic parts such as semiconductor parts forming signal circuits and drive control circuits thereof are becoming smaller. In addition, high-density mounting of printed circuit boards mounting these electronic components and cost reduction are required.

12 to 14 are explanatory views for soldering a surface-mounting type semiconductor component to a printed circuit board which constitutes a liquid crystal display device.

Surface-mounted semiconductor parts such as ICs on a printed circuit board and other parts (hereinafter also simply referred to as parts)
As a soldering method, a flow soldering method and a printing method using a solder paste have been conventionally known.

FIG. 12 is a top view of a printed circuit board to which the present invention is applied. 1 is a printed circuit board, 2 is a board side alignment mark, 3 is a mask side alignment mark,
4, 4A is a mask, 11 is an A part, 11a is a lead pin of the A part, 11b is an A opening, 12 is a B part, 12a is B
Lead pin of parts, 12b is B opening, 13 is C part, 1
3a is a C component lead pin, 13b is a C opening, and 14 is D
It is a component (tape carrier package: TCP).

As shown in FIG. 1A, printed wiring (not shown) formed on the printed circuit board 1 has an A component 11,
A case where the B component 12 and the C component 13 are mounted and the TCP 14 is further mounted by soldering as the D component will be described. A board-side alignment mark 2 is formed at the corner of the printed circuit board 1.

The A component 11 and the B component 12 are SOJ type, and the pitch of the lead pins 11a and 12a to be soldered to the printed wiring formed on the printed circuit board 1 is 1.27 mm, and the C component 13 is the SOP type and the lead pin 13a of the SOP type. The pitch is 0.8 mm. The lead pin pitch of the D component 14 is 0.35 mm.

First, as shown in FIG.
And an A opening 11b and a B opening 12b are formed at portions corresponding to the lead pins 11a and 12a of the B component 12, and board side alignment marks 2 formed on the printed circuit board 1 at the corners thereof.
The mask 4 on which the mask side alignment mark 3 is formed is placed at a position corresponding to, and after both are aligned, solder paste is squeezed to print solder on the printed circuit board 1 through the A opening 11b and the B opening 12b. And dry it.

Next, as shown in (c), the C opening 13 is formed.
b and the mask 4A on which the mask side alignment mark 3 is formed are placed on the printed circuit board 1, the positions of both are aligned, and the solder paste is squeezed to form the C opening 13b.
The printed circuit board 1 is printed with solder and dried.

Although not shown, solder is printed and dried on a printed wiring portion to which the D component 14 is soldered through a mask having openings at positions corresponding to the lead pins of the D component 14.

A component 11, a B component 12, a C component 13, and a D component 14 are mounted on the printed circuit board 1 on which all the necessary solder is printed, and heat treatment is performed to perform soldering.

The solder printing masks 4 and 4A are preferably formed of a metal material, but are not limited to the metal material.
A material such as a hard resin can be used.

FIG. 13 is an explanatory diagram of the above-mentioned conventional soldering work process, in which 1 is a printed circuit board and 4, 4A.
Is a mask, 15 is a solder paste, 15a, 15b, 15
c is a printed solder film, and 16 is a squeegee. Note that solder printing for the D component is omitted in FIG.

First, in step 1, a mask 4 is placed on a printed circuit board (simply referred to as a board in the figure) 1 and aligned. This alignment is performed by aligning the substrate side alignment mark 2 and the mask side alignment mark 3 formed on the printed circuit board.

In step 2, the solder paste 15 is placed on the upper surface of the mask 4, and the squeegee 16 is pressed and moved to move the solder paste from the openings A and B formed in the mask 4 to the wiring formed on the printed circuit board 1. Part A and B
The solder films 15a and 15b are printed and applied to the soldered portions of the component.

In step 3, the mask 4 is removed from the printed circuit board 1 and the printed solder films 15a and 15b are printed.
To dry.

Next, in step 4, the printed circuit board 1
Another mask 4A is placed on and aligned as described above.

In step 5, the solder paste 15 is placed on the mask 4A, the squeegee 16 is pressed and moved, and the solder paste is soldered from the C opening formed in the mask 4A to the C component of the wiring formed on the printed circuit board 1. The solder film 15c is applied by printing onto the attachment portion.

In step 6, the mask 4A is removed from the printed circuit board 1 and the printed solder film 15c is dried.

In the next step work of step 7, the A component, B component, and C component are mounted on the printed circuit board 1 having the dried solder films 15a, 15b, 15c, and heat treatment is performed.
Each lead pin is soldered and fixed to the corresponding wiring of the printed circuit board 1.

As described above, the solder paste is repeatedly printed using the mask in which the openings are formed according to the soldering density of the electronic component, that is, the pitch size of the lead pins of the electronic component.

[0022]

In recent years, electronic parts corresponding to the needs of electronic devices have been diversified, and lead pins have various shapes and arrangements, as represented by the plastic mold parts exemplified below. It has a morphology.

14 and 15 are explanatory views of the shapes of various electronic components molded by plastic and the arrangement examples of the lead pins thereof.

In FIG. 14, (a-1) is a DIP type I.
C is a top view, (a-2) is a side view of (a-1) viewed from the arrow direction, 17 is an IC body, and 17a is a lead pin.

Further, (b-1) is a top view of the SOP type IC, (b-2) is a side view of (b-1) viewed from the direction of the arrow, 18 is an IC main body, and 18a is a lead pin. is there.

Further, (c-1) is a top view of the QFP type IC, (c-2) is a side view of (c-1) seen from the arrow direction, 19 is an IC body, and 19a is a lead pin. is there.

In FIG. 15, (d-1) is a top view of the PLCC type IC, (d-2) is a side view of (d-1) viewed from the direction of the arrow, 20 is the IC body, and 20a is It is a lead pin.

Further, (e-1) is a top view of a BGA type IC (similar product is a PGA type IC), (e-2) is a side view of (e-1) seen from the arrow direction, (e -3) is a bottom view of (e-2) seen from the arrow direction, in which 21 is an IC body and 21a is a lead pin.

The number of lead pins has increased and the pitch thereof has become smaller in accordance with the miniaturization accompanying the high-density mounting of electronic components.

FIG. 16 is an explanatory view of the shape of the lead pin of the plastic mold and its parallelism. (A-1) is S
OP type IC partial top view, (a-2) side view seen from the arrow direction of (a-1), (b-1) SOJ type IC partial top view, (b-2) (b It is the side view seen from the arrow direction of -1). 22 is the body of the SOJ type IC, 22
a is the lead pin.

As shown in FIG. 2 (a-2), the tip bent portion of each lead pin 18a of the SOP type IC is in the range of 0 to 10 ° with respect to the plane of the main body 18 (that is, the parallelism is 0.
10) and as shown in (b-2), the SOJ
The tip curved portion of each lead pin 22a of the IC IC has an error of about 0.15 with respect to the plane of the main body 22 (that is, parallelism of 0.15).

Since the parallelism of each lead pin varies depending on the electronic component, and the difference in the parallelism greatly affects the reliability of soldering, it is necessary to control the thickness of the solder film according to the electronic component. is there.

17A and 17B are schematic views for explaining the relationship between the thickness of the printed circuit board and the solder film and the parallelism between the lead pins of the electronic component. FIG. 17A is a partial plan view and FIG. 17B is a sectional view thereof. Is.

In the figure, 1 is a printed circuit board, 1
Reference numeral a is a wiring pattern, 15a and 15a 'are solder films, 23 is an electronic component, 23a is a lead pin of a soldering portion, 24 is a portion where the parallelism of the lead pin is lowered, and 25 is a required solder film thickness.

As shown in (a), the wiring pattern 1a is formed on the surface of the printed circuit board 1, and if the parallelism of the lead pins 23a is good, the wiring pattern 1 is formed.
The electronic component 23 can be soldered by applying the solder film 15a on a.

However, at the portion 24 where the parallelism of the lead pin is lowered as shown in (b), the lead pin and the solder film 15a are separated from each other and are not soldered.

Therefore, the required solder film thickness 25 must be the solder film 15a plus the solder film 15a '.

The thickness of the solder film needs to be controlled according to the density of the lead pins of the electronic component, that is, the pitch of the lead pins.

FIG. 18 is a schematic diagram for explaining the relationship between the pitch of the lead pins and the thickness of the solder film in the soldering of electronic parts having different lead pin pitches, and shows a flat package as an example of the electronic parts.

In the figure, (a-1) is a partial top view of a printed circuit board on which an electronic component having a lead pin pitch of, for example, 1.27 mm is soldered, and (b-1) is a lead pin pitch of, for example, 0.8 mm. Is a partial top view of a printed circuit board for soldering the electronic component of FIG. 1, (a-2) is a sectional view of (a-1) before soldering, and (a-3) is (a-
1) is a sectional view after soldering, (b-2) is a sectional view before soldering (b-1), and (b-3) is a sectional view after soldering (b-1).

As shown in (a-1) and (b-1),
By applying the solder film 15a on the wiring pattern 1a formed on the printed circuit board 1 by printing using a mask, and mounting and heating the electronic components 23 and 23 'having different pitches of the lead pins 23a and 23a', respectively. Solder.
(A-2) and (b-2) have shown the state before mounting an electronic component and soldering.

As shown in (a-3) and (b-3),
After mounting the electronic parts, heat them and lead pins 2
When 3a and 23a ′ are soldered to the wiring patterns 1a and 1a ′, in the electronic component 23 in which the lead pin pitch is as large as 1.27 mm, even if the solder 15a hangs between the wiring patterns, the adjacent wiring patterns are not short-circuited. However, in the electronic component 23 ′ having a small lead pin pitch of 0.8 mm, there is a problem that the solder 15a ′ hangs between the wiring patterns and short-circuits between the adjacent wiring patterns as shown in the portion 26. It was

In order to solve the problem of controlling the thickness of the solder film by the parallelism of the lead pins and the short circuit between the wiring patterns due to the finer pitch of the lead pins, as shown in FIG.
The direction in which the plate thickness of the mask described in FIG. 6 is selectively used according to the pitch of the lead pins of the electronic component is adopted.

However, with the diversification of electronic parts and the diversification of printed circuit boards, it is costly to use various kinds of solder printing masks for each type of electronic parts, and it is necessary to repeat solder printing. There was a problem of quality deterioration.

A first object of the present invention is to solve the above-mentioned problems of the prior art and to provide a solder printing mask capable of printing a high quality solder film without repeating the solder printing. .

A second object of the present invention is to provide a liquid crystal display device equipped with a printed circuit board manufactured by using the above mask.

[0047]

In order to achieve the first object, the first invention according to claim 1 is to mount a lead pin of an electronic component by soldering on a printed wiring of a printed circuit board. In a solder printing mask for printing a solder film for printing, the thickness of the solder printing mask is set in the vicinity of the electronic component and printed wiring for mounting the electronic component, and the pitch of the lead pins of the electronic component to be mounted. It is characterized in that it is locally changed according to the size of.

In order to achieve the above first object,
A second aspect of the present invention is characterized in that the local change in the plate thickness of the printed circuit board is thick at a portion where the lead pin pitch of the electronic component is large and thin at a portion where the lead pin pitch is small.

In order to achieve the above-mentioned second object, the third invention according to claim 3 forms at least a color filter, a common transparent electrode and an alignment film on one transparent substrate, and the other transparent substrate. A liquid crystal cell in which a liquid crystal layer is sandwiched between a pair of transparent substrates on which at least transparent electrodes for pixel selection and an alignment film are formed on a substrate, and pixels of the liquid crystal cell are provided on the periphery of the pair of transparent electrodes of the liquid crystal cell. In a liquid crystal display device having at least a printed circuit board on which one or a plurality of electronic components for applying a driving signal for driving are mounted, the printed circuit board is mounted on its printed wiring, and the electronic component is soldered. In the vicinity of the printed wiring, a solder film formed using a solder printing mask in which the plate thickness is locally changed according to the pitch size of the lead pins of the electronic component to be mounted. And characterized by being put fields.

[0050]

1 is a schematic diagram for explaining a solder printing mask according to the present invention, in which (a) is a printed circuit board, (b) is a solder printing mask, and (c) is (b). Side view, (d) is an enlarged plan view of part a of (b) and its A-
A'sectional view, (e) is an enlarged plan view of part b of (b) and its BB 'sectional view.

In the figure, as in FIG. 12, 1 is a printed circuit board, 2 is a board side alignment mark, 3 is a mask side alignment mark, 5 is a mask, 11 is an A part, and 11a is an A part. Lead pin, 11b is A opening, 1
2 is B part, 12a is B part lead pin, 12b is B
Opening, 13 is a C component, 13a is a C component lead pin, 1
3b is a C opening, and 14 is a D part (tape carrier package: TCP).

As shown in FIG. 3A, printed wiring (not shown) formed on the printed circuit board 1 has an A component 11,
A case where the B component 12 and the C component 13 are mounted and the TCP 14 is further mounted by soldering as the D component will be described. A board-side alignment mark 2 is formed at the corner of the printed circuit board 1.

The A component 11 and the B component 12 are SOJ type, the lead pins 11a and 12a to be soldered to the printed wiring formed on the printed circuit board 1 have a pitch of 1.27 mm, and the C component 13 is the SOP type and the lead pin 13a of the SOP type. The pitch is 0.8 mm. The lead pin pitch of the D component 14 is 0.35 mm.

As shown in (b), the mask 5 for solder printing has lead pins 11a of the A component 11 and the B component 12,
An A opening 11b and a B opening 12b are formed in a portion corresponding to 12a, and a mask side alignment mark 3 is formed at a position corresponding to the board side alignment mark 2 formed on the printed circuit board 1.

As shown in the side view of (c), this mask 5 has a plate thickness of 0.15 mm and is provided on a printed circuit board to which the lead pins of the A component and the B component having a large lead pin pitch are soldered. A opening 11b corresponding to printed wiring,
The portion where the B opening 12b is formed (the portion b) remains the plate thickness of the mask 5, but the C opening 13b corresponding to the printed wiring on the printed circuit board to which the lead pin of the C component having a small lead pin pitch is soldered. The plate thickness of the forming portion (a portion) is thin.

As shown in (d), the mask plate thickness of the portion a where the pitch of the lead pins is small (the arrangement density is also high) is as thin as 0.1 mm, but as shown in (e), the lead pins are Has a large pitch (the arrangement density is low) b
The mask plate thickness of the part remains unchanged.

The mask 5 is superposed on the printed circuit board 1, the board-side alignment mark 2 and the mask-side alignment mark 3 are aligned, and the solder paste is squeezed to form the A opening 11b, the B opening 12b, and the C opening. Opening 13b
The printed circuit board 1 is printed with solder and dried.

The thickness (and therefore the amount) of the printed solder film depends on the thickness of the openings formed in the mask, and is thick (0.
15 mm thick), and the lead pin is printed thin (0.1 mm thick) on a portion having a small pitch.

As described above, by using the mask of the present invention, it is possible to print a solder film for electronic parts having different lead pin pitches with one mask. Note that the same applies to the D component, and a description thereof will be omitted.

Therefore, it is possible to prevent the short circuit between the adjacent wiring patterns as in the above-mentioned conventional technique when the electronic parts are soldered, and the number of masks is reduced to one, so that the number of steps can be reduced, and the whole can be reduced. Significant cost reduction can be obtained.

FIG. 2 is an explanatory view of a soldering work process of an electronic component using a solder printing mask according to the present invention.
1 is a printed circuit board, 5 is a mask, 11 is an A part, 1
2 is B component, C is C component, 15 is solder paste, 15
Reference numerals a, 15b, and 15c are printed solder films, and 16 is a squeegee. Note that solder printing for the D component is omitted in FIG.

First, in step 1, a mask 5 is placed on a printed circuit board (simply referred to as a board in the figure) 1 and aligned. This alignment is performed by aligning the substrate side alignment mark 2 and the mask side alignment mark 3 formed on the printed circuit board.

In step 2, the solder paste 15 is placed on the upper surface of the mask 5 and the squeegee 16 is pressed and moved.

In step 3, the mask 5 is removed, so that solder paste is applied from the openings A, B, and C formed in the mask 5 to the parts A and B and C of the wiring formed on the printed circuit board 1. Solder films 15a, 15b, 15c are printed on the soldered portions of the component.

In step 4, predetermined electronic parts (A part 11, B part 12, C part 13) are formed on the solder films 15a, 15b, 15c printed on the predetermined part of the printed circuit board 1.
With.

Then, in step 5, heat treatment is performed to fix the lead pins of each electronic component to the corresponding wiring of the printed circuit board 1 by soldering.

Although not shown, the same applies to the D component 14.

FIG. 3 is an explanatory view of a typical example of the pitch of the lead pins to be soldered of the surface mount type electronic component, the plate thickness of the mask for solder printing, and the interval of the lead pins. ), And the vertical axis represents the mask thickness (●)
(Mm) and the lead pin pin spacing (◯) (mm).

With the high integration of electronic components, the number of lead pins to be soldered to the wiring pattern formed on the printed circuit board has increased, and the distance between them has become smaller as shown by the broken line graph in FIG. Further, the shape is also as shown in FIGS.
It is diversified as explained in.

Accordingly, it is necessary to reduce the thickness of the solder printing mask that determines the amount of solder for preventing the above-mentioned short circuit between the lead pins.

The solder printing mask 5 is preferably formed of a metal material, but not limited to a metal material, a hard resin or other material can be used.

As described above, by changing the plate thickness of the mask according to the accuracy of the electronic component used in one mask, short-circuiting or connection failure between lead pins can be eliminated, the work process can be simplified, and the cost can be reduced. A high quality printed circuit board is obtained.

As described above, as a condition for soldering a surface-mounted electronic component such as a semiconductor component on the printed circuit board by the printing method, the thickness of the solder film is determined by the accuracy of the electronic component (lead pin interval, parallelism, pitch). Etc.), it is possible to perform soldering with high quality and high reliability by controlling the amount of solder (film thickness, print width) corresponding to the above.

This amount of solder locally changes the plate thickness of the mask used during printing in conformity with the accuracy of each electronic component and each wiring pattern of the printed circuit board.

By using this printed circuit board, high-performance liquid crystal surface devices and other electronic devices can be obtained.

[0076]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 4 is an explanatory view of one embodiment of a mask for solder printing according to the present invention, in which (a) is a plan view, (b) is a side view, and (c) is A-A of (a). 'Partial cross section, (d)
Is a partial sectional view taken along line BB ′ of (a), and (e) is taken along line C- of (a).
It is a C'partial sectional view.

In the figure, 6 is a mask, 31 is a first part, 32 is a second part, and 33 is a third part. The lead pin pitch of the first part 31 is 0.4 mm, and the second part 3 is
The lead pin pitch of 2 is 0.8 mm, and the lead pin pitch of the third component 33 is 1.27 mm.

The mask 6 of this embodiment is an example of a case where the printed circuit board to be printed has a large number of electronic components 33 similar to the third component 33 shown in (a).

The plate thickness of the main part of the mask 6 is 0.15 mm as shown in (b), the plate thickness of the first part 31 is 0.075 mm as shown in (c), and the second part is The thickness of the portion 32 is 0.10 mm as shown in (d), and the thickness of the mounting portion of the third component 33 is the same as that of the main portion 0.1.
5 mm.

As described above, according to the present embodiment, the mask for solder printing has a plate thickness corresponding to the pitch of the lead pins of the electronic components having a large number of mountings, and the mask is used for the electronic components having a smaller pitch. By reducing the plate thickness, the solder films for all the electronic components to be mounted can be printed with one mask.

FIG. 5 is an explanatory view of another embodiment of a solder printing mask according to the present invention, in which (a) is a plan view and (b) is a plan view.
Is a side view, and (c) is a DD 'partial sectional view of (a).

In the figure, 7 is a mask, 7'is an auxiliary mask plate, 34 is a first part, 35 is a second part, and 36 is a third part.
The component 37 is the fourth component, and the lead component pitch of the first component 34, the second component 35, and the third component 36 is 0.4 m.
m, the pitch of the lead pins of the fourth component 37 is 1.27 mm
Then, this mask is applied to the printed circuit board when the number of the fourth components 37 mounted is small.

In this embodiment, the mask 7 has a thickness of 0.07.
In the solder printing opening portion having a thickness of 5 mm and corresponding to the fourth component 37 having a small number of mounted components, an auxiliary mask plate 7'having a thickness of 0.075 mm is superposed on the mask 7 to increase the plate thickness to 0.15.

The mask 7 is used instead of the auxiliary mask plate 7 '.
It may be a structure in which the plate thickness of the corresponding part of itself is raised.

According to this embodiment, the solder printing mask has a plate thickness corresponding to the pitch of the lead pins of the electronic components having a large number of mountings, and the mask plate thickness is increased for electronic components having a larger pitch. By doing so, the solder films for all the electronic components to be mounted can be printed with one mask.

Next, an active mask type liquid crystal display device will be described as an example of an electronic device on which a printed circuit board soldered using the above mask is mounted.

The active matrix type liquid crystal display device is provided with a non-linear element (switching element) corresponding to each of a plurality of pixel electrodes arranged in a matrix. Since the liquid crystal in each pixel is theoretically always driven (duty ratio 1.0), the active method has better contrast than the so-called simple matrix method that employs the time-division driving method. Then it is becoming an indispensable technology. A typical switching element is a thin film transistor (TFT).

An active matrix type liquid crystal display device using a thin film transistor is disclosed in, for example, Japanese Patent Laid-Open No. 63-309921, "Redundant configuration is adopted.
2.5-inch active matrix color LCD ", Nikkei Electronics, pages 193-210, 1986 12
Known on the 15th of March, published by Nikkei McGraw-Hill, Inc.

FIG. 6 is an exploded perspective view for explaining a structural example of a TFT type liquid crystal display module which constitutes a liquid crystal display device on which a printed circuit board using a solder printing mask according to the present invention is mounted.

In the figure, MDL is a liquid crystal display module, SHD is a metal shield case that is an upper frame, WD is a display window that defines the effective screen of the liquid crystal display module, PNL is a liquid crystal panel composed of liquid crystal display elements, and PC.
B1 is a drain side printed circuit board, PCB2 is a gate side printed circuit board, PCB3 is an interface printed circuit board, PRS is a prism sheet, SPS is a diffusion sheet, GLB is a light guide, RFS is a reflection sheet, BL is a backlight, LP. Is a cold cathode fluorescent lamp that constitutes the lamp of the backlight BL, LS is a reflection sheet, GC is a rubber bush, LPC is a lamp cable, and MCA is a light guide GLB.
Lower case with opening MO for installing
2, JN3 is a joiner connecting the printed circuit boards, TCP1 and TCP2 are tape carrier packages,
INS1, INS2, INS3 are insulating sheets, GC is a rubber cushion, BAT is a double-sided adhesive tape, and ILS is a light-shielding spacer.

The above-mentioned components are laminated between the metal shield case SHD and the lower case MCA and are sandwiched and fixed to form the liquid crystal display module MDL.

Various printed circuit boards are attached to the periphery of the liquid crystal panel PNL to drive for image display. The mask according to the present invention is used for printing a solder film for soldering an electronic component such as an IC to the printed circuit board.

On the back surface of the liquid crystal panel PNL, there is provided a backlight BL which is formed by laminating various optical sheets on the light guide GLB, and the image formed on the liquid crystal display panel PNL is illuminated and displayed on the display window WD. indicate.

FIG. 7 shows a wiring diagram of an equivalent circuit of the display matrix section of the liquid crystal display module according to the present invention and its peripheral circuits. Although the figure is a circuit diagram, it is drawn corresponding to the actual geometrical arrangement. AR is a matrix array in which a plurality of pixels are two-dimensionally arranged.

In the figure, X means a video signal line DL, and subscripts G, B and R are added corresponding to green, blue and red pixels, respectively. Y represents the scanning signal line GL, and subscripts 1, 2, 3, ..., End are added according to the order of scanning timing.

The video signal lines X (subscripts omitted) are alternately connected to the upper (or odd) video signal drive circuit He and the lower (or even) video signal drive circuit Ho.

The scanning signal line Y (subscript omitted) is connected to the vertical scanning circuit V.

The SUP is a TFT liquid crystal display device for displaying information for a CRT (cathode ray tube) from a power supply circuit or a host (upper processing unit) for obtaining a plurality of divided and stabilized voltage sources from one voltage source. It is a circuit including a circuit for exchanging information for use.

The storage capacitor element Cadd acts to reduce the influence of the gate potential change ΔVg on the midpoint potential (pixel electrode potential) Vlc when the thin film transistor TFT switches. This situation is represented by the following equation.

ΔVlc = {Cgs / (Cgs + Cadd + Cpix)} × ΔVg Here, Cgs is the gate electrode G of the thin film transistor TFT.
Parasitic capacitance formed between T and source electrode SD1, C
pix is a capacitance formed between the transparent pixel electrode ITO1 (PIX) and the common transparent pixel electrode ITO2 (COM), ΔV
lc represents the amount of change in the pixel electrode potential due to ΔVg.

This change ΔVlc causes a direct current component applied to the liquid crystal LC, and the value can be reduced as the holding capacitance Cadd is increased. Further, the storage capacitor element Cadd also has the function of prolonging the discharge time, and stores the image information for a long time after the thin film transistor TFT is turned off. The reduction of the direct current component applied to the liquid crystal LC is
, And the so-called burn-in in which the previous image remains when the liquid crystal display screen is switched can be reduced.

As described above, since the gate electrode GT is made large enough to completely cover the i-type semiconductor layer AS, the overlap area with the source electrode SD1 and the drain electrode SD2 is increased, and thus the parasitic capacitance Cgs is increased. The reverse effect is that the midpoint potential Vlc is easily affected by the gate (scanning) signal Vg. However, this demerit can be eliminated by providing the storage capacitor element Cadd.

The storage capacitance of the storage capacitor Cadd is 4 to 8 times (4.
Cpix <Cadd <8 · Cpix) and a value about 8 to 32 times (8 · Cgs <Cadd <32 · Cgs) with respect to the parasitic capacitance Cgs.

[0105] initial stage of the scanning signal lines GL, which is used only as a storage capacitor electrode line (Y _O) is common transparent pixel electrode ITO2
(Vcom) same potential.

FIG. 8 is a top view showing a state in which the video signal drive circuit printed circuit board and the vertical scanning circuit printed circuit board are connected to the display panel.

CHI is a driving IC chip for driving the display panel PNL (the lower three are driving ICs on the vertical scanning circuit side).
Chips, 6 each on the left and right are drive I on the video signal drive circuit side
C chip).

FIG. 9 is a sectional view of a tape carrier package in which an IC chip constituting a drive circuit is mounted on a printed circuit board, and FIG. 10 shows a state in which the tape carrier package is connected to a video signal circuit terminal of a liquid crystal display panel. It is a principal part sectional view shown.

In FIG. 8, TCP is a tape carrier package in which the driving IC chip CHI is mounted by the tape automated bonding method (TAB) as shown in FIGS. 9 and 10, and PCB1 is the above TCP or capacitor. A printed circuit board for a drive circuit on which a CDS or the like is mounted is divided into three.

FGP is a frame ground pad,
A spring-like fragment FG provided by cutting into the shield case SHD is soldered. FC is a flat cable that electrically connects the lower drive circuit board PCB1 and the left drive circuit board PCB1 and the lower drive circuit board PCB1 and the right drive circuit board PCB1.

As the flat cable FC, a plurality of lead wires (phosphor bronze material plated with Sn) sandwiched between a striped polyethylene layer and a polyvinyl alcohol layer are used.

In FIG. 9, an integrated circuit chip CH constituting the scanning signal drive circuit V and the video signal drive circuits He and Ho.
I is mounted on a tape carrier package TCP mounted on a flexible printed circuit board.

As shown in FIG. 10, the tape carrier package TCP is connected to the video signal circuit terminal DTM of the liquid crystal display panel PNL.

TTB is an input terminal / wiring portion of the integrated circuit CHI, TTM is an output terminal / wiring portion of the integrated circuit CHI, and is made of, for example, Cu, and an integrated circuit CHI is provided at each inner tip portion (commonly called inner lead). The solder pads (bonding pads) PADs of the wiring patterns are connected by the so-called face-down bonding method.
The outer end portions (commonly called outer leads) of the terminals TTB and TTM correspond to the input and output of the semiconductor integrated circuit chip CHI, respectively, and are connected to the CRT / TFT conversion circuit / power supply circuit SUP by soldering or the like and the anisotropic conductive film ACF. Is connected to the liquid crystal display panel PNL.

The TCP is connected to the panel so that its tip portion covers the protective film PSV1 exposing the connection terminal DTM on the panel PNL side, and therefore, the external connection terminal DTM.
Since (GTM) is covered with at least one of the protective film PSV1 and the package TCP, it is strong against electric contact.

BF1 is a base film made of polyimide or the like, and SRS is a solder resist film for masking the solder so that it will not stick to unnecessary places during soldering. The gap between the upper and lower glass substrates outside the seal pattern SL is protected by an epoxy resin EPX or the like after cleaning, and a silicone resin SIL is further filled between the package TCP and the upper substrate SUB2 for multiple protection.

FIG. 11 shows a printed circuit board P for a drive circuit.
It is a top view explaining the connection state of CB1 and printed circuit board PCB2 for power supplies.

The printed circuit board PCB2 for driving the liquid crystal display unit LCD which is held and housed in the intermediate frame MFR is L-shaped and has electronic parts such as ICs, capacitors and resistors mounted thereon.

Printed circuit board PCB for this drive circuit
Reference numeral 2 denotes a power supply circuit for obtaining a plurality of divided and stabilized voltage sources from one voltage source, and a TFT liquid crystal display device for displaying CRT (cathode ray tube) information from a host (upper processing unit). A circuit SUP including a circuit for converting into information for use is mounted.

CJ is a connector connecting portion to which a connector (not shown) connected to the outside is connected.

The printed circuit board PCB2 for the drive circuit and the printed circuit board PCB3 for the inverter circuit are electrically connected by a backlight cable through a connector hole provided in the intermediate frame MFR.

The printed circuit board PCB1 for the drive circuit and the printed circuit board PCB2 for the drive circuit are electrically connected by a foldable flat cable FC, and at the time of assembly, the printed circuit board PCB for the drive circuit.
The flat cable FC is bent 180 ° and is overlaid on the back side of the printed circuit board PCB1 for the drive circuit.

As described above, in the liquid crystal display device of the present invention, various electronic components mounted on the printed circuit board are highly reliable, and low-cost, long-life and high-quality image display is possible.

[0124]

As described above, according to the present invention,
The work process is simplified by using one printing mask for printing the solder film on the wiring pattern formed on the printed circuit board that mounts multiple electronic components with different lead pin pitches and areas. It is possible to prevent the deterioration of the solder quality in the process, prevent the occurrence of a short circuit between the adjacent lead pins, and perform highly accurate soldering.

Further, by mounting a printed circuit board on which electronic parts are mounted by soldering using the solder printing mask according to the present invention, the quality and performance of liquid crystal display devices and other precision electronic equipment are improved. Therefore, the cost can be reduced and the life can be extended.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a solder printing mask according to the present invention.

FIG. 2 is an explanatory diagram of a soldering work process of an electronic component using a solder printing mask according to the present invention.

FIG. 3 is an explanatory diagram of a representative example of a pitch of lead pins to be soldered of a surface mount type electronic component, a plate thickness of a mask for solder printing, and a gap between the lead pins.

FIG. 4 is an explanatory diagram of one embodiment of a solder printing mask according to the present invention.

FIG. 5 is an explanatory view of another embodiment of the mask for solder printing according to the present invention.

FIG. 6 is a developed perspective view illustrating a structural example of a TFT type liquid crystal display module that constitutes a liquid crystal display device on which a printed circuit board using a solder printing mask according to the present invention is mounted.

FIG. 7 shows a wiring diagram of an equivalent circuit of a display matrix section of a liquid crystal display module according to the present invention and a peripheral circuit thereof.

FIG. 8 is a top view showing a state where a video signal drive circuit printed circuit board and a vertical scanning circuit printed circuit board are connected to a display panel.

FIG. 9 is a cross-sectional view of a tape carrier package in which an IC chip forming a drive circuit is mounted on a printed circuit board.

FIG. 10 is a main-portion cross-sectional view showing a state in which the tape carrier package is connected to the video signal circuit terminals of the liquid crystal display panel.

FIG. 11 is a top view illustrating a connection state between a printed circuit board PCB1 for a drive circuit and a printed circuit board PCB2 for a power supply.

FIG. 12 is a top view of a printed circuit board to which the present invention is applied.

FIG. 13 is an explanatory diagram of a conventional soldering work process.

FIG. 14 is an explanatory diagram of shapes of various electronic components molded by plastic and arrangement examples of lead pins thereof.

FIG. 15 is an explanatory diagram of shapes of various electronic components molded by plastic and other examples of arrangement of lead pins thereof.

FIG. 16 is an explanatory diagram of a lead pin shape of a plastic mold and its parallelism.

FIG. 17 is a schematic diagram illustrating the relationship between the thickness of the printed circuit board and the solder film and the parallelism between the lead pins of the electronic component.

FIG. 18 is a schematic diagram illustrating the relationship between the pitch of the lead pins and the thickness of the solder film when soldering electronic components having different lead pin pitches.

[Explanation of symbols]

1 Printed Circuit Board 2 Board-side Alignment Mark 3 Mask-side Alignment Mark 4,4A, 5, 6, 7 Solder Printing Mask 7'Auxiliary Mask Plate 11 A Part 11a A Part Lead Pin 11b A Opening 12 B Part 12a B part lead pin 12b B opening 13C part 13a C part lead pin 13b C opening 14 D part (tape carrier package: TCP), 15 Solder paste 15a, 15b, 15c Printed solder film 16 Squeegee 31, 34 1st part 32, 35 Second component 33, 36 Third component 37 Fourth component MDL Liquid crystal display module SHD Metallic shield case that is the upper frame WD Display window that defines the effective screen of the liquid crystal display module PNL Liquid crystal panel composed of liquid crystal display elements (Or liquid crystal display panel) PCB1 drain Printed circuit board PCB2 Gate printed circuit board PCB3 Interface printed circuit board PRS Prism sheet SPS Diffusion sheet GLB Light guide RFS Reflective sheet BL Backlight LP Backlight LP Cold backlight Cathode fluorescent lamp LS Reflective sheet GC Rubber Bushing LPC Lamp cable MCA Lower case with opening MO for installing light guide GLB JN1, JN2, JN3 Joiner TCP1, TCP2 Tape carrier package INS1, INS2, INS3 Insulating sheet GC Rubber cushion BAT Double-sided adhesive tape ILS Light-shielding spacer SUB1, SUB2 Transparent glass substrate GL Scan signal line DL Video signal line PSV1, PSV2 Protective film BM Light-shielding film LC Liquid crystal g, d Conductor Electrolytic film Cadd Storage capacitor GTM Gate terminal DTM Drain terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Ozone, 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd. (72) Inventor Toshio Shiga, 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd.

Claims (3)

[Claims] 1. A solder printing mask for printing and forming a solder film for soldering and mounting a lead pin of an electronic component on a printed wiring of a printed circuit board, wherein the thickness of the solder printing mask is A solder printing mask, which is locally changed in the vicinity of a component and a printed wiring on which the electronic component is mounted, according to a pitch size of lead pins of the electronic component to be mounted. 2. The mask for solder printing according to claim 1, wherein the local change in the thickness of the printed board is thicker at a portion where the lead pins of the electronic component have a larger pitch and thinner at a portion where the pitch is smaller. . 3. A liquid crystal layer between a pair of transparent substrates in which at least a color filter, a common transparent electrode, and an alignment film are formed on one transparent substrate, and at least a pixel selection transparent electrode and an alignment film are formed on the other transparent substrate. And a printed circuit board on which one or a plurality of electronic components for applying drive signals for driving pixels of the liquid crystal cell are applied to the periphery of the pair of transparent electrodes of the liquid crystal cell. In a liquid crystal display device having at least the printed circuit board, in the vicinity of the printed wiring for soldering the electronic component and the electronic component mounted on the printed wiring,
A liquid crystal display device, characterized in that it is soldered with a solder film formed by using a solder printing mask whose plate thickness is locally changed according to the size of the lead pin pitch of the electronic component to be mounted.