JPH07336047A - Insulating layer forming method for multilayer printed board - Google Patents

Abstract

PURPOSE:To form a high-density circuit conductor by accurately effectively utilizing it over the entire area of a board material. CONSTITUTION:A method for forming the insulating layer of a multilayer printed board 20 comprises the step of alternately forming at least circuit conductors 22, 24 and insulting layers 23, 25 covering the conductors 22, 24 on the main surface of a board material 21. The layer 23 is printed to be formed on the conductor 22 by a screen printing method for extruding insulating paste 10 from printing holes 34 provided at a screen printing plate 30 by a squeegee 11. The plate 30 is so formed with a buffer printed area in which the many holes 34 are so opened from the periphery of an insulating layer printed area 31 toward the outer periphery as to be gradually reduced at the opening rate between the area 31 and a non-printed area 32 corresponding to the conductor 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the above-mentioned insulation in a multilayer printed circuit board in which at least a circuit conductor portion and an insulating layer covering the circuit conductor portion are alternately formed in a laminated state on the main surface of a substrate material. Regarding the method for forming a layer, more specifically, the insulating layer of a multilayer printed circuit board is formed by a screen printing method in which an insulating paste is extruded from a plate opening of a screen plate by a squeegee and a pattern is printed on a circuit conductor portion. It relates to a forming method.

[0002]

2. Description of the Related Art A printed circuit board mounted on an electric or electronic device has a circuit conductor portion or a mounting component laminated on a main surface of a substrate material as the device becomes smaller, lighter and more sophisticated. A so-called multilayer printed circuit board formed in multiple layers is being attempted. For example, a two-layer printed circuit board is configured by alternately stacking two layers of circuit conductor portions and insulating layers on the main surface of a substrate material.

This multilayer printed circuit board is a first circuit conductor formed of a copper foil pattern on the main surface of a substrate material such as a heat-resistant resin substrate, a ceramic substrate, a resin substrate containing glass fiber, etc. by, for example, a photo etching method. After forming the portion, the first insulating layer is formed of the insulating resin material so as to cover the first circuit conductor portion. Then, a second circuit conductor portion is formed on the first insulating layer by using, for example, a copper paste, and a second insulating layer is formed on the second circuit conductor portion by an insulating resin material. To be done.

The circuit conductor portion is generally formed on the substrate material by printing such as photo-etching method, screen printing method, offset printing or the like, and the insulating layer is generally screen printing method, offset printing method or coating method. Formed by. The insulating layer is made of epoxy resin material, polyester resin material, vinyl formal resin material, or the like. Also,
Along with the higher density of the circuit conductors, positioning marks and the like that are read by an image recognition mechanism or the like are also formed on the printed circuit board.

The screen printing method includes a screen plate arranged on a screen such as silk and a squeegee.
And a paste (ink) is a relatively simple printing method that is a basic requirement, and is a method that can produce a relatively accurate printed image with mass productivity. , Printed circuit boards, thick film hybrid ICs, etc. are also actively used during manufacturing processes in the field of electronics. For example, in the manufacturing process of a printed circuit board, this screen printing method is used for a cream solder part for connecting an etching resist for forming a circuit conductor pattern to a copper-clad resin substrate, resist printing of a solder resist, or connecting an electric component to be mounted. It is used in cream solder printing to form

The screen printing method, as shown in FIG. 10 and FIG.
It is also used when the first insulating layer 4 covering the first circuit conductor portion 3 formed on the main surface of the substrate material 2 is formed by printing. The second circuit conductor portion 5 is formed on the first insulating layer 4 by screen printing or offset printing using copper paste or the like. Furthermore, the second
Although not shown, a second insulating layer is formed by printing on the circuit conductor portion 5 of FIG. The first insulating layer 4 described above is formed by printing the insulating paste 10 on the main surface of the substrate material 2 so as to cover the entire surface of the first circuit conductor portion 3 in a so-called solid coating state as described later. Therefore, the screen printing plate 6 shown in FIG. 8 is used.

The screen printing plate 6 constitutes an insulating layer printing region 8 having a plate opening in a region corresponding to the formation region of the first circuit conductor 3 in the paste impermeable plate material. Therefore, the screen printing plate 6 has the insulating layer printing area portion 8
A peripheral portion surrounding the is configured as a non-printing area portion 9 that does not allow the insulating paste 10 to pass therethrough.

As shown in FIG. 9, this screen printing plate 6 is opposed to the main surface of the substrate material 2 on which the first circuit conductor portion 8 which is the object to be printed placed on the device base is formed. It is arranged so as to be held by a plate frame holder (not shown) and joined to the screen 13. The insulating paste 10 having an appropriate viscosity is supplied to the screen 13 to which the screen printing plate 6 is joined, and the squeegee 11 is moved on the surface of the screen 13 as shown in FIG.
The squeegee 11 presses the insulating paste 10 to pass through the fine mesh of the screen 13, and the insulating material printing area portion 8 which is the plate opening of the screen printing plate 6 is passed through the substrate material 2
Supply on the main surface of. As a result, the insulating paste 10
As shown in FIG. 9, the first insulating layer 4 is formed by printing on the first circuit conductor portion 3 formed on the substrate material 2.

The insulating layer 4 printed and formed on the substrate material 2 by the screen printing method has a squeegee speed, a squeegee pressure, a printing gap between the main surface of the substrate material 2 and the screen printing plate 6 or a viscosity of the insulating paste 10. Depending on the conditions, the film thickness is formed differently depending on the amount of the insulating paste 10 extruded from the insulating layer printing area portion 8 which is the plate opening provided in the screen printing plate 6. Therefore,
These conditions are well controlled and the multilayer printed circuit board 1
Is manufactured.

The insulating layer printing area portion 8 of the screen printing plate 6 has the first insulating layer 4 as a frame, which is larger than the outer dimension of the substrate material 2 regardless of the formation area of the first circuit conductor portion 3. It is also considered to print the entire surface of the material 2. However, in such a screen printing method, since the phenomenon that the insulating paste 10 wraps around the end portion or the bottom surface side of the substrate material 2 occurs, the screen printing plate 6 generally includes the insulating layer printing area portion 8 as described above. The non-printing area portion 9 is formed in the peripheral portion.

[0011]

As described above, in the conventional screen printing plate 6, the insulating layer printing area portion 8 and the non-printing area portion 9 in the area corresponding to the first circuit conductor portion 3 are clearly separated. Is configured. Therefore, the first insulating layer 4 formed by printing on the main surface of the substrate material 2 has a raised portion 12 of the insulating paste 10 in the outer peripheral portion, as shown in FIG. For example, the squeegee 11 is moved from one side to the other side of the screen printing plate 6 as shown by an arrow in FIG. 7 when the first insulating layer 4 is formed by printing. Although the insulating paste 10 is pressed onto the main surface of the substrate material 2, the insulating layer printing area 8
Insulating paste 1 at the boundary between the non-printing area 9 and
This is due to the fact that 0 is not well cut and remains. The occurrence of the raised portion 12 becomes more remarkable as the thickness of the insulating layer 4 increases.

The second circuit conductor portion 5 is formed on the first insulating layer 4 formed by printing on the substrate material 2, but when it is formed over the raised portion 12 described above, Since the thickness dimension of the first insulating layer 4 is not uniform, there arises a problem that a high density circuit conductor portion cannot be formed with high precision due to distortion or the like. Therefore, in the conventional multilayer printed circuit board 1, the second circuit conductor portion 5, the positioning mark, or the like is formed in the area inside the first insulating layer 4 avoiding the raised portion 12.

Further, in the conventional multilayer printed circuit board 1, when the second circuit conductor portion 5 is formed by utilizing the raised portion 12 as well, it is difficult to form a highly accurate circuit conductor portion. On the other hand, when the formation area of the second circuit conductor portion 5 with respect to the substrate material 2 is limited, there is a problem that the so-called yield of the substrate material 2 is poor.

Therefore, the present invention provides a method for forming an insulating layer of a multi-layer printed circuit board, which is capable of forming a high-density circuit conductor portion with high precision and effectively using it over substantially the entire area of a substrate material. It was proposed for the purpose.

[0015]

A method for forming an insulating layer of a multilayer printed circuit board according to the present invention, which achieves this object, comprises at least a circuit conductor portion and an insulating layer covering the circuit conductor portion on a main surface of a substrate material. Is a method for forming an insulating layer of a multilayer printed circuit board which is alternately formed in a laminated state, wherein the insulating layer is formed by extruding an insulating paste with a squeegee from a printing hole provided in a screen printing plate to cover a circuit conductor portion. It is formed by a screen printing method of printing on. In the screen printing plate on which the insulating layer is formed by printing, a large number of printing holes are formed between the insulating layer printing area portion and the non-printing area portion corresponding to the circuit conductor portion from the peripheral portion of the insulating layer printing area portion to the outer peripheral portion side. A screen printing plate is used in which a buffer area portion is formed in which the opening ratio is gradually reduced toward.

Further, in the method for forming an insulating layer of a multilayer printed circuit board according to the present invention, the insulating layer has a large number of printed holes insulated between the insulating layer printed area portion and the non-printed area portion corresponding to the circuit conductor portion. Printing is performed using a screen printing plate in which a buffer printing area portion is formed in which the number of holes is gradually reduced from the peripheral portion of the layer printing area portion toward the outer peripheral portion side.

Further, in the method for forming an insulating layer of a multilayer printed circuit board according to the present invention, the insulating layer has a plurality of printing holes insulated between the insulating layer printed area portion corresponding to the circuit conductor portion and the non-printed area portion. Printing is performed using a screen printing plate in which a buffer printing area portion is formed in which the diameter is gradually reduced from the peripheral portion of the layer printing area portion toward the outer peripheral portion side.

Furthermore, in the method for forming an insulating layer of a multilayer printed circuit board according to the present invention, the insulating layer has a large number of printing holes between the insulating layer printed area portion and the non-printed area portion corresponding to the circuit conductor portion. A screen printing plate is used in which the buffer printing area portion is formed such that the number of the printing holes is gradually reduced from the peripheral portion of the insulating layer printing area portion toward the outer peripheral portion side and the opening diameters of these printing holes are gradually reduced. And formed by printing.

[0019]

According to the method for forming an insulating layer of a multilayer printed circuit board according to the present invention having the above-described structure, the insulating layer has a large number of printing holes in the outer peripheral portion in the peripheral portion of the insulating layer printing area portion. By forming by printing using a screen printing plate having a buffer printing area portion that is gradually reduced toward the side, the thickness of the wall rises at the boundary portion between the printing area portion and the non-printing area portion. Printing is performed in a state where the thickness of the peripheral portion is gradually reduced toward the outer peripheral portion without generating a portion. Therefore, the multilayer printed circuit board can efficiently form the second circuit conductor portion or the positioning mark on the peripheral portion of the insulating layer, so that the board material can be effectively used and the high density circuit conductor portion can be effectively used. Are formed with high precision over substantially the entire area of the substrate material.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below in detail with reference to the drawings. The embodiment multilayer printed circuit board 20 is also a so-called two-layer printed circuit board, and as shown in FIG. 2, the first circuit conductor portion 2 is formed on the main surface of the substrate material 21.
2, the first insulating layer 23, the second circuit conductor portion 24 and the second
The insulating layer 25 and the insulating layer 25 have a basic structure formed in a laminated state. The multilayer printed circuit board 20 has a first circuit conductor formed by forming a solder resist layer 26 between the first circuit conductor portion 22 and the first insulating layer 23 formed on the substrate material 21. Portion 22 and second circuit conductor portion 24
And jumper 27 are connected.

FIG. 3 shows an embodiment two-layer printed circuit board 20 in which each constituent layer is formed through each manufacturing process on a substrate material 21 formed of a heat-resistant resin substrate, a ceramic substrate, a resin substrate containing glass fiber, or the like. It is explanatory drawing of the main processes of. The first circuit conductor portion 22 is formed on the substrate material 21 by, for example, a well-known photo etching method or the like, as shown in FIG. Next, the substrate material 21 is covered with the first circuit conductor portion 22 by using an appropriate method such as a known coating method or a screen method as shown in FIG. Layer 26 is formed. It should be noted that the solder resist layer 26 is not particularly necessary when the connection processing of the first circuit conductor portion 22 is unnecessary.

Screen printing using a screen printing plate 30 described later is performed on the solder resist layer 26, so that the first insulating layer 2 is formed as shown in FIG. 3 (D).
3 is printed. Then, a second circuit conductor portion 24 having a predetermined circuit pattern is formed on the first insulating layer 23 by a screen printing method, an offset printing method, or the like using a copper paste or the like. As shown in E), it is formed by printing. In this case, the second circuit conductor portion 24
Is appropriately connected to the first circuit conductor portion 22 via a jumper 25 via a through hole penetrating the first insulating layer 23 as necessary. Further, as with the first insulating layer 23, the second insulating layer 25 is formed on the second circuit conductor portion 24 by the screen printing method or the coating method.
The two-layer printed circuit board 20 is completed by the formation as shown in FIG.

The manufacturing process itself of the two-layer printed circuit board 20 shown in FIG. 3 is the same as the conventional manufacturing process, but the first circuit conductor part 24 of high precision is formed in the upper layer. The present invention is characterized in that a screen printing process for forming the insulating layer 23 is performed, particularly screen printing is performed using a screen printing plate 30 described later. Of course,
The screen printing plate 30 has a solder resist layer 26 as a second layer, and is suitable for application also when manufacturing a multilayer printed circuit board in which the solder resist layer 26 is formed by a screen printing process.

The screen printing process itself is performed in the same manner as the above-mentioned conventional screen printing method described in detail with reference to FIG. That is, the screen printing plate 30 is held by a plate frame holder (not shown) so as to face the main surface of the substrate material 21 on which the first circuit conductor portion 22 and the solder resist layer 26 are formed by the first and second steps. Are arranged so as to be joined to the screen 13. The screen 13 to which the screen printing plate 30 is joined
Is supplied with an insulating paste 10 having an appropriate viscosity, and the squeegee 11 is moved along the surface of the screen 13. The squeegee 11 presses the insulating paste 10 through a fine mesh of the screen 13 and supplies the squeegee 11 onto the main surface of the substrate material 21 from the opening of the screen printing plate 30. As a result, the insulating paste 10 is formed as shown in FIG.
As shown in (D), the first insulating layer 23 is formed by printing on the solder resist layer 26 formed on the substrate material 21.

As shown in FIG. 1, the screen printing plate 30 used for forming the above-mentioned first insulating layer 23 is a region corresponding to the region where the solder resist layer 26 is formed on the paste impermeable plate material. An insulating layer printing area portion 31 configured as an opening portion is provided on the inner surface of the sheet, and a buffer printing area portion 33 is formed in an area between the insulating layer printing area portion 31 and the outermost non-printing area portion 32. It is configured.

As shown in FIG. 1, the buffer printing area 33 is formed as an area in which a large number of printing holes 34 are formed in the plate material. The printing holes 34 are formed in a dense state with a large number in the peripheral portion of the insulating layer printing region portion 31, but the number is gradually reduced toward the outer peripheral portion side of the screen printing plate 30. In this way, it is drilled in a rough state. In other words, the screen printing plate 30 is provided with a large number of printing holes 34 whose opening ratio is gradually reduced from the peripheral portion of the insulating layer printing area portion 31 toward the outer peripheral portion side. Note that FIG. 1 schematically shows an arrangement state of these printing holes 34, and each printing hole 34 has an independent shape in which insulating pastes 10 extruded and printed as described later are overlapped with each other. They are arranged at intervals not identified by.

That is, as shown in FIG. 4, when the insulating paste 10 is extruded from the printing hole 34 by the squeegee 11, the solder resist layer 26 or the substrate material 21.
Spread along the main surface of. As shown in FIG. 5, the spread of the insulating paste 10 is substantially concentric with the printing hole 34 as a center, and is formed with a diameter slightly larger than the diameter of the printing hole 34. Each printing hole 34 has a continuous insulating layer 23 in which the extruded insulating paste 10 overlaps each other.
Is printed on the solder resist layer 26 or the substrate material 21.

As described above, the screen printing plate 30
Is the buffer printing area portion 33 in which the printing start point and the printing end point of the first insulating layer 23 are located on the outer peripheral side of the solder resist layer 26. The plurality of printing holes 34 formed in the buffer printing area 33 are provided in the insulating layer printing area 31.
Since the openings are arranged so that the opening ratio is gradually reduced from the peripheral portion toward the outer peripheral portion, the insulating paste 10 extruded in the region near the insulating layer printing region portion 31.
Is increased, and an insulating layer having a large thickness dimension is formed. Further, in the area away from the insulating layer printing area portion 31, the amount of the insulating paste 10 pushed out gradually decreases, and the thickness dimension becomes small.

Therefore, the first insulating layer 23 printed and formed on the substrate material 21 using the screen printing plate 30.
As shown in FIG. 2, the printed portion is formed on the solder resist layer 26 without forming a thick raised portion in the peripheral portion of the solder resist layer 26 corresponding to the insulating layer print area portion 31. A uniform insulating layer 23A having a uniform thickness dimension,
A buffer insulating layer 23B which is continuous with the uniform insulating layer 23A formed by printing on the peripheral portion of the solder resist layer 26 corresponding to the buffer printed portion area 33 and whose thickness is gradually reduced toward the outer peripheral portion of the substrate 21. Composed by.

Therefore, the two-layer printed circuit board 20 is held to have a uniform thickness dimension in the vicinity of the outer peripheral portion of the substrate material 21 corresponding to the first circuit conductor portion 22, and is equivalent to the first circuit conductor portion 22. On the first insulating layer 23 in the region of
It is possible to form the circuit conductor portion 24. Also,
In this two-layer printed circuit board 20, it becomes possible to accurately print and form the positioning marks and the like required for forming the second circuit conductor portion 24 on the outer peripheral portion of the first insulating layer 23. As a result, the material efficiency of the substrate material 21 can be improved, and the size and weight of the device can be reduced, or the cost can be reduced.

FIG. 6 is a diagram schematically showing another example of the structure of the printing holes provided in the buffer printing area 33 of the screen printing plate 30. This second embodiment screen printing plate 3
In FIG. 0, as shown in the figure, a large number of printing holes 35 provided in the buffer printing area portion 33, which are the printing start point and the printing end point, are formed from the peripheral portion of the insulating layer printing area portion 31 toward the outer peripheral portion side. It is configured so that the opening diameter is gradually reduced. The screen printing plate 30 configured as described above supplies a larger amount of the insulating paste 10 from the large-diameter printing hole 35 onto the solder resist layer 26 or the substrate material 21 in a region close to the insulating layer printing region portion 31. The supply amount of the insulating paste 10 from the printing hole 35 having a gradually smaller diameter gradually decreases toward the printing region portion 32 side.

The first insulating layer 23 formed by printing on the substrate material 21 by using the screen printing plate 30 having the printing holes 35 provided in the buffer printing area 33 as described above is the first embodiment described above. As in the case where the screen printing plate 30 is used, a thick ridge portion does not occur in the peripheral portion of the solder resist layer 26 corresponding to the insulating layer printing area portion 31, and the solder resist layer 26 is formed above the solder resist layer 26. A uniform insulating layer 23A having a uniform thickness dimension formed by printing and a uniform insulating layer 23A formed by printing on the peripheral portion of the solder resist layer 26 corresponding to the buffer printing area portion 33 are continuous to the outer peripheral portion of the substrate 21. And a buffer insulating layer 23B whose thickness is gradually reduced.

FIG. 7 is also a diagram schematically showing another configuration example of the printing holes provided in the buffer printing area portion 33 of the screen printing plate 30, which is similar to the screen printing plate 30 of the second embodiment described above. In addition, a large number of printing holes 36 provided in the buffer printing area 33 serving as the printing start point and the printing end point are configured such that the opening diameter is gradually reduced from the peripheral portion of the insulating layer printing area portion 31 toward the outer peripheral side. Has been done. The screen printing plate 30 of the third embodiment is characterized in that the printing holes 36 that are adjacent to each other from the insulating layer printing area portion 31 toward the outer peripheral side are formed with their centers displaced from each other. .

Also in the screen plate 30 having such a structure, in a region close to the insulating layer printing region portion 31, a larger amount of the insulating paste 10 is transferred from the large-diameter printing hole 36 onto the solder resist layer 26 or the substrate material 21. The supply amount of the insulating paste 10 is gradually reduced in the region where the printing holes 36 having the diameter that is supplied and is gradually reduced toward the non-printing region portion 32 side are formed. The printing holes 36 are formed by offsetting the centers of adjacent printing holes from each other, so that the insulating pastes 10 extruded from the printing holes 36 are reliably overlapped to form a continuous buffer insulating layer 23B. To do.

[0035]

As described in detail above, according to the method for forming an insulating layer of a multilayer printed circuit board according to the present invention, a thick raised portion is formed in the peripheral portion on the first circuit conductor portion. The insulating layer having a uniform thickness dimension is printed without any need, and the second circuit conductor portion or the positioning mark can be efficiently formed in the peripheral portion of this insulating layer. In addition, the high-density circuit conductor portion can be formed with high accuracy over substantially the entire area of the substrate material.

[0036]

[Brief description of drawings]

FIG. 1 is a plan view schematically showing a configuration of a screen plate used in an insulating layer forming method for a multilayer printed circuit board according to the present invention.

FIG. 2 is a longitudinal sectional view of an essential part of a two-layer printed circuit board manufactured by the method for forming an insulating layer of the same multilayer printed circuit board.

FIG. 3 is a diagram illustrating a main step of a two-layer printed circuit board manufactured by the method for forming an insulating layer of the same multilayer printed circuit board.

FIG. 4 is a longitudinal sectional view of a main part for explaining the principle of screen printing.

FIG. 5 is a plan view of relevant parts for explaining a state of an insulating paste after printing.

FIG. 6 is a main part plan view schematically showing another configuration of the screen plate.

FIG. 7 is a plan view of an essential part schematically showing another configuration of the screen plate.

FIG. 8 is a plan view schematically showing the configuration of a conventional screen plate.

FIG. 9 is a longitudinal sectional view of an essential part for explaining a conventional printing operation of an insulating layer.

FIG. 10 is a longitudinal sectional view of an essential part for explaining a formation state of a first layer of a conventional printed board.

FIG. 11 is a longitudinal sectional view of an essential part for explaining a formation state of the second layer.

[Explanation of symbols]

 10 Insulating Paste 11 Squeegee 13 Screen 20 Two Layer Printed Circuit Board 21 Board Material 22 First Circuit Conductor Part 23 First Insulating Layer 24 Second Circuit Conductor Part 25 Second Insulating Layer 30 Screen Plate 31 Insulating Layer Printing Area Part 32 non-printing area 33 buffer printing area 34 printing hole

Claims (4)

[Claims] 1. A method for forming an insulating layer of a multilayer printed circuit board, wherein at least a circuit conductor portion and an insulating layer covering the circuit conductor portion are alternately formed in a laminated state on a main surface of a substrate material. The insulating layer formed by the screen printing method in which the squeegee is pushed out from the printing hole provided in the screen printing plate to print so as to cover the circuit conductor portion is an insulating layer printed area portion and a non-printed area corresponding to the circuit conductor portion. A screen printing plate having a large number of printing holes between the printed circuit board and a peripheral portion of the insulating layer printing area portion is formed with a gradually decreasing opening ratio to form a buffer printing area portion. A method for forming an insulating layer on a multilayer printed circuit board, characterized in that a thickness dimension of a peripheral portion is gradually reduced toward an outer peripheral portion by printing. 2. The insulating layer has a large number of printing holes between the insulating layer printing area portion and the non-printing area portion corresponding to the circuit conductor portion from the peripheral portion of the insulating layer printing area portion toward the outer peripheral portion side. 2. The method for forming an insulating layer on a multilayer printed circuit board according to claim 1, wherein the screen printing plate is used to form a buffer printing area portion which is gradually reduced in number and is formed. 3. The insulating layer has a large number of printing holes between the insulating layer printing area portion and the non-printing area portion corresponding to the circuit conductor portion from the peripheral portion of the insulating layer printing area portion toward the outer peripheral portion side. 2. The method for forming an insulating layer on a multilayer printed circuit board according to claim 1, wherein the screen printing plate is used to form a buffer printing area portion having a gradually reduced diameter and formed therein. 4. The insulating layer has a plurality of printing holes between the insulating layer printing area portion and the non-printing area portion corresponding to the circuit conductor portion from the peripheral portion of the insulating layer printing area portion toward the outer peripheral side. The screen printing plate is formed by using a screen printing plate in which a buffer printing area portion is formed in which the number of the printing holes is gradually reduced and the opening diameters of these printing holes are gradually reduced. A method for forming an insulating layer of a multilayer printed circuit board.