CN219935886U

CN219935886U - Mainboard ICT testing arrangement

Info

Publication number: CN219935886U
Application number: CN202320970967.7U
Authority: CN
Inventors: 许昌青; 徐晓华; 白卫锋
Original assignee: LCFC Hefei Electronics Technology Co Ltd
Current assignee: LCFC Hefei Electronics Technology Co Ltd
Priority date: 2023-04-25
Filing date: 2023-04-25
Publication date: 2023-10-31
Anticipated expiration: 2033-04-25

Abstract

The utility model provides a mainboard ICT testing device, which comprises: the test host comprises an upper module, a lower module and a transmission module, wherein the transmission module is used for transmitting the printed circuit board between the upper module and the lower module, a first avoidance member for avoiding components on the upper surface of the printed circuit board is arranged on the upper module, a second avoidance member for avoiding circuits on the lower surface of the printed circuit board is arranged on the lower module, the test host comprises a test state and a transmission state, and the first avoidance member and the second avoidance member are respectively abutted to the smooth surface of the printed circuit board in the test state; in the conveying state, the upper module and the lower module are separated from the printed circuit board. The main board ICT testing device can reduce the rejection rate of the printed circuit board caused by ICT testing.

Description

Mainboard ICT testing arrangement

Technical Field

The utility model relates to the field of printed circuit board testing, in particular to a main board Information and Communication Technology (ICT) testing device.

Background

In-Circuit-Tester is an automatic on-line Tester, and is a test device for PCBA (Printed-Circuit Board Assembly, printed Circuit Board Assembly) production necessary for modern electronic enterprises. The ICT test mainly detects the open circuit, short circuit and welding condition of all parts of the PCBA by contacting the exposed test point of the PCBA through the test probe, and can be divided into open circuit test, short circuit test, resistance test, capacitance test, diode test, triode test, field effect tube test, IC pin test and the like, so as to obtain faults such as neglected loading, wrong loading, parameter value deviation, welding spot continuous welding, circuit board open circuit and short circuit and the like of general and special components.

ICT is anchor clamps structure, including accepting the face and holding the face with pressing, accept face and hold the face and increase milling part according to PCBA's part overall arrangement and give way, the remaining part reserves the plane, with PCBA direct contact during the test.

When foreign matters remain on the smooth surface of the main board, the double-sided pressing of the test fixture easily causes the pressed deformation of the PCBA upper surface components. The PCBA lower surface circuit is intensive, often has the circuit to pass through in the pressure wound position, and the circuit is pressed and is wound the deformation and cause the fracture, can't maintain to lead to PCBA to scrap.

Disclosure of Invention

The main objective of the present utility model is to provide a motherboard ICT testing device, which at least solves the above technical problems existing in the prior art.

In order to achieve the above object, the present utility model provides a motherboard ICT test device, comprising: the test host comprises an upper module, a lower module and a transmission module, wherein the transmission module is used for transmitting a printed circuit board to the position between the upper module and the lower module, a first avoidance member for avoiding components on the upper surface of the printed circuit board is arranged on the upper module, a second avoidance member for avoiding circuits on the lower surface of the printed circuit board is arranged on the lower module, the test host comprises a test state and a transmission state, and in the test state, the first avoidance member and the second avoidance member are respectively abutted to the smooth surface of the printed circuit board; and in the conveying state, the upper module and the lower module are separated from the printed circuit board.

In an implementation manner, the upper module comprises an upper pressing plate and a driving electric cylinder for driving the upper pressing plate to move towards the conveying module, the driving electric cylinder is fixedly arranged in the test host, the first avoiding member is arranged on one face of the upper pressing plate, which faces towards the conveying module, and the first avoiding member comprises a plurality of nail-shaped structural members, and the nail-shaped structural members are located on the upper surface of the printed circuit board.

In an embodiment, the lower module is fixedly arranged, the lower module comprises a carrier plate for placing the printed circuit board, the second avoidance member is arranged on the carrier plate, the second avoidance member comprises a plurality of strip-shaped structural members, and the strip-shaped structural members are away from a circuit on the lower surface of the printed circuit board.

In one embodiment, the transmission module includes: the pressing mechanism is used for driving the printed circuit board to move towards the lower module under the test state until the lower surface of the printed circuit board abuts against the second avoiding member.

In one embodiment, the pressing mechanism includes: the device comprises a pressing driving mechanism, a rebound mechanism and a lifting pressing plate parallel to the conveying direction of the printed circuit board, wherein the lifting pressing plate is arranged at equal height positions on two sides of the conveying direction of the printed circuit board, the rebound mechanism is abutted to the bottom of the lifting pressing plate, the pressing driving mechanism is arranged on the upper side of the lifting pressing plate, a pressing piece is arranged at the output end of the pressing driving mechanism, the pressing piece can move downwards under the driving of the pressing driving mechanism and drives the lifting pressing plate to move from a first height to a second height, the first height corresponds to the height position of the lifting pressing plate in the conveying state, and the second height corresponds to the height position of the lifting pressing plate in the testing state; after the pressing piece moves upwards, the lifting pressing plate is restored to the first height from the second height under the action of the rebound mechanism.

In an embodiment, a first clamping groove is formed in the bottom of the lifting pressing plate, and the conveying mechanism is arranged in the first clamping groove.

In one embodiment, the transfer mechanism includes: the conveying shaft is fixedly arranged on the inner wall of the first clamping groove, the conveying wheel is rotatably arranged on the conveying shaft, and when the printed circuit board is conveyed onto the conveying belt, the printed circuit board moves in a clamping gap formed by the top wall of the first clamping groove and the conveying belt.

In an implementation manner, the cleaning mechanism comprises a first conveying runner and a spray gun, wherein the cleaning mechanism is arranged at the front position of the test host, the air outlet of the spray gun faces the first conveying runner, and when the lifting pressing plate is located at the first height, the output end of the first conveying runner is connected with the input end of the conveying belt.

In an implementation manner, the sorting mechanism comprises a second conveying runner, a good runner, a bad runner and a pushing plate mechanism, wherein the sorting mechanism is arranged behind the testing host, when the lifting pressing plate is located at the first height, the input end of the second conveying runner is connected with the output end of the conveying belt, the good runner and the bad runner are both arranged on the side edge of the second conveying runner, and the printed circuit board is pushed from the second conveying runner to the good runner or the bad runner through the pushing plate mechanism.

In one embodiment, the first conveying runner is provided with a first sensor for positioning the cleaning position of the printed circuit board; and a second sensor for positioning the test position of the printed circuit board is arranged on the lifting pressing plate.

According to the main board ICT testing device, the cleaning mechanism is utilized to clean the surface foreign matters of the printed circuit board in advance, so that the probability of crushing the upper surface components of the printed circuit board can be reduced when the test host machine performs ICT testing. A first avoiding member is additionally arranged on an upper module of the test host to avoid components on the upper surface of the printed circuit board; the second avoidance member is additionally arranged on the lower module to avoid the circuit on the lower surface of the printed circuit board, so that the printed circuit board during ICT test is further protected, and the rejection rate of the printed circuit board due to the pressure loss caused by ICT test is reduced.

It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the utility model or to delineate the scope of the utility model. Other features of the present utility model will become apparent from the description that follows.

Drawings

The above, as well as additional purposes, features, and advantages of exemplary embodiments of the present utility model will become readily apparent from the following detailed description when read in conjunction with the accompanying drawings. Several embodiments of the present utility model are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

in the drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

FIG. 1 is a schematic diagram of a motherboard ICT test apparatus according to an embodiment of the present utility model;

FIG. 2 is a schematic diagram of a cleaning mechanism and a test host according to an embodiment of the present utility model;

fig. 3 is an enlarged view of a portion a in fig. 2;

FIG. 4 is a schematic diagram of an upper module structure according to an embodiment of the present utility model;

FIG. 5 is a schematic view of a lower module structure according to an embodiment of the present utility model;

fig. 6 is a schematic view of a part of the structure of a sorting mechanism according to an embodiment of the present utility model.

Wherein the above figures include the following reference numerals:

1. a cleaning mechanism; 11. a first transfer flow path; 12. a spray gun; 2. testing a host; 21. an outer case; 22. an upper module; 221. driving the electric cylinder; 222. an upper press plate; 223. a first bypass member; 2231. a spike-shaped structural member; 23. a lower module; 231. a carrier plate; 232. a second bypass member; 2321. a strip-shaped structural member; 241. a conveying mechanism; 2411. a conveyor belt; 2412. a transfer wheel; 2413. a conveying shaft; 2414. a clamping gap; 242. a pressing mechanism; 2421. a pressing-down driving mechanism; 2422. a rebound mechanism; 24221. a positioning rod; 24222. a support column; 24223. a rebound spring; 24224. a positioning ring; 2423. a lifting pressing plate; 24231. a first clamping groove; 2424. a pressing piece; 3. a sorting mechanism; 31. a second transfer flow path; 32. a good product runner; 33. inferior product flow passage; 34. a push plate mechanism; 35. good product positioning sensor; 36. inferior product positioning sensor; 37. a collecting device; 4. a printed circuit board.

Detailed Description

In order to make the objects, features and advantages of the present utility model more comprehensible, the technical solutions according to the embodiments of the present utility model will be clearly described in the following with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present utility model, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Referring to fig. 1, the present utility model provides a motherboard ICT test device, including: the cleaning mechanism 1, the testing host 2 and the sorting mechanism 3 are arranged at the front position of the testing host 2, and the cleaning mechanism 1 is used for cleaning the surface of the printed circuit board 4 before entering the testing host 2, so that the automatic cleaning of the surface of the foreign matters can be realized, and the occurrence of the residual crush event of the foreign matters is reduced in the ICT test; the sorting mechanism 3 is arranged at the rear position of the testing host 2 and is used for sorting and circulating the qualified products and unqualified products after the ICT of the testing host 2 on the printed circuit board 4 is completed.

In the embodiment of the present utility model, the test host 2 includes a test state and a transmission state, and in the test state, the test host 2 performs an ICT test on the printed circuit board 4; the transfer state includes a process in which the printed circuit board 4 is transferred to the test position and the printed circuit board 4 is transferred from the test position to the sorting mechanism 3, wherein the test host 2 is switched from the transfer state to the test state when the printed circuit board 4 is transferred to the test position.

Referring to fig. 2, the test host 2 includes an upper module 22, a lower module 23, and a transfer module, wherein the transfer module is located between the upper module 22 and the lower module 23 and is used for transferring the printed circuit board 4 to a testing position, and the upper module 22 and the lower module 23 are respectively in contact with the upper and lower surfaces of the printed circuit board 4 during an ICT test process on the printed circuit board 4.

Referring to fig. 2 and 3, in an embodiment of the present utility model, a transfer module includes: the conveying mechanism 241 and the pushing mechanism 242, the pushing mechanism 242 is used for driving the printed circuit board 4 to move towards the lower module 23 in the testing state, and the pushing mechanism 242 comprises: the pressing driving mechanism 2421, the rebound mechanism 2422 and the lifting pressing plates 2423 parallel to the conveying direction of the printed circuit board 4 are symmetrically arranged at the two sides of the conveying direction of the printed circuit board 4, the rebound mechanism 2422 is abutted to the bottom of the lifting pressing plates 2423, on one hand, the action of supporting the lifting pressing plates 2423 is achieved, on the other hand, after the lifting pressing plates 2423 are subjected to downward pressure movement, the pressing force is removed, and the lifting pressing plates 2423 can rebound. The pressing driving mechanism 2421 is arranged on the upper side of the lifting pressing plate 2423 and is fixedly connected with the outer case 21 of the test host 2, the pressing piece 2424 is arranged at the output end of the pressing driving mechanism 2421, the pressing piece 2424 can move downwards under the driving of the pressing driving mechanism 2421 and drives the lifting pressing plate 2423 to move downwards from a first height to a second height, the first height corresponds to the height position of the lifting pressing plate 2423 in a conveying state, and the second height corresponds to the height position of the lifting pressing plate 2423 in a test state; after the hold-down gear 2424 moves upward, the lifting press plate 2423 is restored from the second height to the first height by the resilient mechanism 2422.

Referring to fig. 2 and 3, specifically, the rebound mechanism 2422 includes a positioning rod 24221, a supporting column 24222 and a rebound spring 24223, wherein a top of the positioning rod 24221 is fixedly disposed with the supporting column 24222 through a connecting piece, such that the positioning rod 24221 is disposed vertically parallel to the supporting column 24222, the lifting platen 2423 is slidably disposed on the positioning rod 24221, the rebound spring 24223 is sleeved on the positioning rod 24221, and a top of the rebound spring 24223 abuts against a bottom of the lifting platen 2423, and the rebound spring 24223 is compressed after the lifting platen 2423 moves downward along an extending direction of the positioning rod 24221. The positioning rod 24221 is provided with a positioning ring 24224, the positioning ring 24224 is arranged on the upper side of the lifting pressing plate 2423, and when the lifting pressing plate 2423 is abutted against the positioning ring 24224, the lifting plate is located at the first height, and the positioning ring 24224 can limit the rebound height of the lifting pressing plate 2423 upwards from the second height.

Referring to fig. 3, in the embodiment of the present utility model, a first clamping groove 24231 is provided at the bottom of the lifting platen 2423, the transfer mechanism 241 is provided in the first clamping groove 24231, and the transfer mechanism 241 includes: the conveyor belt 2411, the conveyor wheel 2412 and the conveyor shaft 2413, the conveyor shaft 2413 is fixedly disposed on the inner wall of the first clamping groove 24231, the conveyor wheel 2412 is rotatably disposed on the conveyor shaft 2413, and a clamping gap 2414 is formed between the top wall of the first clamping groove 24231 and the conveyor belt 2411, and when the printed circuit board 4 is conveyed onto the conveyor belt 2411, the printed circuit board 4 moves in the clamping gap 2414.

Referring to fig. 1 and 2, in the embodiment of the present utility model, the cleaning mechanism 1 includes a first conveying channel 11 and a spray gun 12, the spray gun 12 is controlled by a solenoid valve, an air outlet of the spray gun 12 faces the first conveying channel 11, a first sensor (not shown in the figure) for locating a cleaning position of the printed circuit board 4 is disposed on the first conveying channel 11, when the first sensor detects that the printed circuit board 4 reaches the cleaning position, the solenoid valve automatically opens a valve, and compressed air is blown to the surface of the printed circuit board 4 through the spray gun 12 to clean sundries on the printed circuit board 4.

When the lifting/lowering plate 2423 is located at the first height, the output end of the first conveying runner 11 is connected with the input end of the conveying belt 2411, and after the surface of the printed circuit board 4 is cleaned, the printed circuit board 4 is conveyed from the first conveying runner 11 to the clamping gap 2414, and the ICT test is continuously completed through the test host 2.

Referring to fig. 1, 2 and 4, in the embodiment of the present utility model, the upper module 22 includes an upper platen 222 and a driving cylinder 221 for driving the upper platen 222 to move toward the transmission module, the driving cylinder 221 is fixedly disposed in the test host 2 and is fixedly connected with the outer chassis 21 of the test host 2, the upper module 22 is provided with a first avoiding member 223 for avoiding components on the upper surface of the printed circuit board 4, the first avoiding member 223 is disposed on one surface of the upper platen 222 facing toward the transmission module, the first avoiding member 223 includes a plurality of nail-shaped structural members 2231, and the nail-shaped structural members 2231 are specifically disposed according to the layout conditions of the components on the printed circuit board 4 with different types, so as to avoid the components on the upper surface of the printed circuit board 4 from being damaged by pressure in the ICT test process.

Referring to fig. 1, 2 and 5, in the embodiment of the present utility model, the lower module 23 is fixedly disposed at the bottom of the outer chassis 21 of the test host 2, the lower module 23 includes a carrier plate 231 for placing the printed circuit board 4, a second avoidance member 232 is disposed on the carrier plate 231, the second avoidance member 232 is used for avoiding the circuit on the lower surface of the printed circuit board 4, specifically, the second avoidance member 232 includes a plurality of strip-shaped structural members 2321, and the strip-shaped structural members 2321 are disposed according to the circuit layout conditions on the printed circuit board 4 with different types, so as to avoid the circuit on the lower surface of the printed circuit board 4, so as to prevent the circuit on the lower surface of the printed circuit board 4 from being crushed in the ICT test process.

In the test state, the first avoiding member 223 and the second avoiding member 232 are respectively abutted against the smooth surface of the printed circuit board 4; in the transfer state, the upper die set 22 and the lower die set 23 are separated from the printed circuit board 4.

In an embodiment of the present utility model, a second sensor (not shown) is provided on the lift plate 2423 for locating the test position of the printed circuit board 4, and when the lift plate 2423 is at the first elevation and the second sensor detects that the printed circuit board 4 is moved to the test position in the clamp gap 2414, an ICT test is initiated.

During ICT testing, the hold-down gear 2424 is driven by the hold-down drive mechanism 2421 to move downward and drive the lift platen 2423 from the first height to the second height until the lower surface of the printed circuit board 4 abuts the second bypass member 232.

Referring to fig. 1, 2 and 6, in the embodiment of the utility model, the sorting mechanism 3 includes a second conveying channel 31, a good product channel 32, a bad product channel 33 and a pushing plate mechanism 34, where the good product channel 32 and the bad product channel 33 are disposed at the sides of the second conveying channel 31, and the printed circuit board 4 is pushed from the second conveying channel 31 into the good product channel 32 or the bad product channel 33 by the pushing plate mechanism 34. When the lifting platen 2423 is at the first height, the input end of the second conveying runner 31 is connected with the output end of the conveying belt 2411, that is, after the ICT test is completed on the printed circuit board 4, the rebound mechanism 2422 drives the lifting platen 2423 to recover from the second height to the first height, so that the clamping gap 2414 in the test host 2 is in butt joint with the input end of the second conveying runner 31, and the printed circuit board 4 can be circulated into the sorting mechanism 3 to facilitate further sorting operation.

On the second conveying flow channel 31, a good product positioning sensor 35 corresponding to the good product flow channel 32 and a bad product positioning sensor 36 corresponding to the bad product flow channel 33 should be further arranged, when the good product positioning sensor 35 detects that the qualified printed circuit board 4 reaches the inlet of the good product flow channel 32, the qualified printed circuit board 4 is pushed into the good product flow channel 32 by the push plate mechanism 34, and the subsequent processing is performed; when the inferior positioning sensor 36 detects that the unqualified printed circuit board 4 reaches the inlet of the inferior flow channel 33, the unqualified printed circuit board 4 is pushed into the good flow channel 32 by the push plate mechanism 34 and finally collected by the collecting device 37, and reprocessed or destroyed uniformly.

It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps described in the present utility model may be performed in parallel, sequentially, or in a different order, so long as the desired results of the technical solution disclosed in the present utility model can be achieved, and are not limited herein.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. Terms referring to directionality such as "first direction", "second direction", and the like, all refer to a straight line direction unless explicitly defined otherwise. In the description of the present utility model, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

The foregoing is merely illustrative of the present utility model, and the present utility model is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present utility model. Therefore, the protection scope of the present utility model shall be subject to the protection scope of the claims.

Claims

1. Mainboard ICT testing arrangement, its characterized in that includes: the test host (2), the test host (2) includes an upper module (22), a lower module (23) and a transmission module for transmitting the printed circuit board (4) between the upper module (22) and the lower module (23), a first avoidance member (223) for avoiding components on the upper surface of the printed circuit board (4) is arranged on the upper module (22), a second avoidance member (232) for avoiding circuits on the lower surface of the printed circuit board (4) is arranged on the lower module (23), the test host (2) includes a test state and a transmission state, and in the test state, the first avoidance member (223) and the second avoidance member (232) are respectively abutted to the smooth surface of the printed circuit board (4); in the transfer state, the upper module (22) and the lower module (23) are separated from the printed circuit board (4).

2. The motherboard ICT testing device according to claim 1, wherein the upper die set (22) comprises an upper platen (222) and a driving electric cylinder (221) for driving the upper platen (222) to move towards the transfer die set, the driving electric cylinder (221) is fixedly arranged in the testing host (2), the first avoiding member (223) is arranged on one surface of the upper platen (222) facing towards the transfer die set, the first avoiding member (223) comprises a plurality of nail-shaped structural members (2231), and the nail-shaped structural members (2231) avoid components on the upper surface of the printed circuit board (4).

3. The motherboard ICT testing device according to claim 1, wherein the lower module (23) is fixedly arranged, the lower module (23) comprises a carrier plate (231) for placing the printed circuit board (4), the second avoidance member (232) is arranged on the carrier plate (231), the second avoidance member (232) comprises a plurality of strip-shaped structural members (2321), and the strip-shaped structural members (2321) are away from a circuit on the lower surface of the printed circuit board (4).

4. The motherboard ICT testing device of claim 1 wherein the transfer module comprises: the conveying mechanism (241) and the pushing mechanism (242), the pushing mechanism (242) is used for driving the printed circuit board (4) to move towards the lower module (23) in the test state until the lower surface of the printed circuit board (4) abuts against the second avoidance member (232).

5. The motherboard ICT test device according to claim 4, wherein the hold-down mechanism (242) comprises: the device comprises a pressing driving mechanism (2421), a rebound mechanism (2422) and lifting pressing plates (2423) parallel to the conveying direction of the printed circuit board (4), wherein the lifting pressing plates (2423) are arranged at equal heights on two sides of the conveying direction of the printed circuit board (4), the rebound mechanism (2422) is abutted to the bottom of the lifting pressing plates (2423), the pressing driving mechanism (2421) is arranged on the upper side of the lifting pressing plates (2423), pressing pieces (2424) are arranged at the output ends of the pressing driving mechanism (2421), the pressing pieces (2424) can move downwards under the driving of the pressing driving mechanism (2421) and drive the lifting pressing plates (2423) to move from a first height to a second height, and the first height corresponds to the height position of the lifting pressing plates (2423) in the conveying state; after the pressing piece (2424) moves upwards, the lifting pressing plate (2423) is restored to the first height from the second height under the action of the rebound mechanism (2422).

6. The motherboard ICT testing device according to claim 5, wherein a first clamping groove (24231) is provided at the bottom of the lifting pressure plate (2423), and the transfer mechanism (241) is provided in the first clamping groove (24231).

7. The motherboard ICT test device according to claim 6, wherein the transfer mechanism (241) comprises: the conveying belt (2411), conveying wheels (2412) and a conveying shaft (2413), wherein the conveying shaft (2413) is fixedly arranged on the inner wall of the first clamping groove (24231), the conveying wheels (2412) are rotatably arranged on the conveying shaft (2413), and when the printed circuit board (4) is conveyed onto the conveying belt (2411), the printed circuit board (4) moves in a clamping gap (2414) formed by the top wall of the first clamping groove (24231) and the conveying belt (2411).

8. The motherboard ICT testing device according to claim 7, comprising a cleaning mechanism (1) disposed in front of the testing host (2), wherein the cleaning mechanism (1) comprises a first conveying runner (11) and a spray gun (12), an air outlet of the spray gun (12) faces the first conveying runner (11), and when the lifting press plate (2423) is located at the first height, an output end of the first conveying runner (11) is connected with an input end of the conveying belt (2411).

9. The main board ICT testing device according to claim 7, characterized by comprising a sorting mechanism (3) arranged behind the testing host (2), wherein the sorting mechanism (3) comprises a second conveying runner (31), a good product runner (32), a bad product runner (33) and a pushing plate mechanism (34), when the lifting pressing plate (2423) is located at the first height, the input end of the second conveying runner (31) is connected with the output end of the conveying belt (2411), the good product runner (32) and the bad product runner (33) are both arranged on the side edge of the second conveying runner (31), and the printed circuit board (4) is pushed from the second conveying runner (31) to the good product runner (32) or the bad product runner (33) through the pushing plate mechanism (34) respectively.

10. The motherboard ICT testing device according to claim 8, wherein the first transfer flow channel (11) is provided with a first sensor for locating a cleaning position of the printed circuit board (4); the lifting pressing plate (2423) is provided with a second sensor for positioning the test position of the printed circuit board (4).