Inspection machine for printed circuit board

1. An inspection machine for a printed circuit board on which a plurality of electronic components is mounted, comprising:

an imaging device having a function for capturing a close-up of an inspection target portion of the printed circuit board by approaching the printed circuit board;

a detection unit that detects heights of electronic components on the printed circuit board to be subjected to inspections by irradiation light that is irradiated onto the printed circuit board in a first direction that is along a surface of the printed circuit board;

a displacement unit that relatively displaces the detection unit and the printed circuit board along the surface of the printed circuit board in a second direction that crosses the first direction; and

a control unit that controls the detection unit and the displacement unit,

wherein:

the control unit controls the detection unit to detect the heights of the electronic components mounted on the printed circuit board by activating the detection unit and the displacement unit before capturing the printed circuit board by the imaging device, the control unit sets a limit distance to a position higher than the highest electronic component among heights detected from the electronic

components, thereby restricting a facing distance, by which the imaging device is approachable to the printed circuit board, to be the limit distance.

2. The inspection machine for a printed circuit board according to claim 1 , further comprising:

a storage unit adapted to store a minimum approaching distance that is preset as a facing distance by which the imaging device is approachable to the shortest electronic component among the electronic components mounted on the printed circuit board subjected to inspection, a maximum approaching distance that is preset as a facing distance by which the imaging device is approachable to the highest electronic component among the electronic components mounted on the printed circuit board subjected to inspection, and an intermediate approaching distance that is preset as a facing distance between the maximum approaching distance and the minimum approaching distance,

wherein:

the detection unit includes a bottom sensor that detects the heights of the electronic components at a height corresponding to the minimum approaching distance; and

an intermediate sensor that detects the heights of the electronic components at a height corresponding to the intermediate approaching distance.

3. The inspection machine for a printed circuit board according to claim 2 , wherein:

the control unit sets the limit distance to the maximum approaching distance when the intermediate sensor detects the electronic components at the intermediate approaching distance;

the control unit sets the limit distance to the intermediate approaching distance when the intermediate sensor does not detect the electronic components at the intermediate approaching distance and the bottom sensor detects the electronic components at the minimum approaching distance; and

the control unit sets the limit distance to the minimum approaching distance when the bottom sensor does not detect the electronic components at the minimum approaching distance.

4. The inspection machine for a printed circuit board according to claim 1 , further comprising a board table that holds the printed circuit board, wherein the driving unit serves functions as the displacement unit.

5. The inspection machine for a printed circuit board according to claim 4 , further comprising:

a frame that is disposed under the board table and supports the driving unit; and

a guide feature that connects the board table to the frame so that the board table are relatively displacable with respect to the frame along the second direction,

wherein:

the detection unit is installed in the frame and is constituted by reflection type photoelectric switches in which a light emitting portion and a light receiving portion are assembled integrally; and

a mirror, adapted to reflect irradiation light irradiated from the light emitting portion to the light receiving portion in all strokes where the board table and the frame are relatively displaced, is installed in the board table at a position facing the detection unit via the printed circuit board held by the board table.

6. The inspection machine for a printed circuit board according to claim 4 , wherein:

the driving unit moves the board table to a loading entrance of the printed circuit board linearly along the second direction when the printed circuit board is loaded; and

the detection unit irradiates the irradiation light in the first direction when the board table loads the printed circuit board from the loading entrance.

7. The inspection machine for a printed circuit board according to claim 1 , further comprising a detection movement means adapted to move the detection unit between an inspection position where the irradiation light is irradiated in a space where the printed circuit board is moved for inspection, and a retracted position where the printed circuit board is retracted from the space.

8. The inspection machine for a printed circuit board according to claim 1 , wherein the imaging device has an X-ray irradiation unit that is disposed so as to be capable of approaching and separating from the printed circuit board, and an X-ray camera that receives an X-ray transmitted through the printed circuit board.

9. The inspection machine for a printed circuit board according to claim 1 , wherein further comprising:

a setting device adapted to set a required approaching distance in advance;

a determination unit that determines whether the imaging device is allowable to approach at the approaching distance based on the result obtained by the detection unit; and

an alarm unit for warning an alarm when the determination unit determines that the imaging device is unallowable to approach at the approaching distance.