JPH0723104Y2 - Reflow furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a reflow furnace which prevents and / or corrects warpage of a substrate and has high solderability.

[Technical background of the invention] As electronic products have become thinner, surface-mounted printed circuit boards have recently become about 0.5 mm thick. When the printed circuit board is thinned in this way, this type of printed circuit board is exposed to a high temperature inside the reflow furnace, so that the printed circuit board is softened and a downward warp and an upward warp of the front and rear ends occur. When a printed circuit board that has been warped in this way is rapidly cooled in the cooling zone, the solder solidifies and shrinks at the pads and component electrode parts, which causes distortion in the component body, which may cause damage or impair the reliability of the device. Become. Therefore, there is a demand for a transport mechanism that can prevent or correct the warp of the printed circuit board in the cooling zone, but the reality is that there is still no satisfactory transport mechanism.

An object of the present invention is to prevent and / or forcibly correct warpage of a printed circuit board that intervenes in a cooling zone.
There is no warp due to rapid cooling in the cooling zone while maintaining this posture, and we will provide a reflow furnace that can continuously obtain printed circuit boards with mounted components with high solderability. It is a thing.

[Means for Solving the Problems] The structure of the present invention for solving the problems of the prior art is to install the printed circuit board in the path of the printed circuit board which is carried by a carrier constituted by two parallel endless strips. In order to continuously heat-treat to a desired temperature profile, at least a preheating zone (elevating zone), a cream solder melting zone (reflow zone), and a cooling zone are arranged in series in this order, and the cooling zone is provided with a printed circuit board. In a reflow furnace provided with a warp prevention means, the material moves to a central portion between the two endless strips 1a and 1b constituting the carrier at a speed substantially equal to the carrier speed of the carrier and at least the melting An endless strip 38 having a warp prevention means and / or a correction means of the printed circuit board is provided between the upper side of the zone (reflow zone) and the end of the cooling zone. Therefore, the endless linear body 38 is configured to be vertically adjustable and horizontally adjustable, while the endless linear body 1a, 1b is directly above the cooling zone from the vicinity of the start end to the end thereof. 1a,
The endless strips 9a and 9b are arranged to move in the same direction at substantially the same speed as 1b and to have warp correction means for the printed circuit board.

[Operation] The printed circuit board supplied into the reflow furnace is heated and preheated in the preheating zone, the cream solder is melted and soldered in the melting zone, and is rapidly cooled and recovered in the cooling zone. The warp of the printed circuit board due to heating at least after the melting zone and the warp of the front and rear parts of the printed circuit board can be prevented by the endless strip 38, or can be rapidly cooled and recovered in a corrected state. The final correction is performed regardless of the presence or absence, and there is no warpage and a product with high solderability is obtained.
In addition, the endless strip 38 can be lowered and retracted during reflow work of the printed circuit board that does not warp, while the endless strip 38 can be moved horizontally to the left or right according to the size of the printed circuit board to ensure proper warpage. It can be prevented.

[Embodiment] Next, details of an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway side view of the main part of the reflow furnace equipped with the device of the present invention, with a part omitted, FIG. 2 is a plan view of the main part of the same, FIG. 3 is an enlarged front view of the main part of the same, FIG. 4 is a front view of a chain raising / lowering mechanism for warping prevention and / or correction, and FIG. 5 is a partially enlarged front view of a chain for warping prevention and / or correction.

A is a state in which both ends of the printed circuit board 2 are supported by a carrier constituted by two parallel endless chains 1a and 1b,
In order to continuously heat the printed circuit board 2 to a desired temperature profile, at least a preheating zone (heating zone) 3
Such a reflow furnace A is generally known as a reflow furnace in which a, a melting zone (reflow zone) 3b, and a cooling zone 4 are arranged in series in this order.

As shown in FIG. 3, the endless chains 1a and 1b constituting the above-mentioned transporting body are respectively suspended around one endless chain 1b on a fixed rail 5 and the other endless chain 1a on a horizontally moving rail 6 by a flexible suspension. The horizontal moving rail 6 can be moved in the direction of the arrow by changing the width of the printed circuit board 2. The fixed rail 5 and the horizontally moving rail 6 are long holding pieces 7 extending over the entire forward path of the carrier.
They are attached to a and 7b respectively.

On the upper surfaces of both the holding rods 7a, 7b, between the vicinity of the start end of the cooling zone 4 and the end thereof, the endless chains 1a, 1b.
Corresponding rails 8a and 8b are provided directly above b, respectively, and provided on the rails 8a and 8b in the range from the vicinity of the start end of the cooling zone 4 to the conveyance end of the printed circuit board 2. An endless chain 9a, 9b for warping correction is encircling and suspended, and the endless chains 9a, 9b are horizontally inwardly opposed to mount and support the printed circuit board 2 provided on the endless chains 1a, 1b. Attachments 11a, 11b corresponding to the pins 10a, 10b and pressing both side edges of the printed circuit board 2 from the upper side to the lower side to correct the warp of the front and rear portions of the printed circuit board 2.
Are continuously provided. In addition, reference numeral 12 in the drawing denotes a metal fitting for preventing the attachments 11a, 11b from being bent inward and for surely correcting the warp of the printed circuit board 2. Also. In FIG. 1, 13 and 14 are idle sprockets, 15 is a tension sprocket, and 16 is a drive sprocket, and these are all holding pieces 7a and 7b.
Further, reference numerals 17 and 18 denote cold air units constituting the cooling zone 4.

Next, details of the warp prevention and / or correction mechanism of the printed circuit board 2 will be described with reference to FIGS.
Reference numerals 9 and 20 denote plates provided in the reflow furnace A in parallel with the conveying direction of the endless chains 1a and 1b. The plates are attached to the front and back and the top and bottom of the inner surfaces of the plates 19 and 20 facing each other. The pieces 21 and 22 are provided horizontally, and both plates 19 and 22 are
An elevating frame 23 having a U-shaped planar shape is interposed between the 20 and both side plates 23a and 23b of the elevating frame 23 are arranged along the inner side surfaces of the plates 19 and 20. Then, the rod 24 is inserted into the upper and lower mounting pieces 21 and 22 provided on the plates 19 and 20, respectively, and the upper end of the rod 24 is projected above the upper mounting pieces 21 and 22 to form the rod 2
A retaining head 24a is provided at the upper end of 4, and a horizontal mounting piece 25 provided on the upper and lower side plates 23a, 23b of the elevating frame 23 is fixed to each rod 24 through the side plates 23a, 23b. twenty three
The spiral spring 26 is elastically provided between the lower surface of the mounting piece 25 of b and the upper surfaces of the mounting pieces 21 and 22 below the plates 19 and 20. In addition, a semicircular engagement recess 27 is formed at the center of the upper end of one side plate 23a of the elevating frame 23.

On the other hand, a horizontal shaft 28 that penetrates the plate 19 is pivotally supported on the upper center of the plate 19, and the lower end of the operation handle 29 is fixed to the outer end of the shaft 28, and the inner end of the shaft 28 is fixed to the outer end. Is in contact with the upper end surface of one side plate 23a of the elevating frame 23 at the lower end, and by rotating the operation handle 29,
The elevating frame 23 is lowered against the elastic force of each spiral ridge 26, and the upper end of the connecting rod 31 having the rolling wheel 30 that engages with the engaging recess 27 when the operating handle 29 is in the vertical posture is fixed. still,
The connecting rod 31 is arranged so as to be in line with the operating handle 29, and the distance connecting the center of the shaft 28 and the outer peripheral surface of the rolling wheel 30 is the same as that of the shaft 28 in the state shown in FIG. It must be formed larger than the distance connecting the center and the deepest part of the engagement recess 27. The reason is to lower the elevating frame 23. In the figure, 32 and 33 are horizontal rods that hold the space between the side plates 23a and 23b of the side plates 23 of the elevating frame 23.

Between the central portions of both side plates 23a, 23b of the elevating frame 23, a horizontal posture screw rod 34 is provided in a bridge manner. The screw rod 34 penetrates the rods 32, 33 and is an endless chain. 1a, 1b
The middle part of the long moving and holding rod 35 parallel to the conveying direction is threaded. The moving holding rod 35 is the preheating zone.
A rail 36 is formed over the entire length of the movable holding rod 35, which has a length corresponding to the vicinity of the start end of 3a and the end of the printed circuit board 2 conveyance.
Then, on the rail 36, the above-mentioned both endless chains 1a, 1b.
In the endless chain 38, which is provided with an attachment 37 for preventing warpage and / or correction of the printed circuit board 2 located in the center portion between them, and which moves in the same direction at substantially the same speed as the endless chains 1a and 1b. Carry on the outward route. The upper end of the attachment 37 on the outward path of the endless chain 38 is
Match the horizontal line connecting the upper surfaces of the horizontal pins 10a, 10b provided on 1a, 1b, or position them slightly above this horizontal line, and as shown by the phantom line in FIG. The printed circuit board 2 which is going to warp or is warped by heating is prevented or warped as indicated by the solid line.

Reference numeral 39 shown in FIG. 2 is a holding rod that moves horizontally in order to horizontally move the endless chain 1a used in the general reflow furnace A and adapt it to the width of the printed circuit board 2.
7a is a screw rod that is screwed onto the reflow furnace body and horizontally mounted on the main body of the reflow furnace. At one end of the screw rod 39, an operating handle (not shown) for rotating the screw rod forward and backward is provided. Further, as is apparent from FIG. 2, a sprocket 40 is provided on one side of the screw rod 39.
The sprocket 40 is connected via a chain 41 to a sprocket 42 provided on one side of the screw rod 34. The gear ratio between the sprockets 40 and 42 is 1:
It is formed in 2 and one screw rod 34 makes one rotation for one rotation of the screw rod 39.
In detail, the amount of movement of the endless chain 38 attached to the moving and holding rod 35 by the screw rod 34 is smaller than the amount of movement of the endless chain 1a supported by the holding rod 7a by the screw rod 39 so that it rotates twice.
The endless chain 38 is always positioned at the center between the endless chains 1a and 1b so that the warp correction of the printed circuit board 2 can be properly performed regardless of the width of the printed circuit board 2. This is something that can be done.

Reference numeral 43 in FIG. 1 denotes the endless chains 9a, 9b, and
A motor for driving the endless chain 38, 44 is a drive sprocket,
45 is a chain connecting the motor 43 and the drive sprocket 44, 46, 47, 48 and 49 are sprockets which are bent around the endless chain 38, 50 is a sprocket for tension, these sprockets, namely, 44, Although not particularly shown, 46, 47, 48, 49 and 50 are attached to the moving holding piece 35 via stays. Reference numeral 51 in FIG. 3 denotes a metal fitting for preventing the attachment 37 from bending.

In the above embodiment, the endless chain 38 having the attachment 37 for preventing the warp of the printed circuit board 2 to be heated and / or for correction is provided between the vicinity of the start end of the preheating zone 3a and the end of the cooling zone 4. Although it has been shown that it is provided, it is not limited to the one shown in the drawing because it is effective even if provided at least from the upper side of the melting zone 3b to the end of the cooling zone 4. In this case, the attachment 37 serves to correct the warp of the printed circuit board 2 which is predicted to occur in the preheating zone 3a.

Further, in the above-described embodiment, the endless chain 38 having the attachment 37 is always located at the center portion according to the width of the printed circuit board 2. However, the endless chain 38 is horizontally moved independently in the left-right direction. This is not possible, but it is also possible to touch an arbitrary part of the printed circuit board 2 so as to be able to deal with the uneven warp phenomenon caused by the uneven mounting of the mounted components. It will not be done.

[Effect of the Invention] According to the configuration of the present invention as described above, the following effects can be obtained.

(A) The printed circuit board on which the mounting components supplied in the reflow furnace are temporarily attached is heated up and down in the preheating zone to melt the solder in the melting zone, and then rapidly cooled in the cooling zone to be recovered. Of course,
The warpage phenomenon due to heating at least after the melting zone of the printed circuit board is prevented and / or corrected by the endless strip having the warpage correction means, and the solderability is reliable. A high product is obtained.

(B) Whether or not the printed circuit board has a warp,
Not only the final correction of the printed circuit board is performed, but also the fluttering of the printed circuit board due to the cold air unit is prevented, the solderability in the soldering finishing step is further assured, and the reliability can be improved.

(C) The endless chains 9a, 9b for warping correction corresponding to the endless chains 1a, 1b and / or the endless chain 38 for preventing warping and / or correction corresponding to the central portion of the printed circuit board, Since the endless chains 1a and 1b are rotated at substantially the same speed as the endless chains 1a and 1b, a correction pressure may be applied in response to the warp of the printed circuit board, but the attachment does not make sliding contact with the printed circuit board. When reflowing the printed circuit board without damaging the circuit board or mounted parts and causing no warp, it is possible to avoid lowering the endless strip 38 so that it does not come into contact with the printed circuit board. According to endless body 38
By adjusting the horizontal movement to the left and right, it is possible to properly prevent warping.

(D) Since the attachments are connected to the endless chains 9a, 9b, and 38, the printed circuit board can be easily touched, and the printed circuit board does not come into pressure contact with the printed circuit board. Does not damage the mounted components.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of the main part of the reflow furnace equipped with the device of the present invention, with a part omitted, FIG. 2 is a plan view of the main part of the same, FIG. 3 is an enlarged front view of the main part of the same, FIG. 4 is a front view of a chain lifting mechanism for warping prevention and / or correction, and FIG. 5 is a partially enlarged front view of a chain for warping prevention and / or correction. A: Reflow furnace, 1a, 1b ... Endless chain, 2 ... Printed circuit board, 3a ... Preheating zone (heating zone), 3b ... Melting zone (reflow zone), 4 ... Cooling zone, 5 ... Fixed rail, 6 …… Horizontal movement rail, 7a, 7b …… Holding rod, 8a, 8b …… Rail, 9a, 9b …… Endless chain for warping compensation, 10a, 10b ……
Horizontal pin, 11a, 11b …… Attachment, 35 …… Moveable holding rod, 36 …… Rail, 37 …… Attachment, 38 …… Endless chain for warp prevention and / or compensation, 39 …… Screw rod, 40 ...... Sprocket, 41 ...... Chen, 42 ...... Sprocket.

Claims (1)

[Scope of utility model registration request] 1. A preheating zone (at least in order to heat-treat the printed board to a desired temperature profile continuously in a path of the printed board conveyed by a carrier constituted by two parallel endless strips). The transfer body is configured in a reflow furnace in which an elevating zone), a cream solder melting zone (reflow zone), and a cooling zone are arranged in series in this order, and a warp prevention unit for a printed circuit board is provided in the cooling zone. While moving to the central portion between the endless strips (1a) and (1b) of the book at a speed substantially the same as the transport speed of the transport body, at least from the upper side of the melting zone (reflow zone) to the cooling zone. An endless strip (38) having a warp prevention means and / or a correction means is arranged between the end of the end of the printed board and the endless strip (38) can be adjusted up and down and left. It is configured to be horizontally adjustable, and on the other hand, directly above the endless strips (1a), (1b) extending from the vicinity of the start end to the end of the cooling zone, the endless strips (1a), (1b) An endless strip that moves in the same direction at the same speed and that has means for correcting the warp of the printed circuit board (9
Reflow furnace characterized by having a) and (9b).