MXPA00010909A - Soldering device and method - Google Patents

Abstract

The present invention's objective is to provide a soldering device andmethod for suppressing the sneaking of hot air toward a surface side for mounting parts, reducing thermal energy loss, and preventing circuit quality from being lost by soldering. For this aim the following is needed:in a soldering device 1, the side of a soldering surface 310 of the parts of a substrate is heated by a reflow part 12 for electrically connecting non-heat-resistance parts 101, 102, 103, and 104 being mounted on a substrate P. A reflow panel 24 with a hole 24a for jetting for air toward the soldering surface of the substrate at the reflow part is used, a part that opposes the substrate to be soldered is eliminated, and adhesion covers 30 and 31 adhering to the reflow panel are provided at the other part (unused part).

Description

"METHOD AND WELDING MACHINE" BACKGROUND OF THE INVENTION FIELD OF THE INVENTION This invention relates to a welding method and apparatus for electrically connecting the charged parts to a substrate in the substrate.

DESCRIPTION OF THE RELATED TECHNIQUE In a substrate carrying a plurality of circuits of an electronic equipment, such as a printed circuit board, electronic parts constituting the circuits are assembled. These electronic parts are mounted by insertion, such as in the case of the front parts, or by surface mounting such as in the case of integrated circuits. The electronic parts, mounted in this way, are electrically connected to the printed circuit board, by welding. As welding systems, there is a flow welding system and a reflow soldering system. In the flow soldering system, a printed circuit board is passed through a solder vessel containing a molten solder. In the reflow soldering system, the most select solder, for example, is coated on a pre-established site of the printed circuit board and, after mounting the integrated circuit, the solder portion of the printed circuit board is heated in a reflow oven. Electronic parts not resistant to heat, such as the front parts of the tanformers, the Or variable resistance, the air core coil or a chemical capacitor, are welded by flow welding on the printed circuit board, while the heat-resistant electronic parts, such as the parts of the integrated circuits, the resistors, the capacitors or their IC packages, are soldered by reflow welding on the printed circuit board . 15 Usually, electronic parts that are not resistant to heat, that is, electronic parts that • can be welded by the flow welding system, and heat-resistant electronic parts, which can not be welded satisfactorily unless a reflow soldering system, are soldered on a single printed circuit board for better productivity as well as to achieve reduction in size. This applies when, for example, a tuner circuit for a high frequency portion of the TV receiver and an IF circuit are built on a single printed circuit board. Therefore it is necessary to use the flow welding system or a reflow soldering system, depending on the type of electronic parts that are to be mounted on the single printed circuit board. Figure 1 shows a typical process for conventional reflow soldering. Referring to Figure 1A, on an upper surface 110 of a printed circuit board P, the integrated circuit parts 111, 112 have already been assembled as the heat resistant electronic parts, by reflow welding. First, to a leading conductive reservoir of the upper surface 110 of the printed circuit board P, the most select weld 121 is applied, using a manifold (nozzle). Then, as shown in Figure 1Bm, the printed circuit board P is inverted from top to bottom and the front parts 101, 102 and 103, like the electronic parts not resistant to heat, are mounted on the upper surface 100 of the control board. printed circuit P. The printed circuit board P is then charged to the reflow oven and hot air is injected into the lower surface 110, that is, the part of the welding surface, of the printed circuit board P, as shown. in FIG. ID, to melt the most select weld 121 under heating, while blowing cold air towards the upper surface 100, which F is a part adjustment surface, for cooling the front parts 101 to 103. Then, cool air is blown towards the welding surface 110, as shown in Figure 1E, to cool and cure the most select weld 121 to weld the respective connection terminals 120 of the front parts 101 to 103. F However, in the reflow oven described above, the part setting surface 100 is cooled by cold air during the welding fusion process (reflow zone). In this way, the front parts 101 to 103 have already cooled before the cooling process is started. Since only the - part 110 welding surface is cooled with air In the event of a cold, the remaining heat of the part-welding surface 110 is transmitted to the part-setting surface 100, with the result that the front parts 101 to 103 become abnormally heated as indicated in portion A of the Figure 2. In this way, the parties front 101 to 103, as non-heat resistant parts tend to decrease in reliability. Also known is a reflow oven having a cooling means for efficiently cooling the non-heat resistant parts charged to the substrate, In order to prevent the parts from being damaged by thermal hysteresis by cooling the part setting surface 100 with a weak wind. Meanwhile, the reflow oven described above is constructed so that hot air for heating is injected to a printed circuit board P, transported by a conveyor 130, through an opening, not shown, which is provided in a panel reflux mounted 131 facing the adjustment surface of part 110 of the printed circuit board P, as shown in Figure 3A, towards the part setting surface 110 so that it can be discharged through the vent hole 132. An upper portion of a rear area of the reflux panel 131 not facing the printed circuit board P, is provided with a cover 133 for protecting the hot air from the reflux panel opening 131 which does not contribute to the heating of the circuit board printed P. However, in the welding apparatus described above (reflow oven), a part of the hot air expelled through a hole in the bread the reflux 131, that is, the hot air from an area (unused portion) that is not oriented towards the printed circuit board P, is allowed to flow around the cover 133, without contributing to the heating of the printed circuit board P, and then directed to the setting surface of part 100 of the printed circuit board P. On the other hand, the front side of the reflux panel 131 not facing the printed circuit board P is free of cover 133 so that it is always exposed to hot air ejected. The result is that the non-heat resistant parts on the side part surface is also heated by the hot air HW, as shown in Figure 3B, to decrease the cooling effect of parts, while the thermal energy is wasted to decrease the heating efficiency by the reflow panel 131. In this way, if a printed circuit board is too small in size but is charged with a part with a significant thermal load, such as in the case of a printed circuit board which comprises a tuner of the high frequency device for TV receiver and the IF circuit, the power decreases before the welding defects tend to occur. In this way, a problem arises that, due to the aforementioned loss of thermal energy or the decreased cooling effect of parts, the reliability of non-heat resistant parts tend to be lost or the welding quality tends to decrease for it is necessary to carry out additional welding.

COMPENDIUM OF THE INVENTION It is therefore an object of the present invention to provide a welding method and apparatus in which the hot air can be prevented from being directed to the part fitting surface to reduce thermal energy loss without detracting from the quality of the circuit by welding. In one aspect, the present invention provides a welding apparatus in which, to electrically connect a non-heat resistant part charged to a substrate, a side of the welding surface of the substrate part is heated by a reflux unit. The welding apparatus includes a reflux panel of the reflux unit having holes for ejecting or ejecting a hot wind towards a solder surface of the substrate, and an airtight contact cover that intimately contacts the reflow panel except a portion thereof facing the substrate to be welded.

In another aspect, the present invention provides a welding method in which a weld is coated on a substrate, the substrate is inverted from top to bottom, a non-heat resistant part is loaded on the substrate and a solder surface for the part of the substrate is heated by a reflux unit, which method includes the use of a reflux panel of the reflux unit having holes through which hot air is ejected towards the welding surface of the substrate, and placing an airtight contact cover that remains intimately in contact with the reflow panel except for a portion thereof facing the substrate to be welded to prohibit the ejection of hot wind through the holes. In accordance with the present invention, the holes in the reflux panel portion of the reflux unit, other than the panel portion facing the substrate to be welded, are hermetically sealed by the hermetic contact cover. In this way, the holes in the portion of the reflow panel not facing the substrate, that is, the unused portion, are closed, such that the hot wind does not contribute to the heating of the welding surface of the part. of the substrate is not ejected or ejected from the reflow panel.

Since there is no risk of the hot wind rotating around the setting surface of the substrate part, the loaded part is not heated by the hot wind to prevent the part from being affected in its reliability. On the other hand, the thermal energy loss is decreased to improve the heating efficiency of the substrate by the reflux panel. There is no risk of power shortages even when the printed circuit board P is to be subjected to a high thermal load as in the case where the printed circuit board comprises the tuner circuit of the high frequency device for the TV receiver. and an IF circuit. In this way, the welding surface of parts of the printed circuit board can be heated sufficiently to ensure reliable welding. Therefore, in accordance with the welding method and apparatus according to the present invention, the hot wind can be prevented from rotating around the part fitting surface to suppress loss of thermal energy without detracting from the quality of the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a typical conventional welding method, step by step. Figure 2 is a graph showing temperature changes in the weld and parts by the welding method of Figure 1. Figure 3A is a cross-sectional view showing the relationship between the reflow panel and the dashboard. printed circuit in a conventional welding machine. Figure 3B is a plan view showing the relationship between the reflow panel and the printed circuit board in a conventional welding apparatus. Figure 4 is a schematic view showing the structure of one embodiment of the welding apparatus in accordance with the present invention. Figure 5 is an enlarged cross-sectional view of a reflow unit of the welding apparatus of Figure 4, oriented along a direction transverse to the transport direction of the substrate. Figure 6 is an enlarged cross-sectional view of the reflow unit of the welding apparatus of Figure 4, oriented along the transport direction of the substrate.

Figure 7 is a plan view of the reflow panel in the welding apparatus of Figure 4. Figure 8 is a schematic plan view showing the relative positions between the reflow panel in the welding apparatus of Figure 4 , and a transporter. Figure 9A is a cross-sectional view showing a hermetic contact cover of the reflow panel in the welding apparatus of Figure 4. Figure 9B is a plan view showing a hermetic contact cover of the reflow panel in the welding apparatus of Figure 4. Figure 10 shows the process of one embodiment of a welding method in accordance with the welding apparatus of Figure 4, step by step. Figure 11 is a schematic plan view showing the state of continuously welding the printed circuit boards by the welding apparatus of Figure 4.

DESCRIPTION OF THE PREFERRED MODALITIES Referring to Figures 4 to 11, preferred embodiments of the present invention will be explained in detail.

In the following embodiments, a variety of technically desirable limitations are imposed, since these embodiments represent the preferred embodiments of the present invention. However, the present invention is not limited to these modalities in the absence of limit statements. Figure 4 shows the structure of one embodiment of the welding apparatus encompassing the present invention. In Figure 4, a welding apparatus 1 is used as a reflow oven and comprises a preheating unit 10, a reflux unit 12 and a cooling unit 14, interconnected by a conveyor 16. That is, the preheating unit 10, the reflux unit 12 and the cooling unit 14 are placed in sequence along the flow direction of the conveyor 16, ie, in the right-to-left direction in Figure 4. This allows the control board The printed circuit P carrying the variable parts is transported from an inlet 11 through the preheating unit 10, the reflux unit 12 and the cooling unit 14 to be discharged, as indicated by the arrow T. In the Figure 5, the conveyor 16 is positioned in front of and behind the printed circuit board P to retain the printed circuit board, which is on the front and rear sides thereof. The front side conveyor 16a is fixed, while the rear side conveyor 16b is adjustable in its position depending on the width of the printed circuit board P to be welded. First, the structure of the preheating unit 10 will be explained. This preheating unit 10, which preliminarily heats the printed circuit board P, includes a first preheating unit 10A, a second preheating unit 10B and a third preheating unit 10C . The first preheating unit 10A includes the heaters Hl, H2 and a circulation fan Fl, while the second preheating unit 10B includes the heaters H3, H4 and a circulation fan F2. The third preheating unit 10C includes a heater H5 and a circulation fan F3. The heaters Hl, H3 are placed above the conveyor 16, while the heaters H2, H4 and H5 are placed below the conveyor 16. The flow fans Fl to F3 supply the air to the respective heaters to circulate the hot air.

The preheating unit 10, described above, is configured to gradually heat the printed circuit board P in three stages to raise the temperature of the printed circuit board P from the ambient temperature to the pre-graduated temperature. This allows the solder to be activated without straining the printed circuit board P and the electronic parts loaded therein. With reference to Figures 4 to 7, the structure of the reflux unit 12 will be explained below. Of these figures, Figure 5 is an enlarged cross-sectional view showing a reflow unit of the welding apparatus of Figures 1 to 4, oriented along a direction transverse to the transport direction of the substrate, Figure 6 is an enlarged cross-sectional view of the reflow unit of the welding apparatus of Figure 4, oriented along the welding conveying direction and Figure 7 is a plan view of the reflow panel in the welding apparatus of Figure 4. Referring to Figures 4 and 5, the reflux unit 12 includes a heating metering 12A and cooling means 12B. The heating means 12A and the cooling means 12B are placed below and above the conveyor 16, respectively. The heating means 12A is constituted by a reflux heater 20 and, in greater detail, is constituted by a lower heater 21, an upper heater 22, a sirocco fan 23 and a reflux panel 24. As shown in Figure 6B, the lower heater 21 and the upper heater 22 are provided with multiple holes 21a, 22a, respectively. The sirocco fan 23 is placed on the lower side sides of the lower heater 21 and the upper heater 22. The reflow panel 24 includes multiple panel holes 24a, as shown in Figure 7. The heating means 12A, which is described in the foregoing, it is configured to be driven by the sirocco fan 23 to collect the ambient air in the direction indicated by the arrow H in order to send it to the underside of the lower heater 21 of the reflux heater 20, with the ambient air becoming pass in sequence through the holes 21a, 22a of the lower heater 21 and the upper heater 22 to be blown equally towards the welding surface of the printed circuit board P as the hot wind HW of the pre-graduated temperature.

The cooling means 12B includes a box 25, exhaust ducts 26, and an exhaust pipe 27, as shown in Figures 5 and 6. Centrally of the box 25 an opening 25a is formed surrounded by protective plates 25b, 25b, vg of glass. The exhaust ducts 26 are provided on both sides of the box 25. The exhaust pipe 27 is mounted on the sirocco fan 23, as shown in Figure 6. The cooling means 12B, described above, is configured to be driven by a suction blower 28 to admit ambient air in the direction indicated by the arrow C through the opening 25a in the box 25 to send it along the loading surface of the printed circuit board P carrying the electronic parts not resistant to heat to send the same through the exhaust pipe 27 back to the reflux heater 20 from the sirocco fan 23, as shown in the amplified side view of Figure 4. The structure of the Cooling unit 14 will be explained below. The cooling unit 14 includes a suction cooling system 14A and a cooling fan 14B. The suction cooling system 14A and the cooling fan 14B are placed above and below the conveyor 16, respectively. It will be noted that the reflow panel 24 is positioned relative to the printed circuit board P carried by the conveyor 16, as shown in Figures 8 and 9. Figure 8 is a schematic plan view showing the relative positions between the reflux panel in the welding apparatus of Figure 4 and the conveyor, while Figure 9A is a cross-sectional view showing a hermetic contact cover of the reflow panel in the welding apparatus of Figure 4 and Figure 9B is a plan view showing a hermetic contact cover of the reflow panel in the welding apparatus of Figure 4. That is, the reflow panel 24 protrudes in relation to the conveyor 16 by a width Wl on the front side by means of a width W2 on the back side, as shown in Figure 9B. In this way, the portion of the reflow panel 24 corresponding to a central width W3 of the entire width WO is oriented towards the printed circuit board P carried by the conveyor 16 to contribute to the heating of the welding surface of parts of the board. of printed circuit P.

On the other hand, a reflow panel 24 with sealed contact covers 30, 31 is provided on the upper surfaces of portions thereof protruding from both sides of the transporter 16 (unused portions). Of these sealed contact covers 30, 31, the front side hermetic contact cover 30 is fixed relative to the reflow panel 24, because the front side conveyor 16a is fixed. The hermetic contact cover on the rear side 31 is mounted for position adjustment in relation to the reflow panel 24 in the front to back direction, that is, in the left and right direction in Figure 9, because the rear side conveyor 16b can be adjusted in its position depending on the width of the printed circuit board P. Not forming the holes 24a of the reflow panel 24 partially, it is possible that the sealing contact cover 30 is not provided. In the above-described structure of the welding apparatus 1 according to the present invention, the method for carrying out the welding processing using this welding apparatus 1 will be explained referring to Figure 10.

Referring to Figure 10A, the printed circuit parts 201, 202 are already mounted on the upper surface (first surface) 310 of the printed circuit board P by reflow welding. In a front conductive reservoir of the upper surface 310 of the printed circuit board P, a more selective weld 300 is applied, using a manifold (nozzle) 301. Then, as shown in Figure 10B, the printed circuit board P it is inverted from top to bottom and the front parts 101, 102, 103 and 104, like the electronic parts not resistant to heat, are mounted on the upper surface (second surface) 320 of the printed circuit board P. The printed circuit board P is then placed in the inlet portion 11 of the conveyor 16 of Figure 4, with the front parts 101 to 104 remaining on the upper side, and transported in a T direction. The first preheating unit 10A, the second preheating 10B and the third preheating unit 10C of the preheating unit 10, are made to drive to raise the temperature of the printed circuit board P gradually from the room temperature has ta the pre-graduated temperature. This releases the stress of the printed circuit board P and the electronic parts charged therein while activating the more select weld 300. The heating means 12A of the reflow unit 12 is then operated to eject or eject a hot wind HW. towards the lower surface 310 of the printed circuit board P, ie the welding surface of parts, so as to heat and melt the more select weld 300 while the cooling means 12B is also actuated to direct a cold wind to the upper surface 320, that is, the loading surface of parts, for cooling the front parts 101 to 104, as shown in Figure 10D. In this way, the most select weld 300 is made compatible with the space between the connection terminals of the front parts 101 to 104, and the electrical installation conductor of the printed circuit board P, while it is possible to prevent damage to the parts front 101 to 104 by thermal hysteresis. Since the hermetic contact covers 30, 31 are kept in intimate contact with the unused portions of the reflux panel 24, the holes 24a of the unused portions are closed by the tight contact covers 30, 31 to prohibit the wind hot HW has been ejected or ejected from the unused portions of the reflow panel 24. Since the hot wind HW is not rotated around towards a loading surface of parts 320 of the printed circuit board P, there is no risk that the front parts 101 to 104 are heated by the hot wind HW, thus preventing the part from being affected by decreasing in reliability while decreasing the loss of thermal energy. Since this improves the heating efficiency of the printed circuit board P by the reflow panel 24, there is no risk of lack of power even when the printed circuit board P is to be subjected to a high thermal load as in the case of the printed circuit board consisting of the tuner circuit of the high frequency device for a TV receiver and an IF circuit, with the result that the welding surface of the printed circuit board parts is heated sufficiently to ensure a reliable welding. The cooling fan 14B of the cooling unit 14 is then operated to direct the cold wind towards the welding surface of parts 310 to cool and cure the more select weld 300 to weld the connecting terminals of the front parts 101 to 104 in position, at the same time that the suction cooling system 14A is operated to send the cold wind gradually towards the part setting surface 320 to cool the front parts 101 to 104. This electrically connects the respective connection terminals of the front parts 101 to 104 with the electrical installation conductors of the printed circuit board P, while preventing the front portions 101 to 104 from being damaged by the remaining heat. That is, since the adjustment surface of portions 320 as well as the welding surface of parts 310 is cooled by the cold wind in the cooling process, the adjustment surface of parts 320 can be instantly cooled even when the remaining heat from the The welding surface of parts 310 is transmitted to the fitting surface of parts 320, thereby preventing abnormal heating of the front parts 101 to 104. Meanwhile, when welding the printed circuit boards P consecutively in the welding operations shown in Figure 10, an intermediate portion of the reflow panel 24, ie, its area facing the conveyor 16 is cured by the printed circuit board P itself. However, during the start and end of the welding operations, there is no printed circuit board P forward or backward of the printed circuit board P, so that the hot wind expelled from the holes 24a in the reflow panel 24 is rotates around towards the part setting surface which is the upper surface of the printed circuit board P. If when the printed circuit boards P are soldered consecutively in the welding operations shown in Figure 11, a printed circuit board Imitation PO is placed in front of the first printed circuit board Pl and on the back of the printed circuit board Pn last, as a normal operation, the area of the conveyors 16 is covered by the printed circuit board PO of imitation in the course of the welding operation for the printed circuit board Pl or Pn, thus preventing the hot wind HW from rotating around the adjustment surface of parts 320 thereby preventing unusual heating of the front portions 101 to 104. That is, in the previously described embodiment, wherein the reflow panel holes of the reflux unit other than those in the area of the panel facing the printed circuit board to be welded are tightly covered by the tight contact cover, the panel holes are not facing the printed circuit board, that is, the portion of unused panel are covered, prohibiting this way the expulsion of the reflux panel of the hot wind that does not contribute to the heating of the welding surface of parts of the printed circuit board. Since the hot wind does not rotate around the side of the adjustment surface of parts of the substrate, the loaded part is not heated by the hot wind to prevent the part from decreasing in reliability. On the other hand, the loss of thermal energy is decreased to improve the heating effect of the board by the reflow panel. In this way, even in this case where the part subjected to significant thermal load such as the printed circuit board consisting of a tuner circuit of a high frequency device for the TV receiver and an IF circuit, join together , it is loaded onto a substrate, there being no risk of lack of power or energy, so that the welding surface of parts of the substrate is heated sufficiently to ensure reliable welding. In the above-described embodiment, the preheating unit 10 is manufactured from three stage heating portions, namely the first preheating unit 10A, the second preheating unit 10B and the third preheating unit 10C. This is only illustrative in such a way that the preheating unit 10 can be constituted by one, two, four or more heating units. The reflux unit 12 has a reflux heater 20 comprising two heaters, namely the upper heater 22 and the lower heater 21. Again this is not limiting since the reflux unit 12 can be provided with one or three or more reflux heaters.

Claims (7)

CLAIMS:

1. A welding apparatus in which, to electrically connect a non-heat-resistant part charged to a substrate, one side of the welding surface of parts of the substrate is heated by a reflux unit, the welding apparatus comprising: reflux of the reflux unit having holes for expelling a hot wind towards a solder surface of the substrate, and a hermetic contacting cover which intimately contacts the reflow panel except a portion thereof facing the substrate which is going to be soldered The welding apparatus according to claim 1, further comprising: a cooling means for cooling one side of the printed circuit board of welding apparatus carrying a non-heat resistant part. The welding apparatus according to claim 1 or 2, wherein a sealing contact cover is provided in an area facing the conveyors to the outside of the reflow panel placed on both sides of the substrate, the sealing contact cover being it contacts tightly with the reflow panel. 4. A welding method where the weld is coated on a substrate, the substrate is inverted from top to bottom, a non-heat resistant part is loaded on this substrate and a welding surface for the substrate part is heated by a reflux unit, the method comprises: using a reflux panel of the reflux unit having holes through which hot air is expelled towards the welding surface of the substrate; and placing an airtight contact cover that intimately contacts the reflow panel except for a portion of the reflow panel that faces the substrate to be welded to prohibit the expulsion of the hot wind through the holes. The welding method according to claim 4, wherein one side of the printed circuit board carrying parts not resistant to heat is cooled by a cooling medium. The welding method according to claim 4 or 5 wherein in an area facing the reflow panel to the outside of the conveyors placed on both sides of the substrate, the expulsion of the hot wind through the holes is prohibited by an airtight contact cover that intimately contacts the reflow panel. The welding method according to claim 6, wherein a front imitation printed circuit board, a plurality of printed circuit boards and a duplicated back printed circuit board are moved in succession on the conveyor to prevent ejection of hot wind through the spaces between the duplicate printed circuit board, the multiple printed circuit boards and the last printed circuit board.