JP5448081B2 - Heater chip for thermocompression bonding - Google Patents

Description

  The present invention relates to a thermo-compression heater chip used when thermo-compression is performed after a conductor layer of a flexible printed wiring board is superimposed on a circuit pattern of a hard substrate.

  Conventionally, a terminal (lead) such as an IC (integrated circuit) is thermocompression bonded to a printed wiring board, or a conductor layer of a flexible printed wiring board (FPC) is thermocompression bonded to a connector or another hard substrate (hard substrate). Things have been done.

  FIG. 7 shows an example of the heater chip 1 that has been widely used conventionally. FIG. 8 is a sectional view taken along line VII-VII. 7 and 8, reference numeral 2 denotes a horizontal lower side, and upper portions of a pair of left and right arms 3 and 3 standing from both ends of the lower side 2 are power supply terminals 4 and 4. As is apparent from FIG. 8, the heater chip 1 is obtained by processing a material having a constant thickness by a wire cutting method or the like. The material used here is a metal having a large electrical resistance, such as W (tungsten), Mo (molybdenum), nichrome alloy (Ni-Cr), Ti (titanium).

  Bolt holes 5 are provided in the power supply terminals 4 and 4, and these are bolted to a pressure head (not shown) of a joining device (not shown). The heater chip 1 can generate heat by flowing a current (for example, a pulse current) between the power feeding terminals 4 and 4. Solder plating (pre-coating) or solder paste is supplied in advance to circuit pattern joints (pads, lands, etc.), and the heater chip 1 is caused to generate heat in a state where the lower side 2 of the heater chip 1 is pressed against the lead superimposed thereon. The soldering is performed by melting the solder.

  A thermocouple is fixed (welded) to the lower side 2 at a position indicated by reference numeral 6 in FIG. 7, and the heating temperature of the heater chip 1 is detected. The detected temperature of the thermocouple is fed back to a control circuit (not shown) to control the heating current of the heater chip 1.

JP 2009-164400 A

  Patent Document 1 has a pair of iron parts having a substantially U-shaped longitudinal section extending in parallel with a constant interval, and bridging inner sides of both iron parts facing each other with a substantially inverted U-shaped bridge part, A heater chip is shown in which each outer side is raised upward to serve as a power supply terminal. This heater chip is a device that thermocompression-bonds multiple terminals (leads) arranged on two parallel sides of SOP (Small Outline Package) and QFP (Quad Flatpack Package) with gull-wing type terminals around the package to the circuit pattern of the board. It is.

  In recent years, HDMI (High-Definition Multimedia Interface), which is a connection standard between PCs (personal computers) and displays, has been widely used as an interface for digital home appliances. This HDMI uses a single cable that integrates video, audio, and control signals, simplifies the wiring of AV equipment, and facilitates cooperation between AV equipment by allowing connected devices to recognize each other. .

  Some types of cables have a power line along with a signal line. In this case, the allowable current capacity is increased by making the power line thicker (or having a larger cross-sectional area) than the signal line. When such a cable is connected to the board, the AV device side socket (connector) to which the connection terminal (connector) of the HDMI cable is connected may be connected to another board such as a mother board by thermocompression bonding using a flexible board. is there.

  In this case, since the thickness (or cross-sectional area) of the power supply line and the signal line (hereinafter also referred to as control line) is different, the heating temperature and heat amount suitable for connection of each line are different. In other words, a thick power supply line (having a large cross-sectional area) has a large heat capacity and a large heat transfer amount in the conductor layer, so that the heating temperature is desirably higher than that of the signal line.

  Since the heater chip shown in Patent Document 1 is premised on soldering (thermocompression) a large number of gull-wing terminals of the same size at a time, some terminal shapes and thicknesses are different and the heat capacity is high. The thermocompression bonding temperature cannot be changed in different cases. For this reason, all terminals cannot be thermocompression bonded under optimum conditions.

  Further, in hybrid ICs incorporating power control circuits, it is conceivable to have power line terminals (power leads) and signal control line terminals (control leads), but this case also has the same problem as described above. Can occur. Therefore, conventionally, when leads having different heat capacities are used, a heater chip having a different temperature is attached to each lead, and thermocompression bonding is performed in a plurality of times. For this reason, replacement of the heater chip and a plurality of heater chips (or joining devices) have to be prepared, leading to problems that the reliability of each thermocompression bonding is lowered and the work efficiency is deteriorated.

  The present invention has been made in view of such circumstances, and when thermocompression bonding of leads having different heat capacities or the like, it is not necessary to perform thermocompression work a plurality of times using heater chips having different temperatures. An object is to provide a heater chip for thermocompression bonding capable of thermocompression bonding of leads under appropriate conditions.

According to the present invention, this object is provided with a horizontal lower side and a pair of left and right arms that rise from both ends thereof, and the upper ends of both arms are used as power supply terminals for fixing to the pressure head of the pressure device, heat is generated by supplying a heating current between power supply terminals, the lower side in the thermal compression heater chip you joined at a time by pressing a plurality of thermocompression bonded portions, the bottom side, the pressing portion of the lower side a plurality of A detour that bypasses the heating current with both ends connected to the pressing portion across a gap to be separated is formed in a space surrounded by a frame shape between the lower side and the left and right arms, and the electric resistance of the detour The heat-compression heater chip is characterized in that the amount of heat transmitted from the detour to the different pressing portions is made different by changing the temperature in the longitudinal direction so that the temperatures near the both ends of the detour are different. Achieved by It is.

  Each of the pressing parts is formed by forming a detour that bypasses the heating current by partitioning the pressing surface of the horizontal lower side, and the amount of heat transmitted from this detour differs in different pressing parts partitioned by this detour. A temperature difference can be generated. For this reason, pressing the thermocompression bonding part with a large heat capacity such as an electric power line with a high temperature pressing part, and pressing the thermocompression bonding part with a small heat capacity such as a signal line (control line) with a low temperature pressing part, Each crimping part can be thermocompression bonded at an appropriate temperature. Therefore, the reliability of joining of each thermocompression bonding part can be improved. Moreover, since the thermocompression bonding part from which these joining conditions differ can be joined at once, work efficiency is good. That is, it is not necessary to perform the thermocompression work a plurality of times with heater chips having different temperatures.

The front view which shows Example 1 of this invention Same left side view The figure which shows the example of a dimension of this Example The figure which shows the time change of the temperature distribution of a press part similarly Perspective view showing usage example of heater chip Perspective view showing another example of use of heater chip Front view showing a conventional example IV-IV sectional view in FIG.

  In order to provide a difference in the amount of heat transferred from both ends of the detour to the lower side, for example, the cross-sectional area of the detour (the area of the plane perpendicular to the longitudinal direction) is changed continuously, discontinuously, and stepwise in the longitudinal direction. Therefore, the temperature in the vicinity of both ends of the detour may be made different (claim 2). This is because if the cross-sectional area is small, the electrical resistance of the portion increases, and if the current is constant, the heat generation amount increases.

  If the cross-sectional area of each pressing portion on the lower side partitioned by the detour is made different, a difference occurs in the electrical resistance of each pressing portion. Item 3). Accordingly, a difference is provided in the cross-sectional area in the vicinity of both ends of the detour (Claim 2), and the temperature of each pressing part is further appropriately controlled by combining the difference in the amount of heat generated by the difference in the cross-sectional area of each pressing part be able to.

  Moreover, you may provide a difference in right and left in the cross-sectional area of the connection part vicinity of the lower part of a pair of right and left arm parts, and the both ends of a lower side (Claim 4). In this case, since a difference occurs in the amount of heat flow (heat conduction) in the vicinity of the connection portion, similarly, the temperature control of each pressing portion can be further finely controlled.

  If the cross-sectional area of the pressing part is made larger than the cross-sectional area near both ends of the detour, the amount of heat generated by the depressing part can be relatively reduced to increase the influence of the detour by heat generation (influence on the temperature of the pressing part). (Claim 5). Further, in this case, since the heat capacity of each pressing portion is increased, the temperature drop when pressed against the joint portion (lead) can be reduced.

  When the cross-sectional area of a lead such as a power supply line is large, the thickness and thickness of the lead may be larger than the lead of the control line. For such a lead, there is a difference in the height of each pressing surface. (Claim 6). That is, a difference is provided in the height of the pressing surface corresponding to the difference in the height of the leads.

  The lower side may be divided into two pressing parts by one detour (Claim 7), but may be divided into three or more pressing parts by two or more detours (Claim 8). In this case, the heat capacity It is convenient to use it for a joint part having changed in three or more stages.

  In this heater chip, since the amount of heat accumulated in the detour is increased, the temperature distribution of the detour and the pressing portion is made uniform over time. Then, the time to wait until the detour is sufficiently cooled before the next thermocompression bonding becomes longer, the waiting time becomes longer, and the work efficiency is lowered. In order to prevent this, it is preferable to provide a heat radiating means in the bypass (claim 9). For example, the air cooling effect can be improved by providing heat radiation fins or vent holes on the detour, or by applying irregularities to the surface. Moreover, it is good to provide the ventilation apparatus which supplies cooling air to these heat radiating means in a joining apparatus.

  1, 2, and 5, reference numeral 10 denotes a heater chip according to an embodiment of the present invention. The heater chip 10 is obtained by wire-cutting a metal material having a high resistance and a constant thickness, such as W (tungsten), as in the conventional heater chip 1 shown in FIGS. The lower side of the heater chip 10 is divided into left and right pressing portions 14 and 16 by a bypass 12. That is, the lower surface of the lower side is divided by the detour 12 into two pressing surfaces 14A and 16A.

  The detour 12 is formed in a substantially Ω shape so that the lower side and the left and right arm portions 18 and 20 substantially occupy a space surrounded by a frame. Upper portions of the arm portions 18 and 20 are power supply terminals 22 and 24. Reference numerals 22A and 24A denote bolt holes through which bolts for fixing the power supply terminals 22 and 24 to a pressing head (not shown) are passed.

  Detailed dimensions of the heater chip 10 are as shown in FIG. Numbers in this figure indicate dimensions in mm. Since the heater chip 10 has a constant thickness as apparent from FIG. 2, the dimensions shown in FIG. 3 are proportional to the cross-sectional area (and hence the electrical resistance) of each part.

  The detour 12 separates the pressing portions 14 and 16 with a gap A of 0.4 mm, and one end thereof is connected to the pressing portion 14 via a narrow portion B having a width of 1.6 mm. A portion continuous with the narrow portion B is a linear narrow portion C having a width of 2.5 mm. The other end of the detour 12 is connected to the pressing portion 16 via a narrow portion D having a width of 2.0 mm. A portion continuous with the narrow portion D is a U-shaped wide portion E having a width of 2.0 mm.

When a heating current is supplied to the power supply terminals 22 and 24, the current flows through the arm portions 18 and 20, the pressing portions 14 and 16, and the bypass 12, and each portion of the heater chip 10 generates heat. At this time, the heat generation amount of the detour 12 is larger in the narrow portion C (2.5 mm) having the narrow width than in the wide portion E (3.0 mm) having the wide width. Therefore, the amount of heat transferred from the detour 12 to the pressing portion 14 is larger than the amount of heat transferred to the pressing portion 16.

  Since the narrow portion B (width 1.6 mm) on the pressing portion 14 side is narrower than the narrow portion D (width 2.0 mm) on the pressing portion 16 side, the heat generation amount of the former B (width 1.6 mm) is the latter D. (Part with a width of 2.0 mm). For this reason, the narrow portions B and D contribute to making the temperature of the pressing portion 14 higher than that of the pressing portion 16.

  Further, the connecting portion F (width 0.8 mm) connected to the pressing portion 14 below the arm portion 18 is narrower than the connecting portion G (width 1.0 mm) connecting to the pressing portion 16 below the arm portion 20. For this reason, the heat generation amount of the connecting portion F on the pressing portion 14 side increases the heat generation amount of the connecting portion G on the pressing portion 16 side, which contributes to making the pressing portion 14 have a higher temperature than the pressing portion 16.

  Furthermore, since the pressing part 14 (width 2.8 mm) is narrower than the pressing part 16 (width 3.0 mm), the amount of heat generated by the pressing part 14 is greater than the amount of heat generated by the pressing part 16. As described above, the amount of heat transmitted to both ends of the pressing portion 14 via the narrow portion B and the connecting portion F is different from the amount of heat transmitted to both ends of the pressing portion 16 via the narrow portion D and the connecting portion G, and the pressing portion 14. , 16 also has a difference in the amount of heat generated, and as a result, the pressing portion 14 becomes higher in temperature than the pressing portion 16 more quickly.

  FIG. 4 shows the measurement result of the temperature change of the pressing portions 14 and 16 accompanying the supply of the heating current. The measurement sites are denoted by reference symbols a, b, and e in FIG. 1, and the temperature measurement results of the thermocouples welded to the respective sites a to e correspond to the curves a to e in FIG. As apparent from FIG. 4, the temperature of the pressing portion 14 rises more rapidly than the pressing portion 16 and is maintained at 400 to 450 ° C. and 250 to 280 ° C. after 2 to 4 seconds, respectively. That is, in a predetermined time range, a two-stage temperature of high temperature and low temperature can be obtained.

  If the heater chip 10 is heated while being pressed against the bonding target as shown in FIG. 5 and the respective pressing portions 14 and 16 are divided into two stages of temperatures (after about 4 seconds), the heating current is cut off. The temperature of each part is made uniform by heat transfer and converged to a substantially constant temperature. This measurement was performed using a GR-3500 (manufactured by KEYENCE) as a temperature measuring instrument with a sampling period of 100 ms.

  Note that the pressing surface 16 </ b> A that is the lower surface of the pressing portion 16 is lower than the pressing surface 14 </ b> A of the pressing portion 14 by 0.2 mm. The reason for the difference in height is that the thickness of a lead, which will be described later, is different for power and control.

  Next, a usage example of this embodiment will be described with reference to FIG. In this figure, reference numeral 30 denotes a flexible substrate (FPC), one end of which is a bare conductor (flying lead structure) having no insulating layer. Among these conductors, a part (four) is a large-diameter power lead 32 and the other (nine) is a small-diameter control lead 34. These leads 32 and 34 are arranged in parallel in a range corresponding to the length range of the high temperature side pressing portion 14 and the low temperature side pressing portion 16 of the heater chip 10. Reference numeral 36 denotes a hard board (hard printed board), for example, a reinforcing plate for fixing a connector (not shown) or a mother board. A power circuit pattern 38 and a control circuit pattern 40 corresponding to the leads 32 and 34 of the FPC 30 are formed on the hard substrate 36. Solder is supplied in advance to the joint portions (pads) of these circuit patterns 38 and 40 by solder plating.

The power lead 32 of the FPC 30 is aligned with the circuit pattern 38, the control lead 34 is aligned and overlapped with the circuit pattern 40, and thermocompression bonding is performed by pressing the pressing portions 14 and 16 of the heater chip 10 from above. . That is, when a heating current is supplied while the heater chip 10 is pressed, it is heated to the two-stage temperature shown in FIG. 4, and when the solder starts to melt in this state (after about 2 seconds), the temperature becomes substantially constant during the melting. (2-4 seconds). When the melting of the solder is almost finished, the temperature at the temperature measurement point c rises slightly higher than the other measurement points d and e (point P in FIG. 4, about 4 seconds later). This increase in temperature is considered to be due to the fact that the melting of the solder ends and the heat of fusion becomes unnecessary, while the overall temperature of the detour 12 is made uniform and the amount of heat transferred from the detour 12 to the low temperature side pressing portion 16 increases. .

  The heat capacity of the large-diameter power lead 32 is larger than the heat capacity of the control lead 34, but when the high temperature side pressing portion 14 is pressed and heated, the power lead 32 and the circuit pattern 38 are soldered with an appropriate amount of heat. Is sufficiently heated and is thermocompression bonded satisfactorily. Although the heat capacity of the small-sized control lead 34 is smaller than that of the lead 32, the low-temperature side pressing portion 16 is pressed here, so that it is sufficiently heated with a heat amount suitable for the lead 34 and is well thermocompression bonded. .

  If the heating current is interrupted after about 4 seconds (point P in FIG. 4), the pressing parts 14 and 16 are cooled, and the heater chip 10 gradually cools to a uniform temperature and becomes below the solidification temperature of the heater chip. Later, thermocompression bonding is completed. When the thermocompression bonding is finished, the heater chip 10 is raised to prepare for the next pressure bonding.

  Since the power lead 32 is thick, the height at which the power lead 32 starts to contact the pressing portion 14 is higher than the height at which the pressing portion 16 starts to contact the control lead 34. For this reason, in Example 1, as described above, the pressing surface 14A of the pressing portion 14 is higher than the pressing surface 16A of the pressing portion 16 (0.2 mm, see FIG. 3). Instead of increasing the thickness of the power lead 32, the thickness can be made the same as that of the control lead 34, and the width can be expanded to correspond to a large current. In this case, the pressing surface 16A may be the same height as 14A.

  In FIG. 6, reference numeral 50 denotes a hybrid IC, which incorporates a power control semiconductor element and its control circuit. This IC has a gull wing type power lead 52 and a control lead 54 on two opposite sides of the package. The four power leads 52 are adjacent to one end of the package, and the nine control leads 52 are adjacent to the other end. Reference numeral 56 denotes a hard substrate (PCB), on which an unillustrated circuit pattern (land, pad, through hole, etc.) corresponding to the leads 52 and 54 is formed. Solder is previously supplied to the circuit pattern by solder plating or the like.

  The heater chip 10 is the same as described above, and the high temperature side pressing portion 14 is aligned with the power lead 52 and the low temperature side pressing portion 16 is aligned with the control lead 54 and pressed down. By controlling the heating current as in the first embodiment, the power lead 52 and the control lead 54 having different heat capacities can be heated with an appropriate amount of heat and soldered in a good state.

  A cooling fin 58 serving as a cooling means may be formed in the bypass circuit 12 of the heater chip 10. Since the heater chip 10 uses the heat capacity of the bypass 12 to heat the pressing parts 14 and 16 to different temperatures, conversely, when the heat capacity of the bypass 12 is large, the cooling of the pressing parts 14 and 16 is delayed. For this reason, it is considered that the time until the molten solder is solidified becomes longer, and the processing efficiency is deteriorated. The cooling fins 58 increase the cooling rate and shorten the time required for one solder pressing process.

  Further, the pressure bonding device may be provided with a blowing means for supplying cooling air to the cooling fins 58 in a timely manner. In this case, the cooling fins 58 may be omitted and the entire heater chip 10 may be air-cooled. Instead of the cooling fins 58, a ventilation hole may be provided in the bypass 16 so that the cooling air passes therethrough, or the surface area may be increased by performing uneven processing on the surface.

DESCRIPTION OF SYMBOLS 10 Heater chip 12 Detour 14 High temperature side press part 16 Low temperature side press part 14A, 16A Press surface 18, 20 Arm part 22, 24 Feeding terminal 30 Flexible board 32, 52 High power lead 34, 54 Control lead 36 Hard board 50 Hybrid IC
56 Hard substrate 58 Cooling fin

Claims (9)

It has a horizontal lower side and a pair of left and right arms that rise from both ends, and the upper ends of both arms serve as power supply terminals that are fixed to the pressure head of the pressure device, while supplying a heating current between both power supply terminals in thermal compression heater chip to generate heat, you joining a plurality of thermocompression bonded portions at a time by,
The bottom side, detour to both ends across the gap to separate the lower side in a plurality of pressing portions is connected to the pressing portion bypassing said heating current, surrounded by a substantially frame shape between the lower side and the left and right arms Formed in the space
The amount of heat transmitted from the detour to the different pressing portions is made different by changing the electrical resistance of the detour in the longitudinal direction so that the temperatures near both ends of the detour are different. Heater chip for thermocompression bonding. The longitudinal direction is changed, detour around both ends thermocompression heater chip of claim 1 in which the temperature was different in the cross-sectional area of the bypass passage.   The heater chip for thermocompression bonding according to claim 1 or 2, wherein a cross-sectional area of each pressing portion on a lower side partitioned by a detour is different.   The heater chip for thermocompression bonding according to claim 1, 2 or 3, wherein a cross-sectional area in the vicinity of a connection portion between a lower portion of a pair of left and right arm portions and both ends of a lower side is different.   The heater chip for thermocompression bonding according to any one of claims 1 to 4, wherein a cross-sectional area of the pressing portion is larger than a cross-sectional area near both ends of the bypass.   The heater chip for thermocompression bonding according to any one of claims 1 to 5, wherein in some of the pressing portions, the height of the pressing surface is different from that of the other pressing portions.   The heater chip for thermocompression bonding according to any one of claims 1 to 6, wherein two pressing portions are formed by one detour.   The heater chip for thermocompression bonding according to any one of claims 1 to 6, wherein three or more pressing portions are formed by a plurality of detours.   The thermocompression bonding heater chip according to any one of claims 1 to 6, wherein a heat radiating means is formed in the bypass.

Images