JP2017080753A - Ultrasonic soldering method and ultrasonic soldering device - Google Patents

Abstract

PURPOSE: To provide an ultrasonic soldering method and an ultrasonic soldering device capable of performing soldering to an electrode or the like which does not contain Ag or lead, or has a reduced amount of inclusion thereof, as a part to be soldered.CONSTITUTION: An ultrasonic soldering method includes: a preliminary heating step in which a substrate made by applying a paste containing no Ag, Cu or Pb onto an arbitrary part and sintering the paste or a paste part on the substrate is preliminarily heated at a first prescribed temperature lower than a melting point of solder; and an ultrasonic soldering step in which a solder iron tip part is abutted on the paste part or is moved while being abutted on the paste part and soldering is performed on the paste part, in such a state that the solder supplied while applying the ultrasonic onto the solder iron tip part abutted on the paste part of the substrate of the first prescribed temperature preliminarily heated in the preliminary heating step is molten, and in such a state as to be adjusted to a second prescribed temperature lower than the temperature at which the solder is molten when the ultrasonic is not applied.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ultrasonic soldering method and an ultrasonic soldering apparatus in which a paste is applied to an arbitrary part on a substrate and soldered to a sintered part.

  Conventionally, solar cells, which are one of the uses of renewable energy, have been developed based on semiconductor technology, which is the leading role in the 20th century. It is an important development at the global level that affects the survival of humankind. The challenge of the development is progressing while facing not only the efficiency of converting sunlight into electric energy but also the problem of reduction in manufacturing costs and pollution-free. In efforts to achieve these, it is particularly important to reduce or eliminate the amount of silver (Ag) and lead (Pb) used in the electrodes.

  In general, as shown in the plan view of FIG. 18A and the cross-sectional view of FIG. 18B, the solar cell has an N-type / P-type silicon substrate 43 that converts solar energy into electric energy, and a silicon substrate. 43 has a function of preventing reflection of the surface of the silicon nitride film 45, which is an insulating thin film, a finger electrode 42 for extracting electrons generated in the silicon substrate 43, a bus bar electrode 41 for collecting electrons extracted by the finger electrode 42, a bus bar It consists of each element of an extraction lead electrode 47 for taking out the electrons collected on the electrode 41 to the outside.

  Among these, silver (silver paste) and lead (lead glass) are used for the bus bar electrode (bus electrode) 41 and the finger electrode 42, and the amount of silver used is eliminated or reduced. It is desired to reduce or eliminate the amount of (lead glass) used, and to reduce costs and pollution.

  In particular, a silver paste (or a part of Cu paste) has been conventionally used to sinter and form the electrodes (the bus bar electrode 41 and the finger electrode 42). The silver paste includes a silver component (powder), a glass component ( (Lead glass), organic material component, organic solvent component, resin component, so the first two silver components (powder) and glass component (lead glass) are eliminated and replaced with (for example, It is desired to solder an extraction lead wire or the like to an electrode (without Ag, Cu.Pb) formed by screen printing and sintering this (replaced with NTA glass (described later)).

  For example, the silver component (powder) and glass component (lead glass) in the conventional silver paste are eliminated and replaced in order to sinter and form the electrodes (such as the bus bar electrode 41 and the finger electrode 42) that constitute the solar cell described above. In the electrode part formed by sintering with NTA paste (Japanese Patent Application No. 2015-191857) in which silver or lead has been eliminated or reduced, for example, there is no Ag or the like (or Ag etc.) For this reason, the conventional soldering cannot be performed.

  It is desired to solve this problem and to solder to a portion (electrode or the like) having no Ag or the like.

  The present inventors sintered NTA glass (vanadate glass) 100%, which will be described later, into a paste that does not contain Ag or glass (lead glass) or is slightly mixed (hereinafter referred to as NTA paste). I discovered a method that enables soldering on the created bus electrodes. It has also been found that solar cells soldered by this method can produce solar cells having characteristics superior to those obtained when a conventional silver paste is used (described later). The method of soldering the NTA paste to the sintered part (electrodes or the like) is not limited to the above-described solar cell bus electrode or the like, but is a soldering method that can be used when electrodes or the like are produced by screen printing or the like.

  Based on these findings, the present invention is made by sintering a paste (for example, NTA paste) that eliminates or slightly mixes silver and reduces or eliminates the use of lead (lead glass). Ultrasonic soldering, which will be described later, on the battery bus electrode (bus bar electrode) and soldering to the surface (so-called solder plating), and soldering lead wires etc. can be attached as usual, and as a result, Soldering to an electrode or the like that does not contain Ag or lead or has reduced the amount of contamination is made possible.

  Therefore, the present invention relates to a soldering method in which a paste is applied to an arbitrary portion on a substrate and soldered to a sintered portion, and a paste that does not contain Ag, Cu, Pb is applied to an arbitrary portion and sintered. Alternatively, the paste portion on the substrate is brought into contact with the preheating step for preheating the first predetermined temperature lower than the melting temperature of the solder and the paste portion of the first predetermined temperature substrate preliminarily heated in the preheating step. The solder iron tip portion is adjusted to a second predetermined temperature, which is lower than the temperature at which the solder melts when no ultrasonic wave is applied. And an ultrasonic soldering step of soldering to the paste part by moving while abutting on the paste part.

  At this time, the first predetermined temperature is set to a temperature within the range from room temperature to the second predetermined temperature.

  Further, the second predetermined temperature is set to a temperature within a range of 10 to 40 ° C. lower than the temperature at which the solder melts when no ultrasonic wave is applied.

  In addition, as a paste not containing Ag, Cu, Pb, it does not contain Ag, Cu, Pb and vanadate glass is 100 wt%, or it does not contain Cu, Pb and Ag contains 0 to 50 wt% and the rest is vanadine. The NTA paste is an acid salt glass.

  The solder contains at least Sn, Zn, and Cl.

  Further, when soldering in the ultrasonic soldering step, drying or heat drying is performed in advance so that the organic solvent in the paste does not remain in the paste portion.

  Further, the paste portion applied on the substrate is sintered so as to be as smooth as possible.

  The ultrasonic wave has a frequency of 20 KHz to 150 KHz.

  As described above, the present invention includes, for example, a conductive NTA glass 100% NTA paste that does not contain Ag, Cu, and Pb, and an NTA paste that is further reduced to about 50% (the content can be further reduced). The electrode is fired instead of the conventional silver (or Cu) paste, and the solder is ultrasonically soldered to eliminate or reduce the amount of silver used in the conventional silver paste, and lead (lead) It has been discovered that even if the amount of glass used is reduced or eliminated, it is possible to solder the paste sintered part and attach a lead wire or the like. These have the following characteristics.

  First, for example, to form a bus bar electrode (bus electrode) of a solar cell, NTA glass which is a conductive vanadate glass (see registered trademark 5009023, Japanese Patent No. 5333976, etc.) 100%, and further 50% To the extent, instead of silver paste, the amount of Ag used is eliminated or reduced, and even if the amount of lead (lead glass) is reduced or eliminated, paste sintering is performed by ultrasonic soldering of the present invention. It was possible to solder to the part.

  Second, for example, by using about 100% to 50% of NTA glass as a bus bar electrode (bus electrode) (the content can be further reduced), the efficiency of converting solar energy into electronic energy is substantially the same or A slightly higher electrode formation exhibiting the effect as a bus bar electrode was obtained as an experimental result at the present initial stage (see FIG. 17). This is because NTA glass is (1) conductive, and (2) the NTA glass is used so that the finger electrode has the same height as the upper surface of the bus bar electrode (bus electrode) or the portion protruding through the upper surface. These portions are joined by the ultrasonic soldering of the lead electrode according to the present invention, and as a result, the high electron concentration region and the lead electrode are directly connected by the finger electrode, and other factors (for example, the “first” described below) 3) ”).

  Third, unlike the prior art, the finger electrode and the bus bar electrode are formed using a paste containing glass frit that is different. Conventionally, it has been necessary to generate a phenomenon called fire-through in the formation of finger electrodes. This is a finger electrode that breaks through the insulating layer of the silicon nitride film formed on the surface layer of the silicon substrate by the action of component molecules in the glass frit used as a sintering aid for silver, for example, lead molecules in lead glass. As a result, the electrons generated on the silicon substrate were efficiently collected. However, the fire-through phenomenon is not necessary for the formation of the bus bar electrode. Conventionally, the bus bar electrode was also sintered using lead glass containing lead component as a sintering aid, but although the structure is different, an electrical conduction path between the bus bar electrode and the silicon substrate is formed to reduce the conversion efficiency. It was a thing. By using NTA glass that does not cause a fire-through phenomenon as the sintering aid used for forming the bus bar electrode, reduction in conversion efficiency could be eliminated. Then, it becomes possible to take out the electric charge by soldering the lead wire to the portion of the bus bar electrode sintered with the NTA paste by the ultrasonic soldering of the present invention.

  FIG. 1 shows a block diagram of an embodiment of the present invention. FIG. 1 is an example of ultrasonic soldering of electrodes of a solar cell, and will be described in detail below by taking an example of ultrasonic soldering a ribbon 7 as a lead lead wire to a bus bar electrode 5. Here, ultrasonic soldering includes solder plating on electrodes (without lead wires) and soldering leads to electrodes, etc.

  FIG. 1 (a) schematically shows a front view of a main part subjected to ultrasonic soldering, and FIG. 1 (b) schematically shows an enlarged side view of a dotted circular portion.

  1 (a) and 1 (b), the solar cell penetrates the back electrode 2 provided on the back side of the silicon substrate 1, the nitride film 3, the bus bar electrode 5, and the nitride film 3 provided on the front side of the silicon substrate 1. In this manner, it has a structure comprising a finger electrode 4 for taking out electrons generated in the PN layer of the silicon substrate 1 and a ribbon 7 (lead lead wire) ultrasonically soldered on the finger electrode 4 with solder 6 on the finger electrode 4 of the present invention. is there. Here, a state in which the ribbon 7 is ultrasonically soldered with the solder 6 on the bus bar electrode 5 as an electrode is schematically shown.

  The bus bar electrode 5 is formed by sintering NTA paste (Japanese Patent Application No. 2015-202461) which does not contain Ag, Cu, Pb and is 100% by weight vanadate glass discovered by the present inventors. In the bus bar electrode formed by sintering an NTA paste which does not contain Ag, Cu, Pb, or does not contain Cu, Pb and contains Ag from 0 to 50 wt% and the rest is made of vanadate glass. Since Ag is 50% or less, it is an electrode that is impossible or extremely difficult to solder by conventional ordinary soldering. In particular, in the case of the bus bar electrode 5 which does not contain Ag, Cu, Pb at all, the conventional soldering is completely impossible. When the Ag content is 50% or less, only the Ag part can be soldered and the other parts cannot be soldered. The mechanical strength is extremely weak and the film peels off. In the ultrasonic soldering of the present invention, ultrasonic soldering (ultrasonic solder plating) is performed over the entire surface of a portion where the NTA paste is sintered, that is, a portion where there is no Ag, Cu, Pb or the like, or a portion where there is not. As a result of the experiment, it was found that this is possible (see the photographs in FIGS. 7 and 8).

  In FIG. 2, the solder 6 is solder to be ultrasonically soldered onto the bus bar electrode 5 and contains at least Sn, Zn, and Cl, and is melted at the ultrasonic soldering tip portion 24 of the present invention. It is to be soldered.

  The ribbon 7 is a lead wire for taking out electric charge from the bus bar electrode 5 to the outside. Here, pre-solder 72 is preliminarily attached to the upper and lower surfaces of the copper ribbon, and the ribbon 71 of the copper 71 is soldered by the solder 6. 5 is easy to ultrasonic soldering.

  The preheating table 11 is used to preheat the entire solar battery to a first predetermined temperature (room temperature or higher, a temperature within a range of solder melting temperature or less when ultrasonic soldering). By preheating with the preheating table 21, the amount of heat supplied to the soldering portion of the bus bar electrode 5 from the ultrasonic soldering tip portion 24 of the ultrasonic soldering device (not shown) can be reduced, and a small-capacity ultrasonic wave is required. The ultrasonic soldering can be performed by the soldering apparatus, the temperature of the ultrasonic soldering tip portion 24 can be easily controlled, and the ultrasonic soldering can be smoothly performed.

  Next, the configuration when ultrasonic soldering is performed with the configuration of FIG. 1 will be described in detail with reference to FIG.

  FIG. 2 shows a block diagram (part 2) of one embodiment of the present invention.

  2A schematically shows a side view of the main part of the solar cell corresponding to FIG. 1B, and FIGS. 2B and 2C show an ultrasonic soldering iron 22 and a bus bar electrode 5. The front view when soldering is ultrasonically shown schematically. FIG. 2B shows a configuration in which the solder 6 is soldered to the bus bar electrode 5, that is, a configuration in which solder plating is performed on the bus bar electrode 5. FIG. A configuration in which the ribbon 7 is soldered to the bus bar electrode 5, that is, a configuration in which the ribbon 7 is soldered on the bus bar electrode 5 is shown.

  Since FIG. 2A is the same as FIG. 1B, the description thereof is omitted.

  2B and 2C, an ultrasonic soldering iron 22 shows an example of an ultrasonic soldering apparatus according to the present invention. As shown in the drawing, the soldering iron tip portion 24 is heated and superposed. It is comprised from the ultrasonic transmitter and the heater 23 which supply a sound wave (refer FIG. 6). Usually, a frequency in the range of 20 KHz to 150 KHz and 60 KHz was used in the experiment. The heating capacity depends on the temperature of the preheating table 11, but in the experiment, about 10 W (with automatic temperature control) was used (corresponding to the heat capacity depending on the size of the part to be ultrasonically soldered (the part of the bus bar electrode 5)). Use the capacity.)

  The soldering iron tip portion 24 is used for ultrasonic soldering by melting the solder 6 and heating the temperature of the portion of the bus bar electrode 5 to be ultrasonic soldered. As shown in the experiment, the soldering iron tip portion 24 was obtained by cutting the top of a cylinder with a slope of about 45 degrees. However, the shape of the soldering iron tip 24 is not limited to this shape. Further, it may be a rotating body that rotates, a slide base that slides, or any other shape as long as it can conduct ultrasonic waves and heat to the ultrasonic soldering part.

  2B, the solder 6 supplied to the soldering iron tip portion 24 of the ultrasonic soldering iron 22 is ultrasonically soldered onto the busbar electrode 5, so that Solder plating can be performed.

2 (c), the solder 6 supplied to the solder iron tip portion 24 of the ultrasonic soldering iron 22 and the pre-soldered ribbon 7 are ultrasonically soldered onto the bus bar electrode 5. The ribbon 7 (lead lead wire) can be soldered on the bus bar electrode 5.
Alternatively, pre-soldering may be performed in advance as shown in FIG. 2B, and the ribbon 7 may be ultrasonically soldered thereon.

  FIG. 3 is an explanatory diagram of the present invention. FIG. 3 shows solder materials and the like. FIG. 3 shows an example of the material of the bus bar electrode 5 of the solar cell already described in FIGS. 1 and 2, the material of the solder 6 for soldering the ribbon 7 and the like.

Order of process Conventional invention (ultrasonic soldering)
-Bus bar electrode 5 Silver, about 100 wt% NTA glass 100 wt%
(See (b) of FIG. 1) (˜50 wt%)
・ Solder 6
(See (b) of FIG. 2) SAC (tin, silver, copper) Solder 6 (tin, zinc, indium
Soldering metals such as antimony and aluminum
Or a combination thereof (tin-zinc alloy, tin 20-40%
Degree, the rest is added)
-Ribbon 7 Copper around the copper, such as SAC The copper around the copper 6 (see Fig. 2 (c)) Coating with solder Coating (ultrasonic soldering)
As described above, in the present invention, since the bus bar electrode 5 is formed by firing NTA glass paste (NTA paste), soldering is impossible or extremely difficult with conventional solder. In addition, by soldering with the solder 6 in a preheated state, solder plating or ribbon 7 (lead lead wire) can be soldered onto the bus bar electrode 5 by ultrasonic soldering very well. This was confirmed by experiments (see the photographs in FIGS. 7 and 8).

  Next, the procedure of ultrasonic soldering of the electrode part (for example, bus bar electrode 5) of the solar cell will be described in detail according to the order of the flowcharts of FIGS.

  FIG. 4 is a flowchart for explaining the operation of the present invention.

In FIG. 4, S1 forms an NTA bus bar electrode. The bus bar electrode 5 of FIGS. 1 to 3 is formed by screen printing NTA glass 100 wt% (˜50 wt%) NTA paste and sintered to form the bus bar electrode 5 made of NTA. And, as described on the right side, the NTA bus bar electrode 5 is
1. The paste is treated so that the organic solvent disappears (solvent removal).

  2. Sinter so that the NTA glass electrode surface becomes flat.

  In addition, 1. To remove the organic solvent in the paste (free solvent), dry or heat dry the organic solvent in the NTA paste so that the solvent in the paste is sufficiently evaporated (fly away). And lose) If the solvent remains, the phenomenon that ultrasonic soldering does not work appears.

  In addition, 1. To remove the organic solvent in the paste (free solvent), dry or heat dry the organic solvent in the NTA paste so that the solvent in the paste is sufficiently evaporated (fly away). And lose) If the solvent remains, the phenomenon that ultrasonic soldering does not work appears.

  This 2. When the NTA glass electrode is sintered so as to be flat, the NTA paste is screen-printed on the portion to be the bus bar electrode 5 in FIGS. 1 and 2 so that it becomes as flat as possible. Care is taken to screen print and sinter as flat as possible during firing and after sintering. In other words, care should be taken not to form small irregularities and sintering should be as flat as possible. If it is not flat, the phenomenon that ultrasonic soldering does not work well appears.

  In S2, the substrate is placed on the heating table and raised to a temperature not higher than the temperature at which the solder melts when ultrasonically supplied. This preheating temperature is such that when the ultrasonic soldering iron tip 24 is brought into contact with the solder 6 and heated simultaneously with the supply of ultrasonic waves, the solder 6 melts at a slightly lower temperature than when no ultrasonic waves are supplied. A temperature lower than a temperature at which the solder 6 melts when ultrasonic waves are supplied (referred to as a second predetermined temperature) (first predetermined temperature (above room temperature and below the melting temperature of solder when ultrasonic waves are supplied)) The temperature of the soldering iron tip portion 24 is set (adjusted) to the soldering iron portion 24. The second predetermined temperature is a temperature range in which the solder 6 melts when the solder 6 is heated while supplying ultrasonic waves. The temperature is usually in the range of about 10 to 40 ° C. lower than the melting temperature of the solder 6 when no sound wave is supplied (determined by experiment because it depends on the type of solder).

  In step S3, the temperature of the soldering iron tip 24 is raised within a temperature range that melts when ultrasonic waves are supplied to the solder.

  S4 provides ultrasonic waves 20 to 150 KHz to the soldering iron tip 24. These S3 and S4 are set (adjusted) to a temperature (second predetermined temperature) at which the solder 6 is melted by raising the temperature while supplying the ultrasonic wave 20 to 150 KHz to the soldering tip portion 24.

  By the above S1 to S4, preparation for ultrasonic soldering is completed on the bus bar electrode 5 formed by firing the NTA paste, that is, the solder iron tip portion 24 is brought into contact with the solder 6 and the solder 6 is dissolved. Thus, the preparation for ultrasonic soldering to the bus bar electrode 5 is completed.

  In FIG. 5, S5 is followed by S4, and solder is applied to the upper surface of the bus bar electrode (solder plating). This is because the soldering iron tip portion 24 which has been prepared for ultrasonic soldering by S1 to S4 is supplied to the upper surface of the bus bar electrode 5 while supplying the solder 6 as shown in FIG. The soldering iron tip portion 24 is brought into contact, the solder 6 is melted, and ultrasonic soldering is performed on the bus bar electrode 5. By this ultrasonic soldering, the solder 6 is soldered to the upper surface of the bus bar electrode 5 as shown in FIGS. 7B and 8B.

  As described above, the solder 6 can be ultrasonically soldered (solder plated) on the upper surface of the bus bar electrode 5.

  S6 is the same as S3 and S4 as ribbon attachment 1. In the same manner as S3 and S4 in FIG. 4, in order to ultrasonically solder the ribbon 7 that has been pre-soldered 72 to the bus bar electrode 5, the solder iron tip portion 24 is set (adjusted) to a second predetermined temperature. At the same time, an ultrasonic wave is supplied so that the ribbon 7 can be ultrasonically soldered. If the solder to be melted is the same solder as when the bus bar electrode 5 is solder-plated, the second predetermined temperature and ultrasonic wave are the same as those at S3 and S4. The second predetermined temperature and the ultrasonic wave that are obtained by experiment for each type are supplied (applied).

  In S7, as the ribbon attachment 2, the ultrasonic soldering iron tip is brought into contact with the ribbon and soldered. This is because the ultrasonic soldering iron tip 24 is brought into contact with the ribbon 7 and the solder pre-soldered 72 on the ribbon 7 or the solder plated on the bus bar electrode 5 or the solder supplied from the outside is dissolved. Then, the ribbon 7 is ultrasonically soldered to the bus bar electrode 5.

  S8 is completed. This means that the ultrasonic soldering of the copper ribbon 7 to the upper surface of the bus bar electrode 5 has been completed.

  As described above, solder plating and further ribbon 7 can be soldered by ultrasonic soldering on the bus bar electrode 5 that constitutes the solar cell and is screen-printed and fired with NTA paste.

  FIG. 6 shows an example of characteristics of the ultrasonic soldering apparatus of the present invention. This shows an example of the characteristics of the ultrasonic soldering apparatus used in the prototype experiment described with reference to FIGS.

  In FIG. 6, as the characteristics of the ultrasonic soldering apparatus, the following ones shown in the figure were used for the prototype experiment. Since mass production is considered in mass production, what kind of characteristics can be obtained if ultrasonic soldering can be satisfactorily performed on the upper surface of the bus bar electrode 5 or the like prepared by firing the NTA paste described in FIGS. Good thing to adopt.

Item Contents Remarks ・ Ultrasonic transmission frequency 60KHz ± 5KHz
・ Output power: Maximum 15W (effective 10W)
・ Heater temperature 200 ~ 500 ℃ Power supply capacity 200W
(At the temperature of the heater part,
It is not the temperature of the soldering iron tip. )
The temperature of the soldering iron tip portion 24 is measured with a thermometer (not shown) (for example, a thermocouple is embedded in the soldering iron tip portion 24 and measured. Then, based on this measured value, a second predetermined temperature is measured. Automatically adjust).

  FIG. 7 shows an example of ultrasonic soldering (NTA 100%) of the present invention. The photographs shown in FIG. 4 and FIG. 5 show the pictures before and after ultrasonic soldering of the bus bar electrode (NTA 100%) 5 formed by screen printing and sintering the NTA paste (NTA 100%). Show.

  FIG. 7A shows an example of a photograph before ultrasonic soldering (NTA 100%). In the photograph of FIG. 7A, the bar in the horizontal direction is the finger electrode 4 (Ag 100%, see FIGS. 1 and 2), and the band in the vertical direction so as to cover the finger electrode 4 However, this is a bus bar electrode (NTA 100%) 5 formed by firing the NTA paste (100%) which was experimentally produced this time. In the present invention, a soldering iron tip portion 24 is brought into contact with the bus bar electrode (NTA 100%) 5 for soldering, ribboning, or a trial experiment.

  FIG. 7B shows an example of a photograph in which only the solder 6 is ultrasonically soldered on the bus bar electrode (NTA 100%) 5 in FIG. 7A according to the procedure of FIGS. Actually, the ribbon 7 used as an extraction lead wire for taking out the electric charge is ultrasonically soldered. However, if the ribbon 7 is soldered, the state below the ribbon 7 becomes invisible. This is an ultrasonic soldered product. As shown in the figure, the portion of the bus bar electrode (NTA 100%) 5 shines white and clearly shows that the solder is soldered onto the bus bar electrode (NTA 100%).

  As described above, ultrasonic soldering is performed on the bus bar electrode (NTA 100%) according to the procedure of FIGS. 4 and 5 of the present invention, so that the bus bar electrode 5 of NTA 100%, which is impossible by conventional soldering, can be obtained. It has been confirmed that the solder 6 can be soldered on (discovered by the present inventors).

  Next, FIG. 8 shows an example of a photograph of the bus bar electrode 5 of NTA 50%, similarly to NTA 100% of FIG.

  FIG. 8 shows an example of ultrasonic soldering (NTA 50%) of the present invention. The photographs shown in FIG. 4 and FIG. 5 are photographs of the bus bar electrode (NTA 50%) 5 formed by screen printing and sintering the NTA paste (NTA 50%) before and after ultrasonic soldering. Show.

  FIG. 8A shows an example of a photograph before ultrasonic soldering (NTA 50%). 8A is a finger electrode 4 (Ag 100%, see FIG. 1 and FIG. 2) at the top end of the upper end portion on the photograph. Is a bus bar electrode (NTA 50%) 5 formed by firing the NTA paste (50%) which was experimentally produced this time. In the present invention, a soldering iron tip portion 24 was brought into contact with the bus bar electrode (NTA 50%) 5 for soldering, ribboning, or a trial experiment.

  FIG. 8B shows an example of a photograph in which only the solder 6 is ultrasonically soldered on the bus bar electrode (NTA 50%) 5 in FIG. 8A according to the procedure of FIGS. Actually, the ribbon 7 used as an extraction lead wire for taking out the electric charge is ultrasonically soldered. However, if the ribbon 7 is soldered, the state below the ribbon 7 becomes invisible. This is an ultrasonic soldered product. As shown in the figure, the portion of the bus bar electrode (NTA 50%) 5 shines white and clearly shows that the solder is soldered onto the bus bar electrode (NTA 50%).

  As described above, by performing ultrasonic soldering on the bus bar electrode (NTA 50%) according to the procedure of FIGS. 4 and 5 of the present invention, the NTA 50 which is impossible or extremely difficult by conventional soldering or easily peeled off. It was confirmed that the solder 6 could be soldered onto the% bus bar electrode 5 (discovered by the present inventors).

  Hereinafter, an example (experimental example) when the above-described ultrasonic soldered solar electric bus bar electrode 5 of the present invention is prepared will be described in detail (the following example is Japanese Patent Application No. 2015-180720 (application date)). : Inventor and applicant of September 14, 2015) are examples of the same application).

  FIG. 9 shows a structural diagram of one embodiment of the present invention (process completion drawing: sectional view).

  In FIG. 9, a silicon substrate 11 is a known semiconductor silicon substrate.

  The high electron concentration region (diffusion doping layer) 12 is a known region (layer) in which a desired p-type / n-type layer is formed on the silicon substrate 11 by diffusion doping or the like. This is a region where electrons are generated (power generation) in the silicon substrate 11 when light is incident and the electrons are accumulated. Here, the accumulated electrons are taken out upward by an electron outlet (finger electrode (silver)) 14 (see the effect of the invention).

  The insulating film (silicon nitride film) 13 is a known film that allows sunlight to pass (transmits) and electrically insulates the bus bar electrode 15 from the high electron concentration region 14.

  The electron take-out port (finger electrode (silver)) 14 is a port (finger electrode) that takes out electrons accumulated in the high electron concentration region 12 through a hole formed in the insulating film 13. In the present invention, as shown in the figure, when the bus bar electrode 15 is baked with NTA glass 100% (or about 71%), the finger electrode 14 is the same as the height of the upper surface of the bus bar electrode 15 or A portion protruding through and projecting to the upper surface is formed (fired) (by controlling the thickness of the NTA paste), and electrons in the high electron concentration region 12 directly flow into the lead wire 17 through the finger electrode 14 (Electrons can be taken out directly). That is, the high electron concentration region 12, the finger electrode 14, the bus bar electrode 15, and the route 1 of the lead wire 17 (conventional route 1), and the high electron concentration region 12, the finger electrode 14, and the route 2 of the lead wire 17 (in the present invention). Electrons (current) in the high electron concentration region 12 can be extracted to the outside through the lead wire 17 through two routes including the added route 2). As a result, the high electron concentration region 12 and the lead wire 17 It is possible to make the resistance value between the two very small, thereby reducing the loss and consequently improving the efficiency of the solar cell.

  A bus bar electrode (electrode 1 (NTA glass 100%)) 15 is an electrode for electrically connecting a plurality of electron outlets (finger bar electrodes) 14, and an electrode to be used to eliminate or reduce the amount of Ag used (See the effect of the invention).

  The back electrode (electrode 2 (aluminum)) 16 is a known electrode formed on the lower surface of the silicon substrate 11.

  The lead wire (solder formation) 17 takes out electrons (current I) electrically connected to the plurality of bus bar electrodes 15 to the outside, and in the present invention, the finger electrode 14 has the same height as the upper surface of the bus bar electrode 15. It is a lead wire that takes out the electrons (current) to the outside by ultrasonic soldering the lead wire to the portion or the protruding portion.

  Under the structure shown in FIG. 9, when sunlight is irradiated from above to below, the sunlight passes through the portion without the lead wire 17 and the electron outlet 14 and the insulating film 13 and enters the silicon substrate 11. To generate electrons. Thereafter, the electrons accumulated in the high electron concentration region 12 pass through the electron take-out port (finger electrode) 14, the bus bar electrode 15, the route 1 of the lead wire 17, and the electron take-out port (finger electrode) 14 and the route 2 of the lead wire 17. It is taken out via both paths. At this time, as will be described later with reference to FIGS. 13 to 17, the bus bar electrode 15 is mixed with NTA glass (conductive glass) 100% to 71% (more or less, see FIG. 17) as glass frit in the paste. It is possible to eliminate or reduce the amount of Ag used. Details will be sequentially described below.

  FIG. 10 shows a flowchart for explaining the operation of the present invention, and FIGS. 11 and 12 show the detailed structure of each process.

  In FIG. 10, a silicon substrate is prepared in S1.

  In S2, cleaning is performed. These S1 and S2 cleanly clean the surface (surface on which the high electron concentration region 12 is formed) of the silicon substrate 11 prepared in S1, as shown in FIG.

  S3 is diffusion doped. As shown in FIG. 11B, this involves performing known diffusion doping on the silicon substrate 11 cleaned in FIG. 11A to form a high electron concentration region 12.

  In S4, an antireflection film (silicon nitride film) is formed. As shown in FIG. 11 (c), the high electron concentration region 12 of FIG. 11 (b) is formed, and an antireflection film (sunlight is passed through and surface reflection is made as much as possible. For example, a silicon nitride film is formed by a known method as the reduced film.

  S5 screen-prints the finger electrodes. As shown in FIG. 11 (d), the pattern of the finger electrode 14 to be formed is screen-printed on the silicon nitride film 13 shown in FIG. 11 (c). As the printing material, for example, silver mixed with lead glass as a frit is used.

  In S6, the finger electrode is fired and fired through. This is because the finger electrode 14 pattern (mixed with silver and lead glass frit) screen-printed in FIG. 11 (d) is baked, and the silicon nitride film 13 is formed as shown in FIG. 11 (e). The finger electrode 14 in which silver (conductivity) is formed is formed through fire-through.

  S7 screen-prints the bus bar electrode (electrode 1). As shown in FIG. 12 (f), the pattern of the bus bar electrode 15 to be formed is screen-printed on the finger electrode 14 shown in FIG. 11 (e). For the printing material, for example, NTA gas (100%) is used as a frit.

In S8, the bus bar electrode is fired. This is because the bus bar electrode 15 pattern (NTA glass (100%) frit) screen-printed in (f) of FIG. 12 is fired (fired within 1 minute at most, 1-3 seconds or longer). As shown in FIG. 12G, the bus bar electrode 15 is formed in the uppermost layer, and the finger electrode 14 is the same height as the upper surface of the bus bar electrode 15 formed in the uppermost layer, which is a feature of the present invention. Or a portion that has been penetrated. (This is done by controlling the film thickness.)
Note that S5 and S7 may be printed and both may be fired simultaneously.

  S9 forms a back electrode (electrode 2). For example, an aluminum electrode is formed on the lower side (back surface) of the silicon substrate 11 as shown in FIG.

  S10 solders the lead wire. As shown in FIG. 12 (i), when the lead wires for electrically connecting the bus bar electrodes in FIG. 12 (g) are formed by solder, for example, formed by ultrasonic soldering and electrically connected. High electron concentration region 12, finger electrode 14, bus bar electrode 16, path 1 of lead wire 17 (conventional path 1) and high electron concentration region 12, finger electrode 14, lead wire 17 path 2 (added in the present invention) In both the paths 2) and 2), the electrons (current) in the high electron concentration region 12 can be taken out via the lead wire 17, and the resistance between the high electron concentration region 12 and the lead wire 17 can be extracted. The value can be made very small to reduce loss and improve solar cell efficiency. That is, in the path 2 added in the present invention, one end of the finger electrode 14 is in the high electron concentration region 12, and the other end is a portion that is the same height as the top surface of the bus bar electrode 15 made of NTA glass 100% or a portion that penetrates. Since the lead wire is directly joined to this portion (direct joining by ultrasonic soldering), the path 2 of the high electron concentration region 12, the finger electrode 14, and the lead wire 17 is formed. The route 1 is a conventional route.

  Through the above steps, a solar cell can be formed on the silicon substrate.

  FIG. 13 is a detailed explanatory view (firing of bus bar electrodes) of the present invention.

  13A schematically shows an example in which the bus bar electrode is baked with 100% silver and 0% NTA (weight ratio), and FIG. 13B shows the bus bar electrode with 50% silver and NTA 50% weight ratio. FIG. 13C schematically shows an example in which the bus bar electrode is fired at 100% NTA (weight ratio). The firing time was set to 1 to 3 seconds or longer within 1 minute at the longest.

  In a prototype experiment of a solar cell formed to have substantially the same structure as shown in FIGS. 13A, 13B and 13C, the following experimental results are obtained. It was.

Conversion efficiency of solar cells
Fig. 13 (a) Ag 100%, NTA 0% Average of about 17.0%
Fig. 13 (b) Ag 50%, NTA 50% Average of about 17.0%
13 (c) Ag 0%, NTA 100% Average 17.2%
As a result of trial manufacture, the conversion efficiency when solar cells are formed is almost the same at about 17.0% on average in FIG. 13 (a) and FIG. 13 (b) as materials for printing the bus bar electrode pattern. The result was obtained. Further, in FIG. 13C, an average conversion efficiency of about 17.2% was obtained. It can be seen from the initial experimental results that all of (a) to (c) in FIG. 13 are within the same conversion efficiency range, or that NTA 100% in (c) in FIG. NTA glass is composed of vanadium, barium, and iron. In particular, iron is strongly bonded internally and stays in the interior, and its bonding property is extremely small even when mixed with other materials. (See Japanese Patent No. 5333976 and the like), and it is presumed to be due to the improvement of the path between the high electron concentration region of the present invention and the lead wire (path 1 and path 2 are in parallel).

  14 and 15 are explanatory diagrams (bus bar electrodes) of the present invention.

  14 (a) and 14 (b) are NTA 50% and Ag 50%, FIG. 14 (a) shows an overall plan view, and FIG. 14 (b) shows an enlarged view. . FIG. 15 (c) shows NTA 100% Ag 0%, and FIG. 15 (c) shows an enlarged view.

  14 (a) and 14 (b), the bus bar electrode 15 is a long bar-shaped electrode as shown in the overall plan view of FIG. 14 (a), and this is enlarged by an optical microscope. Then, a structure as shown in FIG. 14B was observed.

  In FIG. 14 (b), the bus bar electrode 15 was fired with the conventional Ag and NTA glass frit when it was fired with the conventional Ag and lead glass frit. In the case of firing within 1 minute for 1 to 3 seconds or more, it has been found that Ag is collected and formed in the central portion of the bus bar electrode 15 as shown in FIG. Therefore, as explained in the column of the effect of the invention, when NTA glass is mixed with Ag and fired for a short time (at least 1 minute, firing for 1 to 3 seconds or more), Ag collects in the central portion and becomes conductive. NTA glass is improved by reducing the Ag ratio due to comprehensive actions such as improved (conventionally improved Ag compared to the case where Ag was dispersed uniformly in the past) and NTA glass itself also has conductivity. As described above, the conversion efficiency when manufactured as a solar cell was about 16.9% even in the experiment.

  The firing temperature is 500 ° C. to 900 ° C., but it is necessary to determine the optimum temperature by experiment when it is produced as a solar cell. If it is too low or too high, the structure as shown in FIG. 14B cannot be obtained, and it is necessary to determine by experiment.

  In FIG. 15C, the bus bar electrode 15 is a bar-shaped electrode having a wide lateral width at the center portion shown in the figure, and shows an example of an enlarged photograph of 100% NTA according to the present invention.

  The bus bar electrode 15 in FIG. 15C has a portion in which the finger electrode 14 narrow in the vertical direction penetrates the bus bar electrode 15 and slightly protrudes upward, and the periphery of the protruding portion is the original finger. It turns out that it is thicker than the width of the electrode 14. Then, ultrasonic soldering is performed on the bus bar electrode 15 as shown in FIG. 16 to be described later in detail with a width that is the same as the width of the bus bar electrode 15, slightly smaller or slightly larger. High in both paths 1 (path 1 of photoelectron concentration region 12, finger electrode 14, bus bar electrode 15, lead wire 17) and path 2 (path 2 of photoelectron concentration region 12, finger electrode 14, lead wire 17) described above. The concentration electron region and the lead wire are conductively connected to reduce the loss of electrons (current) and can be efficiently extracted to the outside. The conversion efficiency is substantially the same as that shown in FIGS. Alternatively, a slightly high conversion efficiency (about 17.2%) was obtained.

  The firing temperature is about 500 ° C. to 900 ° C., which is almost the same as that shown in FIGS. 14A and 14B, but it is necessary to determine an optimum temperature by experiment when it is fabricated as a solar cell. If it is too low or too high, the structure as shown in FIG. 15C cannot be obtained, and it is necessary to determine by experiment.

  FIG. 16 shows an explanatory diagram (ultrasonic soldering) of the present invention. This is the case of NTA 100% in FIG. 15C described above (in the same manner, it may be applied to FIGS. 14A and 14B).

  FIG. 16A shows a state after the finger electrode 14 is fired.

  FIG. 16B shows a conventional method in which a slightly larger (or the same or smaller) lead wire 17 is soldered on the bus bar electrode 15 shown in FIG. An example of In this conventional example, since normal soldering is performed, the portion (Ag) where the finger electrode 14 protrudes and the lead wire 17 are soldered together, but the portion where the finger electrode 14 does not protrude (portion of NTA 100%) The lead wire 17 is not sufficiently soldered and the mechanical strength is not sufficient. On the other hand, when ultrasonic soldering of FIG. 16C described later was performed, solder bonding was performed, and the mechanical strength was greatly improved.

  In FIG. 16C, a slightly larger lead wire 17 indicated by a dotted line is ultrasonically soldered on the bus bar electrode 15 in FIG. 16A (the bus bar electrode 15 in FIG. 15C). The example of this invention is shown. In this example of the present invention, since the soldering is performed by ultrasonic soldering, the portion (Ag) from which the finger electrode 14 protrudes and the lead wire 17 are soldered together, and further, the portion without the finger electrode 14 (portion of NTA 100%) The lead wire 17 is also soldered to significantly improve the mechanical strength, and the conductivity of the path 2 (the high electron concentration region 12, the finger electrode 14, the bus bar electrode 15, the path 2 of the lead wire 17) described above is improved. did.

FIG. 17 shows a measurement example (efficiency) of the present invention. FIG. 17 is a good measurement example when the NTA is changed from 100% to 70% for the bus bar electrode 15 described above. The horizontal axis in FIG. 17 indicates the sample number, and the vertical axis indicates the efficiency. (%). sample,
・ NTA 100% Ag 0%
・ NTA 90% Ag 10%
・ NTA 80% Ag 20%
・ NTA 70% Ag 30%
These were used to make solar cells, and each measurement result (efficiency) was as shown. In addition, since it is an initial experiment, there are considerable variations in the measurement results as shown in the figure, but they are within the range of 16.9 to 17.5, and the bus bar electrode 15 is created with NTA 100% (that is, Even when a solar cell is manufactured without using Ag), it is found that the efficiency is comparable or slightly higher than that of NTA 70% (or 80%, 90%) and can be used even with NTA 100%. (The inventors found this fact).

1 is a configuration diagram of one embodiment of the present invention. FIG. 3 is a configuration diagram (Part 2) of an embodiment of the present invention. It is explanatory drawing (solder material etc.) of this invention. It is an operation | movement explanatory flowchart of this invention. It is an operation | movement description flowchart (continuation) of this invention. It is an example of the characteristic of the ultrasonic soldering apparatus of this invention. It is an example of ultrasonic soldering (NTA 100%) of the present invention. It is an example of ultrasonic soldering (NTA 50%) of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. It is an operation | movement explanatory flowchart of this invention. It is detailed process explanatory drawing (the 1) of this invention. It is detailed process explanatory drawing (the 2) of this invention. It is detailed explanatory drawing (baking of a bus-bar electrode) of this invention. It is explanatory drawing (bus-bar electrode) of this invention. It is explanatory drawing (bus-bar electrode) of this invention. It is explanatory drawing (ultrasonic soldering) of this invention. It is a measurement example (efficiency) of the present invention. It is explanatory drawing of a prior art.

1: Silicon substrate 2: Back electrode 3: Nitride film 4: Finger electrode 5: Bus bar electrode 6: Solder 7: Ribbon 71: Copper 72: Pre-solder 21: Preheating table 22: Ultrasonic soldering iron 23: Ultrasonic transmitter And heater 24: soldering iron tip 11: silicon substrate 12: high electron concentration region (diffusion doping)
13: Insulating film (silicon nitride film)
14: Electron outlet (finger electrode)
15: Bus bar electrode 16: Back electrode 17: Lead wire

Claims (10)

In a soldering method of applying paste to an arbitrary part on a substrate and soldering to a sintered part,
A preheating step of preheating a substrate which is formed by applying a paste containing no Ag, Cu or Pb to an arbitrary portion and sintering the paste or a paste portion on the substrate to a first predetermined temperature lower than the melting temperature of the solder;
Solder supplied in a state where ultrasonic waves are applied to the soldering iron tip portion in contact with the paste portion of the substrate at the first predetermined temperature preheated in the preheating step is melted. Ultrasonic soldering in which the soldering iron tip part is in contact with or in contact with the paste part and is soldered to the paste part in a state adjusted to a second predetermined temperature lower than the melting temperature of the solder And an ultrasonic soldering method.   2. The ultrasonic soldering method according to claim 1, wherein the first predetermined temperature is a temperature within a range from room temperature to the second predetermined temperature.   3. The second predetermined temperature is set to a temperature within a range of 10 to 40 ° C. lower than a temperature at which solder melts when no ultrasonic wave is applied. 3. Ultrasonic soldering method.   As a paste containing no Ag, Cu, or Pb, 100 wt% of vanadate glass without containing Ag, Cu, or Pb, or 100 wt% of vanadate glass, and containing 0 to 50 wt% of Ag and the rest of vanadic acid The ultrasonic soldering method according to any one of claims 1 to 3, wherein the salt glass is an NTA paste.   The ultrasonic soldering method according to claim 1, wherein the solder contains at least Sn, Zn, and Cl.   6. The solder according to any one of claims 1 to 5, wherein when the soldering is performed in the ultrasonic soldering step, the organic solvent in the paste does not remain in the paste portion in advance or is dried by heating. Ultrasonic soldering method.   The ultrasonic soldering method according to any one of claims 1 to 6, wherein a paste portion to be coated on the substrate is sintered so as to be as smooth as possible.   The ultrasonic soldering method according to claim 1, wherein the ultrasonic wave has a frequency of 20 KHz to 150 KHz.   9. The ultrasonic soldering method according to claim 1, wherein a portion of the substrate to which the paste is applied is an electrode portion of a solar cell. In a soldering device that applies paste to an arbitrary part on a substrate and solders it to a sintered part,
A preheating means for preheating a substrate that is formed by applying a paste not containing Ag, Cu, or Pb and sintering the paste or a paste portion on the substrate to a first predetermined temperature lower than the melting temperature of the solder;
Solder supplied in a state where ultrasonic waves are applied to a soldering iron tip portion in contact with the paste portion of the substrate at the first predetermined temperature preheated by the preheating means melts, and solder is applied when no ultrasonic waves are applied. Ultrasonic soldering in which the soldering iron tip part is in contact with or in contact with the paste part and is soldered to the paste part in a state adjusted to a second predetermined temperature lower than the melting temperature of the solder And an ultrasonic soldering apparatus.