CN1886840A - Solar cell module - Google Patents

Abstract

The largest stress is created in the vicinity of the boundary between an edge of a bus bar electrode in a solar cell and a surface of a semiconductor substrate, and stresses are easily concentrated. Accordingly, defects such as micro cracks occur in the semiconductor substrate, which develop into a large craze with the defects as its starting point. In connecting bus bar electrodes 4a and 5a in the solar cell by an inner lead 8, therefore, a solder 6 is not brought into contact with edges along the longitudinal direction of the bus bar electrodes 4a and 5a and portions F from the edges to a predetermined distance a inward therefrom, and is brought into direct contact with a filler 10.

Description

Solar module

Technical field

The present invention relates to a kind of solar module, relate more specifically to a kind of solar module, wherein by inner lead a plurality of solar cells are connected to Semiconductor substrate, each all has the electrode that is formed on wherein described solar cell.

Background technology

Solar cell is made with monocrystalline substrate or polysilicon substrate.Therefore, solar cell must be rainproof when outdoor etc. when solar cell is installed in a little less than aspect the mechanical shock.Because a solar cell is difficult to produce electricity output, must be with a plurality of solar cell polyphones so that can draw actual electricity output.

Therefore; usually adopt and connect a plurality of solar cells; the solar cell of connection is placed between translucent panel and the back of the body surface protection member, and the filler that sealing mainly is made up of EVAc (EVA) etc. among solar cell is made the method for solar module.The solar cell that this linear polyphone connects is known as the solar cell string.

In this solar module, solar cell is interconnective with the narrow conductor that appears at the length that is called outside lead at two ends in the solar cell by the narrow conductor of the length that is called inner lead.Outside lead in a plurality of strings is passed through to connect distribution connection parallel with one another, to make solar battery panel.

Such inner lead, outside lead and to be connected distribution be that the Copper Foil that scribbles scolder of 2～8mm forms by about 0.1～1.0mm of thickness and width usually, the whole surface of described Copper Foil scribbles scolder.They are cut into predetermined length and use.

Scolder normally has the eutectic solder that the lead of the tin of about 63 weight % and about 37 weight % is formed.

When using scolder that inner lead and solar cell are interconnected as mentioned above, the coating that contains scolder is provided in advance the surface that is formed on the current collection busbar electrode on the solar cell surface, and this coating is carried out thermal weld together with the coating that contains scolder in the inner lead.

Alternatively, only provide the coating that contains scolder to inner lead, using solder flux that the scolder direct heat in the inner lead is welded to does not then have on it on busbar of scolder coating electrode.

In the solar cell of routine, the substrate in the solar cell splits along the busbar electrode sometimes.

Fig. 9 is the viewgraph of cross-section of the busbar electrode 5a on the silicon substrate 1 and the connector between the inner lead 8 in the solar cell.The stress that is applied on silicon substrate 1 cross section is drawn with arrow.This viewgraph of cross-section is to draw by the size of amplifying critical piece, so that structure is understood easily, its dimensional ratios is different with actual dimensional ratios.

As shown in Figure 9, the busbar electrode 5a as the output exit is coated with scolder 6 to its longitudinal edge along the busbar electrode.At this moment, find that the boundary vicinity (representing with " Q ") between busbar electrode 5a edge and silicon substrate 1 surface produces maximum tensile stress in Fig. 9, so stress is concentrated easily.

This stress causes some problems.For example, occur the defective such as microcrack near the silicon substrate 1 busbar electrode 5a, this microcrack develops into big crackle in manufacture process subsequently.In addition, output can not fully be drawn or is lowered.

Therefore particularly, solar module is installed in outdoor usually, and the pucker ﹠ bloat that is caused by the temperature cycles of every day is repetition.The stress of this moment is applied in the boundary vicinity between busbar electrode 5a edge and silicon substrate 1 surface.Therefore, on solar cell, produce microcrack, thereby cause long-term reliability to descend.

In making solar module, the inner lead 8 that is coated with scolder in advance is welded to busbar electrode 5a, to connect busbar electrode 5a and inner lead 8.At this moment, when mobile inner lead 8 so that scolder is soldered to the surperficial finger electrode that is connected to the busbar electrode surface, because microcrack etc. more seriously appears in the stress that the difference of thermal expansion, contraction etc. cause between the copper of scolder and composition inner lead 8 in the silicon substrate 1.

In addition, in recent years,, carried out reducing the trial of semi-conducting material consumption by the thickness that reduces silicon substrate 1 from saving cost consideration.If reduce the thickness of silicon substrate 1, then silicon substrate 1 shock resistance or stress ability die down.If apply these stress that caused by scolder, then the frequency of crack appearance increases.

On the other hand, when environmental problem was placed on important position, the lead that contains in the Sn-Pb base eutectic solder also became a problem to the influence of human body.Studied the lead-free scolder that is called lead-free solder energetically.But, when using lead-free solder such as Sn-Ag-Cu, Sn-Zn, Sn-Cu or Sn-Ag-Ni parent metal, be applied near the stress in busbar electrode 5a edge and become remarkable easily.

Be provided in advance at the coating that will contain scolder on the surface of busbar electrode, and with under the situation of inner lead 8 together with the scolder thermal weld of coating, when scolder was present on the busbar electrode surface, the thickness of the scolder that is used to weld increased.Therefore, be applied near the stress in busbar electrode 5a edge and become remarkable easily.

In order to solve such problem, will be used for to coat the Copper Foil of Sn-Ag-Cu parent metal by invar (Invar) material that Fe-Ni etc. forms, to reduce stress.But, the resistance height of conductor, this causes the output loss.

The experiment that the present inventor carries out shows, the stress that shrinks because of solidifying of the scolder that connects solar cell and inner lead and when the stress that uses Copper Foil to shrink during from the working temperature cool to room temperature of scolder as the inner lead of base material is stored as internal stress, and the distortion of storage shows as the most weak solar cell of busbar electrode edge and intensity and the microcrack in the boundary vicinity between the Semiconductor substrate.

An object of the present invention is to provide a kind of solar module, the appearance that it can reduce to be applied in the solar cell stress of boundary vicinity between the busbar electrode edge and Semiconductor substrate and prevent to be caused by stress such as the defective of microcrack.

Summary of the invention

Solar module according to the present invention is so to construct, make scolder not with along the busbar electrode longitudinally the edge and inwardly the part of isolated edge preset distance contact, thereby this part is directly contacted with filler, and the solar cell that is connected by inner lead is sealed in the described filler.

Along the busbar electrode longitudinally the edge and inwardly the part of isolated edge preset distance be coated with the coating member, for example solder resist makes the coating member directly to contact with filler.

By these structures, this part directly or by the coating member is coated with filler, replaces being coated with the scolder with high rigidity, the feasible stress that reduces to be applied to this part easily.Therefore, can reduce and be applied in the solar cell tensile stress of boundary vicinity between the substrate surface and busbar electrode edge.Therefore, can prevent the defective of appearance such as microcrack near the substrate the busbar electrode, make and in process subsequently, to prevent crackle.Solar cell is being installed under the outdoor situation, because the stress that the temperature cycles of every day causes does not concentrate near the electrode.Therefore, even use solar cell for a long time, near the part the busbar electrode also is difficult to break.

Particularly be coated with in the structure of coating member with inside part at the edge longitudinally along the busbar electrode therein from this edge preset distance, when inner lead is thermally welded to the busbar electrode, part in the busbar electrode is coated with the coating member, thus eliminated flow of solder material to this part to cover the possibility of this part.

If the busbar electrode is connected to inner lead in its transverse center part with scolder, then scolder always exists, and particularly at the core of busbar electrode, makes it be connected to inner lead, thereby improves the reliability that connects.

If the width of inner lead is less than the width of busbar electrode, then when inner lead was thermally welded to the busbar electrode, the scolder in the inner lead may be difficult to flow in the busbar electrode edge.

Solar cell comprises a plurality of finger electrodes, and at least one end of described finger electrode is connected to the busbar electrode.If inner lead is directly contacted with filler on whole length, make finger electrode not be connected mutually with scolder with inner lead, the stress that then can limit between finger electrode and the substrate surface is concentrated, thereby makes the defective that can prevent appearance such as microcrack in the substrate.

The end that finger electrode is connected to the busbar electrode can be coated with the coating member.So, be moved if connect the position of inner lead under situation about inner lead being thermally welded on the busbar electrode, an end of described finger electrode is coated with the coating member, thereby makes and can prevent that finger electrode is connected with scolder mutually with inner lead.

If the coating member in the finger electrode also plays the effect of coating member at the busbar electrode, then finger electrode and busbar electrode can be applied in an operation, thereby make the manufacturing cost that can reduce solar module.

If the coating member in the finger electrode is a solder resist, then is easy to reduce stress, thereby can quite easily forms the coating member.

In solar module according to the present invention, the scolder that is used to connect inner lead and busbar electrode contains Sn, and satisfies with following formula:

∑(ViWi)＜2.8(％)

(i represents to form the kind number of the element of scolder, and the constriction coefficient (%) when every kind of element that Vi represents to form scolder solidifies, Wi represent to form the percentage by weight (will always measure and do 1) of every kind of element of scolder, and the summation ∑ is 1～i)

Value in the following formula is that the element of the forming scolder constriction coefficient (%) when solidifying multiply by the summation of the percentage by weight of element, and is the value of the constriction coefficient when solidifying with respect to the scolder of being made up of these element combinations.

Constriction coefficient Vi was with when from molten state during to the phase transformation generation of solid state when every kind of element forming scolder solidified, and the ratio during the element change in volume (V1-V2)/V represents (V1: the volume during fusing, V2: the volume when solid-state).Constriction coefficient Vi when its be on the occasion of the time represent that volume reduces, and represent that when it is negative value volume increases.Among the present invention, constriction coefficient can be got negative value, and promptly the volume of element can increase.

If will use Copper Foil to interconnect with the scolder that satisfies described scope as the inner lead of base material and busbar electrode, the shrinkage degree when then scolder solidifies reduces, thus with use comparing of conventional scolder, can reduce to be applied to the stress of busbar electrode.Therefore, defective can be prevented near the substrate the busbar electrode to occur, thereby the crackle in the operation subsequently can be prevented such as microcrack.Solar cell is being installed under the outdoor situation, the stress that is caused by the temperature cycles of every day does not concentrate near the electrode.Therefore, even use solar cell for a long time, the busbar electrode also is difficult to break.

Preferred solder contains Bi.Bi is the material that volume increases when solidifying, and the constriction coefficient when promptly it solidifies is a negative value.Therefore, the value of following formula ∑ (ViWi) that relates to the constriction coefficient of the scolder that contains Bi reduces, thereby can reduce stress.In addition, can loosen condition such as working temperature.

In addition, be under the situation of 3～85 weight % at Bi content, can reduce stress the most satisfactorily.

It is desirable to when the busbar electrode mainly is made up of Ag, scolder contains the Ag of 0.5～6.5 weight %.By such structure, the wettability of busbar electrode pair scolder is improved.Therefore,, also can limit the phenomenon that Ag is leached by scolder even use Ag, thus the feasible reliability that can improve the connection of scolder.

Solar module according to the present invention comprises the connection distribution that is used to connect outside lead, and described outside lead is connected to the end of a plurality of solar cells, and described a plurality of solar cells interconnect by inner lead.Outside lead is to be electrically connected mutually with the scolder of mainly being made up of tin, silver and copper with being connected distribution.Busbar electrode and inner lead are to be electrically connected mutually with the scolder of mainly being made up of tin, bismuth and silver.

The main scolder of being made up of tin, silver and copper has high bonding strength.Therefore, even will be applied to outside lead by the stress that temperature cycles causes and connect on the welding portion between the distribution, in this part crack or fracture do not appear yet.The scolder of being made up of tin, silver and copper greatly shrinks when solidifying.Scolder with this composition only is used for the solar cell near the solar module end, and is used in the optical receiving surface of solar cell and the back of the body surface on the side of any.Therefore, when pressure being applied to the solar cell that connects in solar module manufacturing process subsequently, solar cell also breaks hardly or is cracked.

Be used for inner lead and the interconnective scolder of busbar electrode mainly being made up of tin, bismuth and silver at solar cell.This scolder shrinks when solidifying hardly.Therefore, when when being welded to connect the busbar electrode, solar cell is warpage not.In solar module manufacturing process subsequently, even when pressure is applied on the solar cell, solar cell also breaks hardly or is cracked.

If mainly be the silver of 1.0～5.0 weight %, the copper of 0.4～7.0 weight % and the tin of residuals weight percentage the forming of being made up of tin, silver and copper of scolder, even apply the stress that causes by temperature cycles, also can make the effect that reduces crack or fracture generation more reliable.

If mainly be the bismuth of 20～60 weight %, the silver of 0.5～5 weight % and the tin of residuals weight percentage the forming of being made up of tin, bismuth and copper of scolder, the effect of shrinking the appearance of the warpage that causes in the time of can making minimizing by the welding after coagulation becomes more reliable.

The accompanying drawing summary

Fig. 1 shows the view of formation according to the cross-sectional configurations of the solar cell X of solar module of the present invention.

Fig. 2 (a) is the plane graph that shows an example of the electrode shape on the solar cell optical receiving surface side (surface).

Fig. 2 (b) is the plane graph that shows an example of the electrode shape on the non-optical receiving surface side of solar cell (back of the body surface).

Fig. 3 (a) is the viewgraph of cross-section of the solar module Y that constructs by combined solar battery X.

Fig. 3 (b) is the local amplification sectional view of solar module Y.

Fig. 4 is the view that shows the connection status in the solar cell that constitutes solar module.

Fig. 5 is the viewgraph of cross-section of solar cell along the A-A line shown in Fig. 3 (b).

Fig. 6 is along the viewgraph of cross-section of the A-A line shown in Fig. 3 (b) in another embodiment of solar cell.

Fig. 7 (a) is the partial cross-sectional view that solar cell is watched from the D-D direction shown in Fig. 2 (a).

Fig. 7 (b) is the partial cross-sectional view of watching from the D-D direction shown in the Fig. 2 (a) that shows another structure of solar cell.

Fig. 8 (a) is the local amplification view of portion C shown in Fig. 2 (a).

Fig. 8 (b) is the local amplification view that shows portion C shown in Fig. 2 (a) of another structure of solar cell.

Fig. 9 is along the viewgraph of cross-section of the A-A line shown in Fig. 2 (b) among the conventional solar cells X.

Implement best mode of the present invention

To describe in detail according to solar module of the present invention based on accompanying drawing below.

Fig. 1 shows the cross-sectional configurations figure that constitutes according to the solar cell X of solar module of the present invention.

Among Fig. 1, reference number 1 expression is as the p-type silicon substrate of Semiconductor substrate, reference number 1a represents the n-type diffusion layer in the p-type silicon substrate 1, and reference number 2 expressions are formed on p-type silicon substrate 1 lip-deep anti-reflective film, and reference number 3 expression semiconductor junction surfaces.

Reference number 4a represents to carry on the back surperficial busbar electrode, and reference number 4b represents to carry on the back surperficial collecting electrodes, reference number 5a presentation surface busbar electrode, and reference number 5b presentation surface finger electrode (referring to Fig. 2 (a)).In some cases, surperficial busbar electrode 5a and surperficial finger electrode 5b can be referred to as " surface electrode 5 ".In some cases, carry on the back surperficial busbar electrode 4a and the surperficial collecting electrodes 4b of the back of the body and can be referred to as " back of the body surface electrode 4 ".

The manufacture method of solar cell X will be described herein.At first, the silicon substrate 1 formed by p-N-type semiconductor N such as monocrystalline silicon or polysilicon of preparation.Silicon substrate 1 is to contain to have an appointment 1 * 10 ¹⁶～1 * 10 ¹⁸Individual atom/cm ³Semiconductor impurities such as boron (B) and resistivity be the substrate of about 1.0～2.0 Ω cm.When silicon substrate 1 is monocrystalline substrate, its by on draw (pull-up) method etc. to form, and when silicon substrate 1 is the polysilicon substrate, it is by formation such as casting methods.The polysilicon substrate can be produced in a large number, has more advantage than monocrystalline substrate aspect manufacturing cost.

To be cut into that to be of a size of about 10cm * 10cm～15cm * 15cm and to be sliced into thickness be about 300 μ m by the semiconductor billet that last pulling method or casting method form, with formation silicon substrate 1.Then, in order to clean the cutting surface of silicon substrate 1, use hydrofluoric acid, fluorine nitric acid its surfaces of trace etching such as (fluorine nitricacid).

Then silicon substrate 1 is placed in the diffusion furnace, and is comprising impurity element such as phosphorous oxychloride (POCl ₃) gas heat treatment, go up that to form film resistor be the n-type diffusion layer 1a of about 30～300 Ω/ thereby make phosphorus atoms be diffused in silicon substrate 1 surface.Border surface between the p-N-type semiconductor N of n-type diffusion layer 1a and composition silicon substrate 1 is semiconductor junction surface 3.

Only on silicon substrate 1 surface, stay n-type diffusion layer 1a, remove other parts, clean with ionized water subsequently.Remove n-type diffusion layer 1a in order to following method: resist film is coated on silicon substrate 1 surface, and uses the mixed liquid of hydrofluoric acid and nitric acid to etch away the lip-deep n-type diffusion layer 1a of silicon substrate 1 back of the body.After n-type diffusion layer 1a is removed in etching, remove resist film.

In addition, on silicon substrate 1 surface, form anti-reflective film 2.For example, anti-reflective film 2 is made up of silicon nitride film.Silicon nitride film is by adopting glow discharge to decompose silane (SiH ₄) and ammonia (NH ₃) mixed gas be transformed into plasma and depositing silicon substrate 1 and form.This method is called plasma CVD method.Consider and the refractive index difference of silicon substrate 1, form anti-reflective film 2, make that its refractive index is about 1.8～2.3, and the thickness that forms is about 500～1000 .Anti-reflective film 2 has passivation effect when it forms, and has the effect of improving the solar cell electrical property together with anti-reflection function.

Surface electrode 5 and back of the body surface electrode 4 are respectively formed on the surface and back of the body surface of silicon substrate 1.

Fig. 2 (a) is the view that shows the electrode shape on the solar cell X-ray receiving surface side (surface), and Fig. 2 (b) is the view that shows the electrode shape on the non-optical receiving surface side of solar cell X (back of the body surface).

Shown in Fig. 2 (a), surface electrode 5 comprises and is used for drawing from the surface the surperficial busbar electrode 5a of output and perpendicular to its surperficial finger electrode 5b that is used for current collection that provides.

Shown in Fig. 2 (b), for example, the back of the body surface collecting electrodes 4b that back of the body surface electrode 4 comprises the surperficial busbar electrode 4a of the back of the body and forms with solid shape.

In order to make surperficial busbar electrode 5a, the surperficial busbar electrode 4a of the back of the body and surperficial finger electrode 5b, preparation silver paste, described silver paste are in the silver powder that joins 100 weight portions respectively by organic carrier and glass dust (glass flit) with 10～30 weight portions and 0.1～5 weight portion and with the paste preparation.Etch away the part corresponding to surface electrode 5 of the silicon substrate 1 that wherein is formed with anti-reflective film 2, by for example silk screen print method silver paste is printed thereon, drying is then 600～800 ℃ sintering temperature 1～30 minute.Silver paste can be at first by being called method roasting direct on anti-reflective film 2 of burning (fire through).

Form the surperficial collecting electrodes 4b of the back of the body then, make it at the top of carrying on the back surperficial busbar electrode 4a marginal portion at least.

As for the surperficial collecting electrodes 4b of the back of the body, preparation aluminium cream, described aluminium cream are in the aluminium powder that joins 100 weight portions respectively by organic carrier and glass dust with 10～30 weight portions and 0.1～5 weight portion and with the paste preparation.By for example silk screen print method aluminium cream is printed on the part of the busbar electrode 4a marginal portion, back of the body surface that comprises silicon substrate 1 at least, and dry.After drying, about 1～30 minute of 600～800 ℃ sintering temperature aluminium cream, thus the aluminium of roasting on silicon substrate 1.Thereby, form the surperficial collecting electrodes 4b of the back of the body.During sintering, can prevent that aluminium is distributed to the charge carrier that upward produces with reorganization back of the body surface in the silicon substrate 1.

Can form surperficial busbar electrode 4a of the back of the body and the surperficial collecting electrodes 4b of the back of the body with opposite order.In addition, back of the body surface electrode 4 can not have said structure, but has the structure that comprises busbar electrode and finger electrode, and described finger electrode is similar to surface electrode 5, mainly is made up of silver.

Because the electric energy that is produced by a solar cell made from aforesaid way is low, must be with a plurality of solar cell polyphones and in parallel, to draw actual electricity output.Be called solar module by a plurality of solar cell polyphones and the assembly of constructing that is connected in parallel.

The viewgraph of cross-section of solar module Y is shown among Fig. 3 (a).

Shown in Fig. 3 (a), a plurality of solar cell X are electrically connected mutually by inner lead 8, and place between transparent panel 9 and the back of the body surface protecting material 11.Will be mainly wait the filler of forming 10 hermetic to be sealed in transparent panel 9 and carry on the back between the surface protecting material 11 by EVAc (EVA).Least significant end solar cell X is connected to by outside lead 12 and connects on the distribution 13.

Fig. 3 (b) is the in-built partial enlarged drawing of solar module Y shown in Fig. 3 (a).A plurality of solar cell X represent with X1, X2 and X3.

Shown in Fig. 3 (b), surperficial busbar electrode 5a among the solar cell X1 and the back of the body among adjacent solar battery X2 surface busbar electrode 4a interconnects by inner lead 8, and the surperficial busbar electrode 5a among the solar cell X2 and the surface of the back of the body among adjacent solar battery X3 busbar electrode 4a interconnect by inner lead 8.By this way, a plurality of solar cell X are contacted mutually electrical connection.

On the whole length of surperficial busbar electrode 4a of the back of the body and surperficial busbar electrode 5a or in a plurality of parts, weld by thermal weld such as hot-air, inner lead 8 and outside lead 12 are connected on surperficial busbar electrode 4a of the back of the body and the surperficial busbar electrode 5a.

The example of inner lead 8 and outside lead 12 is by Copper Foil being cut into the lead-in wire that predetermined length obtains, about 100～300 μ m of the thickness of described Copper Foil, and it is the scolder of 20～70 μ m that its whole surface coated has thickness.

Fig. 4 is the plane graph that shows connection status among the solar module Y.Fig. 4 understands that for example two were ganged up the state that connects distribution 13 polyphone connections, wherein contains aforesaid with the linear a plurality of solar cell X that connect of serial arrangement in each string.Among Fig. 4, connecting distribution 13 will interconnect at the outside lead 12 of the respective end of going here and there.

Among the present invention, it is desirable to inner lead 8 among the solar cell X and busbar electrode 4a and 5a and be not by in advance with the surface of scolder coating busbar electrode 4a and 5a, but by with solder fusing on the top surface of inner lead 8 and interconnective.

Therefore, the scolder that is not coated with scolder and fusing inner lead 8 on busbar electrode 4a and 5a surface continues description under with the prerequisite that realizes being connected.

Fig. 5 is the viewgraph of cross-section along the A-A line shown in Fig. 3 (b).This viewgraph of cross-section is to draw by the size of amplifying critical piece, so that structure is understood easily, its dimensional ratios is different with actual dimensional ratios.

Shown in the viewgraph of cross-section of Fig. 5, among the present invention,, but directly contact with filler 10 along the back of the body surperficial busbar electrode 4a and/or surperficial busbar electrode 5a edge and be not coated with scolder 6 longitudinally apart from the part F of the inside preset distance a in described edge.Although the whole surface of busbar electrode 4a and 5a has been coated with the scolder 6 of high rigidity according to routine, the substitute is in the present invention with filler 10 coated portion F.Therefore, reduce to be applied to stress on busbar electrode 4a and the 5a easily.Therefore, can reduce to be applied to the tensile stress of the boundary vicinity between edge and silicon substrate 1 surface longitudinally, and the stress that is limited on the silicon substrate 1 is concentrated along busbar electrode 4a and 5a.This can prevent to occur near busbar electrode 4a and 5a the silicon substrate 1 defective such as microcrack, thereby can prevent crackle in the manufacturing process subsequently.

For the front F that makes busbar electrode 4a and 5a so is not coated with by scolder, when busbar electrode 4a and 5a interconnect by inner lead 8, can be with 8 cores that are welded on busbar electrode 4a and 5a of inner lead.For example, if the width of inner lead 8 is less than the width 4a and the 5a of busbar electrode, in the time of then on inner lead 8 being thermally welded to busbar electrode 4a and 5a, can make along busbar electrode 4a and 5a to be difficult to be covered with inside part F in the edge longitudinally by scolder 6 apart from the edge preset distance.

In addition, solder flux is applied in the core of the back of the body surperficial busbar electrode 4a and/or surperficial busbar electrode 5a, and solder flux is not applied in part F, thereby busbar electrode 4a and 5a core can be coated with by scolder 6 and part F is not coated with by scolder 6.

Alternatively, can be coated with scolder in advance by a core busbar electrode 4a and 5a.

Among the present invention, it is desirable to be not less than 50 μ m from the length a of busbar electrode edge, to reduce tensile stress apart from the part F of the inside preset distance in edge that vertically directly contacts with filler along the busbar electrode.

If length a is oversize, be difficult to guarantee the connection between busbar electrode 4a and 5a and the inner lead 8.That is, it is desirable to busbar electrode 4a and 5a are connected to inner lead 8 at their core at least, with the bonding strength between abundant acquisition busbar electrode and the inner lead.Therefore, the higher limit of length a changes according to size of busbar electrode etc., rather than well-determined.But under busbar electrode (the about 2mm of its width) situation in the embodiment that describes after a while, higher limit can be 1/4 (that is, the width at the busbar electrode is about under the situation of 2mm 500 μ m) of width.

At last, along busbar electrode edge and inwardly can satisfy following expression longitudinally apart from the length a of the part F of edge preset distance:

50 μ m＜a＜(width of busbar electrode 1/4)

When with inner lead 8 and busbar electrode 4a and 5a when core is connected, not every core all must connect.

In some cases, may be difficult to judge clearly the border between substrate and the electrode, because be similar to the edge of the electrode that forms with printing and sintering method, the edge thinning of electrode.In this case, by being that the part that forms the material of electrode is got and made the edge with the lip-deep key component of silicon substrate 1 least significant end, the length a of part F can be in above-mentioned scope.

Fig. 6 for example understands another syndeton between inner lead 8 and busbar electrode 4a and the 5a.Be similar to Fig. 5, Fig. 6 also is the viewgraph of cross-section along the A-A line shown in Fig. 3 (b).

Be coated with solder resist 7 with inside part F in the edge longitudinally along surperficial busbar electrode 4a of the back of the body and/or surperficial busbar electrode 5a in this embodiment apart from the edge preset distance.Part F and filler 10 contact with the state that solder resist 7 wherein is inserted between them.

As solder resist 7 are organic cured resins.The example of organic cured resin comprises ultraviolet curable resin and thermosetting resin.

Because part F contacts with filler 10 by solder resist 7, part F is coated with solder resist 7 and filler 10, rather than as uses the scolder 6 with high rigidity to be coated with the entire upper surface of busbar electrode 4a and 5a in conventional example.Therefore, can reduce to be applied to the tensile stress of the boundary vicinity between busbar electrode 4a and 5a edge and silicon substrate 1 surface, and the stress that alleviates on silicon substrate 1 is concentrated, thereby makes the appearance such as the defective of microcrack that can prevent to be arranged in silicon substrate 1 under busbar electrode 4a and the 5a.

In order to realize connection as shown in Figure 6, will be coated with solder resist 7 in advance with inside part F in the edge longitudinally along busbar electrode 4a and 5a apart from edge preset distance a, the inner lead 8 that will be coated with scolder then is thermally welded on busbar electrode 4a and the 5a.Therefore, even scolder 6 goes between internally and 8 flows into busbar electrode 4a and 5a, scolder 6 does not cover the edge of busbar electrode 4a and 5a yet.

If make the width of the width of inner lead 8 less than surperficial busbar electrode 4a of the back of the body and/or surperficial busbar electrode 5a, in the time of then on inner lead 8 being thermally welded to busbar electrode 4a and 5a, the part F of busbar electrode 4a and 5a may be difficult to be covered by the scolder in the inner lead 86.

In addition,, and on its part F, be not coated with solder flux, can cover cores and part F can not covered by scolder 6 with scolder 6 by core coating solder flux at the back of the body surperficial busbar electrode 4a and/or surperficial busbar electrode 5a.

Describe below according to the syndeton between inner lead 8 in the solar module of the present invention and the surperficial finger electrode 5b.

Fig. 7 (a) and 7 (b) are the part viewgraph of cross-section of watching from the D-D direction shown in Fig. 2 (a), and inner lead 8 are connected to the surface of solar cell.Surface finger electrode 5b is illustrational with vertical cutting form.

Shown in Fig. 2 (a), solar module has perpendicular to the upwardly extending a plurality of surperficial finger electrode 5b in surperficial busbar electrode 5a side.Surface at least one end of finger electrode 5b is connected to surperficial busbar electrode 5a.

The invention is characterized in that surperficial finger electrode 5b and inner lead 8 are not directly interconnective.The zone that comprises surperficial finger electrode 5b and inner lead 8 is represented by " E " at Fig. 7 (a) and 7 (b).

In area E, inner lead 8 and surperficial finger electrode 5b can only be in contact with one another.Inner lead 8 and surperficial finger electrode 5b can be spaced from each other preset distance, and described preset distance is determined according to the shape and the ordered state of each member.With filler 10 hermetic in the method for sealed inside lead-in wire 8 and surperficial finger electrode 5b, inner lead 8 and surperficial finger electrode 5b can be spaced from each other as EVA by the filler that flows 10 when forming solar module.But inner lead 8 and surperficial finger electrode 5b must interconnect without scolder.

Fig. 7 (a) and 7 (b) for example understand the state that inner lead 8 is moved to the left when the front is watched.So, inner lead 8 often is projected on the surperficial finger electrode 5b, and this depends on the positional precision that connects the device (bucket jockey) of inner lead 8 with scolder.

Shown in Fig. 7 (a), the scolder 6 that inner lead 8 and surperficial busbar electrode 5a are electrically connected mutually is present between inner lead 8 and the surperficial busbar electrode 5a.But inner lead 8 and surperficial finger electrode 5b are not directly interconnective with scolder.Because inner lead 8 and surperficial finger electrode 5b are not interconnective with scolder, the stress that may be limited between surperficial finger electrode 5b and silicon substrate 1 surface is concentrated, thereby can occur the defective such as microcrack in silicon substrate 1.

In order to realize that inner lead 8 and surperficial finger electrode 5b are not the state that is connected with scolder mutually, for example, when using inner lead 8, by melting solder during with the mutual thermal weld of a plurality of solar cells, solder flux can be coated in advance on the surperficial busbar electrode 5a that wishes to connect, and solder flux be coated on the surperficial finger electrode 5b.The part of coating solder flux is carried out surface active by heating, and remove oxide-film, to improve wettability scolder.On the other hand, in the part that is not coated with scolder, surface film oxide can not be removed, thereby poor to the wettability of scolder.Therefore, if there is not solder flux to be coated in surperficial finger electrode 5b, can obtain wherein inner lead 8 and the interconnective the present invention's structure of surperficial finger electrode 5b scolder of no use.Particularly, by connecting the so-called open type solar cell that electrode surface wherein is not coated with scolder, produce clearly effect.

Can be with solder adhesion to surperficial finger electrode 5b itself.If inner lead 8 and surperficial finger electrode 5b interconnect without scolder, then produce effect of the present invention.

As shown in Fig. 7 (b), the coating member 14 that is used for coating surface finger electrode 5b and surperficial busbar electrode 5a can be provided in part E ', wherein surperficial finger electrode 5b is connected to surperficial busbar electrode 5a, makes inner lead 8 and surperficial finger electrode 5b interconnect without scolder.

Fig. 8 (a) is the local amplification view of portion C shown in Fig. 2 (a).

As shown in Fig. 8 (a), the part that wherein surperficial finger electrode 5b is connected to surperficial busbar electrode 5a is coated with coating member 14.

Fig. 8 (b) is the plane graph that shows a kind of like this state, wherein surperficial finger electrode 5b is connected to the part of surperficial busbar electrode 5a and also surfacewise the whole longitudinally edge of busbar electrode 5a all use coating member 14 ' coating.

Provide coating member 14 or 14 ' with the situation of thermal weld inner lead 8 to the surperficial busbar electrode 5a under, shown in Fig. 7 (a) and 7 (b), even connecting the position of inner lead 8 has been moved, part surface finger electrode 5b still is coated with coating member 14, thereby can prevent that surperficial finger electrode 5b and inner lead 8 usefulness scolders from interconnecting.Therefore, can limiting surface finger electrode 5b and substrate 1 surface between stress concentrate, thereby make and can prevent to occur in the silicon substrate 1 defective such as microcrack.

It is desirable to, coating member 14 is made up of heat stable resin, because heat applies on it in the process that forms solar module.Particularly, if use solder resist, surperficial finger electrode 5b is coated with by filler by coating member 14, and described coating member 14 is solder resists.As a result, reduce stress easily.

In addition, solder resist is desirable, can quite easily make the coating member have reservation shape because its use makes by printing or lithoprinting, and it has anti-scolder.

When coating member 14 ' formed with the shape of Fig. 8 (b), coating member 14 ' can have simultaneously and is used to be coated with the function of the solder resist 7 of the part at busbar electrode 5a edge surfacewise, and this function is described in detail among Fig. 6.Therefore, this is desirable on cost, because coating member 14 ' can form simultaneously with solder resist 7, thereby can reduce the quantity of operation.

It is desirable to, provide the length s in the zone of coating member 14 or 14 ' being no more than in the scope of 5mm apart from surperficial finger electrode 5b is connected to surperficial busbar electrode 5a one end.Reason is, if length s surpasses this scope, becomes remarkable because of stopping up the regional effect that reduces transformation efficiency of photoirradiation.As for the lower limit of length s, this lower limit can be set like this, make the scope of position precision that connects the device (bucket jockey) of inner lead 8 with scolder, promptly wherein inner lead 8 can move with outstanding scope and is coated with reliably by the coating member.

Finger electrode described in Fig. 7 and 8 is limited on the described surface be described although be, it is desirable to when the lip-deep electrode of the back of the body is busbar electrode and the finger electrode mainly be made up of silver, be similar to lip-deep electrode, finger electrode and inner lead be with the identical mode of lip-deep electrode be not with scolder interconnective.

Describe below according to being used for inner lead 8 in the solar module of the present invention and the surperficial busbar electrode 4a of the back of the body interconnects and with the composition of inner lead 8 and the interconnective scolder of surperficial busbar electrode 5a.

Inner lead 8 is Copper Foils of about 100～300 μ m of thickness, and its whole surface coated has the scolder of about 20～70 μ m of thickness.

Among the present invention, selecting is the Sn parent metal that satisfies ∑ (ViWi)＜2.8 (%) as the scolder that is used to be coated with inner lead 8.Herein, i represents to form the kind number of the element of scolder, and the constriction coefficient (%) when every kind of element that Vi represents to form scolder solidifies, Wi represent to form the percentage by weight (will always measure and do 1) of every kind of element of scolder, and the summation ∑ is 1～i.Value in the following formula is the summation that the corresponding percentage by weight of element of composition scolder multiply by the constriction coefficient (%) when solidifying, and described constriction coefficient (%) is element to take place from being melted to the change in volume under the solid-state phase transformation situation.

Value in the following formula is the value of the constriction coefficient when solidifying with respect to the scolder of being made up of these element combinations.

Table 1 shows the known single constriction coefficient of element when solidifying of planting.

[table 1]

Element	Constriction coefficient when solidifying (%)
		Ag	3.80
Al	6.00
		Au	5.10
Bi	-3.35
		Cu	4.15
Fe	3.00
		Hg	3.70
Li	1.65
		Mg	4.10
Na	2.50
		Ni	4.47
Pb	3.50
		Si	-9.60
Sn	2.80
		Ti	3.65
Zn	4.20

For example, normally used Sn-Pb parent metal is the alloy that obtains by with mixed Sn of about 6 to 4 weight rate and Pb, and melts being not less than under the promptly about 183 ℃ temperature of eutectic point.From table 1, the constriction coefficient when Sn solidifies is 2.8%, and the constriction coefficient of Pb when solidifying be 3.5%, thereby following formula ∑ (ViWi)=2.8 * 0.6+3.5 * 0.4=3.08 (%) (value outside the scope of the invention).

Inner lead 8 uses Copper Foil (linear expansion coefficient: 1.62 * 10 ^-5/ K) as base material, and near working temperature is 200 ℃, be connected to busbar electrode 4a and 5a by thermal weld such as hot-air welding.Inner lead 8 only shrinks about 0.3% when its cool to room temperature (about 20 ℃).Contraction when the Sn-Pb parent metal that routine is used solidifies adds wherein, and internal stress is stored in the scolder, and this causes microcrack occurring in intensity is minimum between the busbar electrode 4a and 5a and Semiconductor substrate 1 in the solar cell the boundary vicinity.

On the other hand, satisfy the scolder of the above-mentioned composition that concerns ∑ (ViWi)＜2.8 when scolder solidifies when cooling off by selecting to have, inner lead 8 according to the present invention has reduced constriction coefficient.As a result, alleviate the tensile stress in the boundary vicinity between busbar electrode 4a and 5a and Semiconductor substrate 1 surface, thereby can prevent near the crack the electrode in the solar module that the temperature cycles stress by every day causes.

It is as follows to think that the present invention produces the reason of such effect.

At first, the constriction coefficient of Copper Foil that is used as base material in inner lead 8 is very low, 1/10 of the constriction coefficient when promptly being about scolder and solidifying.Solder temperature be reduced to from fusing point (for example, 200 ℃, i.e. working temperature) eutectic point (183 ℃) during, the distortional strain energy when scolder solidifies should not stored by normal consumption near scolder.But, when solder temperature during near eutectic point the viscosity of scolder raise gradually, perhaps melt departs from eutectic composition completely slightly, thereby the coexistence of the crystal of melt and deposition.Therefore, although take place from the phase transformation of melt to solid, the distortional strain energy that the contraction when solidifying causes is not absorbed fully and is stored.

It is believed that when shrinking the distortion that causes when being solidified by scolder is added into by inner lead 8 coolings and shrink in the distortion that causes.Owing to have hard and frangible intermetallic compound, for example, react the back as the copper and the component (Sn) of scolder of inner lead 8 base materials and on the interface, form η (Cu mutually ₆Sn ₅) or ε phase (Cu ₃Sn), the possibility that also has obstruction stress to reduce.

Value in the following formula (ViWi) is the summation of the element percentage by weight separately of the forming scolder constriction coefficient (%) when multiply by element and solidifying, and is the effective value of finding when hypothesis is formed retention wire sexual intercourse in the element of scolder.Because actual scolder is the eutectic alloy of substituted type solid solution for example, and the part metals element is because the slight variation of forming is emanated, and linear relationship is not strict maintenance.But as the result of test, the present inventor finds that under situation about will be solidified within the scope of the present invention by the scolder that the combination of described element is formed, effective value is very relevant with constriction coefficient.Even do not carry out actual measurement, this value also compares, thereby makes and can judge whether scolder is suitable for the present invention.

The scolder that satisfies above-mentioned condition can be selected the scolder of the combination while reference table 1 with the element that wherein obtains suitable fusing point in the scolder with the composition that contains Sn, as Sn-Ag, Sn-Ag-Cu, Sn-Bi, Sn-Bi-Ag, Sn-Cu-Bi, Sn-Cu, Sn-Zn-Bi and Sn-Sb parent metal.

It is desirable in having the scolder of combinations thereof, contain the scolder of Bi especially.Reason is, Bi is similar to the material that volume when solidifying such as water increases (3.35%), therefore by containing Bi to satisfy the relation that relates to the following formula ∑ (ViWi)＜2.8 of constriction coefficient when solidifying in above-mentioned scolder, can reduce the constriction coefficient when solidifying.

In these materials, the material that volume increases when forming solidifying of solder alloy with Sn is unknown except Bi, thereby requires quite meticulous composition in the structure that does not contain Bi.Being easy to is to contain Bi not contain the scolder of Pb with acquisition, thereby the solar module of considering natural environment can be provided.

The content that it is desirable to Bi is 3～85 weight % of whole scolder.In above-mentioned scope, can reduce stress the most satisfactorily.In addition, because between Sn and Bi, form eutectic composition, can reduce working temperature.

It is desirable to, under the situation of using main back of the body surface busbar electrode 4a that is made up of low-resistance Ag and surperficial busbar electrode 5a, scolder contains the Ag of 0.5～6.5 weight %.Reason is, may be limited to the Ag leaching phenomenon that obtains silver (Ag) in the course of work in scolder by contain Ag in scolder, thereby improves the reliability that scolder connects.

When Ag content in the scolder during less than 0.5 weight %, wettable effect that can not effectively be improved is and if Ag surpasses 6.5 weight %, then frangible Ag in the interface of scolder and busbar electrode 5a and 4a ₃The Sn deposition increases, thereby the scolder impact resistance dies down.Therefore, the content that it is desirable to Ag is not less than 0.5 weight % or is not more than 6.5 weight %.

As mentioned above, it is desirable to as inner lead 8 be coating eliminating minute impurity outer mainly by tin, bismuth and silver form the lead-in wire of scolder.

In lead-free scolder, lower by the fusing point of tin, bismuth and the silver-colored scolder of forming, and when the cooling after coagulation, shrink hardly.Therefore, the thermal dilation difference between inner lead 8 and the substrate 1 is little, and when solidifying warpage hardly after the shrink welded.

In order to make such inner lead 8, Copper Foil etc. is pre-soaked in the scolder bucket, so that a surface coated of Copper Foil has about 20～70 microns scolder of thickness, and Copper Foil is cut into suitable length.

Be the bismuth of 20～60 weight % the forming of scolder by tin, bismuth and silver, the tin of the silver of 0.5～5 weight % and residuals weight percentage (for example, the tin of 42 weight %, the silver of the bismuth of 57 weight % and 1 weight %).

Therefore, according to the present invention, the constriction coefficient when solidifying by selecting scolder to form to make is little, the tensile stress of boundary vicinity between the end that can reduce to be applied to busbar electrode 5a and 4a and silicon substrate 1 surface, and limit stresses is concentrated.Therefore, can prevent near busbar electrode 5a and the 4a the silicon substrate 1 appearance such as the defective of microcrack.Solar cell is being installed under the outdoor situation, the stress that is caused by the temperature cycles of every day does not concentrate near the busbar electrode, even thereby use solar cell for a long time, the busbar electrode does not break yet.

In addition, if the scolder of hypothesis coating inner lead 8 is Bi, it can be the scolder that does not contain Pb, thereby the solar module of considering natural environment can be provided.

Though do not specify in the foregoing description, among the present invention, the surface of busbar electrode 5a and 4a is not coated with scolder but the coating solder flux in advance among the solar cell X, scolder by fusing inner lead 8 surfaces can interconnect busbar electrode 5a, 4a and inner lead 8 among the solar cell X.

The composition that is used to be connected the scolder that uses the connection distribution 13 between the string that Fig. 4 describes is described below.

Although connect distribution 13 and be by metal as silver, copper, aluminium or iron with satisfactory electrical conductivity, consider its conductivity and the easness that is coated with scolder, it is fit to use copper production.Definite although connect the thickness of distribution 13 and width and be the output of considering solar module for example, descend thickness and width to be respectively about 0.2～1.0mm and 3～8mm in many cases.

It is desirable to, whole basically connection distribution 13 surfaces are coated with the scolder of mainly being made up of tin, silver and copper in advance.

More specifically, the scolder that consists of the tin of the copper of silver, 0.4～7.0 weight % of 1.0～5.0 weight % and residuals weight percentage is effectively, because it produces big effect.

For example, use tin, 1% silver and 0.5% the copper of scolder (a) 98.5%, (b) 97.5% tin, 2% silver and 0.5% copper, (3) 95% tin, 1% silver and 4% copper, (4) 96.5% tin, 3% silver and 0.5% copper, and (5) 92% tin, 2% silver and 6% copper.

Its reason is, mainly the scolder of being made up of tin, silver and copper has high bonding strength, even thereby will be applied to outside lead 12 and the welding portion that is connected distribution 13 by the stress that temperature cycles causes, also break hardly or rupture in the bonding part.Therefore, can prevent that solar module output from descending.

The scolder of being made up of tin, silver and copper has the value of higher following formula ∑ (ViWi) or the constriction coefficient when solidifying.But even use the scolder of being made up of tin, silver and copper in connecting distribution 13, the part that is connected to connection distribution 13 also is the outside lead 12 at the front or the back side of scolder cell device.Therefore, solar cell is difficult to break or is cracked.

Use outside lead 12 and be connected distribution 13 in order to following method: Copper Foil etc. is pre-soaked in the scolder bucket, so that a surface coated of Copper Foil has about 20～70 microns scolder of thickness, and Copper Foil is cut into suitable length.

Embodiment of the present invention are not limited only to above-mentioned example.Can in the scope that does not depart from main idea of the present invention, carry out various variations.

For example, the quantity of busbar electrode and finger electrode or figure are not limited to above-mentioned those.The busbar electrode is connected to inner lead, and the electrode that is connected to the busbar electrode is the finger electrode that is used to collect electric energy.

Although be by wherein the end of surperficial finger electrode 5b being connected to surperficial busbar electrode 5a so that perpendicular subsequently example is described, it can connect from incline direction, and not perpendicular.In addition, surperficial finger electrode 5b two ends all can be connected to surperficial busbar electrode 5a to have closed shape.

Although description is that the solar cell that uses p-type silicon substrate is carried out, even under the situation of using n-type silicon substrate, if the polarity reversal in will describing also can obtain structure of the present invention by identical method.Although what describe is the situation of unijunction type solar cell, the present invention also can be applicable to wherein many junction types solar cell of stacking semiconductor multi layer film on main substrate.

Although description is to carry out as example with the polysilicon substrate that uses casting method, substrate is not necessarily limited to use the substrate of casting method.The material of forming substrate is not necessarily limited to polysilicon or is not limited to silicon materials.Usually it can be applied to semiconductor.That is, the present invention also can be used for using compound and organic semi-conductor solar cell.

＜embodiment 1 〉

With external shape is that 15cm * 15cm and relative resistance are p-type polysilicon substrate 1 lip-deep affected layer alkaline etching and the cleaning of 1.5 Ω cm.Then silicon substrate 1 is placed in the diffusion furnace, and at phosphorous oxychloride (P0Cl ₃) middle heating, go up to have 1 * 10 thereby make phosphorus atoms be diffused in silicon substrate 1 surface ¹⁷Individual atom/cm ³Concentration, form n-type diffusion layer 1a.The thickness that has formed anti-reflective film 2 effect by plasma CVD method is the silicon nitride film of 850  thereon.

In order to form the surperficial collecting electrodes 4b of the back of the body on silicon substrate 1 back of the body surface, the aluminium cream for preparing with paste in the aluminium powder that will join 100 weight portions respectively by organic carrier and the glass dust with 20 weight portions and 3 weight portions applies by silk screen print method and is dry.In order on silicon substrate 1 back of the body surface, to form back of the body busbar electrode 4a and to form surface electrode 5 (surperficial busbar electrode 5a and surperficial finger electrode 5b) on its surface, aluminium cream with the paste preparation in the aluminium powder that will join 100 weight portions respectively by organic carrier and the glass dust with 20 weight portions and 3 weight portions applies and drying by silk screen print method, subsequently 750 ℃ of roastings 15 minutes, to form surperficial busbar electrode 5a and the surperficial busbar electrode 4a of the back of the body simultaneously on surface and back of the body surface, making its width is 2mm.

,, solder resist 7 is printed on that the part F that comprises surperficial busbar electrode 5a edge goes up and dry herein as for sample No.1, by dipping method with scolder 6 coating electrodes, to form solar cell shown in Figure 7.

As for sample No.2, under the situation of not using solder resist 7,, use the whole surface of scolder 6 coating surface busbar electrode 5a similarly, to form the solar cell of conventionally form shown in Figure 9 by dipping method.Use Sn-3Ag-0.5Cu base Pb-free solder as scolder 6.

As for sample No.3, use distributor under the situation of not using solder resist 7, solder cream only is coated in busbar electrode 4a and 5a core transversely, form solar cell.

In addition, as for sample No.4 and No.5, prepare the wherein uncoated sample that scolder 6 is arranged of electrode.

As for above-mentioned solar cell No.1～No.5, to be that 1.8mm and thickness are that the inner lead 8 that the Copper Foil of 200 μ m is made sticks on busbar electrode 4a and the 5a whole length separately by thermal weld such as hot-air welding by the solder layer that has the about 30 μ m of thickness, width, to connect and the distribution solar cell.

At this moment, in sample No.3 and No.4, only fix with the hot weld connection at the core of inner lead 8.

In sample No.5, what be used as inner lead 8 is that width is the lead-in wire of 2.2mm, and described width is greater than the width of the electrode that will connect.Inner lead 8 is thermally welded on the entire electrode surface.

Then; form solar module by following method: shown in Fig. 3 (a) with cross-sectional structure shown in Fig. 3 (a); connect as described above and the distribution solar cell, and use EVA (EVAc) as the described solar cell of filler 10 sealings between translucent panel 9 and the back of the body surface protecting material 11.

For solar cell, carry out fracture strength test, to measure fracture strength (N) by four-point bending.

In addition, in solar module Y, check to be sealed in wherein to apply 3000N/m ²The occurrence rate of microcrack in the solar cell in the dead load test of pressure." occurrence rate of microcrack " is to use the binocular microscope of 40 times powers to check, and represents that the solar cell X quantity of microcrack and the ratio of all solar cell X sums appear in the solar module Y that is used for the dead load test.

The results are shown in the table 2.

[table 2]

Sample No.	Condition				The result		Remarks
								The coating of electrode scolder	Electrode width	The inner lead width	The solder resist of electrode end	Fracture strength (N)	The incidence of microcrack
	1	Zero is coated with at the center	2mm	1.8mm	○	25								0％	The present invention
2							Zero whole coating	2mm	1.8mm	×	15	50％	Outside the scope of the invention
	3	Zero is coated with at the center	2mm	1.8mm	×	23								0％	The present invention
4							The welding of * inner lead center	2mm	1.8mm	×	24	0％	The present invention
	5	The whole welding of * inner lead	2mm	2.2mm	×	15								40％	Outside the scope of the invention

Sample No.1 is the sample with structure shown in Figure 6 among the present invention, and wherein solder resist 7 is inserted in surfacewise busbar electrode 5a longitudinally between edge and the EVA as filler 10.Its fracture strength is 25N, and the microcrack incidence is 0%, has therefore confirmed effect of the present invention.

Sample No.2 is the outer sample of the scope of the invention, and wherein the edge of all busbar electrode 4a and 5a is coated with scolder 6, and does not directly contact or be not in contact with it by solder resist 7 with EVA as filler 10.Fracture strength is 15N, and the microcrack incidence is 50%, and this result is unsatisfactory.

Sample No.3 is the solar module of finishing with the result of welding inner lead 8 cores with the core of scolder 6 coating busbar electrode 4a and 5a as only.This sample has according to shape shown in Figure 5 of the present invention, and wherein the edge of busbar electrode directly contacts mutually with filler 10.In this case, the fracture strength of solar cell is 23N, and the microcrack incidence is 0%, thereby confirms effect of the present invention.

Sample No.4 is that wherein busbar electrode 4a and 5a are not coated with the sample of scolder 6.Have according to shape shown in Figure 5 of the present invention as the solar module that utilizes coating inner lead 8 to finish with the result of the scolder of welding inner lead 8 cores, wherein electrode edge directly contacts mutually with filler 10.In this case, the fracture strength of solar cell is 24N, and the microcrack incidence is 0%, thereby confirms effect of the present invention.

Sample No.5 is that wherein busbar electrode 4a and 5a are not coated with the sample of scolder 6, this sample has the outer structure of the scope of the invention, wherein when using the inner lead 8 have greater than the 2.2mm width of the width of busbar electrode 4a and 5a by the whole surface of hot-air welding, with the edge of scolder 6 coating busbar electrode 4a and 5a, thereby the edge of electrode is directly contacted mutually with filler 10.As a result, fracture strength is 15N, and the microcrack incidence is 40%, and this result is unsatisfactory.

Therefore, according to the present invention, the edge of busbar electrode 4a and 5a is not coated with scolder 6 but directly or by solder resist 7 contacts with filler 10, thereby confirmation may be limited to the stress of the boundary vicinity between busbar electrode edge and the substrate surface and concentrates, therefore improve fracture strength, and can limit the appearance of the microcrack in the substrate under the busbar electrode.

＜embodiment 2 〉

Form solar cell in the mode identical with embodiment 1.Then, with solder resist with the pattern printing shown in Fig. 8 (b) be coated to such zone, this zone is positioned at surperficial finger electrode 5b side, from a end that surperficial finger electrode 5b is connected to surperficial busbar electrode 5a to distance apart from its 1mm, and thermosetting is to form coating member 14 '.Then, the inner lead 8 of the Copper Foil that is coated with scolder is used in thermal weld.In this case, carried out having a mind to the position of mobile inner lead 8 so that inner lead 8 stretches out the trial of surperficial busbar electrode 5a to be intended to they are contacted with scolder.But, as for the sample that wherein provides as the coating member 14 ' of solder resist, in any case they also can't be in contact with one another.In addition, as for the sample that coating member 14 ' wherein is not provided, they interconnect under the situation that solder flux is coated to surperficial finger electrode 5b.As the scolder that is coated with Copper Foil is Sn-3Ag-0.5Cu base Pb-free solder.

Sample No.6 is the sample that does not wherein provide coating member 14 ' and inner lead 8 not to move from surperficial busbar electrode 5a.Sample No.7 is the sample that wherein provides coating member 14 ' and inner lead 8 not to move from surperficial busbar electrode 5a.Sample No.8 and No.9 wherein do not provide coating member 14 ' and inner lead 8 to move the sample of 0.3mm from surperficial busbar electrode 5a.Sample No.10 wherein provides coating member 14 ' and inner lead 8 to move the sample of 0.3mm from surperficial busbar electrode 5a.Sample No.11 and No.12 wherein do not provide coating member 14 ' and inner lead 8 to move the sample of 0.5mm from surperficial busbar electrode 5a.Sample No.13 wherein provides coating member 14 ' and inner lead 8 to move the sample of 0.5mm from surperficial busbar electrode 5a.

Sample No.6～No.13 as for preparing thus utilizes the microcrack incidence described in the embodiment 1 to assess.The results are shown in the table 3.

[table 3]

Numbering	Mobile (mm) of inner lead	Whether there is solder resist	Use the connection of scolder between inner lead and the finger electrode	The incidence in crack (%)
					6	0	×	×	0
7	0	○	×	0
					8	0.3	×	×	0
9	0.3	×	Zero uses solder flux	30
					10	0.3	○	×	0
11	0.5	×	×	0
					12	0.5	×	Zero uses solder flux	50
13	0.5	○	×	0

In sample No.6 and No.7, inner lead 8 does not move from surperficial busbar electrode 5a.No matter whether there is coating member 14 ', between inner lead 8 and surperficial finger electrode 5b, do not carry out the connection of scolder, the crack therefore do not occur as solder resist.

Wherein inner lead 8 is as follows to sample No.8～No.10 that surperficial finger electrode 5b moves 0.3mm:

Under providing (sample No.10) as the situation of the coating member 14 ' of solder resist, between inner lead 8 and surperficial finger electrode 5b, do not use the connection of scolder, therefore the crack does not appear.

Under situation about not providing as the coating member 14 ' of solder resist, when solder flux being coated to surperficial finger electrode 5b (sample No.9) when having a mind to form connection between inner lead 8 and the surperficial finger electrode 5b with scolder, the microcrack incidence is 30%.There not being (sample No.8) under the situation of coated with flux, between inner lead 8 and surperficial finger electrode 5b, do not use the connection of scolder, therefore the crack does not appear.

Wherein inner lead 8 is as follows to sample No.11～No.13 that surperficial finger electrode 5b moves 0.5mm:

Under providing (sample No.13) as the situation of the coating member 14 ' of solder resist, between inner lead 8 and surperficial finger electrode 5b, do not use the connection of scolder, therefore the crack does not appear.Under situation about not providing as the coating member 14 ' of solder resist, when solder flux being coated to surperficial finger electrode 5b (sample No.12) when having a mind to form connection between inner lead 8 and the surperficial finger electrode 5b with scolder, the microcrack incidence is 50%.But, under the situation of coated with flux not (sample No.11), between inner lead 8 and surperficial finger electrode 5b, do not use the connection of scolder, therefore the crack does not appear.

＜embodiment 3 〉

Form solar cell in the mode identical with embodiment 1.

Then, using width is 200 μ m and the Copper Foil that has the solder layer of the about 30 μ m of thickness as 2mm thickness, inner lead 8 is sticked on the whole length of the busbar electrode 5a of coated with flux and 4a, to connect and the above-mentioned solar cell of distribution by the welding of thermal weld such as hot-air.

At this moment, the composition with scolder changes over multiple composition.Be used for the scolder that the scolder of sample No.21～28 is made up of the Sn of the Ag of Bi, the 2 weight % of 1～90 weight % and residuals weight percentage.Be used for the scolder that the scolder of sample No.29～32 is made up of the Sn of the Ag of Bi, 0.1～9 weight % of 50 weight % and residuals weight percentage.Scolder among the sample No.33 consist of Sn-5Ag-0.5Cu, the scolder among the sample No.34 consist of Sn-5Ag-0.5Cu, and among the sample No.35 scolder consist of Sn-0.4Pb.

Only in sample No.34, use at the Copper Foil core to have the inner lead that remains on the invar material of forming by Fe-36Ni in the Copper Foil.In other sample, the inner lead that is to use Copper Foil of employing.

Whether satisfy ∑ (ViWi)＜2.8 (Vi: the constriction coefficient (%) when every kind of element of composition scolder solidifies, Wi: select every kind of sample in the time of the percentage by weight (will always measure and do 1) of forming every kind of element of scolder) in consideration.

Then; inner lead 8 is adhered to surface and the lip-deep busbar electrode 5a of the back of the body and the 4a of each solar cell; to connect and the distribution solar cell; and shown in Fig. 3 (b); use EVA (EVAc) as the filler 10 sealed solars energy battery between translucent panel 9 and the back of the body surface protecting material 11, form solar module.

Use solar simulator under the condition of 25 ℃ and Am-1.5, to measure electrical property, and measure the productive rate when making solar module.

[table 4]

Sample number	Solder types (weight %)			∑(ViWi)	Isc (A)	Voc (V)	FF	Pm (W)	Productive rate (%)
										Bi	Ag	Sn
	21	1	2										Residue percentage	2.76	7.658	0.601	0.719	3.309	90.3
22				3	2.64	7.662	0.602	0.721	3.326	94.8
	23	29									1.04	7.686		0.603	0.725	3.360	98.3
24				50	-0.26	7.780	0.604	0.724	3.402	99.6
	25	57									-0.69	7.680		0.603	0.726	3.362	99.4
26				70	-1.49	7.668	0.602	0.724	3.342	98.5
	27	85									-2.41	7.664		0.602	0.724	3.340	93.1
28				90	-2.72	7.661	0.602	0.722	3.330	90.7
	29	50									0.1	-0.27		7.647	0.601	0.712	3.272	99.7
30			0.5	-0.27	7.654	0.601	0.717	3.298	98.6
	31									6.5	-0.21	7.664		0.602	0.723	3.336	95.1
32			9	-0.19	7.658	0.602	0.721	3.324	90.2
	33									Sn-5Ag-0.5Cu				2.86	7.662	0.601	0.718	3.306	69.6
34		Sn-5Ag-0.5Cu (Cu-(invar)-Cu)			2.86	7.597	0.600	0.696	3.173				94.8
	35									Sn-Pb				3.08	7.687	0.603	0.722	3.347	85.5

※※※

The sample that the ※ scope of the invention is outer

From table 4, sample No.33～No.35 is the outer sample of the scope of the invention, does not wherein satisfy according to condition ∑ of the present invention (ViWi)＜2.8.The solar cell properties or the productive rate of any of these samples are inferior, and it is unsatisfied result.

On the other hand, use to be coated with the sample No.21～No.32 that satisfies according to the Copper Foil of the Sn-Bi-Ag parent metal of condition ∑ of the present invention (ViWi)＜2.8 and to have good solar cell properties, and its productive rate is not less than 90%.Particularly for sample No.22～No.27, wherein Bi content is 3～85 weight %, confirms that the productive rate of solar module is not less than 93%, and its electrical property do not reduce, and therefore produces effect of the present invention satisfactorily.

In addition, for sample No.21 or No.28,, think that therefore productive rate descends slightly owing to thermal stress according to the content rising working temperature of Bi.

For sample No.29, the content of Ag is 0.1 weight %, thereby the wettability of electrode part is not improved.Therefore, think a little less than the adhesion between inner lead and the busbar electrode, thereby electrical property descends slightly.

In addition, for sample No.32, Ag content is 9 weight %.Therefore, think that productive rate descends slightly, because deposited frangible Ag ₃Sn.

Claims (26)

1. solar module, it comprises a plurality of solar cells and the inner lead of writing board shape, described inner lead is used to be electrically connected the busbar electrode on the non-optical receiving surface that is provided at a busbar electrode on the solar cell optical receiving surface and is provided at another solar cell that is adjacent, wherein

Be sealed in the filler by the interconnective solar cell of described inner lead, and

Make along described busbar electrode and directly contact with described filler with inside part at the edge longitudinally apart from this edge preset distance.

2. solar module according to claim 1 wherein is connected to described inner lead in its transverse center part with scolder with described busbar electrode.

3. solar module according to claim 1 and 2, the width of wherein said inner lead is less than the width of described busbar electrode.

4. according to any one described solar module of claim 1～3, wherein said solar cell has a plurality of finger electrodes, and at least one in the described finger electrode end is connected to the busbar electrode that is formed on its optical receiving surface and/or the non-optical receiving surface.

5. solar module according to claim 4 wherein makes described finger electrode directly contact with filler on its whole length.

6. solar module according to claim 4, an end that is connected to the busbar electrode of wherein said finger electrode is coated with the coating member.

7. solar module according to claim 6, the coating member in the wherein said finger electrode is a solder resist.

8. according to any one described solar module of claim 1～7, the scolder that wherein is used to connect described busbar electrode and inner lead contains Bi.

9. according to any one described solar module of claim 1～8, the scolder that wherein is used to connect described busbar electrode and inner lead contains Sn, and satisfies following formula:

(wherein i represents to form the kind number of the element of scolder to ∑ (ViWi)＜2.8 (%), constriction coefficient (%) when every kind of element that Vi represents to form scolder solidifies, Wi represents to form the percentage by weight (will always measure and do 1) of every kind of element of scolder, and the summation ∑ is 1～i).

10. solar module, it comprises a plurality of solar cells and the inner lead of writing board shape, described inner lead is used to be electrically connected the busbar electrode on the non-optical receiving surface that is provided at a busbar electrode on the solar cell optical receiving surface and is provided at another solar cell that is adjacent, wherein

Be sealed in the filler by the interconnective solar cell of described inner lead,

Be coated with the coating member with inside part in the edge longitudinally along the busbar electrode apart from this edge preset distance, and

Described coating member is directly contacted with described filler.

11. solar module according to claim 10, the coating member in the wherein said busbar electrode is a solder resist.

12., wherein described busbar electrode is connected to described inner lead in its transverse center part with scolder according to claim 10 or 11 described solar modules.

13. according to any one solar module of claim 10～12, wherein said solar cell has a plurality of finger electrodes, and at least one in the described finger electrode end is connected to the busbar electrode that is formed on its optical receiving surface and/or the non-optical receiving surface.

14. solar module according to claim 13, an end that is connected to the busbar electrode of wherein said finger electrode is coated with the coating member.

15. solar module according to claim 14, the coating member in the wherein said finger electrode also plays the effect of the coating member in the busbar electrode.

16. according to claim 14 or 15 described solar modules, the coating member in the wherein said finger electrode is a solder resist.

17. according to any one described solar module of claim 10～16, the scolder that wherein is used to connect described busbar electrode and inner lead contains Bi.

18. according to any one solar module of claim 10～17, the scolder that wherein is used to connect described busbar electrode and inner lead contains Sn, and satisfies following formula:

(wherein i represents to form the kind number of the element of scolder to ∑ (ViWi)＜2.8 (%), constriction coefficient (%) when every kind of element that Vi represents to form scolder solidifies, Wi represents to form the percentage by weight (will always measure and do 1) of every kind of element of scolder, and the summation ∑ is 1～i).

19. solar module, it comprises a plurality of solar cells and the inner lead of writing board shape, described inner lead is used to be electrically connected the busbar electrode on the non-optical receiving surface that is provided at a busbar electrode on the solar cell optical receiving surface and is provided at another solar cell that is adjacent, wherein

Described inner lead and busbar electrode are electrically connected mutually with scolder, and

Described scolder contains Sn, and satisfies following formula:

(wherein i represents to form the kind number of the element of scolder to ∑ (ViWi)＜2.8 (%), constriction coefficient (%) when every kind of element that Vi represents to form scolder solidifies, Wi represents to form the percentage by weight (will always measure and do 1) of every kind of element of scolder, and the summation ∑ is 1～i).

20. scolder battery component according to claim 19, wherein said scolder contains Bi.

21. scolder battery component according to claim 20, wherein said scolder contains the Bi of 3～85 weight %.

22. according to any one described solar module of claim 19～21, wherein said busbar electrode mainly is made up of Ag, and described scolder contains the Ag of 0.5～6.5 weight %.

23. a solar module, it comprises:

A plurality of solar cells of writing board shape;

Inner lead, described inner lead are used to be electrically connected the busbar electrode on the non-optical receiving surface that is provided at a busbar electrode on the solar cell optical receiving surface and is provided at another solar cell that is adjacent;

Outside lead, described outside lead is connected to the end by the interconnective a plurality of solar cells of described inner lead; With

Connect distribution, described connection distribution is used to connect described outside lead,

Described outside lead is to be electrically connected mutually with the scolder of mainly being made up of tin, silver and copper with being connected distribution, and

Described busbar electrode and inner lead are to be electrically connected mutually with the scolder of mainly being made up of tin, bismuth and silver.

24. solar module according to claim 23, wherein said busbar electrode and outside lead are to be electrically connected mutually with the scolder of mainly being made up of tin, bismuth and silver.

25. according to claim 23 or 24 described solar modules, be the silver of 1.0～5.0 weight % wherein said the forming of mainly being made up of tin, silver and copper of scolder, the tin of the copper of 0.4～7.0 weight % and residuals weight percentage.

26. according to any one described solar module of claim 23～25, be the bismuth of 20～60 weight % wherein said the forming of mainly being made up of tin, bismuth and silver of scolder, the tin of the silver of 0.5～5 weight % and residuals weight percentage.

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