Conductor for connecting parallel cells into submodules in series to form solar cell matri

Yasui, R. K.

English

NASA Technical Reports Server

Sept. 9, 1969 JAMES E. WEBB 3,466,198 
ADMINISTRATOR OF THE NATIONAL AERONAUTICS 
AND SPACE ADMlNlSTRATlON 
SOLAR CELL MATRIX 
, 
Filed Sept. 26, 1967 2 Sheets-Sheet 1 
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ROBERT K. YASUI 
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https://ntrs.nasa.gov/search.jsp?R=19710010070 2020-03-17T02:44:17+00:00Z
Spt .  9, 1969 JAMES E. WEBB 3,466,198 
ADMINISTRATOR OF THE NATIONAL AERONAUTICS 
A N D  SPACE ADMINISTRATION 
SOLAR CELL MATRIX 
Filed Sept. 26, 1967 2 Sheets-Sheet 2 
FIG. 2 FI G . 3  
30 
13 14 
55 57 55 
FIG. 4 .- 
ROBERT K .  YASUI 
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1 a 
Another object is an assembly and -mounting arrange- 
ment for a cell matrix in which each cell is removable 
and replaceable without disturbing adjacent cells. 
Another object of the present invention is a solar cell 
5 assembly and mounting arrangement which is of substan- 
tially less weight than known, comparable cell arrays of 
equivalent energy conversion capacity. 
A further object of the present iavention is an as- 
sembliy and mounting arrangement for a solar cell matrix 
10 with a maximized surface, exposed to solar energy for 
the matrix size. A B S m C T  OF THJ3 DISCLOSURE 
A novel configuration of a conductor for connecting Still a further object is the provision of a flexible solar 
cells in parallel to form a submodule, which are in turn cell matrix with improved resistance to thermal and/or 
connected in series to form a cell matrix. The conductor vibrational stresses. 
has segments interconnected in series with the entire corn- 15 These and other objects of the invention are achieved 
binations flexible to provide the desired matrix flexibility. by providing an assembly and momting arrangement in 
Each conductor segment has a plurality of perforated Pads which all the solar cells forming the matrix are coplanar, 
used to form an electrical contact with one electrode Or with each cell physicdly separated from the others, while 
terminal of a cell in one submodule. The segmeht also being interconnected by means of flexible current conduc- 
includes at least one contact strip used to form con'tact 20 aive metallic strips. The invention may be utilized with 
with an electrode of a cell in an adjacent submodule and mounting cells, each of which consists of a semiconduc- 
thereby produce the series interconnection between sub- tive PN junction cell which has a conductive lower sur- 
modules. face defining one terminal. The upper surface of the cell 
constitutes the solar sensitive area. I t  includes current 
25 pickup members includhg one member across the tog side 
of the upper surfae defining a second or top terminal. 
The novel arrangement includes a plurality of con- The invention described herein was made in the per- 
formance Of work a NASA and fs subject necting conductive strips each used to connect in parallel 
to the provisions of Section 305 of the National Aero- a group of cells, forming a submodule, me strip has a 
nautics and Space Act of 19% Publk Law 85-568 (72 30 central bus bar from which flexible pads extend to elec- 
Stat. 435; 42 USC 2457). trically connect the conductive strip to the bottom tarni- 
nals of the cells. Each strip also includes a plurality of 
sub-bus bars, each used to connect to the strip the top 
terminal of a cell in an adjacent submodule. The bottom 
This invention generally relates to solar cells and, more 35 side of the entire matrix is then covered by an insulating 
plastic sheet which defines openings through which the 
pads forming points of contact of each cell with the con- 
3,466,198 
SOLAR CELL MAma 
James E. Webb, Administrator of the N ~ i o n a l  Aeronau- 
tics and Space Administration, with respect to an in- 
vention of Robert K. Yasui, Los Angeles, Calif. 
Filed Sept. 26,1969, Ser. No. 670,814 
Int. el. Holm 5/00 
US. CI. 136-89 
ORIGIN O F  THE INVENTION 
BACKGROUND OF THE INVENTION 
Field of the invention 
particularly, to an assembly and mounting arrangement 
for cells to form a solar cell matrix. 
Description of the prior art ductive strip are exposed. Thus, access is provided for dis- 
connecting each cell of the matrix by merely separating 
The use of semiconductor materials, Such as PN junc- 40 the cell from the pads. This is accomdishable without 
tion cells, to convert solar energy to electrical power is 
very well known. Such cells are used in commercial and 
military applications, as well as in Space exploration. The 
amount of electrical power produced by the cells is di- 
rectly related to the solar cells' exposed area. Since the 45 
cells are quite small, of limited Surface area, a large nom- 
ber of cells are generally placed in side-by-side arrange- 
ment to form a matrix, whose total electrical output is 
having to disturb adacent cells. 
The invention may be employed with cells which have 
both terminals on the bottom side thereof to form a CO- 
planar matrix. 
The novel features that are considered characteristic of 
this invention are set forth with particularity in the ap- 
pended claims. The invention will best be understood 
. from the following description when read in connection 
designed to meet the desired output power. 
he: uroblems are often encountered in the fabrication of 
with the accompanying drawings. 
BRIEF DESCRIPTION OF THE DRAWINGS 
Since the cells are small, with fragile terminals, mount- 50 
mounting arrangement whereby each cell may be con- 
veniently removed and replaced without affecting adja- 
cent cells. Also, since solar matrices are employed in 
space exploration, it is desired that the assembly and 
mounting arrangement be sufficiently flexible to resist 
thermal and vibrational environments, without adversely 
affecting the cells. Furthermore, it is desired that the ar- 
rangement be of minimum weight, a factor most signifi- 
cant in the design of instruments for space exploration. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, a primary object of this invention is to 
provide an improved solar cell assembly and mounting 
arrangement. 
a ;ill matrix. TypicalAy, after completing the assembly 
of a cell matrix, if one or more cells are discovered to be 
defective, their removal and replacement generally neces- 
sitates the removal of adjacent cells. This, in addition to 65 respectively of a four submodule matrix; and 
the cost of fabrication, also increases the danger of dam- 
aging the adjacent cells and their subsequent replacement. 
Thus, a need exists for a cell matrix assembly and 
FIGURE 1 is a bottom view of a partial matrix con- 
structed with the novel conductor of the present invention; 
FIGURES 2 and 3 are top and bottom plan views 
FIGURE 4 is a bottom view of a two submodule matrix 
with a different configuration of the novel conductor of 
the invention. 
60 DESCRIPTION OF THE PREFERRED 
EMBODIMENTS 
Reference is first made to FIGVRE 1 which is a bot- 
tom view of a 12-cell matrix during an early stage of 
construction, in accordance with the teachings of the in- 
65 vention. The diagrammed matrix is assumed to consist of 
four submodules A, B, C and D, each of three solar cells. 
Only the three cells of submodule A, designated C1, 422 
and C3 are shown in FIGURE 1, while df submodule 3, 
only a sublhadule major *electricat swip 6 r  conductor 10 is 
three iitentica? sections 22, 13 and Pa, each having a cen- 
70 shown. 
For a 3-cell submodule, conductor 
3,466,198 
3 4 
tral bus segment 16. Adjacent segments are intercon- the insulation sheets 32 removed therefrom. From these 
nected by strips or conductive lines 18 to form a major figures, it should be appreciated that each cell is sepa- 
bus bar which extends the length of the submodule. Pref- rately mounted without overlapping adjacent cells. Thus, 
erably, each segment 16 consists of two interconnected the solar sensitive area of each cell is exposed, thereby 
parallel strips, with strips 18 between adjacent sections maximizing the power which the matrix can produce. 
forming a square-like shape. The function of strips 18 is Any connections made on the top side of the matrix are 
to provide the matrix the desired flexibility under thermal between the cells’ top terminals 30 and strips 28 of con- 
and vibrational stresses. ductors 10, leaving the entire solar sensitive areas ex- 
Each conductor section further includes a plurality of posed to solar energy. This is not the case in prior art 
conductive pads which extend from the central segment 10 matrices in which shingled structures are employed. That 
16. In FIGURE 1, three such pads are shown, two desig- is, some cell overlapping is required which reduces the 
nated 21 and 22, extending from the upper strip of seg- overall solar sensitivity matrix area. 
ment 16 and one, designated 23, from the lower segment Furthermore, by utilizing the novel conductors 10, 
strip. Each pad, shown as circularly shaped, is preferably each cell in the matrix mounted on the novel arrange- 
perforated by holes 24 to permit ease of fluxing and sol- 15 ment of the present invention may be easily removed and 
dering of the pad to the bottom surface of a cell. replaced without affecting any of the adjacent cells. This 
In addition, each conductor section defines a conduc- aspect may best be explained by considering the following 
tive loop 27 surrounding pad 23, with a portion of the explanation. 
loop forming a strip 28 which is parallel to the segment‘ To remove a defective cell, the matrix board 40 is first 
16. The function of strip 28 is to provide contact with 20 removed exposing through sheets 32 the circular pads to 
the conductive terminal on the top of a cell in an ad- which each cell is connected. The pad 24 to which the 
jacent lower submodule, such as C3 of submodule A. Like defective cell is connected is then heated through a hole 
the pads, strip 28 is perforated with apertures 24 to per- 33, such as with a soldering iron, while the front bottom 
mit ease of fluxing and soldering to the cell’s top terminal. part of the cell is gently lifted. Since the conductors 10 
The conductors 10 from the various submodules are 25 are quite flexible and the cells do not overlap, this can 
preferably made to be quite thin, flexible and of a sol- be accomplished quite easily. After pad 23 is separated, 
derable metal so that their contribution to the total matrix pads 21 and 22 are successively separated from the cell 
weight is small and to facilitate the soldering of the cells while the cell is lifted up. As a last step, the strip 28 of 
to the pads and the strips 28. The conductors could be an adjacent conductor 10 to which top terminal 30 of 
easily and relatively inexpensively chemically etched out 30 the defective cell is connected is heated and the cell is 
of a sheet of metal of copper or the like. pulled out from under it and removed. It is replaced by 
In practice, the cells of the lowest submodule, such as reversing the removal process. 
A are first soldered to a conductor 10, by soldering the There has accordingly been shown and described a 
back side or bottom terminal of each cell to the three novel assembly and mounting arrangement for a solar 
pads of one of the sections. Then, the conductor 10 of 35 matrix. Novel conductors are utilized, each one used to 
an upper submodule (such as B) is placed in position support the cells of a submodule, The back of each cell 
and strips 28 soldered to the top terminals of the cells is soldered to a plurality of pads with the top electrode 
in the lower submodule. In FIGURE 1, the top terminals connected to a conductive strip, forming part of the 
are designated by numeral 30. Thereafter, the cells of conductor of an adjacent submodule. The cells do  not 
submodule B are soldered to their respective conductor 40 overlap, thereby maximizing the solar sensitive area of 
10 and so on until all the cells are soldered in position. the matrix. Also, the pads are conveniently exposable for 
This results in a matrix in which all cells of each sub- easy removal and replacement of any cell. The conductors 
module are connected in parallel with the submodules in are flexible wth portions exposed between mounted cells 
series. to absorb flexing stresses. The use of the flexible, light- 
Preferably after the cells of each submodule are sol- 45 weight conductors lend themselves to semiautomatic 
dered to their submodule conductor 10, the bottom side soldering techniques, which reduce the cost of matrix 
of the submodule is bonded to a thin insulation sheet of manufacturing. 
material, designated in FIGURE 1 by 32. It is designed Herebefore, the invention has been described in con- 
to protect the conductor’s pads and the cells’ bottom junction with cells, each one of which has one terminal 
surfaces. Sheet 32 has holes 33 punched therein. The 50 or electrode on the top and one on the bottom. In such 
spacings between holes conforms to the spacings between an arrangement, each conductor is soldered to the bot- 
the various circular pads of the conductor. The purpose of toms of cells in one submodule and to the top electrodes 
holes 33 is to provide access to the pads for subsequent of the cells in an adjacent submodule. This is easily ac- 
cell unsoldering without having to remove the sheet 32. complished because of the flexibility of the conductors 10. 
The sheet 32 with the submodule thereon is then bonded 55 However, it should be apparent that the same conductors 
or otherwise attqched to a matrix insulating board, de- could be used with cells which have both electrodes on 
signed to protect the circular pads, exposed through holes the bottom side. Such an arrangement results in a perfect 
33. coplanar matrix. 
Where the matrix might be subjected to severe stress, a Furthermore, it should be appreciated that the specific 
metal plate may be placed below the matrix insulating 60 arrangement of conductor 10 herebefore described may 
board. It should however be pointed out that even in the be modified without departing from the spirit of the in- 
absence of such a metal plate, the particular shape of con- vention. For example, as seen from FIGURE 4, to which 
ductor 10 of each submodule, minimizes the danger of reference is made herein, each conductor section, such 
damage to the cells due to flexing or tensile stress. This as 52, may include a double line central bus segment 54 
may be appreciated by again referring to FIGURE 1, 65 forming three slotted contact strips 55. These are used 
wherein it is seen that very small portions of strips 18, in to form an electrical contact with one electrode of a 
submodule A, are exposed between adjacent cells C1 and cell such as 57. Also each conductor section includes two 
C2 and C2 and C3. Should the submodule be subjected additional slotted and/or perforated contact strips 58, 
to a flexing stress, the probabilities favor the flexing to used to form contact with a second electrode of an ad- 
take place at these points, thus minimizing possible dam- 70 jacent cell 60. It should be noted that in FIGURE 4, each 
age to the cells. of cells 57 and 60 has its two electrodes on the same side. 
Reference is now made to FIGURES 2 and 3. FIGURE In FIGURE 4, strips 55 correspond to pads 21, 22, and 
2 is a plan top view of the 4-submodule matrix shown 23 of FIGURE 1. Thus, the word “pad” should be inter- 
mounted on a matrix insulating board 40, while FIGURE preted in its broadest sense to include the strips 55. 
3 is a plan bottom view of the matrix with board 40 and 75 Similarly, strips 58 correspond to strips 28 and therefore 
3,466,198 
6 
a separate flexible electrical conductor associated with 
each row of cells, for electrically interconnecting the 
bottom sides of the cells in the row with portions 
of the upper sides of cells in an adjacent row, said 
conductor defining a main bus extending parallel to 
said row along the bottom sides of the cells, a plu- 
rality of groups of flexible pads extending from said 
main bus, each group electrically connected to the 
bottom side of a different cell, and a plurality of 
flexible conductive strips extending from said main 
cells arranged in a plurality of rows, bus, each strip to overlie and electrically engage the 
each row are connected in parallel and each row is con- portion of the upper side of a cell in an adjacent row. 
nected in series with an adjacent row, each cell having a 5. The matrix as recited in claim 4 further including a 
bottom side defining a first terminal and a top side having sheet of insulating material in contact with the electrical 
one edge defining a second terminal, the improvement 15 conductors and the bottom sides of said cells, said sheet 
comprising: defining apertures through which the group of pads elec- 
a conductor strip associated with each row of cells, trically connected to each cell is exposed. 
said strip including a number of sections equal to the 6. The matrix as recited in claim 5 wherein at least 
number of cells in the row, each section having a the pads define perforated openings to facilitate the 
main conductive segment parallel to the row of cells, 20 soldering of each pad to the bottom side of a cell. 
a plurality of pads, all independently electrically con- 7. The matrix as recited in claim 6 wherein each group 
nectable to the first terminal of a cell and a con- of pads includes at least two pads, one of which extends 
ductive member extending from said main conduc- from one side of said main bus and another from the 
tive segment, said conductive member having a por- opposite side of said bus, whereby the bus extends across 
tion parallel to the main conductive segment for 25 the bottom side of each cell in a row between pads elec- 
electrically connecting to the second terminal of a trically connected to the cell’s bottom side. 
cell in an adjacent row; and 8. The matrix as recited in claim 7 wherein said con- 
means for flexibly interconnecting adjacent sections of ductor defines a plurality of flexible conducting loops 
said conductor strip. extending from one side thereof, a portion of each loop 
2. The improvement as recited in claim 1 wherein in 30 defining said strip to overlie and engage a cell in an 
each section of said conductor strip the pads and the por- adjacent matrix, said loop surrounding at least one pad. 
tion of said conductive member which is parallel to the 
main conductive segment are perforated to facilitate the References Cited 
soldering of said pads and said portion to cell terminals. UNITED STATES PATENTS 
2,428,537 veszi et dm _ _ _ _ _ _ _ _ _ _  136--89 
cluding a sheet of insulating material for each row of 3,070,699 12/1962 Lehmann _ _ _ _ _ _ _ _ _  136-89 
cells, said sheet defining apertures for exposing the pads 3,094,439 6/1963 Mann et al. _ _ _ _ _ _ _ _ _  136-89 
connected to the first terminals of the cells in the row. 
FOREIGN PATENTS 
5 
the term “conductive strip” should be interpreted to in- 
clude one or more strips. 
It is appreciated that those familiar with the art may 
make modifications and/or substitute equivalents in the 
arrangements as shown without departing from the spirit 
of the invention. Therefore, all such modifications and/or 
equivalents are deemed to fall within the scope of the in- 
vention as claimed in the appended claims. 
I claim: 
1. In a cell matrix of the type including a plurality of 10 
3. The improvement as recited in claim 2 further in- 35 
4. A solar cell matrix comprising: 
solar cells arranged in coplanar adjacent rows, each 40 1,373,773 10/1964 France. 
row including a plurality of side-by-side coplanar 
cells; ALLEN B. CURTIS, Primary Examiner 


Solar cell matrix Patent

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