Method and device for mounting components on a printed circuit board

Abstract: A printed pattern (36) is formed on the first surface (30) of a substrate (26), and a parts having a lead (22) is mounted on the second surface (24). An eyelet (50) including a curling portion (54) and a head portion positioned on the first (30) and second (24) surfaces of the printed circuit board (26), respectively, and a cylindrical portion (50'), connecting the head and curling (54) portions, inserted into the hole (34) of the printed circuit board (26). A plurality of solder entering portions (52) are formed at equal intervals on the curling portion (54). From the solder entering portions (52), solder (40) enters into space between the curling portion (54) and the first surface (30) of the printed pattern surrounding the hole (34) of the printed circuit board (26) and the eyelet (50).

Description: The present invention relates to a printed circuit board apparatus and, in particular, to a printed circuit board and a method and apparatus for mounting heavy or high heat generating components thereon. Generally, printed patterns such as copper leads are formed on one side of a printed circuit board; components having leads are mounted on the other side. The leads pass through holes on the circuit board and are soldered to lands of the printed patterns. In mounting heavy parts or high heat components on the circuit board, eyelets are first mounted into holes of the circuit board. This is done to prevent the possible breakage of the circuit board due to separation of the copper leaf from the board caused either by the weight of the components or by the heat deterioration of the circuit board. Figure 1 is a perspective view of a printed circuit board apparatus of the prior art. A heavy component or part 20 with leads 22 is mounted on one side (i.e. a part mounting side) 24 of a circuit board 26. Printed patterns 28 are formed on the other side (i.e. printed pattern side) 30 of circuit board 26. Eyelets 32 are fixed to board 26 by positioning them through holes 34 formed on board 26. The ends portion of leads 22, from part mounting side 24, are inserted through holes (cylindrical portions) in eyelets 32 and are soldered to lands 36 of printed patterns 28. Figures 2(A) through (D) are perspective, sectional and plan views of eyelet 32 shown in Figure 1. The manner of fixing eyelet 32 to the circuit board is described below with reference to Figure 2. Eyelet 32, shown in Figure 2(a), is inserted through hole 34 of printed circuit board 26 from part mounting side 24 (Figure 2(B)); the end of eyelet 32 projects from printed pattern side 30. One end of eyelet 32 is then curled by a saw-tooth punch, for example, the present punch shown in Fig. 10. By utilising this curling process, eyelet 32 is fixed to the circuit board, as shown in Figure 2(C). Curling portion 38 is formed in a continuous ring-shaped or annular configuration on printed pattern side 30, as shown in Fig. 2(D). Figs.3 and 4 are perspective views of curling portion 38 after utilising the prior art curling method. As shown in these Figures, portion 38 has a generally annular and convex configuration. During curling, portion 38 may crack to form a small number of interrupted sections at random intervals and Fig. 3 shows eyelet 32 with four interrupted sections 381 of curling portion 38 caused by accidental breakage during the curling process. However, portion 38 does not always crack and Figure 4 shows eyelet 32 having a substantially continuous ring-shaped portion 38. Figure 5 shows a sectional view of a printed circuit board using an eyelet mounted by the prior art method. After the curling of eyelet 32, and lead 22 of component 20 is inserted in the hole of eyelet 32, solder 40 is then applied from printed pattern side 30. Soldering is implemented by using, for example, an automatic flow soldering machine. Due to the high viscosity of solder, it is difficult for solder to enter into curling portion 38 whether eyelet 32 has interrupted sections 381 (see Figure 3) or substantially continuous section (see Figure 4). As a result, a cavity 42 will form in many cases. The presence of cavity 42 will contribute to breaking of the soldered joint if either a load is added to lead 22 or repeated thermal expansion occurs. For example, in TVs using printed circuit boards, it is desirable to decrease the length of lead cords, and preferably position them on the circuit board to facilitate assembly and reduce cost. In the event that heavy or high heat generating components are mounted on the boards, breaking of the soldered joint can occur. US-A-2 915 678 discloses a PCB with an eyelet whose curling portion is split to permit solder to flow therein. Accordingly, the present invention seeks to permit the free flow of solder to minimize the formation of cavities within the curling portion. The present invention further seeks to provide an improved printed circuit board apparatus minimizing the formation of cavities formed within the curling portion during the soldering process. The present invention also seeks to provide an improved method and apparatus for minimizing the formation of cavities within the curling portion. According to a first aspect of the present invention there is provided a printed circuit board apparatus comprising: a printed circuit board including a first surface on which a printed pattern is formed, a second surface on which a part with at least one lead is mounted by solder, and a hole for receiving said lead; an eyelet received in the hole and including a curling portion and a head portion positioned, respectively, on the first and second surfaces of the printed circuit board; and plural crack portions, formed at equal intervals on the curling portion, for permitting the solder to enter into the space between the curling portion and the first surface of the printed circuit board wherein the curling portions alternately contact the printed pattern. According to a second aspect of the present invention there is provided a method of fixing and reinforcing an eyelet to a printed circuit board, said eyelet having a cylindrical portion and a head portion formed on one end of the cylindrical portion comprising the steps of: inserting the cylindrical portion of the eyelet into a hole in the printed circuit board; pre-forming plural cracks at equal intervals on the other end of the cylindrical portion; and curling the crack separated portions so that they alternately contact the printed circuit board; and soldering the eyelet to the printed circuit board. According to a third aspect of the present invention there is provided an eyelet for reinforcing a printed circuit pattern, formed on a surface of a printed circuit board, surrounding a hole formed in the printed circuit board comprising: a cylindrical portion; a head portion on one end of the cylindrical portion; and a plurality of holes formed at equal intervals on the other end of the cylindrical portion, for permitting the free flow of solder. According to a fourth aspect of the present invention there is provided a printed circuit board apparatus comprising: a printed circuit board including a first surface on which a printed pattern is formed, a second surface on which a part with at least one lead is mounted by solder, and a hole for receiving said lead; an eyelet received in the hole and including a curling portion and a heat portion positioned, respectively, on the first and second surfaces of the printed circuit board; the eyelet having a plurality of holes formed at equal intervals on the curling portion near the root of the curling portion, for permitting the solder to enter into the space between the curling portion and the first surface of the printed circuit board. Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications will become apparent to those skilled in the art from this detailed description. For a better understanding of the present invention, and to show how it may be brought into effect, reference will now be made, by way of example, to the following drawings, in which: Figure 1 provides a perspective view of a printed circuit board apparatus of the prior art. Figures 2(A) through (D) show various views of the eyelet shown in Figure 1. Figures 3 and 4 are perspective views of the curling portion of the eyelet shown in Figure 2. Figure 5 shows a sectional view of a printed circuit board shown in Figure 2. Figures 6(A) through (D) are various views of the process of producing a printed circuit board. Figure 7 shows a perspective view of an apparatus used in practising the process of Figure 6. Figure 8 shows a perspective view of an eyelet formed by the process shown in Figure 6. Figures 9(A) through (D) are various views of another process of producing a printed circuit board. Figure 10 shows a perspective view of an apparatus used in practising the process of Figure 9. Figures 11(A) through (D) are various views showing a process for producing a printed circuit board according to a first embodiment of the invention. Figures 12(A) through (D), and Figures 13(A) through (D) are various views showing other processes of producing a printed circuit board. Figures 14(A) through (D) are various views showing a process for producing a printed circuit board according to a second embodiment of the invention; Figures 15(A) through (D) are various views showing a yet further process of producing a printed circuit board. Throughout the drawings, the same numerals are applied to similar elements, therefore, the detailed description thereof are not repeated. Figures 6(A) and (D) show, respectively, a perspective view of an eyelet, a sectional view of a printed circuit board, a plan view of the eyelet, and a sectional view of a printed circuit board. A curling portion 54 of eyelet 50 has a plurality of crack portions 52 (Figure 6(C)). The six separated curling sections 62, are separated by crack portions 52 at equal intervals and have narrow widths. Accordingly, as shown in Figure 6(D), solder 40 will easily enter, through 52, and flow into areas between land 36 and curling portion 54. As a result, a more secure bond occurs between lead 22 and land 36. A method of fixing eyelet 50 to printed circuit board 26 is described below. Cylindrical portion 501 of eyelet 50 (Figure 6(A)) is inserted into a hole 34 of printed circuit board 26 from part mounting side 24, as is done with a conventional eyelet. The free-end portion of cylindrical portion 501 projects from printed pattern side 30 of printed circuit board 26. Thus portion 501 is then curled by a saw-tooth punch 60, such as shown in Figure 7, for securing it to the circuit board. As shown in Figure 7, punch 60 has a projecting cylindrical portion 600 which is inserted into a hole of eyelet 50. Projecting portion 600 project co-axially from a cylindrical body 602. A contact face 604 is formed in body 602 for making cracks in free-end portion of cylindrical portion 501; curling is formed on the surface of body 602 adjacent projecting portion 600. That is, a plurality of equally spaced hemispherical concave portions 606 are formed on face 604 according to the number of the cracks and edge portions 608 desired for cracking the free-end portion of eyelet 50. As shown, the concaves extend radially from the aligned axes of portion 600 and body 602. After curling, the free end portion of eyelet 50 is shown in Figure 8 (and Figure 6(C)). After curling, portion 54 of eyelet 50 is cracked into a plurality of pieces 62 (e.g., 6 pieces in the embodiment shown). Crack portions 52 provide inlets thereby providing paths to the inside of curling portion 54 for the flow of solder 40. After curling, lead 22 of parts 20 is inserted into the hole of eyelet 50 from part mounting side 24 of printed circuit board 26. Solder 40 is then sprayed from printed pattern side 30 and enters into curling portion 54 via crack portions 52. Thus, soldering is implemented without producing cavities. Additionally, it is desirable to having five or more solder entering portions (i.e., crack portions 52). Figures 9(A) is a perspective view of an eyelet 70. Figure 9(B) through (D) correspond to Figures 6(B) through (D). This arrangement is nearly the same as that shown in Figures 6(B) through (D) except for eyelet 70 and the use of a saw-tooth punch for curling eyelet 70. The resulting printed circuit board apparatus shown in Figure 9(D) is nearly the same as the one shown in Figure 6(D). The free-end portion of cylindrical portion 701 of eyelet 70 is cracked in advance thereby forming pre-formed equally spaced cracks 702 on cylindrical portion 701 (Fig. 9(A)). The free-end portion of eyelet 70 is inserted, from part mount side, into hole 34 of circuit board 26 and projects from printed pattern side 30 of circuit board 26. The free-end portion of cylindrical portion 701 is then curled by a conventional saw-tooth punch 72, as shown in Figure 10, for securing it to printed circuit board 26. Punch 72 has a convex portion 720, projecting from body 722,for inserting into a hole of eyelet 70. A contact face 724 is formed on the surface of body 722 adjacent convex portion 720 for curling the free-end of portion 701. In particular, a concave portion 726 is formed on contact face 724 for curling the free-end of portion 701. The use of a conventional punch with pre-formed cracks on eyelet 70 causes the formation of separated curling sections 62 separated by crack portions 52. Figure 11(A) through (D) show a first embodiment of the invention. Figures 11(B) and (C) are a sectional and plan views from the printed pattern side 30 of printed circuit board 26. Figure 11(D) is a sectional view of a printed circuit board apparatus. A curling portion 80 of an eyelet 82 has a plurality of separated pieces 84 (e.g. six pieces) which alternately contact land 36 when curled The six pieces 84 of curling portion 80 are curled in a manner so that they alternately contact land 36. In Figure 11(C), shaded portions 840 are separated curling portions which are curled at a small angle, while separated curling portions 842 are curled at a larger angle to permit their contact with land 36. In accordance with this structure, space 86 is formed between land 36 and the separated pieces 840 which have been curled at a small angle. Space 86 and crack portions 88 provide a solder entering inlet to permit the complete flow of solder throughout the area between the curled portions and land 36. As a result, no cavity is formed inside of curling portion 80. With this embodiment, the adhesion of solder 40 increases while increasing the integrity of the soldered joint. A method of fixing eyelet 82 to printed circuit board 26 is described below. The free-end portion of cylindrical portion 821 of eyelet 82 is first cracked (Fig. 11(A)) in advance thereby forming pre-formed equally spaced cracks 822 on cylindrical portion 821. Cylindrical portion 821 is inserted into hole 34 of circuit board 26 from part mounting side 24. Then, the free-end portion of cylindrical portion 821, projecting from printed pattern side 30, is curled and separated into alternating pieces 840, 842 by a saw-tooth punch which has a structure not shown. As a result, alternating portions are curled at a small angle and a larger angle; only the free end portions of the latter contact land 36 (Figure 11(B)). Then, lead 22 of component 20 is inserted into the hole of eyelet 82. Solder 40 is applied and directly enters into the hole of eyelet 82 to curling portion 84 via space 86 and crack portion 88 (Figure 11(D)). Figure 12(D) is a sectional view of a a further printed circuit board apparatus. A curling portion 90 of an eyelet 92 has a plurality of separated pieces 901 as shown in Figure 12(C). Separated pieces 901 of curling portion 90 are curled at a smaller angle near the free-end portion thereof. While the free-end portion of curling portion 90 does not contact land 36 of printed circuit board 26, its root 91 contacts the lip of hole 34, rather than fully contacting land 36. This rigidly fixes eyelet 92 to hole 34. Solder 40 is applied and directly enters via curled portions 96 into space 94 between land 36 and pieces 901, and also enters into hole 34. A method of fixing eyelet 92 to printed circuit board 26 is described below. The free-end portion of cylindrical portion 921 is first cracked (Figure 12(A)) in advance thereby forming pre-formed equally spaced cracks 922 on cylindrical portion 921 in the same manner described above with the third embodiment. Cylindrical portion 921 is inserted into hole 34 from part mounting side 24. Then, the free-end portion of cylindrical portion 921, projecting from printed pattern side 30, is curled and separated into pieces 901. With this embodiment, curling is performed by a sawtooth punch (not shown) so that the root 91 of curling portion 90 immediately emerging from hole 34 contacts the lip of hole 34, while its remaining portion is angled slightly toward land 36 (Figure 12(B)). After lead 22 of component 20 is inserted into hole 34, solder is applied. Solder 40 enters into space 94 (Figure 12(B)) between land 36 and separated pieces 901 and into curling portion 90 via crack portions 96 and hole 34 (Figure 12(D)). Figure 13(D) is a sectional view of a yet further printed circuit board apparatus. A curling portion 100 is not pre-formed with cracks as shown in Figure 12(D). Figure 13(C) shows a plan view of an eyelet 102. Curling portion 100 is curled at a smaller angle near the free-end portion thereof and does not contact land 36. However, its root 91 contacts the lip of hole 34 in the same manner as previously described. Solder 40 enters into space 104 between land 36 and curling portion 100, and also enters into hole 34. In this case, there is a substantial amount of solder entering curling portions as compared to the other embodiments. A method of fixing eyelet 102 to printed circuit board 26 is described below. A conventional type eyelet is used (Figure 13(A)). The free-end portion 100 of cylindrical portion 1021 is inserted into hole 34 from part mounting side 24. The free-end portion, projecting from printed pattern side 28, is curled so that it does not contact land 36, and root 91 contacts the lip of hole 34. This curling is performed by a saw-tooth punch which has a special structure not shown (Figure 13(B)). After lead 22 of component 20 is inserted into the hole of eyelet 102, solder is applied. Solder 40 directly enters into space 104 between land 36 and the free-end portion of curling portion 100, and also enters into hole 34. The free flow of solder in all areas is provided without the formation of cavities. Figures 14 (A) through (D) shows a second embodiment according to the invention. Figure 14(D) is a sectional view of a printed circuit board apparatus. A curling portion 110 of an eyelet 112 is not pre-formed with cracks. The free-end portion of curling portion 110 contacts land 36 of printed circuit board 26. Curling portion 110 has a plurality of holes 1121 at the root thereof (See Figure 14(C)). Fig. 14(C) shows a plan view of eyelet 112 from printed pattern side 30. Solder 40 enters into a space 114 between curling portion 110 and land 36 through holes 1121 on curling portion 110 without the formation of cavities. A method of fixing eyelet 112 to printed circuit board 26 is described below. Eyelet 112 is a conventional type except that it includes a plurality of holes 1121 formed on cylindrical portion 1122. Cylindrical portion 1122 is inserted into hole 34 of printed circuit board from part mounting side 24. Its free-end portion projects from printed pattern side 30 and is then curled by a conventional saw-tooth punch such as the one shown in Figure 10 (see Figure 14(B)). After lead 22 of component 20 is inserted into hole 34 of printed circuit board 26, solder is applied. Solder 40 enters into space 114 through holes 1121 and also enters into hole 34 (Figure 14(D)). Figure 15(D) is a sectional view of a still further printed circuit board apparatus while Figs. 15(B) and 15(C) are sectional and perspective views, respectively. A curling portion 120 of eyelet 122 is not pre-formed with cracks. During the curling process, a wavy shape is formed on curling portion 120. Space 124 is formed between land 36 and curling portion 120 by the convex and concave wave. This process provides a larger space between land 36 and the free-end portion of the eyelet at one section and a smaller space at another section. Solder 40 enters into space 124 and hole 34 of eyelet 122. A method of fixing eyelet 122 to printed circuit board 26 is described below. Eyelet 122 is a conventional type. Cylindrical portion 1221 of eyelet 122 is inserted into hole 34 of printed circuit board 26 from part mounting side 24. Then, the free-end portion of cylindrical portion 1221 projects from printed pattern side 30 and is curled with a wavy pattern by a saw-tooth punch which has a structure (not shown). After lead 22 of component 20 is inserted into hole 34, soldering is applied. Solder 40 directly enters into space 124 and hole 34 and freely flows into all areas thereby avoiding the formation of cavities.

Claims: A printed circuit board apparatus comprising: a printed circuit board including a first surface on which a printed pattern is formed, a second surface on which a part with at least one lead is mounted by solder, and a hole for receiving said lead; an eyelet received in the hole and including a curling portion and a head portion positioned, respectively, on the first and second surfaces of the printed circuit board; and plural crack portions, formed at equal intervals on the curling portion, for permitting the solder to enter into the space between the curling portion and the first surface of the printed circuit board wherein the curling portions alternately contact the printed pattern. A method of fixing and reinforcing an eyelet to a printed circuit board, said eyelet having a cylindrical portion and a head portion formed on one end of the cylindrical portion comprising the steps of: inserting the cylindrical portion of the eyelet into a hole in the printed circuit board; pre-forming plural cracks at equal intervals on the other end of the cylindrical portion; and curling the crack separated portions so that they alternately contact the printed circuit board; and soldering the eyelet to the printed circuit board. An eyelet for reinforcing a printed circuit pattern, formed on a surface of a printed circuit board, surrounding a hole formed in the printed circuit board comprising: a cylindrical portion; a head portion on one end of the cylindrical portion; and a plurality of holes formed at equal intervals on the other end of the cylindrical portion, for permitting the free flow of solder. A printed circuit board apparatus comprising: a printed circuit board including a first surface on which a printed pattern is formed, a second surface on which a part with at least one lead is mounted by solder, and a hole for receiving said lead; an eyelet received in the hole and including a curling portion and a head portion positioned, respectively, on the first and second surfaces of the printed circuit board; the eyelet having a plurality of holes formed at equal intervals on the curling portion near the root of the curling portion, for permitting the solder to enter into the space between the curling portion and the first surface of the printed circuit board.

Inventors: KAMEI SHIGERU, WATANABE YOSHIMI, KAMEI, SHIGERU, WATANABE, YOSHIMI
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1991
Main classification: H05K3
IPC codes: H05K3, H05K1, H01R4, H01R12