JP2023163755A - Method and device for soldering electronic component to circuit board, computer program product and computer readable medium - Google Patents

Abstract

To provide a new method for soldering an electronic component (1) having a pin (4) inserted to a through hole (3) to a circuit board (2) having the through hole (3).SOLUTION: A method according to the present invention makes a liquefied solder ball (5) adhere, especially spray the ball onto a circuit board (2) so as to fill an annular gap between a pin (4) and a through hole (3) such that a portion of the liquefied solder ball (5) flows into the gap.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method and apparatus for soldering electronic components having pins inserted into the through holes to a circuit board having through holes. The present disclosure further relates to computer program products and computer readable media.

Surface mount technology (SMT) allows electronic components to be mounted directly onto the surface of a circuit board, such as a printed circuit board (PCB). Electronic components mounted in this manner are called surface mount devices (SMD). SMT is a major substitute for through-hole mounting technology (THT), which inserts the pins of insert-mounted components (THD) into through-holes on circuit boards, because it facilitates manufacturing automation, reduces costs, and improves soldering quality. replaced.

However, THT is still required for electronic components that are not suitable for SMT. This is the case where high mechanical strength or heat sinking is required. Typical electronic components are large transformers, power semiconductors including heat sinks (eg, power transistors, lasers, and light emitting diodes (LEDs)), or connectors. In order to ensure a sufficiently strong connection between the THD and the circuit board, it is necessary to fill at least 70% of the annular gap formed between the through-hole and the pin inserted into the through-hole with solder. In the following, a degree of filling exceeding 70% of the volume of the annular gap is also referred to as a high degree of filling.

As a result, circuit boards are often implemented using SMT as well as THT. Hereinafter, this type of circuit board will be referred to as a mixed mounting type circuit board.

In order to create a mixed-mount circuit board, WO 03/079743 teaches the use of the so-called backside reflow method for soldering a THD with a low-temperature housing to a circuit board. . In particular, the method includes pre-assembling the SMD and THD on a first side of a circuit board, rotating the circuit board so that the first side of the circuit board is under a second side of the circuit board, and By pre-assembling only the SMD on the second side, a mixed mounting type circuit board is produced. The SMD is preassembled onto the circuit board by placing contacts of the SMD at respective locations where solder paste was placed on the circuit board. The SMD may be fixed onto the circuit board by adhesive. The THD is preassembled by inserting the pins of the THD into through-holes on the first side such that the pins protrude from the second side at the contact areas where the solder paste is placed. To avoid the THD falling off when rotating the circuit board, fix the THD to the circuit board by adhesive technology or by soft-lock technology with a collar part in the through-hole to retain the pins of the THD. It's okay. The circuit board is then inserted into a reflow oven and heated such that the first side of the circuit board with the attached THD is at least partially shielded from the heat or energy of soldering.

A further development of the above method is disclosed in DE 10 2008 035 405 A1. In this method, the circuit board is pre-assembled with SMDs on both sides and at least one THD is also pre-assembled on the first side. Instead of adhesive or soft-lock fixtures, at least one pin of the THD can be selectively soldered to the circuit board before the circuit board is rotated to mount the SMD on the second side. One THD is secured to the first side of the circuit board. The circuit board is then inserted into a reflow oven to solder the SMD and THD to the circuit board.

DE 10 2005 043 279 A1 discloses another method for producing mixed packaging circuit boards. In this method, only the SMD is mounted on a circuit board and placed in a reflow oven to solder the SMD to the circuit board. At least one THD is then selectively soldered to the circuit board.

To selectively solder the THD pins to the circuit board, the solder pot is driven in three orthogonal directions of the Cartesian coordinate system, namely the X, Y, and Z directions, to each pin protruding from the through-hole. Contact. It is also necessary to apply flux to the pins to suppress oxidation and allow proper soldering. However, due to the Z-direction movement to advance and retract the solder pot individually relative to the pins, THD soldering to circuit boards takes much longer compared to soldering methods using reflow ovens. . Therefore, EP 3 153 270 proposes to use at least two solder pots each independently driven in three orthogonal directions in order to increase the soldering speed. However, when selectively soldering THD pins to a circuit board using a solder pot, there is still a drawback that the amount of solder deposited on the pins cannot be precisely controlled.

Therefore, an object of the present disclosure is to overcome the shortcomings of the prior art and provide an advanced method and apparatus for soldering electronic components with pins inserted into the through holes to a circuit board with through holes. It is. The method and apparatus according to the present disclosure could also be used to manufacture mixed-package circuit boards.

This object is achieved by a method according to independent claim 1 and a device according to independent claim 17. This object is further achieved by a computer program product according to claim 15 and a computer readable medium according to claim 16. Preferred embodiments are the subject of the dependent claims.

The method according to the present disclosure involves applying liquefied solder balls onto a circuit board having a through-hole into which a pin of an electronic component is inserted, such that a portion of the liquefied solder ball flows and fills an annular gap between the pin and the through-hole. This purpose is achieved by depositing, especially by spraying, the solder balls. As a result, the method can also be used for mildly heat sensitive electronic components. It also eliminates the need to advance and retract the solder pot relative to the pins, reducing the time required to solder electronic components with pins inserted into through-holes to circuit boards with through-holes. can. Furthermore, by attaching liquefied solder balls, the amount of solder attached to the through holes can be appropriately adjusted. Note that at least 70% of the volume of the annular gap is filled with a portion of the liquefied solder ball to ensure proper bonding of the pin and through-hole. It should also be noted that the volume of the solder ball is preferably larger than the volume of the annular gap, and after the liquefied solder flows into the annular gap, there is also solder outside the through-hole. After the liquefied solder fills the annular gap, the liquefied solder ball solidifies to form a permanent conductive joint between the pin and the through-hole. As mentioned above, liquefied solder balls are specifically sprayed onto circuit boards. A method and apparatus for depositing, in particular spraying, liquefied solder balls is disclosed in WO 0228588. The contents of which are incorporated herein by reference.

According to one aspect of the present disclosure, the ratio of through-hole diameter to through-hole depth can range from 0.5 to 3. Preferably, this ratio can be equal to 1. Further, the diameter of the through hole can be made 1.5 to 3 times the diameter of the pin. Preferably, the diameter of the through hole can be twice the diameter of the pin. Further, the height of the pin from the surface of the circuit board can be set to 0 or less than 0.5 times the through hole diameter a. Further, the diameter of the root of the solder outside the through hole can be 1.5 to 2 times the diameter of the through hole. Most preferably, the degree of filling of the through hole after soldering can be 0.7 times or more the volume of the annular gap formed between the pin and the through hole. The solder joint between the pin and the through-hole with the above parameters allows adequate mechanical strength and good electrical connection between the pin and the contact area of the through-hole that can be connected to the leads on the circuit board.

According to one aspect of the present disclosure, after a portion of the liquefied solder ball fills the annular gap and the solder solidifies, the solidified solder outside the through-hole is based on a predetermined total volume of the liquefied solder ball before deposition. By measuring the volume of the annular gap, the degree of filling can be determined. Preferably, the volume of solidified solder outside the through hole is measured using three-dimensional image processing. As an example, a 3D scanner, white light interferometer, or light field camera may be used to determine the volume of solder outside the through-hole. By subtracting the measured volume of solidified solder outside the through-hole from the known volume of the solder ball before deposition, the volume of solder that has flowed into the annular gap can be determined. Note that to determine the volume of solder outside the through-hole, it is necessary to subtract the volume of the pins on the circuit board from the volume determined using three-dimensional image processing. Furthermore, since the volume of the pin, the volume of the through hole, and their dimensions are known in advance, the volume of the annular gap can also be determined by subtracting the volume of the pin in the through hole from the volume of the through hole. As a result, the degree of filling of the annular gap can be determined by dividing the volume of the solder that has flowed into the annular gap by the volume of the annular gap. As a result, this method allows on-site confirmation of the quality of solder joints. As a result, the time required to check the quality of the conductive joint between the pin and the through hole can be reduced. In contrast, conventionally, the degree of filling has been determined using X-rays or cross-sectional inspection. When using jet soldering, such as reflow soldering or solder pots, X-ray and cross-sectional inspection are the only methods to determine the degree of filling of the annular gap. As a result, the method according to the present disclosure provides a time-saving and cost-effective quality check, thereby allowing more assembled circuit boards to be checked so as to improve overall production quality. It becomes possible.

According to one aspect of the present disclosure, liquefied solder balls are deposited onto a circuit board from a side of the circuit board opposite the side on which the electronic components are located. As a result, the liquefied solder ball can be easily attached to the location to be soldered, that is, the annular gap.

According to one aspect of the present disclosure, liquefied solder balls may be deposited downward onto a circuit board. Note that the downward direction is defined as the direction of gravity. As a result, some liquefied solder balls flow into the annular gap, making it even easier to fill the annular gap to a higher degree than when depositing liquefied solder balls upwards using a solder pot, for example. Assisted by gravity.

According to one aspect of the present disclosure, liquefied solder balls may be deposited on a circuit board at an oblique angle. This means that the direction of adhesion of the liquefied solder balls is inclined with respect to the circuit board, ie the surface of the circuit board. Preferably, the tilt angle is in the range of 30° to 60° with respect to the circuit board. Preferably, the tilt angle is approximately 45° relative to the circuit board. This allows the liquefied solder ball to be easily attached to the through-hole so that the annular gap is properly filled. Additionally, since the pin length is not limited by the height of the solder wave or the depth of the solder pot, the pin length can be independently selected. In contrast to using a solder pot, there is no need to apply solder to the tips of the pins so that solder material can be saved. In particular, liquefied solder balls can be deposited at an oblique angle when tipped pins are used. In this way, reflection of the laser beam from the tip can be avoided. Further, when using a pin with a tip, by attaching the liquefied solder ball at an inclined angle, it is possible to avoid scattering of the liquefied solder ball.

According to one aspect of the present disclosure, it is possible to direct the adhesion direction of the liquefied solder ball toward the through hole. Preferably, the attachment direction is directed to the point where the pin exits the through hole. As a result, the liquefied solder balls can be properly deposited to achieve a high degree of filling of the annular gap.

According to one aspect of the present disclosure, energy may be applied to the solid solder ball prior to deposition of the liquefied solder ball to create the liquefied solder ball. As a result, the volume of solder to be deposited on the circuit board, ie, the annular gap, is known in advance, and by selecting solid solder balls with an appropriate volume for the volume of the annular gap, a high degree of filling of the annular gap can be achieved.

According to one aspect of the disclosure, the energy may be a laser beam. Preferably, the laser beam is a near-infrared laser beam adapted to provide a power in the range of 200 W NIR to 400 W NIR. Preferably, the laser beam is applied for a period of time ranging from 20ms to 4000ms. As a result, it is ensured that the liquefied solder ball is sufficiently liquefied so that a portion of the liquefied solder ball properly flows and fills the annular gap to achieve a proper bond.

According to one aspect of the present disclosure, a laser beam can be irradiated when a liquefied solder ball is deposited, particularly sprayed, toward a circuit board. More specifically, a laser beam is applied to the liquefied solder ball while the solder ball is flying towards the circuit board. This ensures that the solder balls are liquefied.

According to one aspect of the present disclosure, a laser beam can be permanently or intermittently applied to a solid solder ball or a liquefied solder ball. This ensures that the solder balls are liquefied.

According to one aspect of the present disclosure, in order to keep the liquefied solder ball liquefied, the laser beam is activated when the liquefied solder ball reaches the liquefied solder ball on the circuit board, i.e., on the surface of the circuit board. Can be used to irradiate solder balls. The arrival time can be pre-calculated from the deposition speed and distance to which the liquefied solder ball is deposited, or can be determined by image processing or experimentation. This can ensure that a portion of the liquefied solder ball properly flows into and fills the annular gap.

According to one aspect of the present disclosure, it is possible to measure the temperature of a solder ball while applying energy. Preferably, the application of energy, ie the irradiation of the laser beam, can be stopped when the temperature of the solid or liquefied solder ball exceeds a predetermined threshold. Preferably, the application of energy, ie the irradiation of the laser beam, can be started or restarted when the temperature of the liquefied solder ball falls below a predetermined lower temperature threshold. As a result, solder burning and solder solidification can be avoided. Therefore, it is ensured that a portion of the liquefied solder ball properly flows and fills the annular gap to achieve a proper bond between the pin and the through-hole.

According to one aspect of the present disclosure, the diameter of the solid solder ball can range from 0.8 mm to 2.0 mm. The diameter of the solder ball is preferably in the range of 0.8 to 1.4 of the diameter of the through hole. As a result, a high degree of filling of the annular gap can be achieved.

According to optional aspects of the present disclosure, flux can be applied to the through-holes prior to applying the liquefied solder balls. As mentioned above, flux application is not explicitly required, but can have a positive effect with respect to oxidation of solder, pins, and through-holes. Therefore, proper bonding between the pin and the through hole can be achieved.

According to one aspect of the present disclosure, the flux can be activated prior to depositing the liquefied solder balls. In particular, the flux can be activated by heating to a temperature of 60°C to 130°C. Preferably, the flux can be activated by applying energy, more preferably the applied energy is a laser beam. As a result, pins and through holes can be positively influenced.

According to one aspect of the present disclosure, the circuit board can be heated to a temperature in the range of 60° C. to 90° C. prior to the deposition of liquefied solder balls. As a result, the liquefied solder ball does not cool down strongly after reaching the surface of the circuit board, and the liquefied solder ball remains sufficiently liquefied to properly flow and fill the annular gap. Therefore, a high degree of filling of the annular gap can be achieved.

According to one aspect of the present disclosure, the pin can be heated prior to depositing the liquefied solder ball. Preferably, the pin can be heated by directing a laser beam onto the pin. More preferably, a pin heating laser beam is directed at the pin, comprising light having a wavelength that matches the absorption properties of the pin, ie the material of the pin. Specifically, the pin heating laser beam is a blue laser beam. For example, the light of the pin heating laser beam may have a wavelength in the range 450 nm to 475 nm, particularly 450 nm. In this way, the solidification of the liquefied solder ball when it reaches the pin can be delayed so that a portion of the liquefied solder ball properly flows into and fills the annular gap. As a result, it is possible to achieve a high degree of filling of the annular gap and, in turn, to achieve proper bonding between the pin and the through hole.

According to additional aspects of the present disclosure, the temperature of the pin may be measured during heating. If the temperature of the pin exceeds a predetermined threshold temperature, heating of the pin is stopped. In this way overheating of the pin or the electronic components connected to the pin is avoided.

According to yet another aspect of certain present disclosures, the time for heating the pins may be predetermined. This time may be determined in advance, for example by conducting experiments. In this way overheating of the pin or the electronic components connected to the pin can be avoided.

According to one aspect of the present disclosure, an inert gas can be passively or actively applied to the through-hole. The inert gas may also be nitrogen, argon, helium or formic acid gas. As a result, oxidation of the solder is suppressed, which has a positive effect on soldering pins to through holes.

According to one aspect of the present disclosure, the electronic component and the circuit board can be separated from each other so that a gas exhaust flow path is formed between the electronic component and the circuit board. This may be accomplished by holding the electronic component and the circuit board apart, or by placing a spacer between the electronic component and the circuit board. As a result, gas present in the annular gap, such as an inert gas or air, can be evacuated through the through-hole opening on the side opposite to that on which the liquefied solder balls are deposited on the circuit board. Therefore, in order to achieve a high degree of filling, some of the liquefied solder balls may further flow into the annular gap to facilitate filling.

A computer program product according to the present disclosure includes instructions for performing a method according to the present disclosure. As a result, this instruction causes the computer or control unit to execute the method according to the present disclosure.

A computer readable medium according to the present disclosure stores a computer program product according to the present disclosure. As a result, the computer's CPU or control unit can read instructions from the computer-readable medium to perform each step of the method according to the present disclosure.

A device for soldering electronic components with pins inserted into the through-holes to a circuit board with through-holes is characterized in that an annular gap between the pins and the through-holes is filled with a portion of liquefied solder balls flowing into the annular gap between the pins and the through-holes. A solder ball deposition device is provided for depositing, in particular spraying, liquefied solder balls onto a circuit board in a manner similar to that described above. A device for depositing, in particular spraying, solder balls is disclosed in WO 0228588. The contents of which are incorporated herein by reference. In particular, the solder ball deposition device comprises a capillary movable relative to the circuit board, i.e. an annular gap, and a pressurized gas supplied into the capillary for depositing, in particular spraying, the liquefied solder balls onto the circuit board. a pressure gas source for By using the solder ball deposition device described above, the speed of the soldering process can be increased since there is no need to advance and retract the capillary relative to the pins and through-holes.

According to one aspect of the disclosure, the apparatus may include a control unit for controlling the solder ball deposition device and a drive unit for driving the solder ball deposition device. The control unit includes a CPU, a memory, and an input/output unit. The memory includes a computer-readable medium that stores a computer program product that includes instructions for performing a method according to the present disclosure. The drive unit is an electromechanical device for positioning the capillary of the solder ball deposition device relative to the circuit board, ie relative to the annular gap. It should be noted that the applicant reserves the right to include independent claims relating to a control unit configured to carry out the method according to the present disclosure.

According to one aspect of the present disclosure, the capillary can taper toward the opening such that the inner diameter of the capillary is smaller than the diameter of the solid solder ball used to make the liquefied solder ball. This prevents solid solder balls from falling from the capillary.

According to one aspect of the present disclosure, the capillary can be tilted relative to the surface of the circuit board. The capillary can be set at a fixed angle or with a drive unit or can be tilted at a variable angle. As a result, the liquefied solder balls can be easily attached to the circuit board.

According to one aspect of the present disclosure, the apparatus can include an energy application unit for applying energy to the solid solder ball to create a liquefied solder ball. As a result, the solid solder balls can be sufficiently liquefied to be ejected from the tapered capillary when pressurized gas is supplied into the capillary.

According to a preferred aspect of the present disclosure, the energy application unit may be a laser beam, ie a laser source. The laser beam is preferably a near-infrared laser beam capable of outputting 200W NIR to 400W NIR. It is further preferred that the laser beam is irradiated permanently or intermittently. The power and time of the laser beam can be adjusted by a control unit and the laser beam can be guided through the capillary so as to point in the same direction as the capillary. As a result, the laser beam can properly irradiate the solid solder ball to create a liquefied solder ball, and may also be used to keep the liquefied solder ball in a sufficiently liquefied state. If the laser beam is directed in the same direction as the capillary, the laser beam will reach the liquefied solder ball even after it has been ejected from the capillary. Therefore, the liquefied solder ball can be irradiated with a laser beam during its flight from the capillary to the circuit board or after the liquefied solder ball has reached the circuit board. As a result, it can be ensured that a portion of the liquefied solder ball properly flows into the annular gap so that a high degree of filling can be achieved.

According to one aspect of the present disclosure, the apparatus may include a temperature measurement unit for measuring the temperature of the liquefied solder ball or the solid solder ball. Preferably, the temperature measuring unit can consist of an infrared sensor or optionally an optical infrared sensor. As a result, the temperature can be transmitted from the temperature measurement unit to the control unit and to the energy application unit, in particular to the laser beam. The temperature can be suitably controlled in order to avoid burning of the liquefied solder balls or to avoid solidification of the liquefied solder balls before they flow and fill the annular gap.

According to one aspect of the present disclosure, the apparatus may include a holding unit for holding a circuit board and an electronic component such that pins of the electronic component are inserted into through holes of the circuit board. Preferably, the holding unit can hold the electronic component and the circuit board individually, and the pins of the electronic component can be inserted into the through holes. In particular, the holding unit is configured to hold the electronic component and the circuit board such that the electronic component is placed on a first side of the circuit board and the liquefied solder balls are applied from a second side opposite the first side. can be adapted. It is further preferred that the holding unit is adapted to hold the electronic component and the circuit board in such a way that the liquefied solder balls are applied downwardly. Alternatively, the holding unit may be adapted to hold a circuit board pre-assembled with electronic components.

According to one aspect of the present disclosure, the apparatus can include a volume measurement unit for measuring the volume of solidified solder outside the through-hole. The volume measurement unit may include a three-dimensional detection device such as a 3D scanner, and a control unit that receives the captured image and performs three-dimensional image processing to determine the volume of the solidified solder outside the through-hole. preferable. Alternatively, a white light interferometer or a light field camera may be used as the three-dimensional detection device. As a result, the volume of solidified solder flowing into the annular gap may be determined by subtracting the measured volume of solidified solder outside the through-hole from the total volume of the solid solder ball. Note that to determine the volume of solder outside the through-hole, it is necessary to subtract the volume of the pins on the circuit board from the volume determined using three-dimensional image processing. Since the dimensions and volume of the pin and through hole are known, the volume of the annular gap can be calculated. The degree of filling of the annular gap can then be determined by dividing the volume of the liquefied solder that has flowed into the annular gap by the volume of the annular gap. Note that the above calculations may be performed by the control unit. Thus, the device according to the present disclosure allows on-site confirmation of the degree of filling of the annular gap without the need for X-ray or cross-sectional inspection. This can shorten the time required to check the quality of solder joints.

According to an optional aspect of the present disclosure, the apparatus may include a flux application unit for applying flux to the pin and trough holes. As a result, oxidation of the pins and through holes can be suppressed to enable proper bonding between the pins and through holes.

According to a preferred aspect of the present disclosure, an energy application unit, in particular a laser beam, may be used to activate the flux, in particular by heating the flux to a temperature of 60°C to 130°C. As a result, the soldering process can be positively influenced.

According to a preferred aspect of the present disclosure, the apparatus may comprise a circuit board heating unit for heating the circuit board to a temperature in particular between 60°C and 90°C. The circuit board heating unit may be capable of supplying hot air, or may be a heating section that comes into contact with the circuit board. Preferably, the hot part that contacts the circuit board is included in the holding unit. As a result, cooling of the liquefied solder ball upon reaching the surface of the circuit board is avoided. It is therefore ensured that a portion of the liquefied solder ball properly flows into and fills the annular gap.

According to one aspect of the disclosure, the apparatus may include a pin heating unit for heating the pin. The pin heating unit can be the laser beam described above used to liquefy solid solder balls. The laser beam can be directed through the capillary to the pin and is turned on when no solid solder ball is placed within the capillary. Preferably, the pin heating unit can be a pin heating laser beam capable of emitting light with a wavelength matched to the absorption properties of the pin or the material of the pin. It has been found that a blue laser, for example a laser with a wavelength in the range 450 nm to 475 nm, especially 450 nm, is most suitable for heating the pins. As a result, the solidification of the liquefied solder ball when it reaches the pin is delayed so that a portion of the liquefied solder ball properly flows into and fills the annular gap.

According to yet another aspect of the present disclosure, the temperature measurement unit may be adapted to measure the temperature of the pin during heating. The pin temperature threshold may be predetermined and stored in the control unit. The control unit may be adapted to compare the temperature threshold with temperature measurements obtained from the temperature measurement unit. If the control unit receives a temperature value from the temperature measurement unit that exceeds the temperature threshold, the control unit may stop heating the pin by switching off the pin heating laser beam or the pin heating laser beam.

According to yet another aspect of the present disclosure, the time for heating the pin may be predetermined. This time may be determined by experiment, for example. In this way overheating of the pin or the electronic components connected to the pin can be avoided.

According to one aspect of the present disclosure, the apparatus may include an inert gas supply unit for actively or passively providing inert gas to the through-holes and pins. According to another aspect, the device can be placed in a chamber or container containing an inert gas atmosphere. As a result, oxidation of the liquefied solder is avoided, which has a positive effect on the soldering process.

According to one aspect of the present disclosure, the circuit board and the electronic component are held so that the electronic component and the circuit board are spaced apart from each other so that a gas exhaust flow path is formed between the electronic component and the circuit board. The holding unit may be adapted to the As a result, the gas inside the annular gap, i.e. inert gas or air, reduces the resistance to the liquefied solder ball as it reaches the circuit board and flows into the annular gap to fill it. can exit through the annular gap in order to Therefore, a high degree of filling of the annular gap can be achieved.

Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings.

1 is a diagram schematically showing an apparatus for soldering an electronic component having a pin inserted into a through hole to a circuit board having a through hole according to a first embodiment of the present disclosure; FIG. Apparatus according to a second embodiment of the present disclosure, comprising a 3D scanner as a three-dimensional sensing device for measuring the volume of solidified solder outside the through-hole in order to determine the degree of filling of the annular gap between the pin and the through-hole FIG. It is a figure which shows typically the modification of the apparatus by 2nd Embodiment which is equipped with the interferometer which irradiates the measurement beam as this three-dimensional detection device. FIG. 3 is a diagram schematically showing the definition of size parameters of a through hole, a pin, and a truncated cone of solidified solder outside the through hole. FIG. 6 schematically shows an apparatus according to a third embodiment of the present disclosure, in which the capillary is tilted with respect to the circuit board; FIG. 7 is a diagram schematically showing a modification of the device of the third embodiment, which allows changing the angle of the capillary with respect to the circuit board. FIG. 7 schematically shows an apparatus according to a fourth embodiment of the present disclosure, in which a gap is formed between a circuit board and an electronic component. FIG. 7 schematically shows an apparatus according to a fifth embodiment of the present disclosure, including a pin heating laser beam for heating the pin; FIG. 6 schematically shows an apparatus according to a sixth embodiment of the present disclosure, in which the liquefied solder reaches the circuit board and flows into the annular gap before irradiating the laser beam.

FIG. 1 shows an apparatus for soldering an electronic component 1 with a pin 4 to a circuit board 2 with a through hole 3 into which the pin 4 of the electronic component 1 is inserted, according to a first embodiment of the present disclosure. . One electronic component corresponds to an insertion mounting component (THD). In this embodiment, the three pins 4 of the electronic component 1 protrude upward from the surface of the electronic component 1, that is, from the surface of the housing of the electronic component 1, at a substantially right angle. The pins 4 are inserted into each of the three through holes 3 formed in the circuit board 2 from a first side of the circuit board 2, that is, from the lower side in FIG. That is, it is inserted so that the pin 4 protrudes further from the upper side in FIG. It is noted that the present disclosure is not limited to three pins 4, and the electronic component 1 may comprise at least one pin, two pins, or more than three pins. Moreover, the pin 4 may be inclined with respect to the surface of the electronic component 1 from which the pin 4 protrudes, or may include a bent structure. Similarly, the circuit board 2 may include at least as many through holes 3 as the number of pins 4 of the electronic component 1 . Further, the through hole 3 is arranged on the circuit board 2 such that the position of the through hole 3 corresponds to the position of the pin 4 on the electronic component 1.

By spraying the liquefied solder balls 5 onto the circuit board 2 so that a portion of the liquefied solder balls 5 flows into the annular gap formed between the pins 4 and the through holes 3, the pins 4 are It is joined to the through hole 3. After a portion of the liquefied solder ball 5 flows into the annular gap, it solidifies due to the environmental temperature below the melting point of the solder. In this way, a conductive joint is formed between the pin 4 and the through hole 3 and, in turn, between the pin 4 and the lead of the circuit board 2 connected to the through hole 3.

In the embodiment shown in FIG. 1, liquefied solder balls 5 are produced and ejected using, in particular, a solder ball deposition device comprising a capillary 6 that tapers towards the opening of the capillary 6. In particular, the diameter of the capillary 6 is smaller than the diameter of the solid solder ball (not shown) used to make the liquefied solder ball 5. Thereby, the solid solder ball is held at a position where the diameter of the tapered capillary 6 and the diameter of the solid solder ball match.

Pressure is applied to the capillary 6 by a pressurized gas source in order to blow the liquefied solder ball 5 towards the point to be soldered, i.e. the annular gap, and energy is supplied from the laser source to create the liquefied solder ball 5. A laser beam 7 is irradiated onto the solid solder ball. For this purpose, the laser beam 7 is guided through the capillary 6, as shown in FIG. When the solid solder ball is sufficiently liquefied, the liquefied solder ball 5 is able to exit the capillary 6 due to the pressure inside the capillary 6 and is sprayed from the capillary 6 towards the circuit board 2, i.e. the annular gap. Can be deformed. As a result, there is no need to move the capillary 6 forward or backward relative to the circuit board 2 to deposit the liquefied solder balls 5. In FIG. 1, the capillary is directed exactly at the tip of the pin 4, but the capillary 6 may be directed at a location other than the pin 4 within the circumference of the through hole 3.

The device comprises a control unit and a drive unit (not shown) for controlling and moving the capillary and for controlling the laser beam 7, i.e. the power and time of irradiation of the laser beam 7 and the gas pressure source. . The control unit is realized by a computer including a CPU, memory, and an input/output unit. The memory stores a control program that is executed by the CPU and includes instructions for performing the method according to the present disclosure. The drive unit is realized by an electromechanical drive for driving the capillary 6 and other units of the device, such as a holding unit (not shown) for holding the electronic component 1 and/or the circuit board 2. .

In the embodiment shown in FIG. 1, the liquefied solder balls 5 are sprayed onto the circuit board 2 from a second side opposite to the first side on which the electronic component 1 is arranged. In FIG. 1, liquefied solder balls 5 are sprayed downward. Note that within this specification, the downward direction is defined as the direction of gravity. This arrangement has the advantage that the liquefied solder balls 5 can easily reach the through-hole 3 and that some of the liquefied solder balls 5 flowing into the annular gap between the pin 4 and the through-hole 3 are assisted by gravity. brought about. As a result, the degree of solder filling in the annular gap can be improved compared to the case where the liquefied solder balls 5 are sprayed upward. In order to prevent the electronic component 1 from falling off the circuit board 2, this device includes a holding unit (not shown) for holding at least the electronic component 1 and the circuit board 2. The holding unit may be adapted to hold a plurality of electronic components 1 and circuit boards 2 separately. Alternatively, the electronic component 1 and the circuit board 2 may be pre-assembled using adhesive, and the holding unit is adapted to hold only the circuit board 2.

The irradiation with the laser beam 7 is not limited to the situation where the liquefied solder ball 5 is inside the capillary 6. To ensure that the liquefied solder ball 5 remains sufficiently liquefied, it is also possible to permanently or intermittently irradiate the liquefied solder ball 5 with a laser beam 7 after it has been ejected from the capillary 6. Please note that there is. In order to ensure that the liquefied solder balls 5 are still liquefied when they reach the circuit board 2, the laser beam 7 in particular causes the liquefied solder balls 5 to fly from the capillary 6 towards the surface of the circuit board 2. Sometimes irradiated.

Further, an infrared sensor 9 is used to measure the temperature of the liquefied solder ball 5. The infrared sensor 9 thus corresponds to a temperature measurement unit. The infrared sensor 9 is communicatively connected to the control unit and transmits the measured temperature of the liquefied solder ball 5 to the control unit. As a result, the control unit can control the laser beam 7 such that the temperature of the liquefied solder ball 5 is maintained within a prescribed temperature range defined by the upper temperature threshold and the lower temperature threshold. When the temperature of the liquefied solder ball 5 becomes higher than the upper limit temperature threshold, the irradiation of the laser beam 7 is stopped, or the power of the laser beam 7 is set to an even lower value. Therefore, seizure of liquefied solder can be avoided. Similarly, if the temperature of the liquefied solder falls below the lower temperature threshold, the laser beam 7 may be re-irradiated onto the liquefied solder ball 5, or the power of the laser beam may be set to a higher value. This ensures that the liquefied solder ball 5 is sufficiently liquefied so that a portion of the liquefied solder ball 5 properly flows into the annular gap. Therefore, appropriate bonding between the pin 4 and the through hole 3 can be ensured.

According to the present disclosure, the inert gas 10 is supplied to the locations to be soldered, that is, the through holes 3 and the pins 4. This can be done by actively applying the inert gas 10, for example by supplying the inert gas with a capillary 6 connected to an inert gas source. Capillary 6 therefore corresponds to an inert gas supply unit. However, the present device may include an inert gas supply unit separate from the capillary 6, such as a separate nozzle. In another embodiment, the inert gas 10 may be applied passively by placing the device for soldering the pin 4 to the through-hole 3 in a closed environment filled with inert gas 10. As a result, oxidation of the solder, pins 4 and/or through holes 3 can be suppressed, which has a positive effect on the soldering process.

After reaching the circuit board 2, the liquefied solder ball 5 flows into and fills the annular gap between the pin 4 and the through hole 3. In order to allow a portion of the liquefied solder balls 5 to properly flow into the annular gap, the circuit board 2 is heated such that solidification of the liquefied solder balls 5 is prevented when it reaches the circuit board 2. may be done. The circuit board 2 may be heated using a circuit board heating unit, such as a blower supplying heated air or a component that contacts the circuit board 2. Preferably, a circuit board heating unit that contacts the circuit board 2 is included in a holding unit for holding the electronic component 1 and the circuit board 2.

FIG. 1 shows an annular gap already filled with solidified solder 8. FIG. In this embodiment, since the volume of the solid solder ball, and thus the liquefied solder ball 5, is larger than the volume of the annular gap, not all the solder flows into the annular gap. As a result, a portion of the liquefied solder ball 5 flows into and fills the annular gap, while another portion of the liquefied solder ball 5 remains outside the through hole.

The apparatus according to the present disclosure is capable of soldering an SMD (surface mount device) disposed on a first side to a circuit board using a solder ball attachment device, as described above, and then the circuit board is rotated. This provides the additional advantage that the THD, i.e. the electronic component 1 comprising the pin 4 inserted into the through-hole 3 of the circuit board 2, can then be soldered to the circuit board 2.

It is further preferred that at least one THD is arranged on the first side with the pin protruding from the second side and the liquefied solder ball 5 is applied from the second side. The SMD is also placed on the second side, ie on the top side of the circuit board 2, and is also soldered to the circuit board 2. The circuit board 2 is then rotated so that the first side is above the second side and the THT device is placed on the second side such that the pins 4 protrude from the first side. A liquefied solder ball 5 is then applied to the first side for soldering the pin 4 to the through hole 3. Additionally, an SMD is placed on the first side and soldered to the circuit board using liquefied solder balls 5. In this way, it is easy to create mixed-package circuit boards with electronic components, i.e. SMD and THD, on both sides of the circuit board without using a second soldering method such as reflow soldering or selective soldering. can be manufactured.

FIG. 2 shows an apparatus according to a second embodiment of the present disclosure, including a 3D scanner 12 as a three-dimensional detection device. In this embodiment, the volume of the solidified solder 8a outside the through hole 3 is measured using three-dimensional image processing. Note that in the present disclosure, a conventionally known image processing method for three-dimensional construction may be used. The 3D scanner 12 may be included in the same housing as the infrared sensor 9, or may be provided separately. The 3D scanner 12 is connected to a control unit, and the control unit executes image processing to determine the volume of solidified solder 8b outside the through hole. The 3D scanner 12 and the control unit therefore correspond to a volumetric unit. Note that the three-dimensional image processing may be performed by a computer separate from the control unit.

FIG. 2 shows an annular gap already filled with solidified solder 8. FIG. As mentioned above, it is preferred that the volume of the liquefied solder ball 5 is larger than the volume of the annular gap. In the present disclosure, the degree of filling of the annular gap must be at least 70% to ensure proper electrical and mechanical bonding between the pin 4 and the through hole 3.

According to the present disclosure, since a predetermined volume of solder, that is, a volume of liquefied solder balls 5 corresponding to the volume of the solid solder balls, is attached to the circuit board 2, the volume of the solidified solder 8a outside the through hole 3 is reduced. By measuring, the degree of filling of the annular gap can be determined.

In order to determine the degree of filling, the control unit can be configured to perform the following process. In order to determine the volume of solder 8b that has flowed into the annular gap and solidified, the measured volume of solidified solder 8a is compared with the total volume of liquefied solder balls 5 before deposition. In this regard, it should be noted that when determining the volume of the solder 8a outside the through-hole 3, the volume of the pin 4 outside the through-hole 3 needs to be taken into account. For example, the dimensions of the pins 4 and through holes 3 are known in advance from the specifications of the electronic component 1 and the circuit board 2. Therefore, the volume of the annular gap can also be determined by subtracting the volume of the pin 4 inside the through hole 3 from the volume of the through hole 3. The volume of solidified solder 8b in the annular gap is then divided by the volume of the annular gap in order to determine the degree of filling. If a portion of the solder flows out from the lower through-hole opening, the determined volume of solidified solder 8b is even larger than the volume of the annular gap. In this case, the degree of filling is determined to be 100%.

The determined volume result, degree of filling and captured image are stored in the memory of the control unit. As a result, according to the present disclosure, by determining the degree of filling of the annular gap, the quality of the solder joint can be verified on-site without using X-ray inspection or cross-sectional inspection.

FIG. 3 shows that an interferometer 13 irradiating a measurement beam 14 is used as a three-dimensional detection device to detect the volume of solidified solder 8a outside the through-hole 3 so that the degree of filling can be determined. , shows a modification of the second embodiment. The interferometer 13 and the control unit therefore correspond to a volumetric unit.

FIG. 4 shows the definition of the parameters of the through hole 3, the pin 4, and the solidified solder 8a outside the through hole 3. In particular, the inventors of the present application have found that the solidified solder 8a can almost be considered as a truncated cone. When the height d of the pin from the circuit board is smaller than the height g of the solidified solder 8a, the solidified solder 8a has a conical shape.

Furthermore, the inventors have realized that in order to achieve good results, i.e. a degree of filling of more than 70%, the ratios of the various parameters shown in FIG. 4 must be within the ranges listed in the table below. I found it.

As described in the table above, the ratio between the diameter a of the through hole 3 and the depth b of the through hole 3 can be in the range of 0.5 to 3. The ratio should preferably be 1. Further, the diameter a of the through hole 3 can be 1.5 to 3 times the diameter c of the pin 4. Preferably, the diameter a of the through hole 3 should be twice the diameter c of the pin 4. Further, the height d of the pin 3 from the surface of the circuit board 2 should be 0 or less than 0.5 times the diameter a of the through hole 3. Further, the diameter e of the root of the solder 8a outside the through hole 3 can be set to 1.5 to 2 times the diameter a of the through hole 3. Most preferably, the degree of filling of the through hole 3 after soldering can be 0.7 times or more the volume of the annular gap formed between the pin 4 and the through hole 3. By setting the above ratio, the solidified solder 8 between the pin 4 and the through hole 3 can achieve a proper mechanical bond, resulting in a good electrical connection.

As described above, the control unit and the 3D scanner 12 or the interferometer 13 measure the volume of the solidified solder 8a outside the through hole 3, that is, the size of the truncated cone or cone. The dimensions of the pin 4 and the through hole 3 can be determined from the specifications of the electronic component 1 and the circuit board 2, for example. Therefore, the control unit can calculate the degree of filling of the annular gap by performing the following calculation.

In particular, the volume of the truncated cone V _fc can be calculated by equation (1). Note that if the height d of the pin 4 from the circuit board 2 is smaller than the height g of the solidified solder 8a outside the through hole 3, f in equation (1) becomes 0, and equation (1) Corresponds to the formula for calculating volume. Note that in the following description, the truncated cone is merely an example, and instead, three-dimensional image processing may be used to determine the volume of the solder 8a outside the annular gap.

The volume V _pin of the pin 4 on the circuit board 2 can be calculated using equation (2). In addition, below, the pin 4 is considered to be a cylinder. For other geometries of the pin 4, the volume of the pin 4 on the circuit board 2 needs to be calculated accordingly.

The volume V _so of the solidified solder 8a outside the through hole 3 can be calculated by subtracting the volume V _pin of the pin 4 on the circuit board 2 from the volume V _fc of the truncated cone using equation (3).

Since the volume of the solid solder ball, and thus the volume V _sb of the liquefied solder ball 5, is known in advance, the volume V _si of the solidified solder 8b within the annular gap can be calculated using equation (4).

Further, the volume V _ag of the annular gap can be calculated using the following equation (5). Again, the pin 4 is considered to be a cylinder.

Finally, the filling degree F is calculated by dividing the volume of the annular gap V _ag by the volume V _si of the solidified solder 8b in the through hole 3 (see equation (6)).

Note that the liquefied solder may flow out from the annular gap on the opposite side to the side to which the liquefied solder balls 5 are attached. In this case, although a value exceeding 100% may be calculated as the filling degree F, the filling degree F is considered to be 100%.

FIG. 5 shows an apparatus according to a third embodiment of the present disclosure. The device shown in FIG. 3 differs from the device according to the first embodiment shown in FIG. 1 in that the capillary 6 is arranged at an inclination angle α with respect to the surface of the circuit board 2. Therefore, the liquefied solder balls 5 are deposited at an oblique angle α. In FIG. 2, the tilt angle α is 45°. However, the inclination angle α is not limited to this angle, and can be in the range of 30° to 60° with respect to the surface of the circuit board 2. This embodiment has the advantage that the liquefied solder ball 5 can be attached to the location where the pin 4 emerges from the through hole so that the liquefied solder ball properly flows into and fills the annular gap. As a result, a high degree of filling of the annular gap can be achieved.

FIG. 6 shows a modification of the third embodiment in which the capillary 6 is tilted using a drive unit controlled by a control unit. As a result, the capillary 6 can be tilted depending on the location to be soldered. In FIG. 6, in position 1, the capillary 6 is oriented perpendicularly to the circuit board 2. In FIG. The capillary is tilted at an angle α ₁ in position 2 and at an angle α ₂ in position 3. Particularly, when electronic components such as SMDs are already mounted on the side of the circuit board 2 to which the liquefied solder balls 5 are attached, the inclination of the capillary 6 at various angles is important. Additionally, since the present disclosure may be used in mixed-package circuit boards, changes in the attachment angle may be required to solder other electronic components, such as SMDs, to the circuit board. As a result, according to the present embodiment, the pins 4 and the through holes 3 can be properly bonded, and a mixed mounting type circuit board can be easily mounted.

FIG. 7 shows an apparatus according to a fourth embodiment of the present disclosure. The device shown in FIG. 7 is similar to the device shown in FIG. different from. Therefore, when the liquefied solder ball 5 reaches the through hole 3, the gas present inside the annular gap, i.e. the inert gas 10 or air, exits to the opposite side of the circuit board 2, i.e. the lower side of FIG. I can do it. As a result, the resistance of the liquefied solder ball 5 in flowing into the annular gap is reduced so as to ensure proper filling of the annular gap. The holding unit may be adapted to hold the electronic component 1 and the circuit board 2 spaced apart from each other to form the gas exhaust channel 11 . Apart from this, or in addition to this, one or more spacers may be arranged between the electronic component 1 and the circuit board 2. Although the fourth embodiment is shown with the capillary 6 according to the first embodiment not being inclined with respect to the surface of the circuit board 2, it is also possible for the capillary 6 to have a constant or variable angle with respect to the surface of the circuit board 2. Note that it may also be combined with the third embodiment, which is tilted at .

FIG. 8 shows a fifth embodiment of the present disclosure. As described in the description of the first embodiment, the circuit board 2 may be heated using a heating unit. Alternatively or additionally, the device according to the fifth embodiment may include a pin heating unit. As shown in FIG. 8, the pin heating unit is formed by a laser beam 15 for pin heating that is different from the laser beam 7 used to liquefy the solid solder ball to make the liquefied solder ball 5. Preferably, the pin heating laser beam 15 may be guided through a capillary or focused onto the pin 4. Therefore, the pin heating laser beam 15 may have a smaller diameter than the laser beam 7. Further, the pin heating laser beam 15 has a wavelength that is different from the wavelength of the laser beam 7 and is compatible with the absorption characteristics of the pin 4, that is, the material of the pin 4. In particular, the pin heating laser beam 15 is a blue laser beam, and the wavelength of the pin heating laser beam 15 is about 450 nm. However, the wavelength of the pinned laser beam can be even larger, up to 475 nm. By heating the pin 4 before depositing the liquefied solder ball 5, the solidification of the liquefied solder, especially the solder flowing into the annular gap, is slowed down and more of the solder is connected between the pin 4 and the through hole 3. It flows into the annular gap between the two and fills it. In this way, a higher degree of filling and therefore a better bond between the pin 4 and the through-hole 3 can be achieved. Note that the laser beam 7 may be used to heat the pin 4. However, since the wavelength of the laser beam 7 does not match the pin 4, the time required to heat the pin 4 may become longer.

Further, the above embodiment is not limited to irradiating the pin with the pin heating laser beam 15 before the liquefied solder ball 5 is attached. If the height of the pin 4 is higher than the height of the solder 8a outside the through-hole, the liquefied solder ball 5 reaches the top of the circuit board 2, after some of the liquefied solder has already flowed into the annular gap. The pin 4 may be irradiated with a laser beam 15 for heating the pin.

In the fifth embodiment, the time for heating the pin 4 may be determined in advance. This time may be determined by experiment, for example. In this way, overheating of the pin 4 or the electronic component 1 connected to the pin can be avoided.

Further, the fifth embodiment may be combined with the first embodiment including the infrared sensor 9 as a temperature measurement unit. The infrared sensor 9 may then be adapted to further measure the temperature of the pin 4 during heating. The temperature threshold for pin 4 may be predetermined and stored in the control unit. The control unit may be adapted to compare the temperature threshold with the temperature value obtained from the infrared sensor 9. If the control unit receives a temperature value from the temperature measurement unit that exceeds the temperature threshold, the control unit may stop heating the pin 4 by switching off the pin heating laser beam 15.

FIG. 9 shows a sixth embodiment of the present disclosure in which the laser beam 7 is applied to the solder 8 that has reached the circuit board and has already partially flowed into the annular gap. The time taken to reach the surface of the circuit board 2 may be calculated according to the distance from the surface of the circuit board 2 to the capillary 6 and the pressure inside the capillary 6, or may be determined empirically. Alternatively, the arrival time may be detected by image recognition.

By irradiating the laser beam 7 after reaching the circuit board 2, the solder 8 remains liquefied so that it further flows into the annular gap, as shown by the arrow in FIG. Since the pin 4 may protrude from the solder 8 to the outside of the annular gap, it is also possible to heat the pin 4 with the laser beam 7. Preferably, the temperature of the solder 8 is measured using the infrared sensor 9, and the control unit stops the irradiation of the laser beam 7 when the temperature of the solder exceeds a predetermined threshold. Alternatively, the laser beam 7 may be irradiated for a period of time determined in advance through experiments, for example. In this way, burning of the solder 8 can be avoided. In short, according to the sixth embodiment, since the solder remains liquefied after reaching the circuit board, it is possible to increase the degree of filling of the annular gap.

Furthermore, the fifth embodiment and the sixth embodiment may be combined. Therefore, the pin 4 is preheated using the pin heating laser beam 15, and after the liquefied solder ball 5 reaches the circuit board 2, the solder 8 remains liquefied. Furthermore, when the height of the pin 4 is higher than the height of the solder 8a outside the through hole, the laser beam 7 and the pin heating laser beam 15 are irradiated simultaneously after the liquefied solder ball 5 reaches the circuit board. It's okay. Most preferably, the pin heating laser beam 15 is then focused on the pin 4.

The first to sixth embodiments have been described above. Note that different embodiments may be combined. For example, the first embodiment may be combined with the second embodiment, the fourth embodiment, the fifth embodiment, and the sixth embodiment. Further, the third embodiment may be combined with the second embodiment, the fourth embodiment, the fifth embodiment, and the sixth embodiment.

1 Electronic component 2 Circuit board 3 Through hole 4 Pin 5 Liquefied solder ball 6 Capillary 7 Laser beam 8 Solder 8a Solder 8b outside the through hole Solder 9 inside the through hole Infrared sensor 10 Inert gas 11 Gas exhaust channel 12 3D scanner 13 Interferometer 14 Measuring beam 15 Laser beam for pin heating a Through hole diameter b Through hole depth c Pin diameter d Height of pin from circuit board e Bottom diameter of truncated cone f Top diameter of truncated cone g height

Claims (17)

A method for soldering an electronic component (1) comprising a pin (4) inserted into the through hole (3) to a circuit board (2) comprising a through hole (3), comprising:
The liquefied solder ball (5) is placed in the circuit so that a portion of the liquefied solder ball (5) flows into and fills the annular gap between the pin (4) and the through hole (3). A method, characterized in that it is deposited, in particular sprayed, onto a substrate (2). After the part of the liquefied solder ball (5) is filled into the annular gap, the area outside the through hole (3) is determined based on the predetermined total volume of the liquefied solder ball (5) before deposition. 2. Method according to claim 1, characterized in that the degree of filling of the annular gap is determined by measuring the volume of solidified solder (8a). The liquefied solder ball (5) is attached onto the circuit board (2) from the side opposite to the side on which the electronic component (1) of the circuit board (2) is arranged. 2. The method according to claim 1. 4. Method according to claim 3, characterized in that the liquefied solder balls (5) are deposited downwardly onto the circuit board (2). The liquefied solder balls (5) are deposited on the circuit board (2) at an inclined angle (α), and the inclined angle (α) is preferably between 30° and 60° with respect to the circuit board (2). 5. The method according to claim 4, characterized in that it is in the range of 45°. Direction of Adhesion Characterized in that the direction of adhesion of said liquefied solder ball (5) is directed toward said through hole (3), preferably toward the point where said pin (4) exits said through hole (3). , the method according to any one of claims 3 to 5. 2. Method according to claim 1, characterized in that in order to create the liquefied solder ball (5), energy is applied to the solid solder ball before the application of the liquefied solder ball (5). Method according to claim 7, characterized in that the energy is a laser beam (7), preferably in the range 200W NIR to 400W NIR, and is applied for a time preferably in the range 20ms to 4000ms. During the deposition of the liquefied solder balls onto the circuit board (2), in particular during spraying, the laser beam (7) is directed against the liquefied solder balls (5) in order to keep the liquefied solder balls liquefied. 9. The method according to claim 8, characterized in that the method comprises irradiating . After the liquefied solder balls (5) reach the circuit board (2), irradiating the liquefied solder with the laser beam (7) to keep the liquefied solder liquefied. 9. A method according to claim 8, characterized in that: measuring the temperature of the liquefied solder ball (5) while applying the energy;
stopping the application of energy when the temperature of the liquefied solder ball (5) exceeds a predetermined upper temperature threshold;
Method according to any one of claims 7 to 10, characterized in that the application of energy is started when the temperature of the liquefied solder ball (5) falls below a predetermined lower temperature threshold. The diameter of the solid solder ball is in the range of 0.8 mm to 2.0 mm, preferably the diameter of the solid solder ball is in the range of 0.8 to 1.4 of the diameter of the through hole (3). The method according to claim 1, wherein: Method according to claim 1, characterized in that, before the deposition of the liquefied solder balls (5), the circuit board (2) is heated to a temperature in the range from 60° C. to 90° C. Prior to the deposition of the liquefied solder ball (4), the pin (4) is preferably heated by the laser beam (7), more preferably at a wavelength different from the wavelength of the laser beam (7). 2. Method according to claim 1, characterized in that the heating is carried out by means of a laser beam (15) for heating the pin, which comprises a wavelength adapted to the absorption properties of the pin. A computer program product, characterized in that it comprises instructions for carrying out the method according to claim 1. A computer-readable medium storing a computer program product according to claim 15. In an apparatus for soldering an electronic component (1) comprising a pin (4) inserted into the through hole (3) to a circuit board (2) comprising a through hole (3),
The liquefied solder is placed on the circuit board (2) so that a portion of the liquefied solder ball (5) flows into and fills the annular gap between the pin (4) and the through hole (3). Apparatus, characterized in that it comprises a solder ball deposition device for depositing, in particular spraying, the balls (5).