JPH024390B2 - - Google Patents

Description

[Detailed description of the invention]

OBJECTS OF THE INVENTION AND PRIOR ART The present invention relates to a method for performing soldering by accurately applying the appropriate amount of solder to the soldering site. Solder has been widely used in the assembly of electronic devices, but in recent years electronic devices have become significantly smaller and more dense, and it has become increasingly necessary to apply the appropriate amount of solder to the parts that require solder. Summer. Various attempts have been made for this purpose. For example, it has been considered to perform preliminary solder plating by masking the area other than the area to be soldered and immersing it in a solder bath. However, this method has disadvantages in that it is practically impossible to implement because the patterns of electronic devices to which it is applied are too diverse, and that the amount of solder adhesion cannot be adequately controlled. Also, attempts have been made to knead powdered solder with appropriate flux, adhesive, solvent, etc. and apply it to the soldering area, but this creamy solder has a large viscosity change. Moreover, because the life cycle is short, it is necessary to take measures such as frozen transportation and refrigerated storage when transporting and storing, and there are also drawbacks such as solder scattering during soldering and ball-shaped scattered objects adhering to the surrounding area. I can't say I'm satisfied. In addition, it is also possible to bring a soldered component that has been heated above the melting temperature of the solder in advance into contact with powdered solder to melt the solder and cover it, and then bring this solder-coated component into contact with a mating component and heat it to solder it. was suggested. However, with this method, the soldered parts must be heated above the melting point of the solder, but since the parts are usually thin, thin, or otherwise small, their temperature tends to drop by the time they come into contact with the solder powder. Due to the large heat capacity of the solder and the additional cooling provided by the solder, the soldered parts must be heated to a temperature well above the melting point of the solder, in fact at least 150°C above the melting point of the solder, 183°C.
It must be heated to a high temperature of 330℃ or higher. However, it was originally necessary to avoid exposing the elements of soldered parts, especially parts such as semiconductors, which are susceptible to adverse effects of heat, to temperatures higher than the normal soldering temperature. Further, in this method, since the solder is once melted and coated, it takes time to raise the temperature of the solder to a temperature at which the solder melts, and furthermore, it takes time to plate the soldered area. In other words, this step is the rate-limiting step for soldering. Even if the temperature of the soldered parts is raised to increase the plating speed, the speed of the plating process is much slower than other processes and limits the soldering speed. Moreover, if the temperature is increased, the adverse effects of heat on the components will be even greater. Furthermore, it is extremely difficult to control the amount of solder to coat the surface with an appropriate amount of solder. Furthermore, flux is required to coat the soldered parts with solder, but flux has a much lower melting point than solder, around 100°C, so if a soldered part with a high temperature of 300°C or higher comes into contact with it, the flux will melt. There is a drawback that the solder particles scatter and harden into large lumps, making it impossible to perform solder coating. The inventor has conducted various studies to solve these problems, but has found that it is impossible to uniformly support an appropriate amount of solder on the soldered area by bringing molten solder into contact with the solder. I've come to a conclusion. In other words, whether the solder is brought into contact with pre-molten solder or the powdered solder is brought into contact while being melted, the contact time, contact angle, contact speed, temperature of the part, and direction of movement at the time of contact with the molten solder. This is because the intended purpose cannot be achieved due to the influence of factors such as the difference in the amount of solder deposited between the front and rear parts. The inventor tried applying adhesive to the soldering area to adhere powdered solder, but found that this method could eliminate the effects of heat and also cover the adhesive-applied surface with powdered solder. Good results were obtained in that no further solder adhered and the amount of adhesion was easily controlled by adjusting the adhesive application area, but there was a drawback that the adhesive became an obstacle to the spread of the solder during soldering. Structure of the Present Invention As a result of further research, the present inventor solved the drawbacks of the conventional technique by using flux to bind powdered solder to the soldering area, thereby completing the present invention. The present invention heats the soldering area of a metal member to be soldered to the melting temperature of the flux, contacts the heated area with powdered solder whose surface is coated with flux, and fuses and adheres the flux. Soldering is carried out by heating the soldering part covered with powdered solder by bringing it into contact with the other metal part to be soldered, and by combining and setting the plurality of metal parts to be soldered in advance in a state for soldering. Then, the soldering area is heated to the melting temperature of the flux, and the heated area is brought into contact with powdered solder whose surface is coated with flux to fuse and adhere the flux, and the soldering area is covered with this flux-coated powdered solder. This is a method of soldering by heating. The solder used in the present invention is a powdered solder whose surface is coated with flux. It is sufficient to heat the soldering parts of the soldered parts that come into contact with the solder to a temperature at which the flux softens or melts and becomes sticky (hereinafter referred to as the fusion temperature).
Heating above this temperature will not yield favorable results. When the flux adheres to the soldering site, the solder particles are bonded to the soldering site by the flux. Therefore, the sticky adhesive part of the flux is not sticky and excess solder does not adhere. Furthermore, if the temperature of the soldering area is heated so that the opposite side of the bonding surface of the flux layer on the surface of the solder particles also becomes sticky, other solder powder will adhere there, so controlling the amount of solder adhesion will suppress the temperature. It can be done easily depending on the situation. This means that the flux fusion temperature is 50~
This is achieved by being able to freely set the required temperature, as it is around 100°C, which is much lower than the melting temperature of solder, and has very little effect on the soldered parts. Furthermore, since the flux is made to stick at a low temperature and instantaneously, it does not become a rate-limiting process that governs the speed of the soldering process and does not affect the entire process. The feature of the present invention is that the soldering area is coated with solder particles, but the solder is not melted here and the solder remains in granular form, and the flux necessary for soldering is present in this area. It is that you are. Therefore, if the part covered with powdered solder is brought into contact with the soldering part of another soldered part and heated, soldering can be performed as is. Due to this feature, multiple parts to be soldered are set in advance at the position to be soldered, and in this state, the soldering area is heated to the melting temperature of the flux, brought into contact with the flux-coated solder powder, adhered, and heated as it is. If it is heated during the process (reflow oven, etc.), it is possible to solder it in the set state.
Of course, you are free to add more flux during heating if necessary. The flux-coated powder solder used in the present invention can be produced by simultaneous injection during the powder solder manufacturing process.
Alternatively, it can be produced by dropping it into a flux tank, or in the case of a small amount, by mixing pre-produced flux and solder powder and then pulverizing it. The heating method for the soldering area may be selected depending on the purpose, such as air heating in a reflow oven, hot wire heating in an infrared oven, or resistance heating by passing an electric current through the line. Further, in order to bring the flux-coated powder solder into contact with the heated soldering area, a sprinkling method of sprinkling powder solder or electrostatic coating may be used, but a fluidized dipping method is preferred. This is because the powder solder is highly concentrated and fluid due to the introduced gas, so the soldering area can have low resistance and dense contact.
This is because there is an advantage that the coating speed can be increased.
Moreover, if this method is used, the heating time of the soldering area can be shortened, which is very effective. Above, we explained the method of applying flux-coated powder solder to the metal parts to be soldered and soldering almost immediately after that. It is also possible to solder the mating member. In this case, it is necessary to first heat the powdered solder to a temperature higher than the melting temperature of the flux, and then to heat the powder to a temperature higher than the melting point of the solder. In this case, the soldering process and the soldering process can be performed at different times or at different locations.
However, when soldering, it is necessary to apply flux to the soldering portion of one or the other of the abutting members, as necessary. Examples of fluxes used in the present invention include the following. American gum rosin WW 95wt% Cyclohexylamine hydrochloride 5wt% American gum rosin WW 45wt% Polymerized rosin (Polypale) WW 50wt% Cyclohexylamine hydrochloride 2% Cyclohexylamine bromate 3% American gum rosin WW 50wt% Hydrogenated rosin (stehelite) ) WW 45% Glutamate hydrochloride 5% The powder solder has a particle size of 100 to 400 mesh, preferably 250 to 300 mesh. Furthermore, the amount of flux coated on the powder solder is 5
The content is selected between ~25wt% depending on the application, but is preferably around 10%. Effects and Embodiments of the Present Invention The present invention coats the powdered solder by adhesion due to softening or melting of the flux, so the processing speed is fast and there is no scattering of the flux or clumping of the solder.
Powdered solder also has a long pot life and is simple and easy to handle. Next, examples will be shown.

【table】

[Table] (Note) In all comparative examples, the solder is in the form of granules or blocks.

Claims (1)

[Claims] 1. Heat the soldering area of the metal component to be soldered to the melting temperature of the flux, and bring the powdered solder whose surface is coated with flux into contact with the heated area to fuse and adhere the flux, and this flux-coated powdered solder A soldering method characterized by carrying out soldering by heating and heating a soldering part covered with a metal part to be soldered.