JP2001068848A - Solder composition and solder supply method using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder composition which can form a solder layer with uniform thickness under good control at an electrode part of an electronic component or circuit board, and can form the solder layer without solder bridging even when an electrode interval is small, and a solder supply method using it. SOLUTION: The solder composition has an oxide film on its surface and is composed of 30 to 95 wt.% solder powder containing 0.02 to 0.2 wt.% oxygen, an acid component which dissolves oxides, and a base agent containing its solvent. After the solder composition 2 is applied to or mounted on an electrode array area of a circuit board, the solder composition 2 is heated to fuse solder powder 3 and solder balls 4 of specific size when deposited in multiple layers as solder powder is united together are cooled to form a solder layer 5 on an electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder composition and a solder supply method using the same, and more particularly, to a solder layer having a uniform thickness on an electrode portion of an electronic component or an electrode (pad) portion of a circuit board with good control. The present invention relates to a solder composition capable of forming a solder layer without causing a solder bridge even when the interval between electrode portions is narrow, and a solder supply method using the same.

[0002]

2. Description of the Related Art In surface mounting of an electronic component, it is necessary to supply solder in advance to an electrode portion of the electronic component or an electrode (pad) portion of a circuit board on which the electronic component is mounted. As a method of supplying solder, solder paste (cream solder)
Printing methods are well known. In this solder paste printing method, a solder paste mainly composed of a flux containing a solder powder and a low boiling point solvent is printed only on the electrodes, and the solder powder in the solder paste is melted by reflow to fuse and unite the solder powders. The solder is supplied to the electrode part. FIG.
(C) is a schematic view for explaining the solder supply by the solder paste printing method, (a) shows a state where solder paste 2 is printed on the electrode 1, 3 shows solder powder, and (c) shows a state after reflow. This shows a state in which solder is supplied on the electrode 1 and the solder layer 5 is formed. In this method, if dripping of the paste occurs during reflow, solder short-circuiting (bridge) is likely to occur between adjacent electrode portions. Therefore, a flux containing a low-boiling solvent and having high activity minimizes oxidation of the surface. By using a paste filled with a high amount of solder powder, the low-boiling-point solvent is evaporated as much as possible during preheating to prevent dripping and the molten solder powder is quickly united to form a solder layer on the electrode part. Like that. The amount of supplied solder is
It is controlled by the opening shape of the printing mask and the mask thickness.
However, in order to mount electronic components with high density, it is required that the electrode area is smaller and the electrode pitch is narrower. There is a limit in preventing dripping.

[0003] As a method for solving the problems of print misalignment and solder short-circuit due to solder paste printing, Japanese Patent Laid-Open No. 5-39 discloses
No. 1 discloses a solder supply method using a low solder content paste, and JP-A 1-157796 discloses a solder supply method using a solder deposition composition (paste). In these methods, the solder layer can be formed only on the electrode portion even when the paste is solid-printed on the electrode array region including the non-electrode portion around the electrode.

[0004] The solder supply method using a low solder content paste is a method of using a paste made of a flux containing a solder powder having a low content of 45% by weight or less and cellulose inhibiting the coalescence of the solder powder. The difference from the solder paste printing method is that a solder short circuit hardly occurs even in solid printing. In this method, first, paste is applied to the electrode part to be supplied with solder and the surrounding area by solid printing, and when the solder powder is heated to a temperature higher than the melting point of the solder powder in the paste, the solder powder settles and a multilayer solder powder is deposited. After the layer is formed, the solder powder melts and coalescing of the molten solder powder starts. At this time, more molten solder powder is supplied to the electrode portion having good wettability with the solder while being combined, so that a solder layer can be formed. When the speed of fusion / coalescence is high or the printing thickness is large, the solder short circuit is likely to occur due to the continuous connection of the molten solder powder as in the case of the solder paste, but the metal content is low in the low solder content paste Therefore, by controlling the printing thickness, the frequency of collision between the solder powders is low, and the presence of cellulose that inhibits coalescence prevents solder short-circuiting at the same printing thickness as the solder paste. That is, since the growth of the solder ball formed by the union of the solder powder on the non-electrode portion is slow, it can be removed by washing after cooling, and no solder short circuit occurs.

[0005] The method of using the composition for solder deposition is as follows.
For solder deposition that can deposit solder from metal powder with the highest ionization tendency among the constituent metals of the solder to be supplied and organic acid salts of other metals by a substitution reaction utilizing the difference in ionization tendency This is a solder supply method using a composition. For example, when supplying a tin-lead eutectic solder, a paste-like solder deposition composition comprising a predetermined amount of tin powder, a lead of organic acid, and a flux is used. In this method, first, a paste for solder deposition is solid-coated on an area including an electrode to be supplied with solder, and then the paste is heated to a temperature equal to or higher than a substitution reaction temperature. Formed, in parallel with this, the metal lead precipitated by the reaction of the tin powder surface with the organic acid lead diffuses into the tin powder, forms an alloy, and changes to eutectic solder. The fusion of the molten metal powders proceeds while changing to the eutectic solder composition. At this time, as in the case of the paste having a low solder content, a larger amount of molten solder powder is supplied while being united on the electrode portion having good wettability with solder, so that a solder layer can be formed. In the paste for solder deposition, a solder short-circuit is less likely to occur due to the substitution reaction and the control of the components in the flux and the printing thickness.

FIGS. 2 (a) and 2 (b) are schematic diagrams for explaining a process of supplying solder onto the electrodes by solid printing.
(A) shows a state in which the paste 2 is printed on a region including the electrode portion 1 and its surroundings, and 3 is a settled solder powder.
(B) shows a state in which the paste is being heated, and 4 is a solder ball that is growing by melting and combining the solder powder. (C) shows the solder layer 5 supplied on the electrode 1 after cooling and the solder ball 4 remaining between the electrodes.

[0007]

As described above, with the demand for miniaturization and high-density mounting of electronic components, the arrangement pitch of electrodes of electronic components and circuit boards has become narrower. 0.3 to supply solder with
The limit is about mm pitch. If the pitch is narrower than this, it is not possible to prevent the occurrence of solder bridges due to printing deviation, paste dripping, and the like, and it is difficult to mount components with reliability.

On the other hand, in the method of supplying solder to the electrode portion by the solid printing as described above, the amount of supplied solder is determined by the number of times of melting and coalescing of the solder powder at the electrode portion. Solder can be supplied. In order to increase the number of times of coalescence, it is necessary to thicken the deposited layer of metal powder such as solder powder before melting.This can be achieved by increasing the printing thickness of the paste or increasing the metal content in the paste. Can respond. However, as the number of times of merging increases, the number of solder balls (solder particles formed by melting and merging of solder powder) formed in the non-electrode portion increases. This large solder ball is combined with the solder layer formed on the electrode portion, and the amount of solder supplied to the electrode portion largely varies depending on whether the solder ball is "taken in or taken out of" the solder layer. For example, if the paste flows for some reason during the heating of the paste, the solder balls in a single layer between the adjacent electrodes cannot control the movement, and this contacts and is taken into the solder layer of the electrode portion and is taken in. This causes a variation in the amount of supplied solder depending on the amount of solder balls. FIG. 3 is a schematic diagram for explaining a variation in the amount of supplied solder caused by the movement of the solder ball. Also, in the conventional solder supply method using solid printing,
The amount of solder supplied is strongly affected by the print thickness. Moreover,
If the speed of melting and coalescing of the solder powder is high or the printing thickness is large due to the nature of the flux in the paste, the solder balls grow rapidly, and a solder short circuit occurs as in the case of the solder paste.

In view of the above problem, the present invention does not require positional accuracy or printing thickness accuracy in printing, and forms a solder layer having a uniform thickness on an electrode portion of an electronic component or an electrode portion of a circuit board with good control. It is an object of the present invention to provide a solder composition capable of forming a solder layer without causing a solder bridge even when the interval between electrode portions is narrow, and a solder supply method using the same.

[0010]

SUMMARY OF THE INVENTION The present inventors control the amount of solder supplied while investigating the cause of the variation in the amount of solder supplied to the electrodes in the method of supplying solder by solid printing with a solder paste. Found that it was important to control the fusion / coalescence of the solder powders in the molten state, and to control the use of solder powder with an oxide film on the surface and to control the solder powder in the solder paste (solder composition). It has been found that the above control can be achieved by compounding an acid component such as an organic acid capable of dissolving the oxide film of the present invention or, in the case of a solder powder not oxidized, by further adding an organic acid tin salt to the paste. The invention has been reached. That is, in order to achieve the above object, in the present invention, (1) 30 to 95% by weight of a solder powder having an oxide film on the surface and having an oxygen content of 0.02 to 0.2% by weight; A solder composition comprising an acid component that reacts with the oxide to dissolve the oxide and a base agent containing the solvent, (2) solder powder 30 to
(3) a solder composition containing, as a main component, 95% by weight and a base agent containing an acid component, an organic acid tin salt and a solvent thereof;
The above-mentioned (1) or (2), wherein the acid component is at least one selected from the group consisting of an aliphatic carboxylic acid having 10 to 28 aliphatic groups, rosin, and an acidic phosphate ester. (4) The solder composition according to (1) to (4), wherein the base agent is adjusted so as to have a viscosity necessary to settle the solder powder to a temperature immediately before melting of the solder powder. (5) The solder composition according to any one of (1) to (4), wherein the solder composition according to any one of (3) and (5) is provided in an electrode arrangement region of an electronic component or an electrode arrangement region of a circuit board on which the electronic component is mounted. After applying or placing the solder composition, the solder composition is heated to a temperature equal to or higher than the melting point of the solder powder contained in the solder composition, and the solder powder is melted. Size solder balls deposited in multiple layers (6) The height of the solder layer to be formed is h, and the amount of solder powder in the solder composition is V (volume%). ), The thickness H of the solder composition to be applied or placed is set so as to satisfy the following equation (1): 10 × h × (100 / V)>H> 2 × h × (100 / V) (1) The solder supply method according to the above (5), wherein the height of the solder ball layer deposited in the multilayer is higher than the height of the solder layer formed on the electrode. You.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The solder composition of the present invention (1) comprises a solder powder having an oxide film on its surface, an acid component for dissolving the oxide and a base agent containing the solvent as essential components. I do. In this solder composition, a solder powder having an oxide film on the surface is used, and the oxide on the surface of the solder powder is heated to a temperature equal to or higher than the melting point of the solder after applying the solder composition to the arrangement region of the electrodes. In the process, the acid reacts with the acid component present in the base agent and gradually dissolves in the solvent, so that the surface of the solder powder is covered with the acid metal salt generated by the reaction with the acid. The solder powder in such a state is settled in the base material whose viscosity has been reduced by heating and melts and coalesces while depositing in multiple layers. Further, the coalescence of the solder poles formed by the coalescence of the solder powder is repeated. In the meantime, the solder is appropriately supplied to the electrode portion having high solder wettability, but due to the presence of the metal salt covering the periphery of the solder ball, the coalescence of the solder ball is eventually suppressed or stopped. For this reason, it is possible to prevent the occurrence of a solder short circuit between the electrodes caused by the increase in the diameter of the solder ball, and it is also possible to suppress the variation in the amount of solder supplied to the electrode portions. The composition of the above (2) is composed of ordinary solder powder which is not actively subjected to surface oxidation, and a base agent which contains an acid component and contains an organic acid tin salt in advance. Also in the case of this composition, the organic acid tin salt acts to prevent the occurrence of a solder short circuit between the electrodes due to the enlargement of the diameter of the solder ball, and also to suppress the variation in the amount of solder supplied to the electrode portions. FIG. 1 is a schematic diagram for explaining a process of supplying solder to an electrode portion using the composition of the present invention,
(A) shows a state in which the solder composition 2 is applied to the electrode array region including the electrode portion 1, 3 shows solder powder, (B) shows a state in which the solder composition 2 is being heated, and 4 shows a state in which the solder composition 2 is united. The solder balls are becoming larger, and (c) shows the electrode 1 after cooling.
The state of the solder layer 5 supplied above and the solder balls 4 deposited therearound and stopped to be combined are shown.

As the solder powder in the ordinary solder paste, one having the lowest possible oxidation degree is used, and its oxygen content is about 0.015% by weight. In the present invention (1), an oxide film is formed on the surface. And oxygen content 0.0
A solder powder of 2 to 0.2% by weight, preferably 0.03 to 0.15% by weight is used. When a solder powder having an oxygen content in this range is used, the combination of the solder powder and the solder ball under heating at a temperature equal to or higher than the solder melting temperature can be sufficiently controlled, and the solder ball diameter can be set so as not to cause a solder short circuit. The oxygen content can be measured by an inert gas dissolution-gas chromatography method specified in JIS Z 2613. Specifically, first, 0.25 g of the metal powder to be measured is put in a 0.3 g nickel crucible and sealed, put in a carbon crucible, degassed, and then heated to 2000 to 2300 ° C. in an inert gas. And heat. Thus, the oxygen in the metal powder is extracted as carbon monoxide (CO), and then the carbon monoxide is passed through copper oxide to form carbon dioxide (CO ₂ ). The amount of CO ₂ is quantified by gas chromatography to calculate the content. The oxide film on the surface of the solder powder can be formed by appropriately setting the temperature and the heating time in air at a temperature equal to or lower than the melting point of the solder. For example, a tin-lead eutectic solder has a heating temperature of 150
C, heating for 3 to 120 hours, oxygen content 0.02 to
A solder powder having an oxide film on the surface of 0.2% by weight can be obtained.

The particle size of the solder powder may be the particle size used in a normal solder paste, and may be 100 μm.
In order to cope with the following narrow-pitch electrode arrangement, those having a solder particle diameter of 25 μm or less, more preferably about 10 to 25 μm are used. The amount of the solder powder in the solder composition is 3
About 0 to 95% by weight is preferable. If the amount is less than this range, the thickness of the solder composition to be supplied must be increased in order to obtain a predetermined amount of supplied solder, which is difficult in terms of operation. It is not preferable because the solder ball is re-oxidized because too little base agent is covered. In addition, as solder powder, Sn
Known solder alloys such as -Pb alloy, Sn-Pb-Ag alloy, Sn-Ag alloy, Sn-Pb-Bi alloy and Sn-Sb alloy can be used.

The base agent in the solder composition of the present invention (1) contains an acid component for dissolving an oxide film on the surface of the solder powder and a solvent thereof as essential components. In the base agent of the present invention (2), exactly the same acid component and solvent can be used. As the acid component, an acid having a boiling point equal to or higher than the melting point of the solder powder or a derivative thereof which acts as an acid can be used, and examples thereof include organic carboxylic acids and acidic phosphoric acid esters. As the organic carboxylic acid, for example, rosin or a derivative thereof, heptanoic acid, lauric acid, palmitic acid, stearic acid, oleic acid,
Neodecanoic acid, sebacic acid, aliphatic carboxylic acids such as fumaric acid, benzoic acid, phthalic acid, isophthalic acid, aromatic carboxylic acids such as trimellitic acid, pimaric acid, abietic acid,
Resin acids such as dehydroabietic acid, naphthenic acid, dicarboxylic acids synthesized from monocarboxylic acids such as naphthenic acid and tall oil fatty acids or soy fatty acids, dicarboxylic acids such as polymerized rosin obtained by dimerizing rosin, and the like. And two or more of these. Examples of the acidic phosphoric acid ester include, for example, ethyl dihydrogen.
Phosphate, diethyl hydrogen phosphate, butyl dihydrogen phosphate, dibutyl hydrogen phosphate, oleyl dihydrogen phosphate, dioleyl hydrogen phosphate and the like can be mentioned.

The solvent used for the base agent functions to adjust the strength of the acid. For example, white petrolatum or castor wax can be used. A viscosity modifier such as a carbitol solvent or mineral spirits can be added to the base agent as other optional components. The base agent used in the solder composition of the present invention only needs to have a viscosity that allows the solder powder to sufficiently settle to a temperature immediately before the melting of the solder powder (hereinafter, this state is also referred to as a temperature immediately below the melting temperature). A base agent using a solid acid component, a solvent, or the like as a raw material may be used. In such a case, the composition can be heated to a molten state, mixed with the solder powder, and cooled to room temperature to form a sheet having a predetermined thickness. When supplying the solder, in the case of a sheet, a composition having a predetermined shape may be placed on the electrode array region.

The use of the solder composition of the present invention to supply solder to the electrode portion of an electronic component or the electrode portion of a circuit board can be performed by the following process. First,
A solder composition is applied to the electrode arrangement region of the electronic component or the electrode arrangement region of the circuit board on which the electronic component is mounted by printing using a metal mask having a predetermined thickness and an opening dimension.
When the solder composition is a sheet-like solid, the sheet is placed on the electrode array region. Then, the electronic component or circuit board, the melting point of the solder powder contained in the solder composition or more,
For example, in the case of Sn-Pb eutectic solder, the solder powder is heated at 210 ° C. for about 3 minutes to melt the solder powder, and when the solder powders are coalesced and solder balls of a predetermined size are deposited in multiple layers, heating is performed. Stop and air-cool. After air cooling, the electrode array region of the substrate or the like is immersed in a cleaning solution such as ethanol and washed for a predetermined time by ultrasonic waves to remove the residue of the solder composition and the like, and is dried to complete the supply of the solder to the electrode portion. .

When solder is supplied to the electrodes, it is preferable that the thickness of the multilayer deposition layer of the solder powder is higher than the height of the supplied solder. In practice, the thickness of the deposited layer varies from place to place due to printing variations and solder powder settling variations. Even in such a case, it is desirable that the thickness of the solder ball be higher than the supplied solder height. Conversely, if the solder height is too high, the surface gloss of the lowermost solder ball, which greatly affects solder supply properties, will be lost, and the supplied solder will have poor wettability. This is mainly because when the deposited layer is thick, the oxide film of the solder powder in the lowermost layer is not sufficiently removed. For this purpose, the supply thickness H when the solder composition is applied or placed on the electrode array region is h, the height of the solder layer to be formed is h, and the amount of the solder powder in the solder composition is V (capacity% ) Is set so as to satisfy the following equation (1). 10 × h × (100 / V)>H> 2 × h × (100 / V) (1) By setting as above, the height of the solder ball layer deposited in multiple layers in the solder supply process becomes The height can be higher than the height of the solder layer formed on the electrode. When the solder is supplied to the electrode section in such a state, it is possible to achieve a solder supply with little variation between the electrodes. In addition, the solder composition of the present invention can supply stable solder only to the electrode portion even in solid printing, but it is possible to adopt the same printing method as the conventional solder paste for the electrode array portion not having a narrow pitch. Needless to say.

[0018]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. Here, the oxygen content of the solder powder used in the examples was measured by the above-described inert gas melting-gas chromatography method (JIS-Z-2613).

Example 1 Sn-37Pb solder powder having a diameter of 25 μm or less and an average diameter of 12.5 μm
n-3.5Ag solder powder (Oxygen content is 0.015wt%, 0.01 respectively
3 wt%) and heated at 150 ° C. to obtain solder powders having various oxygen contents. Furthermore, as a base agent,
Oleic acid and white petrolatum were mixed at various ratios, and the base agent and the solder powder were mixed at a weight ratio of 1: 1 (solder powder 50% by weight) to form a paste (solder composition).
This paste was printed on a glass plate (2.5 cm square) to a thickness of 500 μm, and the glass plate was heated at 210 ° C. (Sn-37Pb powder) and 245 ° C. (Sn-3.5 Ag powder)
Heated for minutes. Then, after cooling the average diameter of the solder balls formed on the glass plate, an enlarged photograph was taken from the glass surface, and the diameter of the solder ball shown in the enlarged photograph was measured and corrected by the magnification. Table 1 (1) shows the results of Sn-37Pb powder, and Sn-3.
Table 1 (2) shows the results of the 5Ag powder. From the results of the experiment, it can be seen that with the solder powder having an oxygen content of 0.02 wt% or more, the coalescence can be suppressed even while the solder balls are in contact. It can also be seen that the higher the oxygen content (0.03 wt% or more), the more stable the solder ball size can be formed. These are all effective in stabilizing the solder supply process.

[0020]

[Table 1]

Example 2 A Sn-37Pb solder powder having a diameter of 25 μm or less and an average diameter of 12.5 μm was
Heating at 50 ° C. yielded a powder having an oxygen content of 0.04% by weight.
Further, as a base agent, white petrolatum and various saturated linear fatty acids were mixed to prepare a base agent containing 10% by weight of these acids. The paste was mixed with the solder powder at a weight ratio of 1: 1 to form a paste. This was heated at 210 ° C. in the same manner as in Example 1.
For 3 minutes, and the diameter of the solder ball was measured. Table 2
(1) shows the result. In addition, these pastes
On FR-4 substrate, print 500μm thick with solid coating, heat the substrate to 210 ° C for 3 minutes, cool, then wash the substrate surface with ethanol to remove residual solder balls and base material. , 100μm diameter copper electrode (pad) arranged on the substrate
Was supplied with solder. As a result of observing the solder supply condition,
There was a defective supply pad on which solder was not sufficiently supplied. Table 2 (2) shows the measurement results of the ratio and the like. The measurement results of the poor supply pad indicate that it is desirable that the acid component in the base agent does not boil during heating. This is because the coalescence of the balls becomes non-uniform due to the generation of bubbles due to boiling. In addition, it is understood that a material that generates less air bubbles due to decomposition or the like is desirable as the base agent. From that viewpoint, when the acid component is a fatty acid, it is effective that the aliphatic group has 6 or more carbon atoms, preferably 10 or more carbon atoms.
Furthermore, when the viscosity of the base agent is high, since the solder powder does not settle during heating and a solder ball with little variation is not formed, the carbon number of the aliphatic group is preferably 28 or less. Therefore, when a fatty acid is used as the acid component, the aliphatic group has 6 to 28 carbon atoms, preferably 10 to 28 carbon atoms.
28 are effective.

[0022]

[Table 2]

Example 3 An Sn-37Pb solder powder having a diameter of 25 μm or less and an average diameter of 12.5 μm was heated at 150 ° C. to obtain an oxygen content of 0.04% by weight.
Was obtained. Using stearic acid as an acid component, a base agent having an organic acid content of 40% by weight having different viscosities by changing the addition amounts of white petrolatum and a high-viscosity wax was prepared.
The paste was mixed with the solder powder at a weight ratio of 1: 1 to form a paste. Further, this paste was printed at a thickness of 200 μm on an FR-4 substrate, and solder was supplied to a copper pad having a diameter of 100 μm on the substrate. After heating under the same conditions as in Example 1 and cooling, the remaining solder balls and the base agent were removed. Table 4 shows the results of measuring the sedimentation state of the solder powder (in which state was measured) and the height of the solder supplied on the copper pad. As is evident from the results in Table 3, the more the sedimentation of the solder powder is sufficient, the higher the solder supply height and the smaller the height variation.

[0024]

[Table 3]

Example 4 Sn-37Pb solder powder having a diameter of 25 μm or less and an average diameter of 12.5 μm was heated at 150 ° C., and the oxygen content was 0.120% by weight.
Was obtained. Further, a base agent having an organic acid content of 30% by weight was prepared using stearic acid and white petrolatum. 8 with a circular pad (Al / Ni / Au) 200 μm in diameter
Solder powder was supplied to the inch wafer in various thicknesses, and the base material was supplied thereon so that the total thickness became 2 mm. This was heated at a wafer temperature of 230 ° C. for 5 minutes, and then the solder ball diameter was measured. Thereafter, the residue was removed by washing, and the solder height was measured. Table 4 shows the results.

[0026]

[Table 4]

From the results shown in Table 4, it can be seen that it is desirable to make the final solder ball deposition layer multilayer in order to reduce the variation in the supply of solder. This is because in the case of multiple layers the metal ball hardly changes its relative position,
This is because, while the merging of solder balls proceeds stably, when merging from multiple layers to a single layer, the solder balls start to move freely, and stable merging of solder balls cannot be performed. In addition, it can be seen that it is effective to increase the supply amount so that the thickness of the solder ball deposition layer to be formed is higher than the height of the solder to be formed on the pad.

Example 5 Sn-37Pb solder powders having various average diameters were heated at 150 ° C. for 40 hours to obtain powders whose surfaces were oxidized. Further, stearic acid and a solid wax having a melting point of 80 ° C. were heated and mixed at 100 ° C. to prepare a base agent having an organic acid content of 30% by weight. %). This was then cooled to form a 2 cm square, 1 mm thick sheet-shaped solder composition. This was placed on a resin substrate having a pad of 50 × 100 μm, and the resin substrate was heated to 240 ° C. Even though the solder supply was solid, the solder balls melted and coalesced, after which coalescence stopped. Also, a 30 μm-high solder could be supplied on the pad.

Example 6 Sn-37Pb solder powder having various average particle diameters was heated at 150 ° C. to obtain a powder having an oxygen content of 0.08% by weight. Further, as a base agent, white petrolatum and rosin are mixed,
A base agent of 10% by weight was prepared. The paste was mixed with the solder powder at a weight ratio of 1: 1 to form a paste. Furthermore, paste these pastes on the FR-4 board to a thickness of 500μ each.
printed on the board and a 50 × 1500μm copper pad (pitch
(150 μm) Solder was supplied to the array region. After heating under the same conditions as in Example 1 and cooling, the remaining solder balls and the base agent were removed, and the occurrence rate of solder short circuits at 100 pads was measured. Table 5 shows the results. From the results in Table 5, it can be seen that the average particle size of the solder powder used is desirably 25 microns or less in a narrow-pitch electrode arrangement from the viewpoint of the solder short-circuit occurrence rate.

[0030]

[Table 5]

Example 7 Sn-37Pb solder powder having a solder particle size of 25 μm or less and containing a fine particle size of 10 μm or less and Sn-37Pb solder powder having a solder particle size of 10 to 25 μm were heated at 150 ° C. , Oxygen content 0.08
% Powder was obtained. Further, as a base agent, white petrolatum and rosin were mixed to prepare a 10% by weight base agent. The paste was mixed with the solder powder at a weight ratio of 1: 1 to form a paste. Further, this paste was printed at a thickness of 300 μm on an FR-4 substrate, and solder was supplied to a copper pad having a diameter of 100 μm on the substrate. When the solder balls were observed by heating under the same conditions as in Example 1, solder powder having a solder particle diameter smaller than 10 μm began to flow due to the dripping of the base agent due to the heating, and the position correction recognition at a distance of 500 μm from the electrode was performed. The mark (the same structure as the electrode) was reached and the solder was attached. On the other hand, even when the base material flows out with the solder powder of 10 to 25 μm, the solder powder is settled in the printing portion and the coalescence of the solder balls and the subsequent coalescence stop, so that no solder is supplied to the recognition mark. The solder could be supplied only to the pad below the printing section. To prevent the supply of solder to unnecessary parts caused by who, the minimum solder particle size is 10 μm
The above is desirable.

Example 8 Sn-37Pb solder powder having a diameter of 25 μm or less and an average diameter of 12.5 μm was heated at 150 ° C. to obtain an oxygen content of 0.12% by weight.
Was obtained. Further, as a base agent, white petrolatum and an acid phosphate were mixed to prepare three kinds of base agents having an acid phosphate content of 10% by weight. These were mixed with the solder powder at a weight ratio of 1: 1 to form a paste. These were heated to 210 ° C. in the same manner as in Example 1, and the diameter of the solder ball was measured. Table 6 shows the results.

[0033]

[Table 6]

Example 9 Sn-37Pb solder powder (oxygen content 0.015 wt%) having a diameter of 25 μm or less and an average diameter of 12.5 μm was prepared. Next, the solder powder was heated at 150 ° C., and the heating time was adjusted to obtain powders having different oxygen contents. Next, palmitic acid and oxygen content 0.12wt%
The Sn-37Pb solder powder was kneaded at a weight ratio of 1: 1 and heated at 200 ° C. for 10 hours, and then the solder powder was removed to prepare a palmitic acid solution in which a palmitic acid Sn salt was dissolved in palmitic acid. This solution and white petrolatum were mixed in various ratios to obtain a base agent. The base agent and the solder powder were mixed at a weight ratio of 1: 1 to form a paste. This paste was printed on a glass plate (2.5 cm square, 1 mm thick) to a thickness of 200 μm, and the glass plate was heated to 210 ° C. Then, the diameter of the solder ball formed on the glass plate was measured. Table 7 shows the results.

[0035]

[Table 7] As can be seen from the results in Table 7, when the organic acid Sn salt is contained in the base agent, coalescence of the solder powder is stopped even when a low-oxidation solder powder having an oxygen content of about 0.015 to 0.022% by weight is used. can do. In the solder composition of the invention (1), the coalescence is stopped by a substance (metal salt) generated when the solder composition reacts with the oxidized solder powder to dissolve the oxide. It can be seen that the coalescence suppressing effect is exhibited, and therefore, coalescence can be suppressed even with a solder composition using a solder powder having a relatively low oxygen content.

[0036]

According to the solder composition of the present invention, after the solder composition is applied to the array region of the electrodes and then heated to a temperature equal to or higher than the melting point of the solder, the solder formed by fusion of the solder powder is formed. Repeated coalescence of the balls can be stopped halfway. Therefore, even in the solder supply method of solid printing, it is possible to prevent the occurrence of a solder short circuit between the electrodes due to the enlargement of the diameter of the solder ball, and also to suppress the variation in the amount of solder supplied to the electrode portions.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a process of supplying solder to an electrode portion using the composition of the present invention.

FIGS. 2A and 2B are schematic diagrams for explaining a process of supplying solder on electrodes by solid printing. FIG.

FIG. 3 is a schematic diagram for explaining a variation in a supplied amount of solder caused by a movement of a solder ball;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode part 2 Solder paste (solder composition) 3 Solder powder 4 Solder ball 5 Solder layer

Claims (6)

[Claims] A solder powder having an oxide film on the surface and an oxygen content of 0.02 to 0.2% by weight;
A solder composition comprising an acid component that reacts with the oxide to dissolve the oxide and a base agent containing the solvent. 2. A solder composition containing 30 to 95% by weight of solder powder and a base agent containing an acid component, an organic tin salt and a solvent thereof. 3. The acid component according to claim 1, wherein the acid component is at least one member selected from the group consisting of aliphatic carboxylic acids having 10 to 28 aliphatic groups, rosin, and acidic phosphate esters. Item 3. The solder composition according to Item 2. 4. The method according to claim 1, wherein the base agent is adjusted so as to have a viscosity necessary to settle the solder powder to a temperature immediately before melting of the solder powder. The solder composition according to any one of the above. 5. The method according to claim 1, wherein the solder composition is applied or placed on an electrode arrangement region of an electronic component or an electrode arrangement region of a circuit board on which the electronic component is mounted. Heating the solder composition above the melting point of the solder powder contained in the composition to melt the solder powder,
A method for supplying a solder, comprising: forming a solder layer on the electrode by cooling when a plurality of solder balls of a predetermined size are deposited as a result of merging of the solder powders. 6. When the height of the solder layer to be formed is h and the amount of solder powder in the solder composition is V (% by volume), the thickness H of the solder composition to be applied or placed is defined as follows: 1 × h × (100 / V)>H> 2 × h × (100 / V) (1) The height of the solder ball layer deposited in the multilayer is formed on the electrode. 6. The method according to claim 5, wherein the height of the solder layer is higher than the height of the solder layer.