JPH03151189A - Cream solder - Google Patents

Abstract

PURPOSE:To obtain products having high reliability without short circuiting by incorporating capric acid into a compsn. contg. powder solder, resin, solvent, etc., thereby constituting the cream soldier. CONSTITUTION:The cream solder is constituted by incorporating the capric acid into the compsn. contg. the powder solder, resin, solvent, etc. The solder for non-washing is constituted by adding 5 to 35wt.% capric acid as an activator into flux components. The cream solder for fine patterns are constituted by adding 20 to 35wt.% capric acid to flux components together with other activators. The workability and productivity are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cream solder that does not require removal of flux residue after soldering and a cream solder for fine patterns.

[Conventional technology] In recent years, electronic boards that use cream solder have become increasingly smaller.As elements mounted on printed circuits are made into chips, components become smaller and packaging density increases.
High degree of integration is progressing, and electronic materials':! The distance between the four poles and the spacing between the patterns are becoming increasingly narrower.

Therefore, ensuring high insulation between one circuit, bonding strength,
Cream solders have also come to be highly demanding in terms of bonding accuracy, thermal stability, and the like.

The reflow method is mainly used for cream solder, but it is common to first print cream solder on a board, then mount the chipped element, melt the solder in a heating furnace, and bond. .

In other words, the performance required for cream solder is in addition to the performance required for general solder flux, such as safety for the human body, good solderability, high insulation, non-corrosion, and no deterioration during storage.

Although it is preferable not to clean after printing characteristics and soldering, cleaning is usually necessary. That is, this is because the metal components may be corroded by the residue of the halogen-based activator in the cream solder. Therefore, it is required to have excellent cleaning properties, and is mainly cleaned with Freon.

However, in recent years, fluorocarbons have been considered to be a cause of depletion of the earth's ozone layer, so it is natural that there is a demand for a solder that does not require removal of flux residue.

On the other hand, when using cream solder for precision electronic components, it must have excellent printability and dischargeability from a dispenser, and after printing, the discharged material may smudge or blur. It is necessary that there be no.

[Problems to be Solved by the Invention] The present invention is: ■ Development of cream solder that does not require cleaning and removal of flux residue after mounting and soldering of elements ■ Good printing due to miniaturization of printed patterns The purpose of this project was to develop a cream solder with good properties.

The first purpose of solder cream solder, which does not require cleaning, is to use hydrohalic acid as an activator to remove oxides on the surface of circuit conductors (metals) when melting solder, and to remove oxides on the surface of solder powder in cream solder. This is based on the discovery that caprylic acid can be used to compensate for the need for amines (usually in the form of amine hydrochlorides, etc.).

In conventional cream solder, halogen compounds (e.g. diethylamine hydrochloride, isopropylamine hydrochloride, monoedylamine hydrochloride or hydrobromide, etc.) are added as activators to improve solder wettability and prevent oxidation of solder powder. It is designed to remove substances and prevent re-oxidation.

However, if halogen compounds remain on the surface of a circuit after the elements are soldered, moisture, oxygen, etc. in the air will accelerate corrosion of the metal, causing problems such as reduced insulation, short circuits, and poor circuit connections. It is well known that this is the cause of this, and cleaning is required, and cleaning with Freon or water is usually performed.

However, in recent years, the use of fluorocarbons has been regulated to prevent the destruction of the ozone layer, and there is a possibility that its use will be banned in the near future.

On the other hand, water cleaning is not as efficient as Freon cleaning.

Furthermore, there are various unresolved issues such as waste liquid treatment, and it is necessary to develop a highly reliable cream solder that does not contain halogen-based activators that do not require cleaning, and has the same activating effect without cleaning. It's here.

Apart from this, the trend toward miniaturization of components and high integration of single circuits has created a demand for further miniaturization of the spacing between solder patterns, which inevitably leads to the miniaturization of solder powder, which increases the specific surface area of the solder (
Therefore, the amount of surface oxidation of the powder tends to increase. However, with conventional cream solder formulations, it was necessary to increase the amount of halogen-based activator in order to completely reduce the increased oxides and prevent undissolved solder balls from forming. However, the residue of the halogen-based activator cannot be completely removed by cleaning with Freon or water.

There was a problem that it could lead to corrosion.

Therefore, there was a need to develop cream solder for fine patterns.

Means for Solving Problem L3] The present invention has solved the various problems described above by developing a cream solder containing caprylic acid in a composition containing powdered solder, resin, solvent, etc.

In particular, cream solder for non-cleaning use is a cream solder in which 5 to 35% by weight of caprylic acid is added as an activator to the flux component (in the present invention, this refers to all components of cream solder excluding powdered solder). I will provide a.

In addition, as a cream solder for fine patterns, caprylic acid is added to the flux component along with other active agents.
To provide a cream solder containing 0 to 35% by weight.

The raw materials used in the non-cleaning cream solder consist of solder powder, resin, solvent, viscosity modifier, and caprylic acid.

In this case, the solder powder is eutectic solder (Sn 63%-pb 37%.

Melting point 183℃) Silver-containing solder (Sn 62%-Pb 3G%-Ag 2% Melting point 178
℃) High temperature solder (Pb 95%-8'15%, melting point 305℃) or (Pb 95%-5n 3%-8g 2%, melting point 2
98℃) Low temperature solder (Sn 46%-Pb 46%-Bi 8%, melting point 16
A powder having a temperature of 73 μm (200 mesh) or less is used.

As the resin, mainly rosins, such as polymerized rosin,
Natural rosin (wood rosin, gum rosin), hydrogenated rosin, maleated rosin, disproportionated rosin are used.

As the solvent, many organic solvents can be used, including butylcarpitol, terpineol, texanol, butylcarpitol acetate, and the like.

As the viscosity modifier, hydrogenated castor oil, hydrogenated castor oil, coconut oil, stearic acid, etc. are used.

By adding caprylic acid as an activator, a cream solder can be obtained that eliminates the need for cleaning the solder.

The blending ratio is 87-93% powdered solder and 4-4% resin.
6%, solvent 1.7-5%, viscosity modifier 0.1-0.5%
, 0.5 to 3.5% of caprylic acid, and can be used for printing patterns with line widths of up to about 0.5 mm.

However, currently there is a demand for fine patterns with a width of about 0.3 mm, and in order to meet this demand, it is necessary to separately use ultrafine powder solder of 20 μm or less for fine patterns, but as solder powder becomes finer, The surface area increases, and the amount of oxygen also increases in proportion to the surface area, making it more likely that undissolved solder or solder balls will occur during reflow (this requires improvement).

However, caprylic acid works as an activator when used in combination with conventional hydrohalic acid activators, and even when using ultrafine powder solder of 20 μm or less, solder balls do not occur, for example, 0.3 μm. We have found that even with fine patterns such as , the printability is greatly improved and printing and soldering can be performed smoothly.

That is, as a cream solder for fine patterns, an extremely fine solder powder of 20 μm or less is used, and as an activator, a highly active halogen compound such as a conventionally known amine hydrochloride and caprylic acid are used in combination.

As an activator, 0.2 to 1.0 for cream solder
%, and caprylic acid is preferably blended in an amount of 2.0 to 3.5%.

[Action 1: When caprylic acid is added to cream solder, the effect of the activator is exhibited, although the mechanism is unknown, and it is possible to obtain non-cleanable cream solder without the need to add a halogen-based activator. can.

When adding caprylic acid to solder, it assists the activation effect of the halogen activator, and even though ultrafine powder solder is used, An excellent cream solder with significantly improved printing properties, no short circuits or disconnections, no solder balls, and less activator residue after cleaning is obtained.

[Example 1 1 Non-cleaning cream solder (Examples 1 to 4) Using caprylic acid as an activator, 1 particle size lO ~ 54 μm
A cream solder was prepared by kneading the almost perfectly spherical solder fine powder, a resin, a solvent, and a viscosity modifier in the proportions shown in the examples.

Apply this cream solder to a copper-clad circuit board at a pitch of 0.5m.
Screen printing was performed at 230° C., and reflow was performed at 230° C., and solder sag and solder balls were evaluated. In Examples 1 to 4, there was no solder dripping and no solder balls were generated.
I was able to clearly attach solder to the pattern on the copper board.

Suner +l 7n-j & (7 part #i! JiTA? A1
．． ? Relative humidity 60°C, 90%R) I in 1000
After holding for a period of time, 100 d.c.
A moisture resistance load experiment was conducted in which the insulation resistance was measured by applying a voltage of V. In Examples 1 to 4, the insulation resistance was 1000 MΩ or more even after 1000 hours of the humidity load test, and there were no defects such as short circuits or corrosion.

Comparative Example 1> For comparison, O was used instead of caprylic acid. A similar test was conducted using cream solder using a flux containing inic acid as an activator. When reflowing at 230°C, solder balls were generated and defects occurred.

(Example 1) Sn63-Pb37 90. O% polymerized rosin 5.0% butylcarpitol
3.4% Caprylic #
1.3% castor oil 0.3
% (Example 2) Sn62-Ag2-Pb36 90.0% Disproportionated rosin butylcarpitol caprylic acid castor oil (Example 3) Sn95-Pb5 Polymerized rosin butylcarpitol caprylic acid castor oil (Example 4) n46- B Hydrogenated Rosin Butyl Carpitol Caprylic Acid Castor Oil (Comparative Example 1) Sn63-Pb37 Redemption Rosin Butyl Carpitol 18-Pb46 90°0% 7% 0% 3% 0% 0% 4% 5% 1% 0% 0 % 9% 0% 1 % 0% 0% 7% Oleic acid 0% Castor oil 0°3% (Margin below) 11 Cream solder for fine patterns <Example 5
) Resin, solvent, viscosity modifier, halogen-based activator, and caprylic acid are used in combination, and ultrafine solder powder exhibiting a fine, almost perfect spherical shape with a particle size of about 20 gm or less and 63% tin and 37% lead is prepared in the proportions shown below. I mixed the wires with cream solder. Because the grain size of this cream solder is fine, it is possible to print copper-clad circuits with a pitch of 0.3 mm according to the pattern without any defects.

Suitable for fine pattern soldering.

5n63-Pb37 (20um or less) 90.0% Polymerized rosin 5.0% Butylcarpitol 1.5% Di-thylamine hydrochloride 0.2% Caprylic acid
3.0% castor oil
0.3% (Comparative Example 2-1) When a solder with a particle size of 53 to *Oum was used, a pattern with a narrow gap of 0.3 mm width could not be created even if caprylic acid was blended. (The gaps are connected.) <Comparative Example 2-2> When the particle size of the solder powder is 20 μm or less, a halogen-based activator is used, and the cream composition of the conventional formulation shown below is used, solder poles are generated. There are many cases where a short circuit occurs during an insulation test.

5n63-Pb37 (20gm or less) 90.0% Polymerized rosin 5.0% Butylcarpitol 4.5% Diethylamine hydrochloride
0.2% castor oil
0.3% (blank below) [Effect] As can be seen from the above explanation, caprylic acid, when added to cream solder, serves as a non-corrosive activator and can increase reliability even without cleaning. It was also found that the printing characteristics of fine pattern ink were significantly improved.

Therefore, it has been found that by incorporating caprylic acid, it is possible to easily produce a cream solder for non-cleaning, and to produce an excellent cream solder without dripping or solder balls, and with less clogging of nozzles during printing7. , it does not require cleaning after reflow, greatly improving workability and productivity on the mounting line, and brings great benefits such as eliminating the need for fluorocarbon cleaning processes, equipment such as cleaning tanks, and fluorocarbon recovery equipment. It has become possible to create highly reliable products without short circuits.

In addition, in the case of cream solder for fine patterns, productivity is improved due to improvements in printing characteristics, and the completeness of printing reduces the number of rejected products due to short circuits, insufficient bonding, etc., and the formation of printing bleeds, ink drips, and solder balls. We were able to provide an excellent cream solder with fewer problems such as.

Claims (3)

[Claims] (1) Cream solder characterized by containing caprylic acid in a composition containing powdered solder, resin, solvent, etc. (2) A cream solder for non-cleaning, characterized in that 5 to 35% by weight of caprylic acid is added to the flux component as an activator. (3) A cream solder for fine patterns, characterized in that 20 to 35% by weight of caprylic acid is added to the flux component together with other activators.