JP2674421B2 - No-clean cream solder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-cleaning cream solder which is used in a reflow soldering process and which eliminates the need for cleaning after mounting electronic components and improves printability, reflowability and reliability.

[0002]

2. Description of the Related Art Recently, there is an urgent need to take measures against the total abolition of CFCs used for cleaning printed wiring boards and the like.

Next, a conventional reflow soldering process which requires such cleaning will be described.

FIG. 2 shows a conventional reflow soldering process. In FIG. 2, this example includes a cream solder printing step 21, an adhesive applying step 22, a component mounting step 23, a reflow step 24, an appearance inspection step 25, a cleaning step 26, and an electrical inspection step 27.

Further, these steps will be described in detail.
In the solder paste printing step 21, the solder paste is supplied to the printed circuit board by screen printing. continue,
In the adhesive application step 22, the adhesive is applied to the mount portion of the component that may drop during the back surface reflow. In the component mounting step 23, each component is mounted by a mount machine or the like.
In the reflow step 24, the cream solder is melted by being heated by various heat sources such as infrared rays and hot air, and is cured to be bonded. In the visual inspection step 25, visual inspection is performed by visually observing abnormalities such as bridges, unsoldered portions, component deviations, and solder balls at the solder joints, or by using an inspection machine. In the cleaning step 26, the flux residue is cleaned using a solvent such as freon and trichloroethane. Subsequently, in an electrical inspection step 27, electrical inspection of connection continuity, circuit function and the like is performed.

[0006]

However, in the above-described conventional reflow soldering process, flux residue that impairs mutual insulation remains at the soldering points and lands after soldering. Therefore, the cleaning process 26 for removing the flux residue is required.

As the cleaning, (1) chlorine-based hydrocarbon (fluorocarbon, trichloroethane, etc.) cleaning, (2) alcohol cleaning, (3) saponifying agent cleaning, (4) water cleaning, (5) semi-aqueous solvent cleaning It has been known.

In each of these cleanings, (1) chlorine-based hydrocarbon cleaning cannot be used because it is obliged to abolish ozone in the stratosphere globally based on the Montreal Protocol. (2) In alcohol cleaning, since the flux residue has a weak cleaning power for hydrophobic components (organic components such as rosin) and has flammability, it is necessary to take anti-exposure measures. In (3) saponification agent cleaning and (5) quasi-aqueous solvent cleaning, a water treatment device is required although both hydrophilic components (activator and ionic components) and hydrophobic components of the flux residue have cleaning power. (4) In water washing, the cream soldering agent must be made water-soluble, and a water treatment device is required. As described above, cleaning has problems.

The present invention solves the problems in the prior art as described above, and realizes reflow soldering without the need for cleaning, and is excellent in printability, reflowability and reliability. The purpose is to provide cleaning cream solder.

[0010]

In order to achieve the above object, the non-cleaning cream solder of the present invention contains S as a metal component.
Particle size 30μ containing n, Pb and Ag at 62: 36: 2
88 to 92% by weight of the total weight of the cream solder containing Sn / Pb / Ag alloy of m or more, and ethylamine hydrochloride, diethylamine hydrochloride, dimethylamine hydrochloride as an activator,
Trimethylamine hydrochloride, diclohexylamine hydrochloride, diethylamine hydrobromide, diclohexylamine hydrobromide, n-propylamine hydrochloride, di-n-
Propylamine hydrochloride, tri-n-propylamine hydrochloride, a single or a plurality of flux total weight 100
%, 0.01 wt% or more and less than 0.06 wt%, and fumaric acid, tartaric acid, stearic acid, tartronic acid, glutamic acid, isomalic acid, phthalic acid, citric acid, or a plurality of them. , 100% of total flux, 0.10% by weight or more, 0.60% by weight
Less than 50 wt% or more of rosin, and the cream solder is composed of the metal component and the flux, and the total amount of both is 100 wt%.

[0011]

With such a structure, the non-cleaning cream solder of the present invention realizes reflow soldering without cleaning, has high printability without sagging or bleeding in printability, and has a high solderability. Good flowability and high reliability during reflow can be obtained by blocking.

[0012]

Embodiments of the non-cleaning cream solder of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a reflow soldering process according to the embodiment. In FIG. 1, this example shows a cream solder printing step 11, an adhesive application step 1
2, component mounting process 13, reflow process 14, appearance inspection process 15, and electrical inspection process 16.

Further, these steps and cream solder will be described in detail.

[0014]

[Table 1]

[0015]

[Table 2]

These (Table 1) and (Table 2) show the cream solder components in Examples and Comparative Examples 1, 2, 3, 4, 5, 6, and 7 of cream solder, and this Example and Comparative Example. The results of printability, reflowability, and reliability for 1 to 7 are shown.

In (Table 1) and (Table 2), the cream solder contained Sn, Pb, and Ag in a weight ratio of 62: 36: 2, and had a particle size of 37 to 63 μm. 90% by weight of Pb / Ag alloy based on the total weight of cream solder, and 0.03% by weight of diethylamine hydrochloride alone and 0.30% by weight of phthalic acid as an activator with respect to 100% by weight of the total flux. And then 60 rosin
It is a component containing wt%.

Further, the activators and the amount of activators in Comparative Examples 1 to 7 containing the same metal component and the same rosin are as shown in (Table 1) and (Table 2).

Next, the reflow soldering process of this component cream solder and Comparative Examples 1 to 7 will be described.

In the solder paste printing step 11, (Table 1)
And the cream solder of the components of the examples of (Table 2) are respectively supplied by screen printing to a component mounting printed circuit board and a comb-shaped electrode board (JIS2 type). At this time, observing the cream solder state immediately after printing, a pattern in which the printed cream solder area spreads by 20% or more with respect to the opening area of the metal mask which is the screen plate for printing,
And the occurrence rates of patterns lacking 20% were obtained.

In the adhesive application step 12, the adhesive is applied to the mount portion of the component which may be dropped during the back surface reflow.

Subsequently, in the component mounting step 13, 0.65
mm pitch 100-pin QFP (flat package) 1
Each component such as 0 was mounted by a mount machine.

Further, in the reflow step 14, the solder is melted by heating in a hot-air type reflow furnace, and the solder is hardened and joined.

Then, in the visual inspection step 15, 0.65
Bridge to the solder joint of the lead wire of mm pitch QFP,
Occurrence of unsoldered parts and solder balls was observed. On this occasion,
The solder bridge counts the occurrence rate for all leads, and the unsoldered part counts the occurrence rate for all lead joints. Furthermore, the number of solder balls generated between 10 arbitrary leads was counted, and the average value was calculated.

Here, only the comparative example 1 is washed by the conventional method. In this cleaning step, vapor cleaning is performed by boiling with Freon 113 containing 5% ethanol.

Finally, in the electrical inspection step 16, a heat cycle test is conducted on the mounting board. Conditions are -40 ℃
After leaving it for 30 minutes, raise the temperature to + 85 ° C within 1 minute, and
Let stand for a minute and then lower the temperature again to -40 ° C. This cycle is repeated 1000 times. After the test, the QFP lead peel strength is measured with a bond tester.

The comb-shaped electrode substrate was subjected to a voltage application humidity resistance test. This condition is 60 ℃, 90% RH, DC16
V is applied and left for 1000 hours. After the test, measure the insulation resistance between the counter electrodes.

The results of printability, reflowability and reliability are
As shown in the items in (Table 1) and (Table 2), excellent effects are obtained.

As described above, according to this embodiment, the fine particle diameter of the cream solder metal component is cut to 37 μm or more,
In addition, when the content is 90% by weight of the total weight of the cream solder, which is an appropriate amount, the sagging at the time of printing can be suppressed. That is, as shown in (Table 1) and (Table 2), the printed cream solder area is 20 times the opening area of the metal mask.
The rate of occurrence of patterns that spread by more than 0.1% was 0%.

Furthermore, generation of solder balls during reflow is suppressed. That is, the average number of occurrences between IC leads is 10
Or less.

Further, an appropriate amount (0.01% by weight or more, 0.06% by weight) of a halide (diethylamine hydrochloride, etc.) is used as the activator.
And less than 0.1% by weight of organic acid (phthalic acid, etc.)
0% by weight or more and less than 0.60% by weight), and by further containing a fixed amount (50% by weight or more) of rosin,
By adding metal components and substrate land oxidation during heating, generation of solder balls is suppressed and insulation is maintained. That is, the insulation resistance between the opposing electrodes was 1 × 10 ¹² Ω or more after the voltage application humidity resistance test using the comb-shaped electrode substrate, that is, after the test at 60 ° C., 90% RH, DC16V application, 1000 hours standing.

Maintains wettability and solder joint strength. That is, 1000 cycles of the cycle of 30 minutes at −40 ° C. and 30 minutes at + 85 ° C. in the heat cycle test were used.
The peel strength of the QFP lead wire after 0.7 times is 0.7k
It was more than g.

[0033]

As is apparent from the above description, the non-cleaning cream solder of the present invention contains Sn, Pb, and
S containing Ag of 62: 36: 2 and having a particle size of 30 μm or more
n / Pb / Ag alloy 88-92 of the total weight of cream solder
% By weight, activator ethylamine hydrochloride, diethylamine hydrochloride, dimethylamine hydrochloride, trimethylamine hydrochloride, dichlorhexylamine hydrochloride, diethylamine hydrobromide, diclohexylamine hydrobromide, n-propyl Amine hydrochloride, di-n-propylamine hydrochloride, tri-n-propylamine hydrochloride, a single substance or a plurality thereof, with respect to 100% of the total flux,
0.01 wt% or more and less than 0.06 wt%, and fumaric acid, tartaric acid, stearic acid, tartronic acid,
Glutamic acid, isomalic acid, phthalic acid, and citric acid are contained alone or in plural, and the total flux weight is 100%, 0.10 wt% or more and less than 0.60 wt%, and rosin is 50 wt% or more. Therefore, it is possible to realize reflow soldering without cleaning, and to ensure high printability without sagging or bleeding when printing cream solder , and at the time of reflow soldering.
This has the effect of preventing the generation of solder balls and obtaining good reflowability and high reliability during reflow.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a reflow soldering process according to an embodiment of a non-cleaning cream solder of the present invention.

FIG. 2 is a flowchart showing a conventional reflow soldering process.

[Explanation of symbols]

 11 Cream Solder Printing Process 12 Adhesive Application Process 13 Component Mounting Process 14 Reflow Process 15 Appearance Inspection Process 16 Electrical Inspection Process

Continuation of the front page (56) Reference JP-A-2-290693 (JP, A) JP-A-4-66291 (JP, A) JP-A-4-94891 (JP, A) JP-A-4-100692 (JP , A) JP-A-55-81097 (JP, A) JP-A-6-170581 (JP, A) JP-A-6-262386 (JP, A) JP-A-55-54298 (JP, A) JP-B 6-75796 (JP, B2) Japanese Patent Publication 3-67795 (JP, B2) Translated by Masatake Takemoto et al. "Soldering in Electronics" (Sho 61-8-30), Nikkan Kogyo Shimbun, pp. 160-164

Claims (1)

(57) [Claims] 1. Sn, Pb, and Ag as metal components are 6
Sn / Pb with a particle size of 30 μm or more contained at 2: 36: 2
/ Ag alloy is contained in an amount of 88 to 92% by weight based on the total weight of the cream solder, and ethylamine hydrochloride, diethylamine hydrochloride, dimethylamine hydrochloride, trimethylamine hydrochloride, diclohexylamine hydrochloride, diethylamine hydrobromide, Dichlorohexylamine hydrobromide, n-
Propylamine hydrochloride, di-n-propylamine hydrochloride, tri-n-propylamine hydrochloride alone or in a plurality, 0.0% to 100% of the total flux.
Contains 1% by weight or more and less than 0.06% by weight, and uses fumaric acid, tartaric acid, stearic acid, tartronic acid, glutamic acid, isomalic acid, phthalic acid, or citric acid as a single or a plurality of fluxes to a total weight of 100%. On the other hand, 0.
A non-cleaning cream solder containing 10% by weight or more and less than 0.60% by weight and 50% by weight or more of rosin.