KR100526243B1 - Method for Determinning Solderability - Google Patents

Abstract

The present invention relates to a method for measuring the cyclic voltametry (CV) curve of a plating liquid and using the same to evaluate the solderability of a material such as a chip component in a non-destructive manner. It is intended to provide a purpose that is.

The present invention measures the CV curve of the plating liquid, and the measured CV curve has a current density peak of 4.4 mA / cm 2 to -2.8 mA / cm 2, and when the cross-over does not occur, the plating liquid is acceptable. The main point is a solderability evaluation method including determining that the soldering property is imparted, and otherwise determining that the plating solution imparts unacceptable solderability.

According to the present invention, by measuring the CV curve of the plating liquid to evaluate the solderability in a non-destructive manner, not only can the evaluation time and cost be reduced, but also the effect of more smoothly maintaining the plating liquid can be obtained.

Description

Method for Determinning Solderability

The present invention relates to a method for evaluating solderability when soldering is applied to a material such as a chip component to give solderability, and then soldering. It is about how to evaluate sex in a non-destructive way.

Chip components are small electronic components manufactured on the basis of ceramic bodies and metal electrodes, and include MLCCs, resistors, inductors, and dielectric filters.

 These chip parts are used as core parts of electronic devices such as computers, mobile communication devices, and home appliances, and are mounted on PCB boards by soldering external electrodes of the chip.

At this time, Sn or Sn-Pb alloy plating is finally applied to the external electrode of the chip. In particular, Sn-Pb alloy plating is finer than tin plating or lead plating, and finer in corrosion resistance and solderability. It is widely used in the field.

Therefore, the solderability of the external electrode during soldering performed when the external electrode is mounted on the PCB substrate may be an important factor in determining whether the electronic component is defective.

On the other hand, as a method of evaluating the solderability of chip components (external electrodes), a method of evaluating the solderability in a destructive manner such as reflow or flow is known.

However, in the case of evaluating the solderability by the above method, there is a problem that not only takes a lot of time but also a lot of cost.

The present inventors conducted research and experiments to solve the above-mentioned problems of the prior art, and proposed the present invention based on the results. The present invention measures the CV (Cyclic Voltametry) curve of the plating solution and uses the same. By evaluating solderability in a non-destructive manner, it is intended to provide a method for evaluating solderability faster and more economically.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

In the present invention, in order to impart solderability to a material, soldering is performed using Sn or Sn-Pb plating solution containing at least one additive, and then soldering is performed.

Saturated Calomel Electrode (KCl) was used as a reference electrode, a carbon electrode was used as a counter electrode, and a copper plate of 1 cm 2 was used as a working electrode, and CV (Cyclic) was used. Measuring a CV curve with respect to the plating liquid under a condition of a scan range of -1000 mV to 1000 mV using voltametry); And

When the CV curve measured as described above has a current density peak of 4.4 mA / cm 2 to -2.8 mA / cm 2, and no cross over occurs, it is determined that the plating solution gives acceptable solderability. And determining that the plating liquid imparts unacceptable solderability when the current density peak deviates from the current density peak and / or crossover occurs. .

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

As shown in Figure 1, the solder plating process for imparting solderability to a material such as a chip component is usually a loading step, a cleaning step, an activation step. Ni Plating, Predip, Plating for Imparting Solderability in Sn or Sn-Pb Plating Solution (Sn or Sn-Pb Plating), Neutralization, Hot Washing Step D. I Rinse) and drying.

At least one additive is usually added to the Sn or Sn-Pb plating solution.

The additives include grain refiners, levelers, surfactants, brighteners, stress reducers, and the like.

The present inventors studied the effect of the type and concentration of the additive in the Sn or Sn-Pb plating solution on the alloy ratio and the structure (microstructure) of the plating layer and the correlation between the solderability thereof. It was found that it affects the microstructure of, and based on this, the method of evaluating the solderability by the CVS curve of the plating liquid was completed.

The present invention is preferably applied to a technique of performing solder soldering using Sn or Sn-Pb plating solution containing at least one additive to impart solderability to a material, and then soldering.

The material may be a chip component such as a multi-layer ceramic capacitor (MLCC), a resistor, an inductor, and a dielectric filter.

However, the present invention is not limited to the above-described chip parts, and may be applied to any of the solder-providing platings using at least one additive-containing Sn or Sn-Pb plating solution.

The leveler is a component that is added to smooth the irregularities of the surface of the material while increasing the plating thickness by increasing the current density of the concave area by increasing the current density of the concave area by acting as a barrier material of metal ions due to precipitation on the convex portion of the material surface. It affects the throwing power and gloss.

The particle micronizing agent acts as a nucleus of precipitation and affects smoothness, glossiness, etc. as a component added to refine the particles of the plating layer.

The present inventors confirmed that when an appropriate amount of the leveling agent and the particle fine agent are added, the particles do not aggregate and exist independently, and the particles become fine and dense.

On the other hand, when the leveling agent was added alone, the plating film was not dense, and when the particle micronizing agent was added alone, it was confirmed that the particles were large and agglomerated.

In addition, when an appropriate amount of the leveling agent and the surfactant were added, it was observed that the particles did not aggregate and exist independently, and the particles became fine and dense.

It was confirmed that the leveling agent further affects particle refinement, and the surfactant further affects densification.

In order to evaluate the solderability of the plating liquid according to the present invention, it is necessary to measure the CV curve for the plating liquid.

The CV curve for the plating liquid is a saturated calomel electrode (KCl) as a reference electrode, a carbon electrode as a counter electrode, and a copper plate having a 1 cm 2 area as a working electrode. Measure the scan range using -1000mV ~ 1000mV using CV.

The scan rate during the measurement of the CV curve is preferably set to 100 mV / sec.

Next, when the CV curve measured as described above has a current density peak of 4.4 mA / cm 2 to -2.8 mA / cm 2, and no crossover occurs, it is determined that the plating solution gives acceptable solderability. This is described below.

On the other hand, it is known that the material to be soldered is present independently of the particles, without being agglomerated, and has excellent solderability in the case of having a fine and dense plating layer.

Therefore, if the structure of the plating layer can be accurately predicted, the solderability can be evaluated based on the prediction result.

In the present invention, the structure of the plating layer can be accurately predicted by analyzing the CV curve of the plating liquid, and the solderability is evaluated based on the prediction result.

The plating layer solder-plated using a plating liquid having a CV curve satisfying the current density peak range of the present invention described above does not have agglomeration of particles and exists independently, and the particles have a fine and dense structure.

Therefore, the plated layer plated using a plating liquid having a CV curve satisfying these conditions shows excellent solderability in subsequent soldering.

On the other hand, when the current density peak of the CV curve measured as described above is out of the range of 4.4 mA / cm 2 to -2.8 mA / cm 2 and / or crossover occurs, the plating solution cannot accept the solderability. In other words, the current density peak of the CV curve measured as described above is out of the range of 4.4 mA / cm 2 to -2.8 mA / cm 2 and crossover occurs. In this case, it is determined that the plating liquid imparts unacceptable solderability.

The plating layer plated using a plating liquid having a CV curve outside the current density peak has large, aggregated, and dense structures.

Therefore, the plating layer plated using a plating liquid having a CV curve satisfying these conditions will have poor solderability in subsequent soldering.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example)

CV curves were measured for Sn-Pb plating solutions containing additives as shown in Tables 1 and 2 below, and the results are shown in FIGS. 2 and 3, and were plated with this plating solution using SEM (Scanning Electron Microscope). The plating layer was observed and the result is shown to FIG. 4 and FIG.

When measuring the CV curve, a saturated caramel electrode (KCl) was used as the reference electrode, a carbon electrode was used as the counter electrode, and a copper plate of 1 cm 2 area was used as the working electrode, and the scan speed was 100 mV / up to 1000 mV at a scan range at room temperature. worked in sec.

At this time, the plating liquid was stirred at a speed of 500 rpm / min using a magnetic bar.

Particle Micronizer (ml / l) Leveling agent (ml / l) 0 40 60 80 100 120 150 0 0-4 0-6 0-8 0-10 0-12 0-15 10 1-0 1-4 1-6 1-8 1-10 1-12 1-15 20 2-0 2-4 2-6 2-8 2-10 2-12 2-15 30 3-0 3-4 3-6 3-8 3-10 3-12 3-15 40 4-0 4-4 4-6 4-8 4-10 4-12 4-15 50 5-0 5-4 5-6 5-8 5-10 5-12 5-15 60 6-0 6-4 6-6 6-8 6-10 6-12 6-15

In Table 1, "1-0" and the like are symbols representing test plating solutions to which a particle micronizing agent and a leveling agent are added.

Sulfactant (ml / l) Leveling agent (ml / l) 0 40 100 150 0 - L40-S0 - L150-S0 5 L0-S5 - - - 20 - - L100-S20 - 30 L0-S30 - - L150-S30

In Table 2, "L0-S5" and the like are symbols representing test plating solutions to which a surfactant and a leveling agent are added.

In Fig. 2, (a) shows the CV curve of the plating liquid to which the particle micronizing agent and the leveling agent are not added, (b) and (c) shows the plating liquid to which only the leveling agent is added (test solution '0-4' in Table 1, and '0-15') shows the CV curve, (d) and (e) shows the CV curve of the plating solution (test solution '1-0' and '6-0' of Table 1) to which only the particle micronizing agent was added , (f) shows the CV curve of the plating solution (test solution '4-10' in Table 1) to which the particle micronizing agent and the leveling agent were added at optimum conditions, and (g) the particle micronizing agent and the leveling agent was added at a high concentration. The CV curve of the plating liquid (test solution '6-15' in Table 1) is shown.

In FIG. 3, (a) shows the CV curve of the plating solution to which the surfactant is added at a high concentration (test solution 'L0-S30' in Table 2), and (b) the plating solution to which the leveling agent is added at the high concentration (see Table 2 (C) shows the CV curve of the test solution 'L150-S0'), (c) shows the CV curve of the plating liquid (test solution 'L100-S20' of Table 2) to which the surfactant and the smoothing agent were added optimally, and (d) CV curve of the plating liquid (test liquid 'L150-S30' of Table 2) to which surfactant and leveling agent were added at high concentration is shown.

In FIG. 4, (a) shows a microstructure photograph of a plating layer plated using a plating liquid without a particle micronizing agent and a smoothing agent, and (b) and (c) shows a plating liquid with only a smoothing agent added (the test solution of Table 1). The microstructure photograph of the plating layer plated using '0-4' and '0-15') is shown, and (d) and (e) shows the plating solution (Test solution '1-0 in Table 1) to which only the particle finer is added. ', And' 6-0 ') shows a microstructure photograph of the plating layer plated using, and (f) shows the plating solution (test solution' 4-10 'in Table 1) to which the particle micronizing agent and the smoothing agent were added under optimum conditions. Microstructure photograph of the plated layer plated using, and (g) microstructure photograph of the plated layer plated using the plating solution (test solution '6-15' in Table 1) to which the particle micronizing agent and the leveling agent were added at a high concentration. Indicates.

In Figure 5, (a) and (b) shows a microstructure photograph of the plating layer plated using the plating solution (test solution 'L0-S5' and 'L0-S30' of Table 2) to which only the surfactant is added, (c ) And (d) show the microstructure photograph of the plating layer plated using the plating solution (Test solution 'L40-S0' and 'L150-S0' of Table 2) to which only the smoothing agent was added, and (e) shows surfactant and smoothing The microstructure photograph of the plating layer plated using the plating solution I added as the optimum condition (test solution 'L100-S20' in Table 2) is shown, and (f) shows the plating solution to which the surfactant and the leveling agent are added at a high concentration (Table 2). The microstructure photograph of the plating layer plated using the test solution 'L150-S30').

As shown in FIG. 2, in the case of a plating liquid in which no particle finer and a smoothing agent are added, or only one of the leveling agent and a fine particle is added, the current density peak value of the CV curve is 4.4 mA / cm 2 to -2.8 mA. It can be seen that out of the current density peak range of / cm 2 and crossover occurs.

On the other hand, in the case of the plating liquid in which the particle finer and the smoothing agent are optimally added or the high concentration is added, the current density peak value of the CV curve satisfies the current density peak range of 4.4 mA / cm 2 to -2.8 mA / cm 2 and also crosses over. It can be seen that does not occur.

As shown in FIG. 3, in the case of a plating solution in which one of the surfactant and the smoothing agent is added at a high concentration, the current density peak value of the CV curve is outside the current density peak range of 4.4 mA / cm 2 to -2.8 mA / cm 2. It can also be seen that crossover occurs.

On the other hand, in the case of the plating solution in which the surfactant and the smoothing agent are added under optimum conditions or at high concentrations, the current density peak value of the CV curve satisfies the current density peak range of 4.4 mA / cm 2 to -2.8 mA / cm 2 and crosses. It can be seen that no over occurs.

As shown in FIG. 4, when no additive is added [FIG. 4 (a)], the tissue grows dendrite and is very nonuniform, and only a smoothing agent is added [FIG. 4 (b) and (c)], the more the addition amount increases, the more dense the coating film, and when only the particle micronizing agent [Fig. 4 (d) and (e)] there is no difference according to the increase in the addition amount, but the particles compared to the case of adding only the leveling agent Is large and clustered.

On the other hand, when the leveling agent and the particle fine agent are optimally added (FIG. 4 (f)), the particles do not aggregate and exist independently, and are fine and dense, and when the surfactant and the leveling agent are added at a high concentration. Figure 4 (g) can be seen that there is no significant difference from the case of optimally added.

As shown in Fig. 5, when only the surfactant is added [Fig. 5 (a)], the structure is enclosed, but when an excessive amount of surfactant is added [Fig. 5 (b)], some particles are not present. It can be seen that when it is formed, and only the leveling agent is added ((c) and (d) of FIG. 5), the aggregated state is released and clear particles are formed.

In the case of (d) of FIG. 5, an excessive amount of the leveling agent is added to the particle size of about 1 μm, causing particle fineness, but it may be understood that it is not as dense as in FIG. 5 (c).

In other words, it can be considered from the above result that the leveling agent affects the particle micronization and the surfactant affects the densification.

On the other hand, when the leveling agent and the surfactant are added under optimum conditions (Fig. 5 (e)), the particles do not aggregate and exist independently, and are fine and dense, and the leveling agent and the surfactant are added at a high concentration. In the case of [FIG. 5 (f)], it can be seen that there is no difference from the case of addition under optimum conditions.

As described above, the plating layer plated by using a plating solution in which the current density peak value of the CV curve satisfies the current density peak range of 4.4 mA / cm 2 to -2.8 mA / cm 2 and no cross over occurs. It can be seen that the silver particles do not aggregate but exist independently and have a fine and dense structure.

That is, according to the present invention, the structure of the plating layer can be predicted in advance by analyzing the CV curve of the plating liquid.

On the other hand, when particle | grains do not aggregate and exist independently and have a fine and dense plating layer, it is known that solderability is excellent.

Therefore, according to the present invention, the structure of the plating layer can be predicted in advance by analyzing the CV curve of the plating liquid, and the solderability can be evaluated based on the prediction result.

In addition, in the case of using the present invention, the plating bath composition can be maintained so that the desired CV curve can be obtained, thereby stabilizing the plating solution, thereby providing excellent solderability.

As described above, the present invention can reduce the evaluation time and cost by measuring the CV curve of the plating liquid and evaluating the solderability in a non-destructive manner, and also has the effect of more smoothly maintaining the plating liquid. .

1 is a process chart showing a conventional solder plating process

2A to 2G are graphs showing the CV curve of the Sn-Pb plating solution according to the addition and the amount of the particle finer and the smoothing agent.

3A to 3D are graphs showing the CV curve of Sn-Pb plating solution according to the addition of the surfactant and the leveling agent and the amount thereof

FIG. 4 is a SEM (Scanning Electron Microscope) photograph of a plating layer plated using a Sn-Pb plating solution in which addition and fineness of the particle finer and the smoothing agent are changed.

FIG. 5 is a SEM photograph of a plating layer plated using Sn-Pb plating solution in which a surfactant and a smoothing agent are added and its amount is changed.

Claims (2)

In the method of soldering using a Sn or Sn-Pb plating solution containing at least one additive to impart solderability to the material, and then soldering, Saturated Calomel Electrode (KCl) is used as a reference electrode, a carbon electrode is used as a counter electrode, and a copper plate of 1 cm 2 is used as a working electrode, and CVS (Cyclic) is used. Measuring a cyclic voltametric (CV) curve with respect to the plating liquid under a condition of a scan range of -1000 mV to 1000 mV using voltametry; And When the CV curve measured as described above has a current density peak of 4.4 mA / cm 2 to -2.8 mA / cm 2, and no cross over occurs, it is determined that the plating solution gives acceptable solderability. And determining that the plating liquid imparts unacceptable solderability when the current density peak is out of the current range and when the crossover occurs in any one of the cases. Solderability Evaluation Method The method of evaluating solderability according to claim 1, wherein the additive is one or two or more selected from the group of additives including a particle finer, a surfactant, and a leveling agent.