JPH05226541A - Control of plating device - Google Patents

Abstract

PURPOSE:To provide stable quality and also to enable unmanned operation for an extended hours by inputting various parameters required for desired plating and calculating optimum energy condition through fuzzy inference based upon them so as to operate a plating device under optimum energy condition. CONSTITUTION:A fuzzy calculator 6, based upon input data consisting of plating area S(cm<2>), temperature initial value T( deg.C), plating thickness d(mum), concentration initial value C(g/l), plating hours t(Sec), pulse ON time initial value tauON (mSec) and pulse one cycle(msec), outputs optimum conditions on current value, pulse ON time, pulse OFF time and temperature. Before activation, good quality area is measured at an experiment, and from the measuring result, a representative 4-point good quality value (intermediate value of good quality area between the upper limit and lower limit) is taken to calculate a coefficient by simultaneous equations further to calculate an approximate expression. Based upon this, optimum conditions are calculated using fuzzy inference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a plating apparatus, and more particularly to a method for controlling plating using fuzzy theory.

[0002]

2. Description of the Related Art A lead frame for a semiconductor device such as an IC or an LSI is made of gold, silver or the like at the tip portion of an inner lead or a semiconductor element or a semiconductor element mounting portion in order to favorably perform die bonding or wire bonding. Noble metal plating is applied. When plating the lead frame, it is necessary to clean and activate the surface of the base material in order to improve the quality of the plated layer formed.
Therefore, the plating apparatus is composed of a plurality of tanks including a pretreatment tank such as a degreasing tank, a pickling tank, and a water washing tank, and a plating tank, and a strip-shaped or short-shaped lead frame is sequentially transported to perform desired plating. It has become so.

In order to form a desired plating layer, it is necessary to set the conditions in consideration of conditions such as temperature, current value, plating time, plating solution concentration, plating thickness and plating area. Since the plating solution concentration and other conditions change as the plating progresses, conventionally, the plating solution state such as the plating solution concentration is monitored every predetermined time, and the plating state of the lead frame after plating is further inspected. It is necessary to adjust the current value and plating solution concentration to the optimum values while performing analysis and analysis, and unattended operation for a long time is impossible. There was a problem that a considerable amount of time had to be spent on setting.

Further, as the device becomes smaller, thinner, and highly integrated, the lead width, lead spacing, and plate thickness used in this device also become smaller, while different types of lead frames are used depending on the application. It has been designed and is in the age of so-called small-quantity, high-mix production, and it is necessary to set conditions according to the product when plating.

Therefore, new conditions must be set every time the product type changes, and a great deal of labor is required for control.

[0006]

As described above, conventionally, when controlling the plating, the concentration of the plating solution and the like are monitored every predetermined time, and the plating state of the lead frame after plating is inspected and analyzed. However, it is necessary to adjust the current value, plating solution concentration, etc., and unattended operation for a long time is not possible, and if there are changes in the settings of various conditions, it takes a considerable time to set new optimum conditions. There was a problem of having to spend.

The present invention has been made in view of the above circumstances, and provides a control method of a plating apparatus capable of obtaining stable quality even when various conditions such as temperature change and enabling unmanned operation for a long time. The purpose is to provide.

[0008]

In the first aspect of the present invention, therefore, an electric field is applied to the surface of a conductor and the surface of the conductor is immersed in a solution containing the metal ions to discharge the metal ions on the surface of the conductor to form a metal film. When performing electrolytic plating to form,
Various conditions necessary for performing desired plating are input, optimal energy conditions are calculated by fuzzy reasoning, and the plating apparatus is started based on these conditions.

In the second aspect of the present invention, when an electric field is applied to the surface of the conductor and the surface of the conductor is immersed in a solution containing the metal ions, the metal ions are discharged on the surface of the conductor to perform electrolytic plating for forming a metal film. , The various conditions necessary for performing the desired plating are input and activated, and the state of the plating solution that changes over time is monitored, and the optimum energy condition is determined by fuzzy reasoning according to the state of the plating solution. Is calculated and these conditions are fed back to the plating apparatus.

In the third aspect of the present invention, a pulse is applied to the surface of the conductor, and the surface of the conductor is immersed in a solution containing metal ions to discharge the metal ions on the surface of the conductor to perform electrolytic plating for forming a metal film. The temperature of the plating solution,
Input various conditions necessary for performing desired plating such as plating time, plating current, pulse on / off ratio, etc., start the plating equipment based on this, and monitor the state of the plating solution that changes over time. According to the state of the plating solution, fuzzy inference is used to calculate the optimum conditions such as the solution temperature of the plating solution, the plating time, the plating current, and the pulse on / off ratio, and these conditions are fed back to the plating apparatus. ..

[0011]

According to the first method, various conditions such as the optimum current value and the optimum pulse ratio are calculated by using fuzzy inference, and the plating apparatus is started based on the calculated conditions. Even when the setting is changed, stable quality can be automatically obtained by setting the plating time, the pulse current period, the plating area, and the plating thickness without spending time for setting new optimum conditions.

According to the second method, various conditions such as the optimum current value and the optimum pulse ratio are calculated by using fuzzy reasoning, and the conditions are fed back to the plating apparatus. Therefore, the plating time and the pulse current are calculated. Period, plating area,
Only by setting the plating thickness, stable quality can be automatically obtained even if the temperature or the concentration of the plating solution changes.

According to the third method, it is possible to automatically and easily obtain a plating layer of stable quality.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

The plating apparatus used in the method of the embodiment of the present invention includes a plating tank 1 as shown in the block diagram of FIG.
A liquid temperature detector 2 for detecting the liquid temperature of the plating bath 1, a heater 3 for heating the plating liquid in the plating bath 1, a concentration detector 4 for detecting the silver ion concentration of the plating liquid, and a plating current are supplied. Input various conditions necessary for performing desired plating such as the plating power source 5, the plating solution temperature, the plating time, the plating current, and the pulse on / off ratio, and start the plating apparatus based on these conditions. The state of the plating solution that changes over time is monitored, and in accordance with the state of the plating solution, fuzzy inference is used to calculate optimum conditions such as the plating solution temperature, plating time, plating current, and pulse on / off ratio. The present invention is characterized by being provided with a fuzzy arithmetic unit 6 which feeds back these conditions to the heater 3 and the power source 5, etc., and the silver plating layer M is formed on the lead frame as shown in FIG. 11 is a die pad, 12 is an inner lead, 13 is a support bar, 14 is an outer lead, and 15 and 16 are side bars.

FIG. 3 shows a flow chart of this plating apparatus.

Here, the fuzzy arithmetic unit 6 has a plating area S (cm ² ), an initial temperature value T (° C.), and a plating thickness d (μ
m), initial concentration C (g / l), and plating time t (s
ec), the pulse ON time initial value τ _ON (msec), and the pulse 1 cycle τ (msec) from the input data to output the optimum values of the current value, pulse ON time, pulse OFF time, and temperature. It has become.

Prior to driving, the good product range was first measured by experiments, and from this measurement result, representative four good product values (intermediate value between the upper limit and the lower limit of the good product range) were taken, and the coefficient was calculated by the simultaneous equations. Then, an approximate expression is calculated. Then, it is divided into eight parts according to the three conditions of temperature, concentration and pulse-on time, and the closest one of the approximate expressions is applied to each part as shown in FIG. When not applicable, weight the formula and create a new formula. When inputting, take the minimum value of the antecedent weight of each rule and multiply by the value of each expression of the antecedent. Then, the sum of the values of the consequent part of the eight rules is divided by the sum of the weights of the antecedent parts to obtain an inference value.

First, the weight W of the plated metal is calculated by multiplying the plating thickness d, the plating area s, and the density of the metal (step 100).

Next, the plating time t is set to a rectangular wave period τ (mse
Calculate the pulse number n by dividing by c) (step 2
00).

Further, by dividing the plating metal weight W by the pulse number n (step 300), the metal weight W'consumed per pulse is calculated.

These values and the initial value of the pulse on time τ _ON
Then, the required current value I is calculated according to Faraday's law (I = W '* F / (τ _ON * eq)) (step 10
2) Next, the temperature concentration and the initial value of τ _ON are input to the optimum current value calculation block, and the first inferred value I ₀ is calculated (step 001).

For example, T = 55 ° C., concentration C = 65 g /
It is assumed that l, τ _ON = 4 (ms) is input. At this time, the membership function of temperature, concentration, and on-time is as shown in FIG. 5, and from this figure and FIG. 4, an approximate expression as shown in FIG. 6 is obtained, and from this, current density = {224 × (1 / 2) ＋224 × (1/3) ＋252 × (1/2) ＋185 × (1/3) ＋242.4 × (0) ＋222.5 × (0) ＋185 × (0)} / (1/2 ＋ 1 / It is possible to obtain 3 + 1/2 + 1/3 + 0 + 0 + 0 + 0) = 224.6 A / dm ² .

The optimum current value I calculated by the optimum current value calculation block (fuzzy arithmetic processing unit 6) in this way
_It is determined whether ₀ is smaller than the maximum current value of the device (step 103). If not, an alarm is generated and the device is stopped (step 104). On the other hand, when it is smaller, it is further judged whether or not the required current value I calculated by Faraday's law is smaller than the optimum current value I ₀ (step 105), and τ _ON is subtracted from the initial value τ _ON by Δτ _ON. (Step 106).

On the other hand, the required current value I is the optimum current value I
When it is not smaller than _{0, the} magnitude relation is further checked (step 107). When it is equal, this value is directly output to the plating power source 003 as the plating current value, and when the required current value I is larger than the optimum current value I _0. is a value obtained by adding only .DELTA..tau _oN to an initial value tau _oN the tau _oN (step 10
8).

In this way, τ _ON is increased / decreased, and it is further determined whether or not the pulse _ON time τ _ON exceeds the upper limit τ _ON ^H and the lower limit τ _ON ^L, which are good products (step 109). ), When the lower limit τ _ON ^L is exceeded, the temperature T is lowered by 1 ° C. (step 110). On the other hand, when the upper limit τ _ON ^H is exceeded, the temperature T is increased by 1 ° C. (step 111). The temperature value T thus obtained is stored in the memory (step 112), and is input again to the optimum current value calculation block for recalculation. Then I = I ₀ become until then recomputing the optimal current value, I = output of I the plating power source when a I _0, the pulse on-time of τ _ON, τ-τ _ON
Is the off time and T is the output of the temperature control block 002.

On the other hand, when neither the upper limit τ _ON ^H nor the lower limit τ _ON ^L is exceeded, the value of the pulse on-time τ _ON is stored in the memory (step 113) and an instruction is given to the plating power source 003.
The plating power supply is driven with this value.

The surface of the silver plating layer thus formed is extremely smooth and has a good film quality.

In the lead frame thus formed, the semiconductor chip is connected to the die pad 11, the resin is sealed through the wire bonding process, and the side bar 1
5, 5 and 16 are cut off, the outer leads 14 are bent for surface mounting, positioned on the wiring pattern of the mounting substrate, and the mounting substrate side is heated to fix the same.

The concentration of the plating tank 005 is updated as a value obtained by subtracting the weight used for each plating operation for each shot. Alternatively, a concentration detector may be used for each measurement.

In this way, the outputs of the plating power source and the heater are controlled to be optimal for the apparatus, and unattended high quality plating can be obtained.

Further, since the calculation is performed as it is even when the conditions are changed, the conditions can be set unattended in a short time, and an excellent plating layer having a constant plating thickness and quality can be obtained.

In the above embodiment, fuzzy control was used for both initial setting and condition management during plating, but it may be used only for initial setting.

[0034]

As described above, according to the present invention, various conditions such as the optimum current value and the optimum pulse ratio are calculated by using fuzzy reasoning, and the conditions are fed back to the plating apparatus. By simply setting the plating time, the pulse current period, the plating area, the plating thickness, etc., stable quality can be obtained even if the temperature or the concentration of the plating solution changes.

[Brief description of drawings]

FIG. 1 is a block diagram of a plating apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a lead frame obtained by the device of the embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the plating apparatus according to the embodiment of the present invention.

FIG. 4 is a diagram showing an example of an approximate expression used in an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a membership function used in the embodiment of the present invention.

FIG. 6 is a diagram showing an inference operation according to the embodiment of the present invention.

[Explanation of symbols]

 001 Optimum current value calculation block 002 Temperature control block 003 Plating power supply

Claims (3)

[Claims] 1. A desired plating is carried out when electrolytic plating is performed by applying an electric field to the surface of a conductor and immersing the solution in a solution containing metal ions to discharge the metal ions on the surface of the conductor to form a metal film. A method for controlling a plating apparatus, characterized in that various conditions necessary for carrying out are input, based on this, an optimum energy condition is calculated by fuzzy reasoning, and the plating apparatus is activated under the optimum energy condition. .. 2. A desired plating is carried out when electrolytic plating is performed by applying an electric field to the surface of the conductor and immersing it in a solution containing metal ions to discharge the metal ions on the surface of the conductor and form a metal film. Input the various conditions necessary to perform the operation, start the plating equipment, monitor the state of the plating solution that changes over time, and calculate the optimum energy condition by fuzzy reasoning according to the state of the plating solution. Then, the condition is fed back to the plating apparatus. 3. A solution of a plating solution for applying electrolysis to form a metal film by applying a pulse to the surface of a conductor and immersing the solution in a solution containing metal ions to discharge the metal ions on the surface of the conductor. Input various conditions necessary for performing desired plating such as temperature, plating time, plating current, pulse on / off ratio, etc., and start the plating equipment based on this, and further determine the state of the plating solution that changes with time. The optimum conditions such as the solution temperature of the plating solution, the plating time, the plating current, the on / off ratio of the pulse, etc. are monitored and monitored according to the state of the plating solution by fuzzy reasoning, and the conditions are fed back to the plating apparatus. A method for controlling a plating apparatus, characterized in that