CONSTANT-TEMPERATURE-PULSED THERMOCOMPRESSION BALL BONDER SYSTEM

• US 3,602,684 A
• Filed: 10/27/1969
• Issued: 08/31/1971
• Est. Priority Date: 10/27/1969
• Status: Expired due to Term

• Current Assignee: Richard G. Friess
• Original Assignee: Richard G. Friess
• Inventors: Friess, Richard G.
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Smith, J. G.
• Application Number:
  US04/869,529
• Time in Patent Office: 673 Days
• Field of Search: 219/109,110,121,497,499,501 323/85 29/498 228/9
• US Class Current: 219/110
• CPC Class Codes: B23K 20/007 Ball bonding
• CPC Class Codes: B23K 2101/36 Electric or electronic devices
• CPC Class Codes: G05D 23/1913 delivering a series of pulses
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48 of an individual wire connector
• CPC Class Codes: H01L 2224/85 using a wire connector
• CPC Class Codes: H01L 2224/85203 Thermocompression bonding
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/85 using a wire connector wire bonding in general B23K20/004
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01014 Silicon [Si]
• CPC Class Codes: H01L 2924/01015 Phosphorus [P]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/0102 Calcium [Ca]
• CPC Class Codes: H01L 2924/01023 Vanadium [V]
• CPC Class Codes: H01L 2924/01027 : Cobalt [Co]
• CPC Class Codes: H01L 2924/01032 : Germanium [Ge]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01043 : Technetium [Tc]
• CPC Class Codes: H01L 2924/01046 : Palladium [Pd]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01055 : Cesium [Cs]
• CPC Class Codes: H01L 2924/01058 : Cerium [Ce]
• CPC Class Codes: H01L 2924/01059 : Praseodymium [Pr]
• CPC Class Codes: H01L 2924/01068 : Erbium [Er]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/12035 : Zener diode
• CPC Class Codes: H01L 2924/13034 : Silicon Controlled Rectifier [SCR]
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/19043 : being a resistor

Abstract

A pulsed thermocompression bonder is provided comprising a bonding or capillary tip and an electronics system to regulate the bonding or capillary tip temperature. A switch automatically provides a start bond signal when the operator lowers the bonder tip to bonding position to commence a bonding operation. The start bond signal activates an AC control circuit which causes current flow in a heating transformer until the tip is at predetermined bonding or operating temperature. The AC control circuit then stops current flow from being supplied to the heating transformer for a predetermined cooling time. In subsequent sequential periods iteratively the current is allowed to flow to the heating transformer until a predetermined temperature is reached and is cut off for the predetermined period of cooling. Adjustment means are provided to regulate offand-on current time so that once the predetermined desired temperature is reached an approximately constant desired temperature or flat heat curve is obtained until the end of the bonding operation. A sensing circuit connected to the bonder tip senses a rise in voltage due to an increase in tip resistance when the tip is being heated to the predetermined bonding temperature. After rising to desired predetermined temperature the sensing circuit (1) triggers a timing one shot multivibrator which sets and resets an on-off flip-flop circuit to regulate the heating cycle duration for a given bonding operation and (2) triggers an on-off one-shot multivibrator each time the predetermined temperature is reached in the heating cycle. The voltage outputs of the on-off flip-flop and one-shot multivibrator circuits are mixed and applied to the AC control circuit. The on-off one-shot multivibrator stops current flow to the heating transformer for the predetermined period upon each sensing of reaching the predetermined operating temperature during the bonding cycle. The on-off flip-flop as determined by the timing one shot multivibrator changes state and terminates the bonding cycle.

Claims

1. An apparatus for bonding conductive materials, said apparatus comprising;

a. a bonding tip adapted to be heated with an electrical current and having a resistance that increases with increases in temperature;

b. means for heating said bonding tip with current pulses of substantially constant peak amplitude whereby the voltage drop thereacross increases with increases in temperature;

c. means for sensing a predetermined peak voltage across said bonding tip which occurs whenever its temperature rises to a preselected operating temperature, and d. means responsive to said predetermined peak voltage for commencing a work cycle and for controlling said means for heating said bonding tip to maintain the temperature of said bonding tip substantially at said operating temperature during said work cycle.

2. The apparatus of claim 1 wherein said means responsive to said predetermined peak voltage additionally comprises apparatus operative over a range of input line voltage levels for regulating the peak amplitude of said current pulses employed to heat said bonding tip.

3. The apparatus of claim 2, said apparatus operative over a range of input line voltage levels for regulating the peak amplitude of said current pulses employed to heat said bonding tip further comprising:

a. a silicon-controlled rectifier circuit coupled to said means for heating said bonding tip, b. unijunction transistor means to control the output of said silicon-controlled rectifier circuit, c. means responsive to said input line voltage for selectively biasing off or biasing on said unijunction transistor means, and d. a potentiometer to regulate the peak voltage output of said silicon controlled rectifier circuit, e. means to supply a regulated voltage to said potentiometer, f. means to supply line voltage to said potentiometer, and g. means responsive to line voltage amplitude for providing a proper bias time on said unijunction transistor means thereby to regulate said peak amplitude of said curRent pulses.

4. The apparatus of claim 3 wherein said means for selectively biasing off or biasing on said unijunction transistor means includes:

a. means responsive to said line voltage for generating a series of unidirectional regulated pedestals concurrent with the alternations of said line voltage, and b. integrating apparatus responsive to said regulated pedestals and connected to said unijunction transistor means thereby to bias said unijunction transistor means on at a selected point during each of said regulated pedestals.

5. The apparatus of claim 3 wherein said means for providing a proper bias time on said unijunction transistor means includes:

means responsive to increases in the line voltage amplitude for delaying said selected point during each of said regulated pedestals, and means responsive to decreases in the line voltage amplitude for advancing said selected point during each of said regulated pedestals thereby to maintain the peak amplitude of said current pulses substantially constant for variations in line voltage amplitude.

6. Apparatus for maintaining a bonding tip which changes electrical characteristics with a change in temperature at an approximately constant preselected operating temperature over a predetermined cycle comprising:

a. means responsive to an AC line voltage for generating a series of electrical pulses across said bonding tip, said electrical pulses constituting successive latter portions sine wave alternations, and b. means responsive to successive changes in electrical characteristic of said bonding tip corresponding to said bonding tip reaching said preselected operating temperature for arresting the generation of said electrical pulses thereacross for successive predetermined time intervals thereby to maintain said bonding tip substantially at said preselected operating temperature.

7. The apparatus of claim 6, said apparatus further comprising apparatus responsive to the initial change of said successive changes in electrical characteristics corresponding to said bonding tip reaching said preselected operating temperature for initiating timing of a heating cycle.

8. The apparatus of claim 6 additionally including means responsive to the amplitude of said AC line voltage for regulating the duration of said successive latter portions of sine wave alternations during said predetermined cycle in a manner to maintain a substantially constant peak current flow through said bonding tip whereby said changes in electrical characteristics are indications of changes in temperature thereof.

9. The apparatus of claim 1, said means for sensing said predetermined peak voltage across said bonding tip further including means to adjust the sense level of said predetermined temperature.

10. Apparatus for providing a constant temperature over a predetermined period for an element which changes resistance with change in the temperature, said apparatus comprising:

a. first means for sensing the momentary resistance of said element, b. second means responsive to said first means for actuating a timing cycle of operation, c. third means for increasing the temperature of said element, d. fourth means for controlling the activation of said means for increasing the temperature of said element, e. fifth means responsive to said second means for actuating said fourth means for controlling for the duration of said timing cycle, f. sixth means responsive to said first means for sensing the momentary resistance of said element corresponding to the temperature of said element upon change from a predetermined desired for initiating a time duration of disabling restoration of said element to said desired temperature, g. seventh means for combining the output from said sixth means for initiating said time duration of disabling restoration of said desired temperature and the output of said fifth means, and h. eighth means for coupling said seventh means for combiniNg to said fourth means for controlling thereby to enable activation of said fourth means for controlling in the presence only of an output from said seventh means.

11. A pulsed thermocompression bonder system comprising;

a. a bonding means for applying heat upon contact with electrical elements on a substrate, b. a sense circuit responsive to a physical characteristic representative of the temperature of said bonding means, c. a heating transformer coupled to said bonding means for applying heat thereto, d. adjustable timing pulse forming means responsive to said sense circuit, e. a control circuit having a transistor for providing selectively substantial and unsubstantial current flow in accordance with the output of said sense circuit for controlling current flow in said heating transformer, f. a first source of input line voltage coupled to said control circuit, g. a second source of relatively constant amplitude input voltage pulses, h. said control circuit comprising a transistor which is normally conductive in nonheating condition of said transformer, i. a bleeder resistor arrangement disposed between said first source of voltage pulses and ground, j. means responsive to fluctuations in said first input source voltage for applying a voltage accordingly to said bleeder resistor arrangement, k. said bleeder resistor arrangement comprising a potentiometer and a plurality of resistors, I. peak voltage regulating means comprising a diode coupled in series with said first source of line voltage for regulating current flow therethrough corresponding to deviation of line voltage from said first source, m. a resistor connected in series with said diode at one end and connected at its other end to a junction point in said bleeder arrangement thereby providing voltage corresponding to the change in source voltage at the slider arm of said potentiometer, n. unijunction diode means responsive to said control circuit voltage at the slider arm of said potentiometer for providing a pulse output, o. means for coupling said pulse output when said transistor is providing said at most unsubstantial current flow to said transformer for applying heat to said bonding means, p. a capacitor disposed across said transistor grounded at one end and at the other end coupled to the sliding arm of said potentiometer, q. means for coupling a base of said transistor to said transformer comprising a pulse transformer and a current-rectifying circuit, r. said bleeder resistor arrangement further comprising a resistance path from said second source of voltage pulses to the emitter of said unijunction transistor, such that upon the firing point of said unijunction transistor being exceeded, a connection is made between said transformer, the base of said unijunction transistor coupled to said transformer and the emitter of said unijunction resistor for providing current to said heating transformer for heating said bonding means, s. an on-off flip-flop circuit responsive to said timing pulse forming means, t. an on-off one-shot multivibrator, u. means for simultaneously applying output from said on-off flip-flop and from said on-off one-shot multivibrator to the base of said transistor, said transistor being responsive only to combined output of said on-off flip-flop plus said on-off one-shot multivibrator such that when appropriate output of both are applied simultaneously the base of said transistor is grounded, said transistor having a common emitter for providing nonconduction in the presence of appropriately combined output from said on-off flip-flop and said one-shot multivibrator, such that the absence of conduction through said transistor enables the emitter of said unijunction transistor to be charged positively for enabling pulse output to said pulse transformer.

12. Apparatus operable to heat at least a section of a workpiece to a temperature within a predetermined temperature range aNd to substantially maintain said section within said range for a predetermined period comprising:

a. means for transmitting heat to said workpiece section formed of material having a detectable state of a physical characteristic functionally related to the temperature of said means for transmitting heat, b. means to detect said state and to provide corresponding signals whenever said state indicates the temperature of said material is at an upper extremity of said temperature range, c. means responsive to alternating current line voltage activatable to heat said means for transmitting heat, d. control means to regulate the initiation, peak and duration of operability of said last-named means activatable to heat said means for transmitting heat, and e. means responsive to the initial corresponding signal to permit continued activation of said control means during said predetermined period and to arrest activation of said control means for selected intervals of time commencing within said predetermined period whenever said corresponding signal is provided thereby to allow the temperature of said material to cool the lower extremity of said temperature range.

13. The apparatus operable to heat a section of a workpiece as defined in claim 12 wherein said control means to regulate the initiation, peak and duration of operation of said means activatable to heat said means for transmitting heat further comprises means responsive to line voltage fluctuations for modifying the phase angle of output conduction thereby to maintain constant peak-to-peak current output.