JP2013004789A - Reflow device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflow device in which nonuniformity of temperature distribution can be reduced without increasing the tact time, by additionally providing a structure of reducing the nonuniformity of temperature distribution on the surface of a substrate by performing local heating and cooling.SOLUTION: The reflow device having a plurality of heating zones where a printed-wiring board is heated while being conveyed comprises a conveyor which conveys the printed-wiring board, a plurality of local heating units provided, respectively, for the heating zones in order to heat a part of the printed-wiring board locally, and a heated object passage detection sensor which detects passage of the printed-wiring board. The local heating units can be driven individually so that contact and noncontact with the printed-wiring board can be controlled, and the temperature of the local heating units can be controlled individually.

Description

  The present invention relates to a reflow apparatus used for mounting electronic components on a printed wiring board (hereinafter abbreviated as a board). Furthermore, the present invention relates to a reflow apparatus having a mechanism for reducing non-uniformity of temperature distribution in the substrate surface when the substrate is heated by the reflow apparatus.

  In recent years, the size of a substrate used in a substrate manufacturing process has been increased due to multiple impositions for the purpose of cost reduction and the appearance of large products.

  A conventional reflow apparatus has a structure having heating zones divided into a plurality of areas, and each zone is heated at a set temperature. The substrate to be heated is heated at an arbitrary temperature profile (temperature and time experienced by the substrate). Since the heating zones divided into multiple areas may be set to different temperatures, in that case, when the substrate passes through the boundary between adjacent zones, the temperature difference between the heating zones causes Heating is performed by heat transfer from the high temperature zone side of the substrate to the low temperature heating zone side in addition to heating by the atmosphere in the heating zone. For this reason, there is a difference in the warming of the first and last substrates with respect to the substrate transport direction, and the temperature profiles are different even within the same substrate surface. A substrate having a small size with respect to the size of each heating zone is not a problem, but a large substrate having a size extending over two or more heating zones causes a difference in temperature profile depending on the portion of the same substrate. Due to this difference in temperature profile, local unmelting of the solder occurs in the low temperature portion, and conversely, the thermal damage of the substrate increases in the high temperature portion.

  In order to solve this problem, Patent Document 1 includes a mechanism for locally blowing a gas having a temperature different from the atmosphere in the heating zone to the substrate and adjusting the temperature of the portion of the substrate on which the gas is blown and the surrounding temperature. . However, if a gas with a different temperature is blown onto the substrate, the temperature of the atmosphere in the heating zone changes, and the next substrate cannot be flowed until it returns to the set temperature, greatly increasing the tact time. The problem remains.

Japanese Patent Application No. 2001-567023

  The present invention has been made in view of the above problems, and by locally heating and cooling, by adding a structure that reduces the non-uniformity of the temperature distribution on the substrate surface, without increasing the tact time, An object of the present invention is to provide a reflow apparatus capable of reducing non-uniformity of temperature distribution.

As means for solving the above-mentioned problems, claim 1 of the present invention is a reflow apparatus having a plurality of heating zones for heating while conveying a printed wiring board,
At least a conveyor that conveys the printed wiring board, a local heating unit that locally heats a portion of the printed wiring board, a plurality of local heating units provided for each heating zone, and the printed wiring board A heated object passage detection sensor for detecting that the vehicle has passed,
The local heating unit is a reflow apparatus characterized in that contact and non-contact with the printed wiring board can be controlled individually and can be controlled individually.

  The invention according to claim 2 is characterized in that control of contact and non-contact of the local heating unit to the printed wiring board is performed according to a signal from the heated object passage detection sensor. This is a reflow apparatus.

  The invention according to claim 3 is the reflow apparatus according to claim 1 or 2, wherein the local heating unit is a rod-shaped body, and is in contact with an object to be heated in a cross section of the rod-shaped body.

  The reflow apparatus according to the present invention can reduce the temperature reflow profile unevenness in the plane substrate surface without significantly increasing the tact time by adding a temperature compensation structure.

Schematic showing an example of the basic configuration of a conventional reflow device Schematic showing an example of the basic configuration of the reflow apparatus of the present invention Schematic showing an example in which the rod-shaped local heating unit of the present invention operates and is in contact with an object to be heated Schematic which shows an example of the cross section of the rod-shaped local heating unit of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 relate to an embodiment of the present invention, FIG. 1 is a schematic diagram illustrating an example of the basic configuration of a conventional reflow apparatus, FIG. 2 is a schematic diagram illustrating an example of the basic configuration of the reflow apparatus of the present invention, and FIG. These are examples in which the reflow device of the present invention is operating, and are schematic views showing an example in which the bar-shaped local heating unit of the present invention operates and is in contact with an object to be heated. FIG. 4 is a schematic view showing an example of a cross section of the rod-shaped local heating unit of the present invention.

  FIG. 1 shows an example of a conventional reflow apparatus. In FIG. 1, 1 is a heater, 2 is a cooling fan, 3 is a conveyor for conveying a substrate, and 4 is a small substrate. FIG. 2 shows an example of the reflow apparatus according to the present invention, in which 5 is a local heating unit and 6 is a heated object passage detection sensor. FIG. 3 shows an example in which the local heating unit 5 of the present invention is heating the large substrate 7.

  FIG. 4 is an example of the rod-shaped local heating unit 5 of the present invention, and is a view of a surface that comes into contact with an object to be heated. The local heating unit 5 of the present invention is composed of a plurality of rod-shaped members, and these rod-shaped members come into contact with the substrate to adjust the substrate temperature. The local heating unit 5 needs to have a structure that does not hinder the airflow from the heater 1 of the reflow device. The form of the local heating unit is not limited to this, and for example, the airflow from the heater 1 flows in. A shape having a grid-like opening may be used.

The operation of the reflow apparatus configured as described above will be described below.
The substrate 4 on which the semiconductor element is mounted is transported in the reflow apparatus by the substrate transporting conveyor 3 from the entrance of FIG. 2 (at the same position as the entrance shown in FIG. 1). The small substrate 4 is heated from above and below by the heater 1 and the joint portion after the flux activity, the removal of the oxide film on the metal surface, the joining of the semiconductor element and the substrate through the solder metal by melting the solder metal, and the cooling by an arbitrary temperature profile Is formed.

As one embodiment of the present invention, when a large substrate 7 conveyed through the reflow apparatus by the substrate conveying conveyor 3 from the entrance of FIG. 3 passes under the heated object passage detection sensor 6, it corresponds to the conveying speed. As a result, the local heating unit 5 rises and can be brought into contact with the large-sized substrate 7, and local heating or cooling can be performed. The local heating unit 5 can set the temperature one by one. The individual temperature setting of the local heating unit 5 is performed so as to reduce the non-uniformity of the temperature profile of the substrate 4 to be processed depending on the size of the substrate 4 processed by the reflow apparatus and other specifications.

  As a specific temperature condition, the heating zone for preheating for activating the flux performs heat treatment at 150 to 170 ° C. for 30 to 120 seconds. The heating zone in which the next soldering is performed performs heat treatment at 250 ° C. to 255 ° C. for 10 seconds to 20 seconds.

At this time, since the size of the substrate to be processed is longer than the heating zone in which soldering is performed, the portion of the protruding substrate 4 becomes low in temperature when it protrudes into the heating zone in which preheating is performed in the previous stage. The heating unit 5 is brought into contact with the substrate 4 and heated. Further, even when the substrate 4 does not protrude, if the temperature of the substrate 4 is not uniform in one heating zone, the local heating unit 5 is similarly brought into contact with the substrate 4 in order to approach the set temperature. Heat or cool.
By doing in this way, the nonuniformity of the temperature profile of each part of one board | substrate was reduced conventionally. As a result, it has become possible to reduce soldering defects caused by insufficient flux activation and local unmelted solder generation without changing the tact time.

  The arrangement of the local heating unit 5 is not limited to the lower side of the large substrate 7 and may be installed on the upper side or the upper and lower sides. Alternatively, the local heating unit 5 may be installed on one side or both sides in the vertical direction. Also good.

  Further, as an embodiment of the local heating unit 5 of the present invention, a temperature adjustment mechanism is built in the local heating unit 5, and a heating wire is used as an example of the temperature adjustment mechanism. Can do. As an example of the temperature adjustment mechanism, the local heating unit 5 includes a liquid circulation conduit, and the temperature of the local heating unit 5 can be adjusted by circulating the liquid therethrough. Further, the substance circulating in this conduit is not limited to a liquid but may be a gas. Moreover, a heat pipe can be used as an example of the mechanism for temperature adjustment. Further, a Peltier element can be used as an example of a temperature adjustment mechanism.

DESCRIPTION OF SYMBOLS 1 Heater 2 Cooling fan 3 Substrate conveyance conveyor 4 Small substrate 5 Local heating unit 6 Heated object passage detection sensor 7 Large substrate

Claims (3)

A reflow apparatus having a plurality of heating zones for heating while conveying a printed wiring board,
At least a conveyor that conveys the printed wiring board, a local heating unit that locally heats a portion of the printed wiring board, a plurality of local heating units provided for each heating zone, and the printed wiring board A heated object passage detection sensor for detecting that the vehicle has passed,
The reflow apparatus characterized in that the local heating unit can be individually driven so as to be able to control contact and non-contact with the printed wiring board and can be individually controlled in temperature.   2. The reflow apparatus according to claim 1, wherein the control of the contact and non-contact of the local heating unit with the printed wiring board is performed according to a signal from the heated object passage detection sensor.   The reflow apparatus according to claim 1 or 2, wherein the local heating unit is a rod-shaped body, and is in contact with an object to be heated in a cross section of the rod-shaped body.

Images