JPH0736954B2 - Substrate heating device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for controlling a temperature distribution on a substrate having partially different heat capacities.

Conventional technology Printed circuit boards (hereinafter referred to as “P
It is abbreviated as “board”. ) In the technology trend of high-density mounting of electronic components on the top, the soldering method of elements using a reflow furnace is being adopted. Here, the main heating method will be described by taking the soldering method using the reflow furnace as an example. In the reflow method, the element is placed in the conventional molten solder bath.
Unlike the flow method of dipping a plate, cream-like solder composed of fine solder particles and paste is applied to a predetermined position of a P plate, and then an element is placed and heated and melted by infrared rays to be soldered.

A general reflow furnace is shown in FIG. On the conveyor 1 which moves at a constant speed v, the P plate 2 on which the elements are placed is heated by the heating element 3 which continues to generate a constant amount of heat. The first half A of the furnace is the preheating part, which usually heats the P plate around 150 ° C. Next, at the portion B, a temperature of about 250 ° C. is generated and soldering is performed, and then the product is cooled by fan blowing or the like and taken out. In Figure 4,
The structure of the conventional heating element is illustrated. 4 is a heat insulating material, 5 is a reflector, and 6 is a heating cable. The heat generated from the heating cable 6 is transferred to the P plate 2 via the radiation plate 7,
It is given mainly in the form of radiant heat. The reflection plate 5 is the radiation plate 7
It is provided in order to efficiently flow the heat to the side while suppressing the heat flow to the extra portion.

Problems to be Solved by the Invention However, as a practical problem, a temperature distribution occurs on the P plate due to the difference in heat capacity between the elements on the P plate and the non-uniformity of the arrangement, and in some cases, the temperature of the element may be different. There is a place where soldering cannot be done because it does not rise completely. On the other hand, some elements, such as resin-molded parts, may melt, deform, or cause thermal destruction when the temperature is too high for soldering. In this way, elements that require heating and elements that do not prefer heating are mixed in the same P plate, and it is necessary to solder these elements at the same time.

In view of the above-mentioned problems, the present invention provides a substrate heating device that significantly improves temperature controllability on a P plate by a heater and achieves high-efficiency heating, thereby improving soldering defects and ensuring stable element quality. It is provided.

Means for Solving the Problems In order to solve the above problems, the substrate heating apparatus of the present invention is
A plurality of heating elements each having a variable heating mechanism that operates under the control of the outside, each of which has a minute gap, and a heating element that is adjacent to the heating element and covers one side thereof. And a gap between the reflector and the heating element, and
A heat insulating material arranged in the vicinity of the back surface of the reflection plate; a radiation plate arranged in close proximity so as to cover the surface of the heat generating element opposite to the contact surface with the reflection plate; A heat-sensitive device arranged substantially in the direction of the normal of the heating surface of the substrate arranged close to the element and the radiation plate, and numerically processing the output signal of the heat-sensitive device, and the result thereof being the heating element And a control means for inputting to the control unit.

Operation The present invention has the above-mentioned configuration to change the heating strength of each heating element block according to the magnitude of the heat capacity of the element on the P plate.
The temperature monitoring result is controlled momentarily based on the result of mathematical processing, a flexible temperature distribution is given to the heat source side, and uniform soldering is performed at the same time.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a substrate heating apparatus in an embodiment of the present invention, 2 is a substrate to be heated, 11 is a heat insulating material, and 12 is a reflector. Reference numeral 13 is a heat generating portion composed of an assembly of heat generating element 14. 15 is a radiation plate. As shown in the enlarged view of FIG. 2, the heating element 14 has a heating cable 16 independently embedded therein, and the heating elements adjacent to each other are kept in a heat-insulated state by the heat insulating member 11a. ing. In FIG. 1, 17 is a control unit for independently controlling the temperature output of the heating element 14, 18 is an infrared thermometer (heat sensitive device) for accurately measuring the temperature distribution on the substrate 2, 19
Is a control means for arithmetically processing the data from the infrared thermometer 18 and inputting the temperature correction amount to the control unit 17. The substrate heating method configured as above will be described below. FIG. 5 shows a flow chart showing an outline of software of the control means. The software contains the temperature setting conditions to be given first, and the control unit 17
The heating elements 14 each generate heat through the above and start heating the substrate 2. After an appropriate time, the measurement result of the temperature distribution on the substrate 2 by the infrared thermometer 18 is input to the control means 19, and the corrected calorific value is calculated in response to the input. The above calculation is performed by adding heat transfer and heat radiation from the atmosphere to the Fourier's heat conduction equation in consideration of energy storage conditions. As a result of the calculation, temperature conditions to be applied to the heating element 14 are obtained in the next step, and the information is sent to the control unit 17. As a result, the temperature condition is reset, the infrared thermometer confirms that the P plate has been heated to the soldering temperature, and the heater power off signal is output. In the case of the present embodiment, the relative position between the substrate 2 and the heating element 14 basically does not move, but there may be relative movement depending on the control programming method. Further, it is needless to say that the temperature monitor on the substrate 2 does not necessarily need to use an infrared thermometer, and for example, a thermocouple may be installed at a representative point or may be obtained analytically.

Note that, so far, the description has been given by taking the reflow soldering of the substrate as an example, but it goes without saying that this content can be applied to any general substrate heating.

EFFECTS OF THE INVENTION As described above, according to the present invention, a substrate having a heat capacity distribution can be controlled and heated in a short time with high accuracy.
Furthermore, the heating amount can be continuously and sequentially changed for different types of substrates depending on the programming method. Further, it is possible to save space in the structure of the furnace as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a perspective view of a substrate heating apparatus according to the first embodiment of the present invention, and FIG. 2 is a partially enlarged view of the first embodiment of the present invention.
FIG. 3 is a plan view of a substrate heating apparatus in a conventional example, FIG. 4 is a partially enlarged view of the same, and FIG. 5 is a flow chart of control software in the above embodiment. 11 ... Insulation material, 12 ... Reflector, 14 ... Heating element, 15 ...
… Radiation plate, 17 …… Control unit, 18 …… Heat sensitive device, 19 …… Control means.

Claims (1)

[Claims] 1. A plurality of heating element elements each having a variable heating mechanism which operates under the control of the outside and each of which has a minute clearance, and in proximity to the heating element element, A reflecting plate arranged so as to cover the one side thereof, a gap between the heating element and a heat insulating material arranged in the vicinity of the surface of the reflecting plate, and a contact surface of the heating element with the reflecting plate. A radiant plate placed close to cover the opposite surface,
A heat-sensitive device arranged on the heating surface of the substrate arranged in the vicinity of the heating element and the radiation plate in a substantially square direction, and an output signal of the heat-sensitive device is processed numerically, and the result is A substrate heating apparatus, comprising: a control unit for inputting to a control unit of a heating element.