JPH0479396A - Assembling method for electronic device - Google Patents

Abstract

PURPOSE:To prevent electronic parts from falling off from a printed-wiring board and prevent mounting positions from slipping off surely, by mounting the halved electronic parts on the obverse and reverse of a double printed-wiring board separately, and by reflow-soldering in block these electronic parts mounted on the double board. CONSTITUTION:In the state of turning a mounting face I of a printed-wiring board 1 upward, soldering pastes 4 and bonding agents 5, are applied to the places of the mounting face I, at which electronic parts are mounted. After chip parts 2 and flat package-shaped parts 3, etc., are mounted on these places, the ultraviolet rays are projected on the bonding agents 5, and they are hardened. Then, the printed-wiring board 1 is turned from its obverse side to its reverse side. In the state wherein the mounting face I of parts being mounted completely turns downward and a mounting face II of parts being not mounted turns upward, the soldering pastes 4 are applied to the places to mount the electronic parts on the mounting face II. Continually, different kinds of parts 2, 3 are mounted on these places. Then, leaving the mounting face II turned upward, the printed-wiring board 1 is carried into a reflow furnace. Therein, the electronic parts mounted on both the obverse and reverse are reflow-soldered in a batch.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention targets hybrid integrated circuits, and is a method for mounting and soldering electronic components such as chip components and flat package components on both sides of a double-sided printed wiring board. The present invention relates to a method for assembling an electronic device.

[Conventional technology]

As mentioned above, as a method of assembling electronic devices by mounting electronic components on both the front and back sides of a double-sided printed wiring board,
Conventionally, this has been carried out using the following method.

Method 1: Completely divide the component mounting process into one side of the printed wiring board, and first, apply solder paste with one side of the printed wiring board facing up, attach electronic components, and perform reflow soldering. , Next, the printed wiring board is turned over, and electronic components similar to those described above are mounted on the upper surface side where electronic components are not mounted.

Reflow soldering is used to assemble electronic devices.

Method 2: First, apply solder paste, mount electronic components, and reflow solder with one side of the printed wiring board facing up, and then place the electronic components to be mounted on the remaining side of the printed wiring board. Solder by hand using a soldering iron, or apply adhesive to the component mounting position to temporarily fix the electronic component, and then solder by flow soldering with the component mounting surface facing down. I do.

(Problems to be Solved by the Invention) By the way, the conventional assembly method described above has the following problems in terms of product quality.

In other words, as described in method 1 above, in the method of reflow soldering electronic components on each side of a printed wiring board twice, the electronic components mounted in the previous process are subjected to thermal stress due to solder reflow. This may cause deterioration of the electronic components and deterioration of the physical properties of the solder joints.In addition, when soldering the electronic components, the parts may remelt during solder reflow in the subsequent process, causing the parts to deteriorate. There is a risk that the position may deviate from the normal position. Furthermore, as described in Method 2 above, after electronic components are mounted on one side of the printed wiring board, electronic components to be mounted on the remaining surface are manually soldered. A similar problem also occurs with the flow soldering method.

The present invention has been made in view of the above points, and it is possible to solder electronic components mounted on the front and back sides of a printed wiring board in a single process without repeatedly applying thermal stress associated with soldering to the same electronic components. It is an object of the present invention to provide a method for assembling an electronic device that enables batch reflow soldering.

[Means for Solving the Problems] In order to solve the above problems, in the assembly method of the present invention, first, in the first component mounting step, one side of the printed wiring board is turned upward and the component mounting position on the surface is set. After applying solder paste and adhesive to the core, electronic components are temporarily attached to the core part and the adhesive is cured.In the second component attachment process, components are mounted on the top surface with the printed wiring board turned upside down. After applying solder paste to the position, electronic components are mounted on the core part, and the next reflow soldering is a process.The printed wiring board is held in the position of the second component mounting process and carried into the reflow oven, and the front and back sides are The electronic components mounted on both sides shall be soldered all at once.

(Function) According to the above assembly method, since the electronic components mounted on one side of the printed wiring board in the first component mounting process are fixed in the predetermined mounting position with adhesive, the printed wiring board can be turned over. In the second component mounting process, which is carried out in the process, and the subsequent reflow soldering, electronic components will not fall off the printed wiring board during the process. Since the parts are reflow soldered all at once, the thermal stress applied to the electronic parts is reduced to 1.
It only takes once.

(Example) Embodiments of the present invention will be described below based on the drawings.

Note that FIG. 1 shows an assembly process diagram of an electronic device according to the present invention, and FIG. 2 shows an assembly state diagram of the electronic device.

First, in Fig. 2, 1 is a double-sided printed wiring board, 2 is a chip component, 3 is a flat package type component, 4 is a solder paste, and 5 is an adhesive (ultraviolet curing type adhesive). An electronic device is constructed by mounting various electronic components on both the front and back sides of the L. Here, the second
The lower surface of the printed wiring board 1 in the figure is the mounting surface 1. The top surface is the mounting surface ■.

Next, the assembly process of the electronic device shown in FIG. 2 will be explained based on FIG. 1. First, in the first component mounting step, with the mounting surface I of the printed wiring board 1 facing upward, solder paste 4.
Then apply adhesive 5 to this position and chip parts 2. After the flat package type component 3 and the like are attached, the adhesive 5 is irradiated with ultraviolet rays and cured. Note that it is preferable that a printing method be used to apply the solder paste 4, and that the adhesive 5 be applied from an adhesive dispenser through a nozzle.

Next, the printed wiring board I is turned over, and the second component mounting step is carried out with the mounting surface I on which components have been mounted facing downward and the mounting surface (2) on which one component is not mounted facing upward. In this second component mounting step, solder paste 4 is applied in accordance with the mounting position of the electronic component, and then various components 2.3 are mounted at this position.

The first point mentioned above. After the second component mounting process is completed, the printed wiring board 1 is carried into a reflow oven with the mounting surface (■) facing upward, and the electronic components mounted on both the front and back sides of the printed wiring board 1 are assembled here. Perform reflow soldering and then clean to remove flux residue.

(Effects of the Invention) As described above, according to the assembly method of the present invention, after mounting electronic components on the front and back sides of a double-sided printed wiring board, these electronic components are assembled on both sides. Since reflow soldering is used, the electronic components only need to be subjected to thermal stress once.In addition, the second component mounting process and reflow soldering are performed on the mounting surface of the printed wiring board facing downward during the process. In the first component mounting process, the electronic components are fixed in place with adhesive, which reliably prevents the electronic components from falling off the printed wiring board or shifting the mounting position. can.

It has been confirmed that by adopting the assembly method of the present invention, it is possible to achieve a reduction of approximately 10% in the number of steps and approximately 30% in cost compared to conventional assembly methods.

[Brief explanation of drawings]

FIG. 1 is an assembly process diagram of an embodiment of the present invention, and FIG. 2 is an assembly diagram of an electronic device. 1: double-sided printed wiring board, 2: tinop parts 3: flat package type parts,
4: Solder paste, 5: Adhesive.

Claims (1)

[Claims] 1) A method for assembling electronic devices in which electronic components are mounted and soldered on both the front and back sides of a double-sided printed wiring board, in which one side of the printed wiring board is faced up and soldering is performed at the component mounting position on that side. After applying the paste and adhesive, the first component mounting process involves temporarily attaching the electronic components to the area and hardening the adhesive, and then applying solder paste to the component mounting position on the top surface with the printed wiring board turned upside down. After coating, there is a second component mounting process in which electronic components are mounted on the parts, and while the printed wiring board is held in the position of the second component mounting process, the printed wiring board is carried into a reflow oven and the front and back sides are removed. A method for assembling an electronic device characterized by comprising a reflow soldering process in which electronic components mounted on both sides are soldered all at once.