JPH0227831B2 - PURINTOHAISENBAN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a printed wiring board, and more particularly to a printed wiring board on which surf-ace mount type electronic components are mounted.

Conventional technology To mount surf-ace-mount electronic components such as flat pack ICs (FICs) on printed wiring boards (PWBs), the components are mounted on predetermined mounting positions on the PWB using an automatic component mounting machine, and then Solder the leads of the component to the land flatly using an automatic soldering device.

A guide hole for positioning is provided at the end of the PWB, and the positioning pin of the mounting machine is inserted into the guide hole. The installation position of each part is input into the program based on the position of the guide hole, and the loading machine places the part at the position specified in the program.

However, the land pattern where components are to be mounted actually deviates somewhat from the programmed position. This is mainly due to misalignment of a film mask for forming a resist pattern in the PWB manufacturing process, and differs for each PWB. On the other hand, this type of electronic component, especially FIC, has narrow terminal or lead spacing in order to increase mounting density, and if there is a large error in land position, each lead of the mounted component will be positioned away from the corresponding land. The soldering may be incomplete, or it may bond to printed wiring running between leads or adjacent lands.

Problems to be Solved by the Invention In order to deal with the positional deviation of the land as described above, the land pattern is viewed with a television camera prior to mounting the component, and the error from the programmed position is calculated by image processing, and the mounting position is determined. It is possible to calculate the offset value, but since cream solder is usually applied to mounting or component lands,
Image recognition is difficult.

Means for Solving the Problems In order to solve the above problems, the present invention provides a special marking land that does not require applying cream solder to a predetermined position on a land pattern of a printed wiring board or a set of component lands. By detecting this marking land position through image processing prior to mounting the electronic component, an offset value is provided to correct the positional error of the land pattern relative to the mounting reference position (for example, PWB positioning hole). do.

Embodiment FIG. 1 shows the relative positional relationship of a marking land according to an embodiment of the present invention with respect to an FIC 1 and a set of component lands or land patterns 2 on which it is to be mounted. In FIG. 1, marking lands are provided at points A and B, respectively. One marking land position A is located on a straight line l passing through the tips of each of the first lead rows 1a to 1e and at a predetermined distance k from the center line m of the first lead 1a.
(for example, 5 mm) apart. For the other marking land position B, a perpendicular line p is drawn at a point c on the straight line l that is a distance k away from the center line n of the rear end lead 1e of the first lead row. It is located at the point where it intersects with the straight line g passing through each lead end. Standardizing the position of the marking land in this way is convenient for image processing. Further, each component land 2a to 2n is set to be directly below the corresponding lead 1a to 1n, respectively. Therefore, as can be understood, the positions of the marking lands A and B also have a predetermined positional relationship with respect to the component land pattern 2.

FIG. 2 shows an example of the shape and dimensions of the marking land. The marking land according to the present invention is image-recognized using a television camera prior to component mounting, but at that time, it must not be mistaken for a general component land, printed wiring, through hole, or the like. In this embodiment, the marking land 3 is formed square, which is also advantageous in determining the center positions A, B. Further, around the marking land 3, a pattern in which no conductor is provided and a printing prohibited area 4 are set. The dimension S of the marking land 3 should be set to an appropriate value, for example 1.5, because if it is too large, the viewing angle of the camera will expand and the image will be distorted, and if it is too small, the etching accuracy will decrease and it will be difficult to determine the center positions A and B. Selected as mm. Further, the dimension T of the prohibited area 4 is selected to be 2.5 mm, for example.

Marking lands are formed simultaneously with component lands and other printed wiring in the PWB manufacturing process. In other words, copper foil or other metal foil is placed on a base material such as glass epoxy that has positioning holes or guide holes formed in advance by NC processing.
A PWB according to the present invention may be produced by forming a resist printing pattern including a marking land pattern thereon and then performing an etching process. At this time, if an error occurs in the component land pattern due to misalignment of the mask film, a similar error occurs in the corresponding marking land in the vicinity.

When mounting surf ace mount type electronic components such as FIC on the PWB obtained in this way, cream solder is applied to the component lands, but not to the marking lands. A small television camera is attached to the loading machine, and before loading the parts into the predetermined mounting position or land position, the marking land positions A and B are determined using ordinary image processing technology.
is detected or determined and guide hole position 5 (first
An offset value for correcting the error in the position of the component land pattern with respect to the position shown in FIG. When the mounting machine places the component at the corrected mounting position obtained from the programmed position and the offset value, each lead will ride almost directly above the corresponding component land as shown in FIG.

Although the preferred embodiments of the present invention have been described above, various modifications and changes are possible within the scope of the technical idea of the present invention. For example, the number of marking lands may be one or three.
Two or more marking lands may be provided, or they may be provided inside the component land, and the criteria for the placement position of the marking land can be changed in various ways depending on the type of PWB or mounted component. Further, the shape and dimensions of the marking land may be variously changed depending on the resolution of the television camera, image processing conditions, etc.

Effects of the Invention As described above, according to the present invention, in a printed wiring board on which surface-mounted electronic components such as FICs are mounted, there is a marking land that has little error in relative position to the component land and is not coated with cream solder. This increases the accuracy of image processing for correcting errors in component land positions and enables accurate component mounting.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the arrangement position of a marking land according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the shape and dimensions of the marking land. 1... Flat pack IC (FIC), 1a to 1n...
...Lead, 2a-2n...Parts land, A, B...
...Marking land position, 3...Marking land, 4...Pattern and printing prohibited area, 5...
Guide hole position.

Claims (1)

[Scope of Claims] 1. A surf-ace mount type electronic component is placed at a predetermined position on a set of component lands on which an automatic component mounting machine is to be mounted, by image processing prior to mounting the electronic component. A printed wiring board provided with a marking land that provides an offset value for correcting an error in the position of the set of lands with respect to a mounting reference position by detecting the position. 2. The printed wiring board according to claim 1, wherein the mounting reference position is a position of a printed wiring board positioning hole with respect to the automatic component mounting machine. 3. The printed wiring board according to claim 1, wherein the marking land is formed into a rectangular shape, and a predetermined area around the marking land is a prohibited area where no conductor is provided. 4. The printed wiring board according to claim 1 or 3, wherein a plurality of the marking lands are provided at different predetermined positions.