Flexible circuit board bonding pad windowing manufacturing process using flexible ink

Abstract

A flexible circuit board bonding pad windowing manufacturing process using flexible ink comprises the following steps of: printing a solder mask, and locally printing an area needing to use ink on an etched FPC (Flexible Printed Circuit); curing: pre-curing the flexible ink subjected to silk-screen printing through low-temperature pre-baking; laser depth control is carried out, the pre-cured flexible ink is removed through laser depth control burning, a bonding pad needing to be pasted is exposed, and then windowing is carried out; covering film pasting, wherein the covering film away from the ink printing area is completely hollowed out, and the covering film is pasted to the two faces of the FPC circuit board; and curing, namely curing the printed flexible ink and the attached cover film at high temperature. According to the hardness difference between the ink and copper, the flexible ink is cut through laser in a depth-controlled mode to achieve the purpose of windowing, and the integrity of the bonding pad can be guaranteed while the ink is removed; the method is mainly suitable for the circuit board in a small-spacing dense bonding pad windowing area, and solves the technical problem that the traditional covering film and ink process cannot meet the requirement of precise FPC circuit board processing.

Description

technical field [0001] The invention relates to the field of printed circuit board technology, in particular to a process for making a window of a flexible circuit board pad using flexible ink. The burning window method solves the problem of insufficient spacing between the window covering film and the ink in the precision solder joint area, and improves the application of flexible circuit boards and rigid-flex circuit boards in high-density, small-package devices. Background technique [0002] Like the rigid-flex circuit board, the flexible circuit board has the characteristics of three-dimensional installation. In the flexible circuit board, the surface of the conductor is protected by an insulating cover film. Before the surface cover film is attached, the welding area of ​​the pad will be opened with a machine or a laser, and then the cover film will be opened manually or by automatic equipment. The cover film after opening the window is attached to the surface of the F...

AI Technical Summary

Problems solved by technology

[0004] In this processing process, exposure alignment deviation and film expansion and contraction tolerance are the keys to affect the precision of pad window opening. At the same time, development is to remove unpolymerized ink during exposure through 40%-60% sodium carbonate. In this chemical The side erosion effect of 1.5mil on one side will be produced in the process of potion, and there is a risk of falling off the bridge when the solder bridge between IC and IC is less than 4mil, so that there will be a short circuit phenomenon in the soldering process of packaging IC. Therefore, use The flexible ink process is also unable to adapt to the production of all small-pitch FPC circuit boards

[0005] With the miniaturization and thinning of electronic devices, the required printed circuit boards are becoming more and more precise. In FPC circuit boards, the surface insulation layer is protected by polyimide cover film or flexible photosensitive ink; however, Due to the limitations of the two technologies and processing capabilities, traditional processing methods are no longer suitable for the production of such products in dense window-opening and patching areas and IC packaging FPC circuit boards.

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