Method for welding circuit board

Abstract

The invention provides a method for welding a circuit board. The method comprises the following steps: (1) checking weldability of a PCB welding disc, and coplanarity of an element, wherein a PCB comprises a plane A and a plane B and is designed as a pinhole skip printing template; (2) cleaning the circuit board, and applying a welding paste to elements inserted into through holes in the plane A by using the pinhole skip printing template or an injector; (3) performing plane A pasting, and welding the plane A by using a fixing jig; (4) pasting an element welding paste to a printing surface ofthe plane B; (5) printing the plane B with a hole element welding paste by using the pinhole skip printing template; (6) performing plane B pasting, and inserting through hole elements into the planeB; (7) welding the plane B by using the fixing jig; (8) checking whether unqualified welding points are resulted or not, and performing welding replenishing in time; (9) after welding is completed, checking whether the PCB has distortion or not as a qualification inspection standard, analyzing reasons of distortion, overcoming defects, performing welding again, and discarding products which defects which cannot be overcome.

Description

technical field [0001] The invention relates to the field of welding testing, in particular to a welding method for PCB boards. Background technique [0002] Printed circuit board (PCB) is the support of circuit components and devices in electronic products. The quality of PCB welding has a great impact on electronic products. With the rapid development of electronic technology, the density of PCB is getting higher and higher, and there are more and more layers, and there are mixed circuit boards containing surface mount components and through-hole components at the same time. More and more complex, there are several methods in the prior art: [0003] (1) Manual welding: use manual operation, use electric soldering iron or other heating tools to melt the welding wire to realize the connection between component pins and PCB board pads, manual welding has less investment, quick product changeover, mature technology, and requirements for welding personnel Low, flexible weldin...

AI Technical Summary

Problems solved by technology

[0003] (1) Manual welding: use manual operation, use electric soldering iron or other heating tools to melt the welding wire to realize the connection between component pins and PCB board pads, manual welding has less investment, quick product changeover, mature technology, and requirements for welding personnel Low, flexible welding, wide application range, in theory, any two or more metal contact points that need to be connected by solder can use this method to complete the electrical connection, without special tooling and fixtures, suitable for all surface mount parts , through-hole parts, cables, wire harnesses, terminal posts, etc.; however, it also has the disadvantages of unstable welding quality and difficult control, low efficiency, high manufacturing cost, and is only suitable for the production of small batches of multi-variety products.

[0004] (2) Wave soldering, used in the traditional assembly process, first uses surface mount technology (SMT, Surface Mount Technology) to complete the soldering of surface mount devices, and then uses through hole insertion technology (THT, Through Hole Technology) to insert through holes Components, and finally the assembly of the printed board is completed by wave soldering. However, this soldering process has high requirements for the design and layout of the PCB. First, the B-side components cannot be placed with higher-height surface mount components. The placement of components needs to separate surface mount components from through-hole components as much as possible, otherwise defects such as missing solder, less tin or poor solder joint wetting are prone to occur, and the one-time investment and use costs of wave soldering equipment are extremely high

[0005] (3) Selective soldering, which belongs to a special form of wave soldering, can tailor welding parameters for each soldering point. The equipment is divided into two types: circuit board mobile soldering furnace and circuit board stationary soldering furnace. It is flexible in use, high in welding quality, bold in initial investment and low in trial operation cost, and can solve the problem of soldering of devices with large heat capacity and the problem of soldering through-hole rate when soldering through-hole components on extra-thick circuit boards, but the welding speed is slow and the production efficiency is low.

[0006] (4) Preform solder, punch the rolled solder strip into the desired size, and then make it into different shapes and sizes according to requirements, print solder on the insertion part during assembly, and mount the preformed solder sheet in the solder paste , and then insert through-hole components for reflow soldering. The advantage is that it solves the problem of the amount of solder paste applied, and the disadvantage is that it is difficult to carry out high-density assembly

[0007] (5) Welding robot, which can automatically send tin to weld electronic components, can use traditional soldering iron or non-contact laser welding. The welding principle is similar to manual welding. Therefore, the welding speed is slow and the production efficiency is low. Special design is required. The disadvantages of the fixture show

[0008] It can be seen that there is currently no technology that can simultaneously complete the high-quality soldering of mixed circuit boards composed of through-hole components and SMD components. It lacks follow-up quality inspection procedures and remedial measures, and there is no difference in components Types of targeted welding, the effect is not good

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