Method for gold removal and tin coating of L-shaped welding terminal of QFN packaging device
A technology for soldering terminals and packaging devices, which is used in semiconductor/solid-state device manufacturing, electrical components, circuits, etc., and can solve the problem of poor tinning effect on the side welding surface, poor coplanarity, and difficulty in controlling the uniformity of tinning on the side welding surface. issues of sex
Active Publication Date: 2021-05-18
国营芜湖机械厂
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Problems solved by technology
This technology is not suitable for tinning of L-shaped soldering terminals. There are two reasons: first, the tinning method can only be tinned on the bottom soldering surface, and the side soldering surface cannot be tinned.
The second is that the amount of tin on the soldering terminal cannot be controlled, and the coplanarity is not good. When the amount of tin on the bottom soldering surface is uneven, it will affect the subsequent solder paste printing process
The shortcomings of this technology are: only by lengthening the opening length of the stencil on the bottom welding surface, the liquid flow infiltrates the side welding surface when the solder paste melts, and it is difficult to control the uniformity of the tinning on the side welding surface during reflow, and there will be side welding Some parts of the surface have no risk of solder enamel
The disadvantage of this technology is: Wet the solder to the gold-plated welding surface on the side through the actual opening length of the cover plate and the length of the bottom welding surface of the device at a ratio of 1.1:1. , the side gold-plated soldering surface cannot be fully wetted, and the tinning effect of the side soldering surface is not good
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[0033] In order to make the technical means, creative features, goals and effects achieved by the present invention easy to understand, the present invention will be further elaborated below.
[0034] Such as figure 1 and image 3 As shown, a method for removing gold and tinning for L-shaped soldering terminals of QFN packaged devices includes:
[0035] S1. Prepare unprocessed components;
[0036] S2. Design of gold-coated and tin-coated stencil:
[0037] a: if figure 2 As shown, design and manufacture QFN device tinning tooling mold, including clamps, precise fixed and completely symmetrical left steel mesh and right steel mesh through the clamps, trays set on the left steel mesh and right steel mesh ;The left stencil and the right stencil are designed to be L-shaped, so that the device can fit in;
[0038] b: The bottom opening size and side opening size of the stencil on each side are in one-to-one correspondence with the soldering terminal size of the device body; th...
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The invention relates to the field of electric fitting processes, in particular to a method for gold removal and tin coating of L-shaped welding terminal of a QFN packaging device, and the method comprises the steps: S1, preparing an untreated component; S2, designing a gold-removing tin-coating steel mesh; S3, performing solder paste printing; S4, performing reflow soldering; and S5, completing component pin gold removing and tin coating. Compared with an existing method, the method has the advantages that the bottom welding face and the side face welding face of the L-shaped welding terminal of the QFN packaging device can be evenly subjected to gold removing and tin coating, heating is even during backflow, the reliability of welding spots is guaranteed, and the tin coating steel mesh is low in manufacturing cost, simple and practical; the method is also suitable for solving the problem that the oxidation wettability of the L-shaped welding terminal of the QFN packaging device is poor, the weldability of a welding spot is improved, and the practicability is wide.
Description
technical field [0001] The invention relates to the field of electrical equipment technology, in particular to a method for removing gold and tinning from L-shaped welding terminals of QFN packaging devices. Background technique [0002] With the rapid development of electronic technology, QFN package, square flat leadless devices have good electrical and thermal properties, small size, light weight, and are used in aircraft on-board electronic products. When repairing the faulty electronic product, the technician locates the fault as the failure of the QFN device, and repairs and replaces it. Because the soldering terminals of QFN devices are plated with gold, the compatibility of gold and tin-lead solder is better than that of copper. During soldering, the gold that dissolves into the solder first forms Au-Sn compounds and causes "gold brittleness". Aircraft avionics The product has been in a harsh environment for a long time, the probability of solder joint failure is hi...
Claims
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IPC IPC(8): H01L21/48
CPCH01L21/4885Y02P70/50
Inventor 彭文蕾刘姚军胡猛高灿辉杨彬彬
Owner 国营芜湖机械厂