PCB Coating Film Prevents Solder Loss in Flow Soldering
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Solution Overview
Problem
In printed circuit boards, the solder joining terminal pads on the mother and auxiliary boards is easily taken by the solder bath due to gravity and surface tension during flow soldering, leading to inadequate solder distribution between adjacent electrodes.
Innovation Solution
A printed circuit board design featuring a first insulating substrate with mounting holes and a second insulating substrate with protruding connection portions, where electrodes on both substrates are joined by solder, and a coating film is applied on the connection portion to prevent solder from being taken by the solder bath, thereby increasing the amount of molten solder adhering to the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flow soldering is used to join terminal pads on mother board and auxiliary board, then the boards can be connected efficiently, but the solder joining electrodes adjacent to each other is easily taken by the solder bath side due to gravity and surface tension
Solution Approach 1:
A coating film is applied in advance to the front end side of the connection portion before soldering. This preliminary coating creates a barrier that prevents solder from being taken by the solder bath, ensuring uniform solder distribution without requiring changes to the soldering process itself
Solution Approach 2:
The coating film acts as an intermediary layer between the connection portion and the solder bath. It mediates the interaction by blocking the harmful effect of surface tension and gravity on the solder, while still allowing the solder to adhere properly to the electrodes
2Ease of manufacture
If the printed circuit board is separated from the solder jet in flow soldering, then the soldering process can be completed, but the solder joining the electrodes adjacent to each other is easily taken by the solder bath side
Solution Approach 1:
The coating film is applied beforehand to the connection portion to create a protective barrier. This ensures that when the board is separated from the solder jet, the solder already adhered to the electrodes is protected from being taken by the solder bath, maintaining joint reliability
Solution Approach 2:
The coating film converts the harmful effect of surface tension and gravity (which cause solder to be taken by the solder bath) into a beneficial effect. The coating creates capillary action that retains solder on the electrodes, transforming the problematic physical forces into a protective mechanism
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively prevents solder from being taken by the solder bath and increases the amount of molten solder adhering to the electrodes, enhancing solder thickness and reducing thermal fatigue.
Implementation Method 1
the solder joining the terminal pad provided on the mother board and the terminal pad provided on the auxiliary board is easily taken by a solder bath side due to influence of gravity and surface tension of the solder
Implementation Method 2
a first electrode provided on the second surface and disposed at an edge of the mounting hole; and a second electrode provided on the connection portion, the first electrode and the second electrode being joined by solder
Data Source
AI summary
There is provided a printed circuit board in which an amount of molten solder adhering over electrodes adjacent to each other is increased in flow soldering. The printed circuit board according to the present invention includes: a first insulating substrate (6) having a mounting hole (15) that penetrates through the first insulating substrate (6) from a first surface (6a) to a second surface (6b); a second insulating substrate (18) including a connection portion (23a) that penetrates through the mounting hole (15) from the first surface (6a) side and protrudes from the second surface (6b); first electrodes (7 and 9) that are provided on the second surface (6b) and are arranged at an edge of the mounting hole (15); and second electrodes (19 and 25) provided on the connection portion (23a). The first electrodes (7 and 9) and the second electrodes (19 and 25) are joined by solder. The printed circuit board further includes a coating film (31) that is disposed at least on a front end side of the connection portion (23a) than a portion where the second electrodes (19 and 25) are joined to the first electrodes (7 and 9) by the solder.