Soldering wearable products

In wearable products, not only the board but all the parts are small, and the soldered terminal part (land part) is small and narrow to the limit of visual inspection.
It can be mounted without any problem at a mere experimental level, but in an actual mass production line, management technology such as warpage of surrounding parts and sheet boards is required.
 
At the mass production site of FPC, it can be seen that it is discarded without melting due to individual correction and analysis from the production volume and delivery date.
 
Mounter makers can handle up to 0201 chip size.
For solder supply, the dispenser can handle all sizes, but considering productivity, we want to print all at once.
 
The mask maker proposes printing with a mask with a thickness of 40 to 60 µ in the 0201 chip size class, but it depends on the design whether it can handle the parts leads around it that are mounted at the same time.
It seems to be difficult with a metal mask with a thickness of at least 40µ.
 
Solder makers offer particle size type 6, but type 6 is so fine that it has a lot of oxides on the surface and even if it can be printed, there is still a problem with wettability.
 
Especially in the normal temperature profile, the flux deteriorates and the bonding is performed in a state where it is poorly melted or adheres to the melted solder.
 
In addition, there is a problem of voids, and the quality of the products to be carried is very unstable.
In the old overseas mobile phones, after installing CPS on the FPC, it was hardened with underfill, but there were many defects in the market and it was a problem.
 
Since the production volume is an order of magnitude higher, it was in a state of being discarded.
If it is a mass-produced product, it can be handled even if the initial investment is a little large, but it is difficult to invest at the stage where the lot is small, and if possible, mass production with the current equipment is required.
 
In January, the Kyoto Mounting Technology Study Group received a 0201 chip from the manufacturer and conducted all manual experiments.
 
The metal mask was 60µ and the solder was printed using type 6 and type 4.
The solder maker wanted to support nitrogen reflow, but is experimenting with atmospheric reflow.
 
Wetability varies depending on the flux of the solder used, but it is especially important to create a temperature profile.
Since the flux deteriorates immediately with fine solder particles and amount, the solder will not melt unless a temperature profile (upper and lower heater and fan rotation speed) that melts the solder without deteriorating the flux is devised.
 
In addition, even if it melts, fine solder balls are generated and insufficient wetting occurs.
 

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