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Castellated Module Reflow Problems

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#88076

Castellated Module Reflow Problems | 9 June, 2022

Hi,

We are producing a board that contains an RN4678 bluetooth module, and an STLINK-V3MODS module, both of which are castellated modules. I am constantly having issues with the modules being soldered to the PCB incorrectly. It seems that the RN4678 'bows' sometimes, towards the end with the antenna, and on the STLINK-V3MODS it appears that the solder does not wick up some of the pads occasionally. What could be the causes for these issues? Right now I am solving these issues by hand which is time consuming and annoying, and I cannot find much, if any, information about castellated reflow at all

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#88078

Castellated Module Reflow Problems | 10 June, 2022

Solder connections to the castellated and other components need improvement. Are you profiling on the problem leads?

Microchip Technology Inc. RN4678 Bluetooth module reflow recommendations - http://ww1.microchip.com/downloads/en/DeviceDoc/RN4678-Bluetooth-Dual-Mode-Module-Data-Sheet-DS50002519D.pdf

Some castellated leads look like there's not enough solder. Are vias on the component pad stealing solder?

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#88079

Castellated Module Reflow Problems | 10 June, 2022

Generally we overprint on the exposed part of these pads. When there isn't enough clearance at the end of the pad we place solder preforms with the placement machine.

Jerry

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#88080

Castellated Module Reflow Problems | 10 June, 2022

Yes they are far from ideal. What do you mean by profiling on the problem leads? And yes there is a lack of solder on some, but there are no vias in or near any of the pads that could be stealing solder

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#88081

Castellated Module Reflow Problems | 10 June, 2022

Overprint, that is putting extra solder on with the stencil that is even further out from the pads, with the idea that it will suck that solder up during reflow? I could give that a try. Are there any general recommendations when overprinting? And what is a solder preform?

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#88082

Castellated Module Reflow Problems | 10 June, 2022

Yes. We only do the side not under the component and do 25 mils if there is enough room.

A solder preform is simply a block of solder that is shaped like a SMT component and comes in tape and reel. Most solder manufactures offer these. You can talk to your normal supplier.

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#88086

Castellated Module Reflow Problems | 10 June, 2022

Ah okay, that should be pretty easy to do on the current board design. If overprinting doesn't work, then I might try a preform. I wasn't even aware that was a thing, I might be able to do some of our through-hole components that way if they are rated for reflow.

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#88092

Castellated Module Reflow Problems | 13 June, 2022

Has the part not got a pad underneath and therefore the flow up the castellated side doesn't have to be as crucial?

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#88093

Castellated Module Reflow Problems | 13 June, 2022

No there are no pads except for the castellated ones on the side. These boards are being used on agricultural machinery though so a less than ideal solder joint would likely be prone to failure over time

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#88095

Castellated Module Reflow Problems | 14 June, 2022

Check for warp during reflow or placement, if your board is bowing you are not going to make a good solder connection.

If your board is warping during reflow you may need to make a currier to support the board during reflow if using the edge to transport.

If your board is warping (saggin) during placement your package may be sitting on top of the solder paste not making appropriate contact during reflow.

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