Welding Problems and Improvement for RPT5032N Series VC-TCXO
Shown below in Photo 1, Pluto+ ASIC chip from the RPT5032A-N series use flip-chip packaging.
It is welded to the concave groove of the base from the bottom of the quartz crystal
and overlaid by a colloid, so the bottom of the quartz crystal is a black colloid.
Photo 1. Pluto+ ASIC Flip-Chip
Photo 2. Image of the Bottom of the Product
The bottom welding method in Photo 2 is similar to BGA. Closer spacing can easily cause solder short on the solder balls.
Manual thermit welding heating is prone to superheating and uncontrollable welding factors.
Photo 3. Failure Case
Reason analysis: Due to uncontrollable factors from the temperature of manual welding,
solder short or desoldering of the solder point will occur. This usually results no output on frequency signal.
It may also cause excessive contact resistance and affect performance, for example, producing high frequency deviation.
Photo 4. Visual Inspection: SEM and EDX Analysis of Good Unit
Photo 5. Visual Inspection: SEM and EDX Analysis of Desoldered and Poorly Welded Units
Photos 4 and 5 indicates that the state of Rakon products’ internal hybrid circuit solder
joints under good welding temperature control. It directly affect the performance of the final index output.
Rakon factory does not recommend manual welding, instead suggests clients to use
temperature-controlled soldering station or reflow soldering, with the latter giving a better consistency.
Below is the curve diagram of stable reflow soldering. If there are any enquiries, please contact Walasey FAE.