STDA022 January 2026 MSPM0L1305

3 Procedure

A 16-pin WQFN package was selected as the test vehicle. The 16-pin WQFN package includes preplated NiPdAu leads, nominally dimensioned at 0.2mm in width and 0.6mm in length, with a 0.4mm pitch (see dimensioned footprint in Figure 3-1). First, daisy-chain units with a die resulting in a die-area-to-package-area ratio of 42% were assembled for in situ event monitoring.

XM0L1305SRTRR MSPM0L1305 Test Vehicle Footprint

Figure 3-1 Test Vehicle Footprint

Next, two sets of PCBs were designed for the test vehicle. The first PCB was designed to be 1.6mm-thick with eight metal layers and with leads that overhang the PCB land pads by 100μm. The second PCB was designed to be 1.6mm-thick with eight metal layers and with leads that overhang the PCB land pads by 200μm (visualized from the top in Figure 3-2). The assembled units were then soldered onto the PCBs using SAC305 in two configurations:

Configuration 1: Only two sides are soldered (on the west and east) to simulate a SON configuration
Configuration 2: All four sides are soldered as is typical of a QFN configuration

A sample of the units with only the two sides soldered had optical exterior images taken, along with cross-section images of the soldered leads and measurements of the solder joint thickness prior to starting any testing.

XM0L1305SRTRR MSPM0L1305 Leads Overhanging Land Pads (in Gray)
and Daisy-Chain Connections (in Red) Shown With Test Vehicle Footprint (in Blue)

Figure 3-2 Leads Overhanging Land Pads (in Gray) and Daisy-Chain Connections (in Red) Shown With Test Vehicle Footprint (in Blue)

Thirty-two units with four sides soldered on each PCB set (100μm overhang and 200μm overhang) then underwent temperature cycling according to the JEDEC standard, JESD22-A104D. The chosen temperature profile took the units between –40 and +125 C over the course of a 60-minute cycle, common in automotive applications [2, 3].

An additional twenty-four units on each PCB set that had only the two sides soldered also underwent the same temperature cycling profile but were not monitored for continuity. After 1000 cycles, eight units were removed. Cross-section images of the soldered leads and measurements of the solder joint thickness of these units were taken for comparison to the units prior to starting the BLR test. This was repeated for eight additional units removed after 2000 cycles and eight additional units removed after 3000 cycles.

A summary of the evaluation splits is provided in Table 3-1 and Table 3-2.

Table 3-1 Summary of Evaluation Done on the Units With All Four Sides Soldered

Overhang Amount	Test
100μm	BLR, in situ monitoring – 32 units
200μm	BLR, in situ monitoring – 32 units

Table 3-2 Summary of Evaluation Done on the Units With Two Sides Soldered

Overhang Amount	Test	Pull-Out Cycles
100μm	None	8 units – 0 cycles
	BLR, without in situ monitoring – 24 units	8 units – 1000 cycles
		8 units – 2000 cycles
		8 units – 3000 cycles
200μm	None	8 units – 0 cycles
	BLR, without in situ monitoring – 24 units	8 units – 1000 cycles
		8 units – 2000 cycles
		8 units – 3000 cycles

For reference, a BLR temperature cycle test without overhang using the same test vehicle was previously conducted. This previous test had no electrical failure even after 9740 cycles. Figure 3-3 pictures a cross-section of the corner leads after the completion of this previous test. The cracking seen in the solder joints is due to the extent of testing but demonstrates the integrity of the solder joint in this base case when the overhang is not present.

XM0L1305SRTRR MSPM0L1305 Cross Sections of Leads Soldered
Without Overhang After Nearly 10000 Cycles of BLR

Figure 3-3 Cross Sections of Leads Soldered Without Overhang After Nearly 10000 Cycles of BLR