High Speed Liquid to Liquid
High-Speed Liquid to Liquid PCB Testing – HSL2L – the fastest and must have tool for every reliability engineer.
- HSL2L – High Speed Liquid to Liquid testing was developed in 2013 in order to serve as a gatekeeper to ensure highest PCB reliability in mass production
- Thousands of coupons were tested along the years using HSL2L
- BeyondMaterials brings more than 20 years of experience in PCB industry
- Temperature cycles is the best method to measure PCBs’ reliability
- Beyond Materials strongly recommends implementing HSL2L method as a GateKeeper in mass production, vendor’s qualifications and audits
Why Is Thermal Shock Testing “The” Choice?
- The most frequent PCB failure is in the PTH due to CTE mismatch between copper and epoxy
- Repetitive exposure of the PCB to extreme temperature values challenges the copper interconnection integrity
- The higher the PCB’s reliability, the higher would be the number of cycles to failure
- Thermal Shock testing is the quantitative figure of quality and reliability
- Thermal shock testing started in the 50th, originated by the MIL-STD, and in recent years it is gradually replaced by HATS and IST and now also with HSL2L.
Thermal shock in MIL-STD
MIL-STD-202G, Method 107 (thermal shock) was originated in 1950 and updated in 2002. It contains both Air to Air and Liquid to Liquid methods to test specimens.
Liquid to Liquid is faster than Air to Air but more difficult environment for electrical tests during the run. Liquid to Liquid is considered as more expensive test than Air to Air.
Thermal stress test is one of the best methods to evaluate PCB and PCBA’s reliability, as it tests the most influencing parameters of electrical systems due to CTE mismatch between components and materials
Thermal shock in IPC
IPC ITR-579 published at 1988 a reliability model for PCB plated through holes (PTH) under thermal cycling. Different temperature cycling techniques were compared, two of them are Air to Air and Liquid to Liquid.
1) MIL-T-CYCLE, Air to Air, 120min per cycle (-60ºC/+125ºC).
2) Thermal Shock, Oil to Oil testing, 25min per cycle with long dwell time (-35ºC/+125ºC)
Committee’s conclusion was that the results were similar when Thermal Shock is slightly more severe than MIL-T-CYCLE”
What is HSL2L?
HSL2L is a high-speed temperature cycling technique to measure the quality and reliability of PCBs. Based on the continuous measurement of daisy chain resistance formed in dedicated coupon.
Test coupons are exposed to temperature changes with a swing of 180ºC.
During the test the coupons are immersed in two baths filled with liquid that is held at extreme temperatures. Using liquid for heating and cooling test coupons turns the test to be the
fastest test in the market.
The coupons are tested “as received”, undergo reflow simulations, connector soldering and then are subjected to the high-speed thermal cycles. Results are available after 48 hours.
Regular test includes 500 temperature cycles and can be increased upon request HATS and IST coupons can be tested as well as custom designed coupons
HSL2L can test PCBA as well as PCBs.
HSL2L Tests validation
HSL2L Tests validation HSL2L has been validated theoretically and empirically.
HSL2L differs from traditional Air to Air cycling by two aspects: faster change between extremes, and shorter dwell time. Fast temperature change is supported by IPC standard
Short dwell time is used by other A2A test methods that are commonly used today (HATS and IST)
Coupons from same batches were tested using both methods: HSL2L and HATS
The results compared and found similar – meaning when you get failure with A2A(HATS) system you get failue in HSL2L, and when passing A2A you pass also the HSL2L test.
HSL2L Service Lab
In our test lab, we offer to service option. a standard testing plan that is good for everyone using the most standard and meaningful testing procedure with reflow simulation and full reports and a very fast response time. For more sophisticated and very high operation who need other temperatures and dwell times, we offer a custom testing plan.
HSL2L Standard testing plan
- 6 IPC reflow cycles simulation(option- no additional cost)
- -35°C/ +145°C
- 500 temperature cycles
- 4 nets per coupon
- Fast results 24-48 hours
- Detailed report
- Pay per Coupon
HSL2L Custom testing plan
- Temperature swing in the range of -35ºC/+150ºC.
- Temperature and dwell time can vary per customer request
- Testing of assembled circuits with electrical connectivity is available
comparison between thermal shock testing system
|Temperature Exchange||Air to Air||Current induced||Liquid to liquid|
|Cycle time [minutes]||14||5||2.5|
|Hours to result [500 cycles]||120||40||24|
|Temperature range [ºC]||-40/+145||+25/+175||-35/+145|
|Number of coupons||36||6/8||19|
|Coupon type||HATS||IST||HATS/ IST/IPC/ Custom|
HATS and IST are registered trademark of Bob Neves and PWB Incorporated.