Denser boards make the tester’s own switches matter
As IC integration has moved from through-hole to surface-mount and on to chip-scale packaging, and as signal speeds have climbed, PCBs have moved toward high-density interconnect (HDI), finer pitch and thinner formats. Bare-board test has to keep pace: it must find opens, shorts and insulation defects on nets that sit closer together than ever, often by applying elevated voltage to expose insulation weakness that a low-voltage continuity check would miss. The scanning and switching behind that test is built from high-voltage relays, and sealed high-voltage reed relays are widely used in board testers.
What the relay has to deliver
- High-voltage switching for insulation and dielectric checks between adjacent fine-pitch nets.
- Low, stable contact resistance so four-wire (Kelvin) resistance readings stay repeatable across millions of cycles.
- Fast operation to hold down per-board test time.
- High open-contact and contact-to-ground insulation so relay leakage does not mask the defects being tested for.
- Long life in a matrix that switches thousands of times an hour.
HVR series figures
The HVR high-voltage reed relay is offered in 4/5/6/10/15/20 kV withstand versions.
- Contact switching voltage to 10 kVDC; dielectric (breakdown) withstand to 20 kV
- 3 A switching current; 5 A maximum carrying current
- Pulse current options 5 A / 10 A / 20 A
- Insulation resistance 10 TΩ and above
- Multiple contact forms; PCB through-hole or high-voltage lead-wire mounting
- Operate time 3 ms, release time 1.5 ms
The body is epoxy-encapsulated, with insulation resistance of 1012 Ω and creepage distance greater than 32 mm, which is what lets the part sit in the high-voltage scan matrix of a board tester.
How the matrix is used
A relay matrix connects the measurement electronics to test points across the board and scans net by net: low-voltage continuity first, then insulation and high-potential checks at elevated voltage. Sealed contacts keep continuity readings repeatable because their resistance does not climb with age, and 10 TΩ-class open-contact isolation with generous creepage keeps unselected channels from forming leakage paths that would raise false failures on dense HDI boards.
The economics are direct. A tester that rejects a good board creates rework cost; one that passes a faulty board lets the defect escape. Because the relay matrix actuates on every board tested, contact stability and life are what keep the tester’s pass/fail verdict consistent across years of production — which is why reliability, rather than raw switching speed, is the specification that tends to decide the relay choice in board test.
About SHR AUTOSENSOR
SHR AUTOSENSOR TECH LIMITED (SHR AUTOSENSOR) manufactures high-voltage reed relays, mercury wetted relays and high-voltage DC contactors. Contact: [email protected] | +86 13761571029 | www.reed-relay.com