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Bead Probe Test Solutions​

Bead probe technology is a probing method used to connect electronic test equipment to the device under test (DUT) within a bed of nails fixture. Originally given the name “Waygood Bump” after one of the main proponents, Rex Waygood. They are also commonly referred to as solder bumps. Bead probes were designed for when less than 30 mil is available for test probe points on the PCB. They are used with standard ICT spring-loaded test probes to connect the test equipment to the DUT.


Bead probes are made from a very small "beads" of solder that fit atop of the PCB traces. They are manufactured using the same techniques as other solder features. Construction requires a hole to be opened in the solder mask, exposing the copper trace. This hole is sized to precisely control the amount of metal that forms the bead. Solder paste is applied to the location and reflowed. During reflow, solder flows and is drawn to the copper trace. Surface tension causes the bead to have a curved surface and rise above the solder mask, where it solidifies into a Bead Probe. The bead will be roughly obround in shape and may be 15-25 mils long. A properly constructed bead is the same width as the trace and just enough to clear the surrounding solder mask. The bead is then accessible for testing using a probe with a flat end, which can help compensate for the tolerance build up in the test fixture and PCB.

Bead Probes Technology

pad-on-trance
double-pads-on-trance

Situation:

  • We should get the finest touch on one pad or both of them.
  • Due to thin and soft pads, Probe is strictly not allowed to broke the pads
  • The pads are very small and not so bad situation of flux problem.



bead-probe-pogo-pin
bead-probe-test-head
25-pins-bead-probe-head


Probe Solution

  • We design the plunger size according to ball diameter.
  • As we see the ball is 0.254mm[0.010inch].
  • We should let the tip gap touch >60% surface of the ball.
  • Never let the ball fall inside of the two tips.



Advantages

  • High Catching Accuracy
  • Soft and Smooth Contact pads, Low damage possibility.
  • Supper Stable than other choices
  • Long Lifespan



Test Result

Eg. J100-13-090-06 bead probe 

  • Spring Force
  • Contact Resistance

bead-probe-spring-force
bead-probe-contact-resistance

Test Probe Solutions For Keysight( Agilent) Pad On Trance

Flat-contact-bead-probe
bead-probe-double-cross-head
bead-probe-micro-serrated-probe-tip

Serrated 9 points Contact

Flat Head Contact

Double-Cross Contact

Test Probe Solutions For HP Double Pads On Trance

Flat-contact-bead-probe
Serrated-tips-contact-bead-probe

Flat Head Contact

Serrated 25 points Contact

Probe Part Numbers

50mil   Bead Probes     J050-13-090-06   J050-14-065-10

75mil   Bead Probes     J075-13-090-06   J075-14-065-10

100mil Bead Probes     J100-13-090-06   J100-14-065-10

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