AlphaTest Corporation microHELIX Test-Probes your fine-pitch connection

FAQ ... Frequently Asked Questions

Can these probes be used in burn-in applications?

Yes, the μHELIX® contains no lubricants and the probe operates normally at burn-in test temperatures.  The internal gold-to-gold contact resists tarnishing at these temperatures and the operating range of the metals used in all models is well beyond burn-in test temperatures.


How long will these probes last?

The catalog versions of this probe will provide over a million cycles of operation at the half their maximum compliance.  Laboratory tests subjecting the S500*3800 Series probes to over five million operations showed no degradation in probe force nor series resistance.  The S300 and S200 Series probes provide less compliance (travel) than the two larger diameter probes.  Since applications requiring half mm and quarter mm pitch also require less compliance, this specification has meet with industry approval.  When operated at the recommended compliance, the S300 and S200 probes also provide over a million cycles of operation without coil failures or increased resistance.  Periodic cleaning, of the probe tip, will be necessary if the pad or solder ball contacted by the probe transfers any contaminant or non-conducting material to the probe tip.


How much current will these probes take?

Current ratings, based upon temperatue rise, vary slightly within each diameter group but you can use these rule-of-thumb ratings:
(0.020" diameter probes) ... 2 Amps continuous service.
(0.016" diameter probes) ... 2 Amps continuous service.
(0.012" diameter probes) ... 1.5 Amps continuous service.
(0.008" diameter probes) ... 0.5 Amps continuous service.
Pulsed current, as may often be required to test semiconductor devices, can be much higher because the limiting factor will generally be heat rise, not probe burn-out.


Where are they made?

Manufactured in Shelton, Washington USA by


fine-pitch? What center-to-center spacing can be achieved?

Quarter mm spacing can be achieved in high density arrays with the .
Imbedded fibers in some materials will reduce drilling directional accuracy and so should normally be avoided in favor of homogeneous engineered plastics such as Techtron®, ULTEM®, unfilled TORLON®, DELRIN®, PEEK®, Vespel®, Pomalux®, and etc. (Refer to for manufacturer's specifications and characteristics of these materials.) Using this class of materials, the machine operator can drill straight probe-guide holes and achieve the fine-pitch spacing shown in the following table.

Probe Series: S200 S300 S400 S500
  microns (inches) microns (inches) microns (inches) microns (inches)
Probe Diameters: 200(0.008) 300(0.012) 400(0.016) 500(0.020)
Minimum Centers: 254(0.010) 363(0.0143) 477(0.0188) 592(0.023)
Minimum wall thickness: 13(0.0005) 20(0.0008) 20(0.0008) 20(0.0008)


What size choices do I have?

We offer catalog, custom, and special versions of this versatile probe design.  Our catalog probes run in a production schedule and will usually be available off-the-shelf or in short delivery times.  Custom probes have been built but are not in our production schedule.  Whenever you order a custom probe, you may have to wait for a production slot and pay for the set-up for short runs.   Special versions can be produced satisfying a wide range of characteristics.  If your application requires a length, force, diameter, compliance, and tip shape combination which is not available in the catalog, then a special model might be produced in this unique probe structure which will fit your product plan.

Standard catalog μHELIX® 's include four diameters:

Group IDDiameter
S500 Series500 micron(0.020")
S400 Series400 micron(0.016")
S300 Series300 micron(0.012")
S200 Series200 micron(0.008")

S500 Series probes in eight lengths:

S500 Series Body: μm (inches) Plunger: μm (") i/o Pin: μm(") Overall: mm (")
S500*6350-P1 Group 6350 (0.250) 1900 (0.075)     8,25 (0.325)
S500*6350-P2 Group 6350 (0.250) 1900 (0.075) 1900 (0.075) 10,15 (0.400)
S500*5500-P2 Group 5500 (0.217) 1300 (0.051) 1300 (0.051) 8,10 (0.319)
S500*4500-P2 Group 4500 (0.177) 1300 (0.051) 1300 (0.051) 7,10 (0.280)
S500*3800-P1 Group 3800 (0.150) 1300 (0.051)     5,10 (0.201)
S500*3800-P2 Group 3800 (0.150) 1300 (0.051) 1300 (0.051) 6,40 (0.252)
S500*3000-P1 Group 3800 (0.150) 800 (0.031)     3,80 (0.150)
S500*2440-P1 Group 2440 (0.096) 610 (0.024)     3,05 (0.120)

S400 Series in six lengths:

S400 Series Body: μm (inches) Plunger: μm (") i/o Pin: μm(") Overall: mm (")
S400*6350-P1 Group 6350 (0.250) 1900 (0.075)     8,25 (0.325)
S400*6350-P2 Group 6350 (0.250) 1900 (0.075) 1900 (0.075) 10,15 (0.400)
S400*4500-P2 Group 4500 (0.177) 1300 (0.051) 1300 (0.051) 7,10 (0.280)
S400*3800-P1 Group 3800 (0.150) 1300 (0.051)     5,10 (0.201)
S400*3800-P2 Group 3800 (0.150) 1300 (0.051) 1300 (0.051) 6,40 (0.252)
S400*2440-P1 Group 2440 (0.096) 610 (0.024)     3,05 (0.120)

S300 Series in three lengths:

S300 Series Body: μm (inches) Plunger: μm (") i/o Pin: μm(") Overall: mm (")
S300*3800-P1 Group 3800 (0.150) 1300 (0.051)     5,10 (0.201)
S300*2300-P1 Group 2300 (0.091) 1000 (0.039)     3,30 (0.130)
S300*2050-P1 Group 2050 (0.081) 450 (0.018)     2,66 (0.105)

S200 Series in three lengths:

S200 Series Body: µm (inches) Plunger: µm (") i/o Pin: µm (") Overall: mm (")
S200*3800-P1 Group 3800 (0.150) 1300 (0.051)     5,10 (0.201)
S200*2300-P1 Group 2300 (0.091) 1000 (0.039)     3,30 (0.130)
S200*2300-P2 Group 2300 (0.091) 1000 (0.039) 1000 (0.039) 4,30 (0.169)


What is the probe force?

offers standard Catalog probes with these probe-force options:
(Other force values available upon request, lower force available with reduced travel)

S500 Series Probes; 0,5 mm (0.020 inches) diameter;   30 grams (1.1 oz) and  90 grams (3.5 oz)
S400 Series Probes; 0,4 mm (0.016 inches) diameter;   30 grams (1.1 oz) and  80 grams (3.5 oz)
S300 Series Probes; 0,3 mm (0.012 inches) diameter;   30 grams (1.1 oz) and   60 grams (2.1 oz)
S200 Series Probes; 0,2 mm (0.008 inches) diameter;   30 grams (1.1 oz) and   40 grams (2.1 oz).

rates the μHELIX® force at the typical test compression ( the maximum compliance).
For example, the Descriptive Model Name "S500*3800/900/30@450/S1300s/S0a" denotes a force of 30 grams at 450 microns of compression.

An example of the linear relationship between Probe-Force and probe travel (stroke, compression, compliance) can be seen in this S500*3800/900/30@450// Probe Group force-chart (Probe-Force: vertical axis; Travel: horizontal axis).

Force Chart 30@450


What features can I have in these probes?

Categories (Cat): (1) standard, (2) custom, (3) special
Construction (Const)
Device Under Test (DUT) contact description: Plunger, tube end
input/output (i/o) end description: i/o Pin, wire, tube end
Pin Tip Shapes: sharp (s), radiused (r), flat (f), 4-point crown (c4)
AlphaTest μHELIX tube&spring assembly (probe body)
Diameter (ø)
Cat Const DUT contact> i/o contact + Features Description Drawing
1 2-piece plunger annular Basic μHELIX probe body;
plunger (s,r,f,c4)
Basis uHELIX Probe
1 3-piece plunger i/o pin secondary pin probe body;
plunger (s,r,f,c4);
i/o Pin (s,r,f,c4)
i/o pin version
2 3-piece plunger i/o wire i/o wire probe body;
plunger (s,r,f,c4);
wire installed at i/o end
capture feature
1 2-piece plunger i/o pin capture feature probe body;
reduced ø at i/o end;
plunger (s,r,f,c4)
capture feature
2 1-piece annular annular transposer probe body S0a/S0a
3 1-piece annular annular capturable transposer probe body;
reduced ø at one end
capture feature
2 1-piece annular annular capturable transposer probe body;
reduced ø at both ends
2 2-piece annular annular low resistance, captured transposer probe body;
reduced ø at both ends;
internal Cu wire for high conductivity
2 2-piece plunger crown short, i/o crown probe body;
crown at i/o end;
plunger (s,r,f,c4)
2 2-piece plunger crown short, captured i/o crown probe body;
crown at i/o end;
reduced ø at i/o end;
Plunger (s,r,f,c4)
capture feature
3 Custom Custom Custom Custom Custom  


What plating is applied to these probes?

We apply a gold strike/Type III/Type II Gold plate to a thickness of 60-80 micro inches to all tube/coil assemblies, plungers, and pins used in standard catalog probes.  Other plating including Nickel (used to repel solder buildup) and PdCo (Paladium Cobolt used to repel solder buildup) may be applied on special order.


What equipment do I need to drill the guide-holes for these small probes?

You should have an xy position accuracy of 2,5 microns (0.0001"), the ability to peck the drill, and a spindle speed of at least 7,000 rpm (preferably programmable from under 7000 to 50,000 and ideally programmable from below 7,000 to 120,000 rmp).  CNC drill instructions will vary slightly depending upon the spindle speed available.  Avoid heat build-up in the guide-plate by drilling with a pecking action.  This wll also remove debris from the hole and reduce the tendency for loading in the drill flutes.   Keep the cutting speed up.  Compare the cutting speed of these drills  using a 10,000 rpm spindle speed:

Example: Drill cutting-speed vs Drill Size using 10,000 rpm
cutting-speed in units/time = PI*(Dia in units)*(rpm)/(60 sec/min)
Drill Size Cutting Speed Application
  microns inches mm/sec inches/sec guide-hole for:
#74 572 (0.0225) 300 (11.8) S500 probe body
1/64" 397 (0.0156) 208 (8.2) S500 plunger | i/o pin
#77 572 (0.018) 300 (9.4) S400 probe body
#80 343 (0.0135) 180 (7.1) S400 plunger | i/o pin
S300 probe body
#88 240 (0.0955) 126 (5.0) S300 plunger | i/o pin
S200 probe body
#96 160 (0.0063) 84 (3.3) S200 plunger | i/o pin

Mechanical characteristics of the guide-plate material (ref Tech Note TN0019) will dictate subtle changes in the CNC drill profile to assure debris-removal and flute-cooling. Generally, your CNC machining operation will quickly find an optimum spindle-speed, feed-rate, and peck-pattern for drilling straight holes in each material with their equipment. Call upon AlphaTest for suggestions if problems persist.


What history does the probe have?

developed the μHELIX for use in custom test fixtures. After the initial shipments of test fixtures using these probes, they were made available to the general electronic test &measurement industry. Now, a wide variety of configurations can be purchased including probes featuring fine-pitch, wide-bandwidth, controlled impedance, low inductance, Kelvin connections, and static dissipation. Since their introducton, these probes have gained a solid reputation for quality and durability.


What is your delivery time?

Our Catalog probes are either in inventory or deliverable within 2 weeks.  Custom probes which may have been built in small lots but not included in our catalog can generally be shipped within 3 to 4 weeks.  Special probes, designed from the ground up, may require 2 to 12 weeks.  We can build many non-standard combinations  from stock components, so inquire if you do not find the combination you want and can wait a few weeks.


Does AlphaTest offer other products?

Yes, we still build the "difficult" fixtures for fine-pitch and high frequency applications. This experience continues to be our eyes and ears into the marketplace which predicts future trends in testing and in test probe requirements. AlphaTest also developed and offers the hand-held μKELVIN fine-pitch Kelvin Test Probe which makes the 4-terminal connections necessary for measuring low resistance values on pc traces, rfid antennas, device packages, etc.


How can I get price quotations, order product, or get additional technical support?

Visit our Register page and leave a message there or
Visit our Contact page and send an E-mail message or FAX.
You can contact us by telephone during regular business hours (8:00 AM to 5:00 PM Mon-Fri). Our offices are in the Pacific Northwest and on
Pacific Standard Time (PST){GMT-7 hours} from November-March and on
Pacific Daylight Savings Time (PDST){GMT-8 hours} from March-November.