ISA Slot & Edge Wear

Updated: Aug 19

I have been using ISA slots and ISA edge connectors on many of my recent builds. I was asked some great question about durability (thanks, u/TiiXel!). How quickly will the slots or edge connectors wear out? In the following video, I perform some basic testing -- up to 200 insertions.


Short answer: After some quick testing, I do not have any concerns with ISA slot or edge wear for my homebrew projects.



After 200 inserts, this was the worst pad I could find:


I tested soldering this worn pad. It soldered without issue.


My the tested PCB above:

-Manufacturer: JLCPCB

-Copper weight: 1 oz.

-Surface finish: HASL (with lead)



Additional Testing

A nice suggestion came in from a YouTube viewer. Russell suggested measuring resistance. In the video, I simply checked for continuity. I setup a new test, adding two ISA slots connectors, and I used two new add-in PCBs. I measured resistance between matching pins of the two add-in PCBs, as shown in the images below. I measured resistance of all pins that were routed on the PCBs (card and motherboard). I measured values at 1, 20, 100, and 200 insertions. Measurements were done with a Siglent SDM3045X digital multimeter with room temperature of approximately 73F (23C) and humidity of approximately 50%.



When new, most connections measured between 0.23Ω and 0.25Ω. VCC and GND had multiple connections and measured between 0.07Ω and 0.12Ω. After 20 insertions, no statistically-relevant differences were measured. After 100 insertions, most connections measured the same; however, a handful of connections increased by 0.10Ω to 0.22Ω. After 200 insertions, most connections measured between 0.24Ω and 0.27Ω, with a subset increasing by as much as 0.34Ω. Below are images of the cards after 200 insertions. Also, I summarized some key data in the table below.

# Insertions

Average Ω

% Increase Ω (from new)

Largest Single Increase Ω (from new)

0

0.22

20

0.21

-3%

0.04

100

0.24

10%

0.22

200

0.30

38%

0.34

This data is from a single set of tests, up through 200 insertions. Ideally, I would repeat this entire set of tests, with new hardware each time, another 20 times (which I am not going to do 🙂). One thing to consider in this latest test is that a pair of cards were inserted, and the increase in resistance is based on two cards being worn. Possibly, that implies that a single card will see half of the impact shown in the table above.


Also, the ISA slots begin to loosen up a bit after 100 insertions and could result in a diminished connection to the add-in card. I do not believe this is a concern, but it could be tested by using worn add-in cards in brand new ISA slots; I have not done this testing.


Some potential factors that could affect the quality of the data above:

  • Consistency in how cards are inserted into slots (angled, level of force, etc.)

  • Consistency of using measurement probes on PCBs (contact area, angle, etc.)

  • Temperature, humidity

  • Manufacturing quality differences in PCBs and ISA slot connectors

  • ...


I will continue to monitor how ISA slots work out for me. If I encounter issues in the future, I will post updates.



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