Wrong resistor SMD code

[fedimakni]

Hello,

Today I encountered a weird problem. My design contain a 100K ohm SMD resistor 0603 with SMD code 104. I used a prototype service to assemble the pcb in china. When i received the PCBs i found some of them don't behave correctly, after investigation i found that the resistor value (in some PCB) was around 36M ohm (correct value 100K ohm) the problem that the SMD code is also 104.
Note: Some PCB work normally and their resistor is 100K ohm

Could the factory make mistake by using resistors from the grey market which have the same SMD code? What are the possible reasons of such problem?
Thanks again for your support.

[SeanB]

Probably cracked resistors, or recycled ones that were simply put in a tape for sale after being recovered from ewaste.

[teletypeguy]

Are you sure the marked code is 104?  The 0603 package is sometimes marked like that for 5% values -- 1% values (the E96 series) usually have a 3-digit code (2 numbers and one letter) that needs a lookup table to read.  You find that even the 5% (E24) values, if ordered as 1% will use the E96 markings.  So if you order a 5% 100K it will be marked 104, but if you order a 1% 100K it will (usually) be marked 01D.  However, it depends on the manufacturer -- I have reels of 100K 1% marked both ways, from different manufacturers.

Scroll to table at bottom:
https://learn.sparkfun.com/tutorials/resistors/decoding-resistor-markings

[fedimakni]

Hello,

Thanks for the reply,
Yes I am sure they have 104 code on the top of them.

[bson]

Probably cracked during reflow, cleaning, or in shipping.

[Gyro]

The test is whether it unsolders in one piece or two.

[gamalot]

Probably cracked resistors, or recycled ones that were simply put in a tape for sale after being recovered from ewaste.

No one will recycle such cheap components. A whole wheel of 5,000pcs 0603 resistors is only worth about 2 US dollars in China.