Electronics > Manufacturing & Assembly

Pads of SMD connector falling of PCB

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jusaca:
I have some trouble with a current manufacturing batch of some PCBs.
We use JST connectors handsoldered sideways as SMD connectors. We do this for years already and did some strength tests in the past. We always snapped the pins of the connector before we would lift the pads. Other connectors (including THT) are not an option because of size constraints.

Now with a new production batch we have about 10% (!!!) of the boards failing, because one of the connectors falls of (always the same connector).
As you can see in the image, the pads just came off.

We talked to the PCB manufacturer and the assembly house, but they just point fingers.
Is it possible to decide with the image what the most likely problem is? Is it a problem with PCB manufacture? Or more likely a problem with hand soldering? Maybe to hot soldering temperature?
What puzzels me is that it is always the same connector, while the other ones are quite strong. The layout is pretty identical for all 5 connectors next to each other...

Psi:
The corner edge of a pcb has less heatsinking and so will get hotter and quicker with the same iron temp.
So that would be my guess. They're probably using a really hot tip to solder things quickly.


Could also be a pcb fab issue, maybe one side of each panel was not submerged enough and the bubbles/turbulence at the top of the etch bath made it etch faster than the rest of the board. Resulting in thinner copper along one edge.  But if that were the case you should be able to tell with some calipers.

Another option is a packaging/shipping issue. The corner of the pcb is subjected to more forces and more likely to get damaged by a knock.

mon2:
Agree with the last post. SMD connectors just cannot sustain the force during a hit, especially in the corners like your pcb design. You can see that the nylon boardlock pegs used to secure this edge connector have broken off.

Highly recommend THT but aside from this suggestion, share more details of this part number and also the other JST connectors to the right side in your pic.

Which part numbers were used to the right side ?

Will share more details (when at the office in a few hours) of a mfr we have used in Asia that can customize the JST connectors to suit. They are dirt cheap but MOQ will apply. We customized a similar connector that JST does not mfr. It was a THT connector with body of 18 pins but stuffed with only what we requested for the male pins. This allowed us to build a galvanic isolation between interface ports due to the missing metal male pins.

Perhaps they can customize the smd version to allow for a single SMD connector to be stuffed for the entire horizontal plane.

Then the entire blade of a single nylon connector body will assist to absorb the forces.

Just a suggestion.

Update:

1) can the PCB layout be modified for future PCBAs ?

2) We have used with very positive results, LHE out of Asia:

https://www.lhecn.com/blogs/what-is-smd-connectors/

Note the extra SMD PCB pads to improve the strength of the mounting of this connector.

Here is our last sales contact:

--- Quote ---Ms.Amy
Sales Assistant
Zhejiang Lianhe Electronics Co., Ltd.
Tel:86-577-62383212
Fax:86-0577-62382566
Email:lhecn@lhecn.net
Trade Manager:lhecn@lhecn.net
Skype:lhecn-littlebear
Address: No 8 Innovation Road, Gangwan area, Nanyue Town Yueqing Zhejiang.China  325609
Website:http://www.lhecn.com/      http://www.lhecn.com.cn/

--- End quote ---

Contact Amy to ask for their advice on the issue. Do keep the soldering temp down but do believe you need to reduce the force this 2 pin connector is facing during transit (more bubble wrap?) and/or insertion of the mating cables. This vendor can customize the JST style connectors to suit.

thm_w:
OP, we can see glue holding the connectors together, I assume that was from the manufacturer?
So you've left some information out that the connectors are glued for reinforcement. Was the previous supplier using the same glue? Same amounts? Proper prep?


--- Quote from: mon2 on May 24, 2022, 09:42:32 am ---Agree with the last post. SMD connectors just cannot sustain the force during a hit, especially in the corners like your pcb design. You can see that the nylon boardlock pegs used to secure this edge connector have broken off.
--- End quote ---

What boardlock pegs?
These just look like regular through hole connectors, mounted on the edge of a PCB.

jusaca:
We use JST B2B-ZR connectors, which are just mounted as SMD parts. All five connectors are the same, the ones at the edges to not have extra support.
That glue like stuff is actually nothing that we specified. I only noticed it when taking this picture. I assume the assembler glues five connectors together to increase speed for manual placement, I doubt that it will give any additional support.

A design change for future is possible (and something obviously has to be done), but we have no option to increase neither length nor width of the board. THT is not really an option, because the other side of the board is jsut to dense to make room.

One "solution" might be to just increase strength of the joints by pooring some epoxy over the pins after soldering...?

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