Having difficulty soldering PLCCs to a JLCPCB board - Page 1
Forum section: electronics / general

author: Peacefrog
author_rank: Contributor
timestamp: March 30, 2022, 08:39:55 pm
content: I'm trying to solder PLCC chips to a freshly delivered board from JLCPCB, and am having real trouble getting the solder to flow between the PLCC and the pads - it flows to most, but not all.The footprint on the board is effectively the same size as the chip, so I'm trying to flow solder between the 'gap' at the bottom and the pads - but I've a.) scrubbed the board with 99% isopropyl b.) am using a clean JBC iron at 350 degrees, and c.) am fluxing the pads before and during. I've also tried turning the temperature up to 380 degrees, with no success.Any ideas as to what I could be doing wrong?

author: thm_w
author_rank: Super Contributor
timestamp: March 30, 2022, 09:29:20 pm
content: Photos?Are the PLCCs old parts that may have not been stored well?Can you tin the pads and use hot air to solder it instead?

author: mon2
author_rank: Frequent Contributor
timestamp: March 30, 2022, 09:40:26 pm
content: The devices (PLCC) must be old - does any company even supply parts in a PLCC package these days ?Either way, forget the PLCC and see if the SMD pads can accept the solder. You should be able to apply leaded solder (aka low temp solder) without any issues. If the solder does not flood the SMD pads then the PCBs is defective. Do post the pictures and certainly discuss with your rep @ JLCPCB.We recall having gold flash PCBs where a blow torch could not make the solder stick to the pads. Absolute garbage. Lost about $1k on that PCB order and never dealt with the company again.

author: Peacefrog
author_rank: Contributor
timestamp: March 31, 2022, 01:42:40 am
content: Thanks all! It's actually the recreation of a Macintosh SE/30 motherboard - I'm transplanting parts from another PCB where the battery leaked. For reference, the project is here:https://github.com/TheRealBolle/SE30.Pics are attached - in this case it's the far right pin that won't take, even though I've (rather too literally) flooded the other pads. The SOIC parts are fine, however.It's been pointed out to me offline that I might be better with a stencil and paste instead...

author: thm_w
author_rank: Super Contributor
timestamp: March 31, 2022, 08:49:48 pm
content: You don't need stencil and paste unless this is production. If you have hot air:- flux and tin the pads on the PCB- lightly tin the pads on the PLCC (normally this is not necessary, but, since the parts are old it could help)- put on top, and heat gently with hot airOtherwise, since the pads are quite short, having a knife iron tip (or something else with a sharp edge) might help you get under the pin and heat the pad and the pin at the same time.

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2022, 04:21:11 pm
content: Quote from: mon2 on March 30, 2022, 09:40:26 pmLeaded is NOT the same as low-temperature!!! “Low-temperature” means solders with melting points well below that of standard leaded solder, and low-temperature solders exist in both leaded and lead-free alloys. Nowadays, the most common low-temperature solder is lead-free Sn42Bi58 eutectic (which must be carefully segregated from leaded solder, since adding lead to it can result in an alloy that melts below 100C!)

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2022, 04:25:39 pm
content: Quote from: Peacefrog on March 30, 2022, 08:39:55 pmAre the pads that struggle to flow connected to fatter traces or planes? This could easily explain why some refuse to flow. In this case, preheating the board might fix the problem.What tip are you using? I highly recommend getting a PLCC knife tip. (Heck, they’re great even for things thataren’tPLCCs!)

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: April 07, 2022, 04:32:09 pm
content: I've done a lot of PLCC hand soldering, and what you describe sounds like the PCB pad isn't getting hot or hot enough. First thing I would look at is the soldering tip. As mentioned, you need a tip that will get in there and touch the PCB pad.Also, what soldering technique are you using? Drag soldering with a small bent SMD well tip is what I use for those, and with flux would work well and quickly. You have to have a tip where you can touch not only the PCB but the PLCC at the same time.

author: wraper
author_rank: Unknown
timestamp: April 07, 2022, 04:43:14 pm
content: JLCPCB boards often have a bad solderability which may vary even within the same batch. Solder, especially lead-free simply does not like to flow on the pads. So you may need to tin those pads before placing an IC.

author: Bud
author_rank: Super Contributor
timestamp: April 07, 2022, 05:02:37 pm
content: I agree, as i experienced same issue with JLC made PCBs, it was a solderability problem.

author: thm_w
author_rank: Super Contributor
timestamp: April 07, 2022, 10:21:06 pm
content: 7 days after the question was already answered..