Dip soldering - Page 1
Forum section: electronics / projects

author: jpwack
author_rank: Contributor
timestamp: September 30, 2010, 06:51:58 pm
content: Hi everyone!In my job I have to do the whole PCB process: design, manufacturing (3rd party), acquisition of components, assembly (or instruct technicians to do so) and documentation.My problem is in the assembly stage: all of our boards are for internal use in small numbers (1 of each per week or so), but now there are two boards that are needed in not so small numbers (around a dozen of each per week). So I have 3 alternatives:1 - Push the technicians to assembly all of them.2 - Use small scale dip solderingas in the first part of this videoin a amateurish way with something likethis (230°C max)3 - Send the boards to an assembly companyThe guys inother forum think that dip soldering is so bad that doesn't worth the try. What can I do?best regards from Chile

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: September 30, 2010, 07:42:20 pm
content: Well, from a US perspective, unless you have a tiny shop (and successfully avoid OSHA, DEQ, EPA, and a number of other inspections) you could never get away with dip soldering like that. The solder pot would have to be in a contained area, that area would need some serious filtered ventilation, the worker would have to be wearing a leather apron, full face shield, gloves, and probably a respirator. And there would have to be air samples taken on a regular basis, as well as checking for blood lead levels of the workers a couple times per year.Beyond that, with dip soldering you have absolutely no process controls. Sure you'll solder them faster, but you'll have your techs picking off shorts and filling voids all over the place.I don't know what's available in Chile, but what I would do (and have done) is set up a decent assembly station and then hire a temp to do the build. There are temporary agencies up here where you can hire an assembly worker, a solderer, a tech, whatever you need on a day-at-a-time basis. That is, you could have a really good, qualified assembler come in and work for one day to knock out all of your boards. You wouldn't have to hire anyone as a full time employee, and it would probably be significantly less expensive than sending the whole build out to a job shop.Another option is how Dave get's his uCurrent adapters assembled.

author: jpwack
author_rank: Contributor
timestamp: September 30, 2010, 10:06:20 pm
content: Thanks for your answerI spoke with the ops manager and safety and the fumes were a major drawback, moreover with a recent soldering accident (a field technician didn't have googles on).So, hand soldering it is.cheersPS: in Chile the inspections for environmental issues are very scarce for small businesses too.

author: EEVblog
author_rank: Unknown
timestamp: October 01, 2010, 01:55:25 am
content: Quote from: JohnS_AZ on September 30, 2010, 07:42:20 pmThey (and the uWatch's) are hand assembled by a guy in Melbourne who works out of his garage.There are usually no shortage of one-man-band people like this in every country/state who will hand assemble small qty boards like that for you. They are usually much less fuss than the bigger assembly houses who do things a lot more formally.Dave.

author: TechGuy
author_rank: Regular Contributor
timestamp: October 01, 2010, 06:31:12 pm
content: Quote from: jpwack on September 30, 2010, 06:51:58 pmOption 4: redesign the boards with surface mount devices and use solder reflow. It will be far better to redesign the PCB to use SMT devices than to hand solder DIPs.Solder reflow is very simple and fast:1. get a vendor to cut you a solder mask stencil of the complete board (usually $20 to $60).2. Place and secure the solder mask stencil to the PCB board3. apply Solder paste to the PCB board4. Pick and place SMT devices onto the PCB5. Place the PCB on a aluminum plate or pan and place untop of a hot plate. Heat the PCB until the solder melts, then turn off the hot plate. Wait for the PCB to cool6. Hand solder any thru-hole devices (ie Power/data connectors, electrolyte caps, etc)If you have too many SMT components, you can use an assembler. Its cheaper to use SMT components since they can be picked and placed my machines (which is the most time consuming process of the assembly)

author: jpwack
author_rank: Contributor
timestamp: October 01, 2010, 07:19:30 pm
content: Quote from: EEVblog on October 01, 2010, 01:55:25 amThe technician that I was talking about is pretty fast and accurate, if I was doing this on my own (I have an start-up BTW) surely I'll go for an independent contractor, the smaller the better, "Solder Gun for Hire" doesn't sounds bad at all.Quote from: TechGuy on October 01, 2010, 06:31:12 pmexcellent point, for a low profile board we're going almost entirely SMD, even with hand-soldering is faster than thru-hole.I was searching for solder paste and stencil in Chile but I couldn't find the later, how hard it will be apply it w/o the stencil?.cheers

author: Zero999
author_rank: Super Contributor
timestamp: October 01, 2010, 07:44:06 pm
content: Quote from: TechGuy on October 01, 2010, 06:31:12 pmI think it also depends on how many boards you need making. Where I used to work, we always got the boards assembled by hand because it was small quantities (around 10 simple boards) and the assembly house was still more expensive because of the labour involved in setting up the machine.

author: armandas
author_rank: Frequent Contributor
timestamp: October 01, 2010, 08:26:09 pm
content: Quote from: jpwack on October 01, 2010, 07:19:30 pmPretty hard, depending on the number of components. The other method I know is to use a syringe dispenser, but I don't see many benefits. The system will cost more than laser-cut stencils and application is laborious.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: October 01, 2010, 08:40:06 pm
content: We always used EFD dispensers like this, but they're really expensive.http://www.nordson.com/en-us/divisions/efd/products/fluid-dispensers/pages/default.aspxTalk to whoever makes your circuit boards. Most often they can also make stencils since the process is essentially the same.

author: TechGuy
author_rank: Regular Contributor
timestamp: October 01, 2010, 09:27:32 pm
content: Quote from: jpwack on October 01, 2010, 07:19:30 pmYou could always hand cut the stencil if you can't find a vendor in your region. Ask this guy if he will ship to your country:http://www.ohararp.com/Stencils.html.Since Stencils weigh almost nothing, shipping wouldn't be astronomical.If not hand cutting them might be an option if you have a large number of boards to do. It would be very difficut to apply solder paste without a mask. To hand make a mask I would use the toner transfer method on to a peice of mylar, Polymide or some other reasonably durable plastic. You could also cut the in metal (stainless steel foil or other durable foils, Alum. foil won't work since it tares too easily).

author: jpwack
author_rank: Contributor
timestamp: October 08, 2010, 09:27:48 pm
content: Hi again, just a quick update:Yesterday, some guys where working in high power electrical installations, you know, and before plugging the cables they have to give the tip a solder bath, so they have a little pot with clean solder (w/o flux) at a nice 270°C. I, foolishly, I tried dip soldering a small board, IT WAS HELL!!!, DO NOT EVEN TRY!!!.Cheers

author: Time
author_rank: Frequent Contributor
timestamp: October 08, 2010, 10:03:16 pm
content: haha!

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 09, 2010, 06:57:08 am
content: Quote from: jpwack on October 08, 2010, 09:27:48 pmwhats the deal? i dont see any serious problem except some burnt copper on the bottom part of picture which i hardly see due too low light. if you can do that in one single dip pass i think that is good enough! IMO, all we need are just some adjustment in timing, method etc and more experience on it. maybe you can add some fluxes before you do the dip to avoid bridging and cold joint.

author: Zero999
author_rank: Super Contributor
timestamp: October 09, 2010, 02:19:46 pm
content: It looks like the whole board has been dipped vertically into the solder which isn't the right way to do it. The board should be dipped track side down over the solder and not totally submerged. It also looks like the bath was too hot or it was left in there for too long as the PCB has bubbled.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 09, 2010, 04:15:02 pm
content: Quote from: Hero999 on October 09, 2010, 02:19:46 pmDave has video showing this while he visited the China factory, other places got too (google pls), worth to have a look. I personally havent done or see this myself. But Dave's video worth thousands of lesson

author: Unknown
author_rank: Unknown
timestamp: October 09, 2010, 04:43:22 pm
content: Quote from: shafri on October 09, 2010, 04:15:02 pmI believe Dave showed wave soldering. One of the things required for wave soldering is... a wave. Not just a static pot of solder.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 09, 2010, 05:03:21 pm
content: Quote from: alm on October 09, 2010, 04:43:22 pmis there any major difference, other than the wave? from what i've observed, the wave only enable the solder get out of the container level to reach the horizontally moving PCB. but

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: October 09, 2010, 09:02:21 pm
content: All of the wave solder machines that I have seen/worked with have 4 major components.1- a PCB pre-heat section where the PCB passes over a series of large flat-plate radiant heaters.2- a foam fluxer that applies a fine layer of flux over the entire bottom side of the board.3- the actual solder wave4- a hot air knife that blows excess solder off of the board (and clears most any shorts that might remain)The flow of the solder in the wave helps to eliminate shorts and solder "stalagmites" that almost always form in a dip process.