Solder paste management

0. Importance of Solder Paste Management

1) If the management of solder paste that is a core element of SMT is insufficient, various soldering failure risks increase such as solder short, cold solder.

1. Income

1) Solder paste is warehoused to producing field & material team

   - Warehousing Status: Store in Styrofoam packing box with Ice Pack

2. Check (Warehousing Status)

1) Check if Styrofoam exterior is abnormal or not

2) Check if packing date on Invoice exceeds over 2 weeks or not.

   - if it is exceeded, notify/return to material operator

3) Check if Solder paste package is damaged and be dented in visual

   - If it is found, notify/return to material operator.

3. Attach controlling tag

1) Included contexts of charts(Date is written as M/D, h:min.)

    - Income date / inputted date to refrigerator / Outgoing date to refrigerator / Mixing 

time / Opened date

2) Controlling Tag should be managed with it attached on solder paste’s container

3) Solder paste should be controlled from income time to discarded time

4. Cold storage

1) Temperature for storing: 1~10℃ (Recommended : 2~8℃)

2) Controlling as “first in, first out.”

 ※ If cold storage is not met, the physical properties of the solder paste are changed due to the volatility of the flux.

     → Increase soldering failure risk

5. Storage in room temperature

1) Solder paste should be neglected in unopened and room temperature(25±3 ℃)

        after taking out quantity of the day shift production

    - Storage in room temperature : 2hr ~ 12hr (Recommended : 2~3hr)

    ※ reason to storage in room temperature: In case of low temperature open, Solder

         ball defect occurs by moisture absorption caused by dew condensation

2) In case of no production, store in cold after unopened and room temperature storage

    - Re-storage should be used  after storing over 12 hours. 

6. Mix

1) Solder paste storage in room temperature is agitated in pocket of mix machine

      - Recommended  : 45sec / 1,000 rpm 

      ※ Details :  Refer Solder paste spec sheet on each Maker / Composition (attachment)

   ※ if you do not meet the mix standards, Increase soldering failure risk because solder and flux do not mix evenly\

7. Open / Review

1) If discoloration/mass after agitated Solder paste open, notify/return to material operator.

8. input to printer

1) Spread neglected Solder paste evenly on Stencil with printing machine using

     designated scoop. (Suggested : thickness 15 ~ 20 mm) 

2) Remainders after inputing printing machine should be stored with cap cover

     and use it within 12hours

• Controlling Solder Paste When SMT Line is not Operated

1. Controlling solder paste in case of not operating line

1) If it is not exceeded 4hours, print after roll Solder paste twice

2) If it is exceeded over 4 hours, discard after raking out with

 ※ After 4 hours are over, Solder characteristics are lower.(viscosity, adhesion, 

oxidation, etc.,)

2. Collecting & storing disposal solder

1) Collect Used Solder Paste with designated scoop on original Solder container and 

record disposal date on management chart on Solder container

2) Attach red sticker on Solder container to manage used Solder and normal one 

separately

3. Writing check sheet of disposal solder paste

1) Production division writes discarded reason and date on check sheet, when 

discarded

solder paste stores

4. Disposal solder paste

1) Environment Safety Team sells stored used Solder to industrial waste specialized

  company or Solder Paste manufacturer at mutually agreed price and collect money 

after checking weight in the presence of both material operator and Environment 

Safety 

operator once a month. Material management team arranges computerized inventory

    ※ Manage after deciding operating department following to national disposal management

         standard and subsidiaries using used Solder recycle should use with separated regulation

Material management

  1-1.  Material management 

1-1-1. Standards of BGA / IC / PCB Incoming & management :

[1] Incoming

   1) IC & PCB should be warehoused in vacuum packing.

[2] Inspection : Conduct inspection available in vacuum packing.

    1) When incoming BGA & PCB gets NG after inspection,

      - IQA inspector should inform the person in charge  and receive an order,

        or return to the maker if possible.

   ※ NG criteria

      - When parts are not in vacuum packing, or air flows in due to packing damage.

      - When actual parts are different to the details in inspection record by Maker.

    2) when appear the NG of components about vacuum packing, if NG components
        can not be return, after components baking and then processing the vacuum
        packing.

    3) If the validity of IC had expired, inform  Manager or return it.

        (Even more than one year IC in vacuum packing)

[3] Storage

    1) Must separate parts for ordinary & Pb free.

    2) BGA, IC & PCB must be stored in vacuum packing.

     ※ BGA and IC’s store standards must apply the criteria that attached IC packing

     ※ Standard of storage temperature/humidity : 25 ± 5℃,  50±10% 

    3) Store separately by lot for First-in, First-out (FIFO)

[4] Use

    1)Open IC envelope and PCB box before production.

    2)Remained IC & PCB after opening, vacuum pack in 30 minutes and store.
       (after 30 minutes, vacuum pack after Baking)

    3)After opening, operators must wear anti-static gloves and wrist strap to protect
       IC & PCB.

    4)Write down opening date and time on the envelope to prevent IC from absorbing
       moisture and PCB oxidation. And It should manage envelope and tray
       in attaching tag

    5)Opened IC in standby state must be stored in related line before production
       completed.

5] Remainder handling

    1) Opened IC & PCB must be used in 24 hrs, if it’s impossible,

      ① Store in vacuum packing with silica gel after baking within 30min

      ② After  store in dry chamber  during 24 Hours, use it

          (But, can use within unpacking 24 hours)

    2) Reel parts must be baked on low temperature(40℃)

     ※ But, MSL level 6 immediately use after unpacking within “Time on Label”

     ※Baking standards : 125℃,12~48 hrs. (Refer baking table or part maker’s recommendation)

     ※ Temperature/Humidity standard of dry chamber : 25 ± 5℃, 10%↓

   ※ Reuse process of Silica-gel

    1) Collect remaining Silica gel after open vacuum packing IC, and store it on
        guarantee place.

    2) Silica gel should bake in can see silica gel’s cover conditions.

       

- Baking Standard : 125℃, 16Hrs

      ex)  

                                                                                                                  

                

   

à Baking standards: 118℃(245℉)/16hrs

      

  

   ex)       

        - Standard of storing when baking : It should spread. No fold.

               

    3) Input dry chamber after completing Bake

    4) When vacuum packing remaining IC, It enclose silica gel in dry chamber

       - Enclosed amount : 1unit or 2unit (Obey standard of Maker)

       - If materials let out the storage, material’s quantify must have to limit according
         to used within 24hrs. (If procedure plans of same model is fixed more than a day,
         divide by 24 hours the material is exported.)  

       - Remained material immediately must have to vacuum pack with silica gel.

       - If storage with vacuum packing after proceed a materials baking, in below
         case(include silica gel)

       - Remained IC that it used in SMT line 

       - Over the 24hrs from open time

       - IC incoming  with not vacuum packing

       - Baking chamber caution

       - If  vacuum chamber are used at another IC, baking after store the dry chamber.

       - If  baking is in progress about tray, reel, silica-gel, worker have to use the
         specified temperature/time condition.

       - If baking process is impossible material about the reel components, worker
         must only vacuum packing. (Reel components have to exhaust within use-by date)

To be continued ...

SMT Process & Standards Guide

SMT Process & Standards Guide 

In this part i will share some of  our SMT Process supported with flow charts and standards ...

Note: SMT standards varies from company to another according to the manufacturing type and components 

so Let's Start...

SMT Process : Reflow Oven

Reflow Oven :

A machine that acts as oven to complete the soldering process of components on surface of PCB by passing it through various hot zones reach 10 which are controllable

 Points Of Management :

Making temperature profile according to the standard showing in picture to assure a high quality soldering process

Defects :

Cold Solder  Due To Sufficient Temperature 

Solder Balls Due to Wrong temperature profile

Video :

SMT Process: M-AOI

Mounting Automatic Optical Inspection:

Inspection Stage after adding components to the PCB that inspect the location and condition of each component by taking picture of it and compare it to a reference using a CCD camera

 Defects to inspect:

• Missing Component
• Wrong polarity
• Tombstone 
• twisted component
• wrong part number

Video:

Mounter Machine:

Flexible Chip Mounter:

A Machine that fix big SMT components such as (SOP,QFP,BGA)

Points Of Management:

• Components mount position (X,Y)
• Component Pick up Position
• Components drop rate
• Nozzles cleaning
• Feeder accuracy

Defects & Errors:

• Wrong Polarity
• Shifted
• Up-Side-Down
• Wrong component